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Diagnosis and management of nutrient constraints in bananas (Musa spp.)
C H A P T E R
44 Diagnosis and management of nutrient constraints in bananas (Musa spp.) Kenneth Nyombi* Makerere University, College of Agricultural and Environmental Sciences, Kampala, Uganda *Corresponding author. E-mail: [email protected] O U T L I N E 1 Introduction
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2 Classification, geographical distribution, and major cultivars
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3 Biotic production constraints and yields
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4 Major soil types and nutrient requirements for banana production
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5 Diagnosis of banana nutrient constraints (nutrient deficiency symptoms, soil fertility norms for
different banana cultivars used globally, and leaf nutrient standards)
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6 Physiological disorders due to nutritional and environmental constraints
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7 Management of nutrient constraints
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8 Conclusions
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9 Future research
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References
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1 Introduction Bananas (Musa spp.) are major food crop globally, ranking fourth in the world after rice, wheat, and maize (FAO, 2017). They are large perennial herbs growing to a height of 2–9 m at maturity depending on variety. Native to the Indo-Malaysian, Asian, and Australian tropics, bananas are currently grown throughout the tropics and subtropics between latitudes 33°N and 33°S (Stover and Simmonds, 1987). They have developed secondary loci of genetic diversity in Africa (the great Lakes region), Latin America, and the Pacific (Papua New Guinea and the Solomon Islands). Bananas grow in a wide altitude range from 0 to 2000 m.a.s.l., but lower temperatures at high altitudes reduce the rate of leaf emergence or the growth in leaf area index (LAI), the rate of fruit growth, and length of the crop cycle duration. With increasing altitude from 1174 to 1405 m.a.s.l, Taulya et al. (2014) noted that phenological development of East Africa highland bananas (Musa AAA-EA) involved trade-offs between physiological and chronological age. Generally, bananas require a base temperature of 14°C and the temperate range for optimal growth is 25°C–30°C (Stover and Simmonds, 1987). Under good growth conditions (if soil moisture and nutrients are not limiting), the net assimilation rate (NAR) depends on the total photosynthetically active radiation (PAR), but shading up to 50% in tropical regions may not reduce yields. At higher shading such as in plantations with leaf area index (LAI) greater than 4, growth of ratoon crops is delayed by a couple of months due to the low PAR penetration. Bananas take up large amounts of water owing to the large broad leaves and high leaf area index. Water use is a function of supply, demand (potential evaporation), and soil water holding capacity (Lahav and Turner, 1989). In the tropics, bananas are produced in areas receiving about 1000 mm of rainfall per annum, with no irrigation resulting into moisture stress, reduced nutrient uptake during the dry months, and consequently low yields. In the Caribbean, rainfall may exceed
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44. Diagnosis and management of nutrient constraints in bananas (Musa spp.)
2000 mm per annum, which coupled intensive mineral fertilizer and pesticide use results into leaching and pollution (Godefroy and Dormoy, 1990). Global banana production is estimated at 120 million tons per year (FAOSTAT). Most of the export bananas are desert bananas—Cavendish (AAA)—and export volumes are estimated at 16.741 million tons per year (FAO, 2017), generating about USD 8 billion per year. Latin America and the Caribbean export 84%, Asia 12%, and Africa 4%. The main banana exporters are Ecuador (33%), the Philippines (14%), Costa Rica (12%), Guatemala (11%), and Colombia (11%), with organic bananas mainly exported by Colombia, Peru, and the Dominican Republic. Export destinations are the North American markets, Western Europe, Japan, Russia, and the Asian market, which mainly takes exports from the Philippines. The rest (about 85% of total production) is consumed locally, most especially in large producing countries such as India, China, Brazil, the Philippines, and in some African countries such as Uganda and Rwanda, where per capita consumption exceeds 200 kg of banana. Bananas provide potassium (358 mg/100 g), vitamin B6 (20%), and vitamin C. Potassium reduces the risk of heart disease and lowers blood pressure. Ripe bananas provide up to 90 cal, 12 g of sugars (mainly sucrose, fructose, and glucose), 0.3 g of fat, and 2.7 g of fiber per 100 g. Its nutritional content, health benefits coupled with increasing global population, have kept the banana demand strong.
2 Classification, geographical distribution, and major cultivars There are over 1000 varieties of bananas produced globally, which are grouped according to the ploidy levels and the uses (cooking and desert). Ploidy level refers to the number of chromosome sets and the relative proportion of Musa acuminata (A) and M. balbisiana (B) in their genome (Karamura, 1998). The common cultivated cultivars globally are triploid hybrids: AAA (Cavendish, East Africa highland banana), AAB (Silk, Mysore), ABB (Saba, Bluggoe, Monthan, Simoi), and BBB (Saba). Diploids AA, AB (beer bananas), and BB, which are starchier, are also grown. Tetraploids AAAA (FHIAs), AAAB (PA12.03 and SH-3640), AABB (FHIA03), and ABBB are grown but are not so common. In Southeast Asia, cooking bananas (ABB) and dessert bananas (AAB) are common. In central and South America and China, Cavendish banana (AAA) are grown in commercial plantations and account for about 47% of global production (FAO, 2017). This is attributed to their dwarf stems, implying reduced damage to storms and the ability to recover quickly from natural disasters. In Africa, there are over 200 cultivars of East African highland cooking bananas (AAA-EA) grown in the great Lakes region for home consumption with surplus sold to urban centers. In this region, a number of beer cultivars (AB, ABB, and AAA) and desert types (AAA and AB) are grown. Plantains (AAB) are starchier and are common in West and Central Africa and Central and South America (Stover and Simmonds, 1987).
3 Biotic production constraints and yields The major biotic constraints to banana production, which differ from one region to another (given the soils, temperature, altitude, management, and production orientation), are pests: weevil (Cosmopolites sordidus), nematodes (burrowing nematode, Radopholus similis; root lesion nematode, Pratylenchus goodeyi; spiral nematode, Helicotylenchus multicinctus; reniform nematode, Rotylenchulus reniformis; stunt nematode, Tylenchorhynchus spp.; and ring nematode, Criconemoides sphaerocephalum), moths (scab moth, Nacoleia octasema), and diseases (black Sigatoka, Mycosphaerella fijiensis; bunchy top, banana bunchy top virus (BBTV); Panama disease or Fusarium wilt, Fusarium oxysporum; anthracnose, Colletotrichum musae; and banana bacterial wilt, BBW). The banana weevil is the best known banana insect pest in the great Lakes region. In Uganda, it was first reported in 1908 and mainly affects bananas at altitudes below 1600 m.a.s.l. (Sseguya et al., 1999). The feeding larva eats through the rhizome reducing water and nutrient uptake. Commonly reported yield losses due range between 14% and 20% (Rukazambuga et al., 2002), but heavy attack can lead to 100% yield loss. It is controlled through field sanitation, better agronomic practices, and the use of chemicals (organophosphates and carbamates). Nematodes are a major yield reducing factor in all banana-producing regions, and their populations increase with age of the plantation, if not controlled. They attack roots and rhizomes causing necrosis of root tissues and corm, thus impeding water and nutrient uptake. R. similis is common at altitudes below 1500 m.a.s.l, while the root lesion nematodes are common at altitudes higher than 1500 m.a.s.l. Nematodes are controlled through cultural practices, using nematode-free planting materials, soil treatment before planting or fumigation, crop rotation, fallowing, varietal resistance, and nematicides (Risede et al., 2010). The scab moth larvae enter the banana flower and destroy the growing fruits, causing scars and deformed fingers. It is common in the Southwest Pacific and is controlled by injecting the banana flower after it emerges with an insecticide.
4 Major soil types and nutrient requirements for banana production
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Globally, black sigatoka is the most important fungal banana disease. An attack leads to the development of lesions on leaves significantly reducing the number of green leaves, leaf area to intercept radiation, and the bunch yield (Stover and Simmonds, 1987). Usually, a combination of cultural practices (field sanitation, canopy aeration, pruning, cutting off affected leaves, and resistant varieties) and chemicals (fungicides) are important for controlling this disease. The bunchy top disease is a major problem for banana plantations in Hawaii and the Pacific. It is controlled by using clean planting materials and disinfecting tools used on plantations. The panama disease caused by a soil borne fungus is a major banana disease worldwide. Fungal attack results into stem, root, and rhizome necrosis. Plant death mainly occurs at or during flowering and periods of soil moisture stress. Since the fungus lasts long in soil, control is largely preventive, through planting resistant varieties or clean materials in clean soil. Banana anthracnose disease mainly damages fruits and is controlled by removing affected leaves that are close to the bunches. Banana bacterial wilt (BBW) devastated banana plantations in the great Lakes region, with yield losses up to 100% (Kagezi et al., 2006). Affected plants wilt when the leaves are green and die off. It is controlled by sanitation (planting disease free materials, disinfecting farm tools, and removing male buds). Yields on banana farms are a complex interaction of both the biotic and abiotic (soil moisture stress and soil fertility) constraints. The biotic constraints and moisture stress reduce the recovery efficiency of applied fertilizer and the fertilizer-use efficiencies for farmers who use fertilizers. In Africa, banana production is mainly by smallholder farmers on fields <0.5 ha, with medium size commercial farms (>3 ha) gaining prominence due to increasing demand. In the great Lakes region, actual banana yields on smallholder farms are low (5–20 Mg/ha/yr FW) due the constraints mentioned earlier, far below the estimated potential yield (100 Mg/ha/yr FW) (Nyombi, 2010). Under average farmer management, Smithson et al. (2001) reported yields of 67 Mg/ha FW from Southwestern Uganda. This shows that the yield gap can actually be reduced with proper management. For example, Costa Rica, a leading banana producer and exporter have been able to increase yields from 10 to 20 Mg/ha/yr FW before 1960 to 50–80 Mg/ha/yr FW today for Cavendish (AAA) through better agronomic management and cultivar choice (Stover and Simmonds, 1987). In general, commercial production of the Cavendish variety gives yields ranging 40–60 Mg/ha FW in other regions (India and China), while small producers report yields of about 30 Mg/ha FW. In the Philippines, actual yields are low, with varieties such as Saba (cooking—ABB) and Lakatan (dessert—AAA), yielding 11–20 Mg/ha FW. It is important to note that yields are generally low for locally consumed bananas. Population growth coupled with increasing demand, improved infrastructure, market access, and value addition are likely to increase prices, and compel farmers invest more into management thus raising yields (Bagamba, 2007).
4 Major soil types and nutrient requirements for banana production Globally, bananas are grown on a wide range of soils from the fertile and young Inceptisols (with a large capacity for stocking potassium) and Andisols, moderate K releasing capacity (Delvaux et al., 1987, 1989; Delvaux, 1989) to the old and low fertility Ferralsols and Acrisols (Fig. 44.1). In many areas especially in Africa, banana production systems are built on old soils with soil pH, extractable phosphorus (P), calcium (Ca), and potassium (K) below critical levels and nutrient availability largely depends on mineralization of soil organic matter. Generally, soils must be deep, free draining loams, or light clays, because bananas can’t tolerate extreme water logging especially for clay soils (>60% clay). Rooting depth of bananas determines the ease of root movement through the soil; however, maximum rooting depth of 1.5 m has been reported (Lahav and Turner, 1989). A higher clay content >50% depresses yields due to compaction, poor root movement, and reduced available water (Robinson, 1996) resulting poor emergence of fruit (Fig. 44.2). The best pH range for good banana growth is 5.5–8.0. Low pH (4.5) reduces yield by 50% as compared with the optimal range due to low availability of important nutrients such as phosphorus especially in P-fixing old tropical soils. For acid soils, 600–750 kg of lime per hectare can be plowed into soil at land preparation to raise the pH. Bananas are heavy feeders ( Jones, 1998). Nutrient requirements are in order as follows: potassium > nitrogen > phosphorus (Nyombi et al., 2010). In addition, bananas take up significant quantities of other nutrients such as calcium and magnesium. Typical N, P, and K uptake levels amount to 388, 52, and 1438 kg/ha in a crop cycle for AAA Cavendish dessert banana plants yielding 50 Mg/ha FW at a density of 2400 plants/ha (Lahav and Turner, 1983). Due to the large quantities of potassium taken up by bananas, apparent K recovery fractions are high (75%) as reported by Lopez and Espinosa (2000), if soil moisture is not limiting. Potassium plays a crucial role in regulating the transfer of nutrients to the xylem, regulating water in the plant and the functioning of the stomata. When potassium supply is low, the transfer of nitrogen, phosphorus, calcium, magnesium, and other nutrients across the xylem is restricted
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44. Diagnosis and management of nutrient constraints in bananas (Musa spp.)
FIG. 44.2 Moisture stress from the floral initiation stage to flowering often results into choked bunches and flower abortions in East Africa highland bananas (Musa AAA-EA).
FIG. 44.1
A soil profile pit dug on a haplic ferralsol in central Uganda showing the shallow A horizon, the iron and aluminum oxide-rich B horizon and the stone layer.
(Turner, 1987). Low potassium supply reduces total dry matter production and its allocation within the plant, most especially the bunch. This attributed to the reduced photosynthesis, respiration, and total green leaf area of the plant (Fig. 44.3). Potassium deficiency also impairs protein synthesis, sugar transportation, and N utilization leading to N accumulation in plants (Nyombi et al., 2010). Potassium deficiency also leads into shortening of internodes, delayed flower initiation, choking of bunches, and stunted growth. Nitrogen is component of enzymes and chlorophyll and give leaves a green color. It is very important in green leaf area formation, photosynthetically active radiation interception, and determining its use efficiency (Marschner, 2003). Low nitrogen supply results into pale green leaves, with midribs, leaf sheaths, and petioles turning pink. Phosphorus is crucial for root growth, energy transfer, and fruit formation. Good root growth is important due to the large fresh mass (stem and leaves) and to support the bunch after flowering. Low P supply leads to curling of leaves, and a bluish green color on young leaves. Magnesium uptakes in banana plants can be as high as 55 kg/ha/yr for Grand Naine on an Ultisol (Irizarry et al., 1988). Low magnesium supply results into yellow discoloration of midblade and midrib portion and purple mottling of the petioles and marginal necrosis. Calcium is important in cell wall structure and ensuring the integrity of the banana peel during ripening. Calcium deficiency results into the thickening of veins and the deformation of the leaf lamina. Sulfur is a component of chlorophyll molecule and is crucial for protein synthesis. Sulfur deficiency results into white or yellow patches on young leaves and on leaf margins, thickening of veins, and reduced bunch size. Copper deficiency results into chlorosis of leaves. Zinc deficiencies mostly occur in limed or alkaline soils. FIG. 44.3
Potassium deficiency in a newly established banana plantation on a Lixic Ferralsol at Ntungamo, Southwestern Uganda. Potassium-deficient old leaves turn orange-yellow in color due to K relocation to the young leaves; show scorching along the margins, later curl inward; and die resulting into a reduction in total leaf area.
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5 Diagnosis of banana nutrient constraints
Leaves show a high amount of anthocyanin on the underside, with fruits small and twisted. Manganese deficiency results into light greening of leaf margins of younger leaves. Deficiency of boron results into thickening of secondary veins, delayed flowering, curling of leaves, and lamina deformation. Potassium is sensitive to cation balance, and the assessment of soil K critical levels is dependent on the K/Ca/Mg balance. Therefore, soil analysis is important for monitoring K fertilization to determine the relationship between crop response to the added K, K concentration in soil, and the K/Ca/Mg balance. Soil critical K content was reported at 1.4 meq/100 g of soil, with a K/Mg ratio of 0.28 (Lahav and Turner, 1989). Optimal calcium absorption would require a soil balance K:Mg:Ca of 1:3.5:10.7 (Turner et al., 1989).
5 Diagnosis of banana nutrient constraints (nutrient deficiency symptoms, soil fertility norms for different Banana cultivars used globally, and leaf nutrient standards) Plant nutrient deficiencies are diagnosed using foliar analysis (Hallmark and Beverly, 1991), which helps to accurately assess the need for fertilization. Foliar analysis is based on the assumption that there is always a positive relationship between the quantities of nutrient applied, leaf nutrient status, and consequently the yield. This assumption however may not hold if pests and moisture supply limit uptake of the applied fertilizers. Timely leaf analysis helps to prevent deficiencies rather than correcting them. In most banana-producing countries, not only laminar structure of third leaf is sampled, but also samples of the central vein of third leaf and the petiole of seventh leaf can also be used. Usually, a strip of tissue 10-cm wide, on both sides of the central vein, is taken (Lopez and Espinosa, 2000) and analyzed using standard laboratory methods for assessing leaf nutrient contents. The critical levels of foliar nutrients of Dwarf Cavendish (AAA) dessert banana are presented in Table 44.1. However, as already discussed, nutrient uptake and distribution are affected by interactions within the plant; therefore, multinutrient approaches have been derived. There are two common methods used to diagnose nutritional imbalances: diagnosis and recommendation integrated system, DRIS (Walworth and Sumner, 1987) and compositional nutrient diagnosis, CND (Parent and Dafir, 1992). DRIS norms are considered as best and are commonly used. They envisage that the ratios N:P, N:K, P:K, Ca:Mg, and their reciprocals remain constant in the leaf irrespective age. Therefore, nutrient concentration ratios rather than concentrations of single nutrients themselves are used (Beaufils, 1971, 1973) to identify the imbalances. These norms are usually developed for specific locations (climate and soils), cultivar, and under a given crop and soil management regime. For example, Wortmann et al. (1994) developed DRIS norms for AAA-EA cooking banana cultivars in the Kagera region of Northwest Tanzania as N (3.15), P (0.25), K (3.04), and Ca (1.13). Wairegi and van Asten (2011) using foliar analysis data from different banana growing zones in Uganda for similar cooking bananas reported that foliar N, P, K, Ca, and Mg ranged between 1.35%–3.89%, 0.10%–0.38%, 1.54%–5.83%, 0.23%–1.74%, and 0.25%–0.85%. This shows that on average, Wortmann et al. (1994) had higher N (3.15% vs 2.79%), P (0.25% vs 0.21%), Ca (1.13% vs 0.91%), and lower K (3.04% vs 3.84%) as compared with the findings of Wairegi and van Asten (2011). Smithson et al. (2001) in a study at Rubale, Southwest Uganda, suggested that the norm for K in AAA-EA cooking banana was lower than the 4.49 suggested by Angeles et al. (1993) but higher than 3.04 obtained by Wortmann et al. (1994). This emphasizes the TABLE 44.1 Critical levels of foliar nutrients of Dwarf Cavendish (AAA) dessert banana.
Nutrient
Leaf 3 Lamina %
Leaf 3 Central vein %
Leaf 7 Petiole %
Nitrogen
2.6
0.65
0.4
Phosphorus
0.2
0.08
0.07
Potassium
3.0
3.0
2.1
Calcium
0.5
0.5
0.5
Magnesium
0.3
0.3
0.3
Sodium
0.005
0.005
0.005
Sulfur
0.23
–
0.35
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44. Diagnosis and management of nutrient constraints in bananas (Musa spp.)
TABLE 44.2 Diagnosis and recommendation integrated system (DRIS) and critical nutrient levels in the 3rd leaf lamina. Nutrient (%)
DRIS
Critical value range
Average of published values
Nitrogen
3.04
1.81–4.00
3.03
Phosphorus
0.23
0.12–0.41
0.22
Potassium
4.49
1.66–5.40
3.40
Critical levels of micronutrients: boron (10 mg/kg), iron (100 mg/kg), manganese (160 mg/kg), zinc (20 mg/kg), and copper (9 mg/kg). Based on Angeles, D.E., Sumner, M.E., Lahav, E., 1993, Preliminary DRIS norms for banana. J. Plant Nutr. 16, 1059–1070.
location and management specificity of DRIS norms even for the same cultivar. Angeles et al. (1993) reported higher K (4.49%), N (3.04%), and P (0.23%) in a high yielding banana plantation—70 Mg/ha (Table 44.2).
6 Physiological disorders due to nutritional and environmental constraints In most fruit crops, physiological disorders associated with micronutrients as compared with macronutrients are more common given their perennial nature and the focus mainly on macronutrients (N, P, and K) during fertilizer applications (Hanson, 1987). In bananas, high K:Mg ratios above 0.6–0.7 induce typical mottling of the petiole (blue), which reduces crop yields. For example, Delvaux (1988) working on an old and highly leached acid Ultisols in Cameroon reported that a K:Mg ratio of over 0.7 induces blue, only when root depth is shallow (<20 cm) and when both exchangeable Mg concentration and total Mg soil reserve are below 1.3 and 45 meq/100 g of soil, respectively. However, blue can also be associated with a low K:Mg ratio in the field caused by potassium deficiency and was not related to high magnesium supply. Micronutrient deficiencies (Zn, Mn, and B) are more common in banana (Robinson, 1996), and these must be detected before the visual symptoms and addressed to reduce their effect on yields and fruit quality. These are also attributed to expansion of banana production to poor soils, limited use of organic manures, imbalanced NPK fertilizers, and high intensity crop production (>2500 plants/ha). To correct the micronutrient deficiencies, appropriate foliar, and soil nutrient applications are necessary. Disorders caused by micronutrient deficiencies include the following: bronzing (the development of bronze or copper color on leaves), chlorosis (the loss of green color resulting into pale yellow tissues), tip dieback (collapse and death of the growing tip or the younger leaves), lesions (small wounds on the leaf or stem tissue followed by discoloration), and necrosis or death of plant tissues. Under field conditions, disturbances in the plant metabolic and physiological activities can occur resulting from an excess or deficit of environmental variables like temperature, light, and aeration, coupled with micronutrient deficiencies. Banana choke throat is due to low temperature, which turns the leaves yellow and in severe cases, lead to tissue necrosis. At flowering, the bunch is unable to emerge from the pseudostem properly and is deformed, and bunch maturity is delayed by 1–2 months. Tree shelter belts can be planted in the wind direction, or low-temperature tolerant cultivars can be planted at that location. Another common disorder is chilling injury. This occurs when preharvest or postharvest temperatures fall below 14°C for various time periods. Banana peels become dark, and the fruits do exhibit uneven ripening. In the commercial Cavendish and Gros Michel banana, chilling injury manifests its self at temperatures below 12.5°C. To avoid this problem, the major banana exporting companies ship bananas at a controlled temperature of 13–14°C. Other physiological disorders happen during ripening, thus reducing postharvest fruit quality, quantity, and marketability. Peel cracking is common disorder, but it largely depends on genetic, environmental, and physiological factors before harvest and environmental conditions of storage after harvest. This exposes the banana pulp to pathogen infections. Peel cracking can be controlled by managing the humidity levels in the ripening, storage, and transportation chambers. Peet (1992) argued that splitting may also be attributed to preharvest conditions, as calcium and potassium deficiency. Most of the export bananas are sold as clusters of fingers in supermarkets. Finger drop usually occurs during ripening, with individual fingers dropping off from the cluster, reducing market value, and increasing susceptibility to pathogens. A weak finger neck may have three possible causes: genetics, nutrition, and postharvest conditions. Balanced banana nutrition is very important to deter neck breakage. Usually, the application of boron, calcium, magnesium, or silicon enforces cell structure and deters this disorder (Putra et al., 2010). It is important to ensure balance nutrition to have good quality banana fruits (Raghupathi et al., 2002).
7 Management of nutrient constraints
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7 Management of nutrient constraints In Africa, few banana farmers use fertilizers; therefore, nutrient supply largely depends on the mineralization of soil organic matter, but the size the active pool is always small. Organic fertilizers (grasses, composts, crop residues, and animal manures) were proposed as the first line remedy to soil fertility decline from the 1930s in Africa. In the great Lakes region, research done in the 1940s and 1950s focused on the quantification of organic fertilizers applied and yield data collection on farms. But the yield increases above the control reported were low—<10 Mg/ha/yr (Nyombi, 2013). In the Americas and the Caribbean, from the 1960s, the focus was on integrated pest management and the use of mineral fertilizers to increase banana yield to meet the growing demand for the fruits. These efforts have largely paid off with yields of more than 70 Mg/ha FW in high yielding banana plantations today. In Africa, from the 1980s, studies focused principally on diagnosing plant nutrition status, the use of mineral fertilizers, and the combined application of organic and mineral fertilizers. The integrated plant nutrition approach was advocated for giving the range of nutrients from organic materials and other benefits such as soil structure improvement and soil water retention. But increasing land pressure and shrinking farm sizes have reduced farmers capacity to obtain off-farm organic resources from communal areas (Baijukya et al., 2005), with additional supply of N, P, and K expected to come from mineral sources (Hallmark et al., 1987). Increasing commercialization of banana trade from the Americas from the 1960s led to increases in mineral fertilizer use and efforts to make production more efficient and profitable to maintain and attract new markets. Today, these efforts have led to a number of companies that are famous for trade in banana such as Chiquita, Del Monte, Dole Foods, and Fyffes, with a net worth valued at billions of dollars. Science has played a crucial role to determine the optimal amount of fertilizer or fertilizer amounts to apply for a target yield. Janssen et al. (1990) developed the quantitative evaluation of the fertility of tropical soil (QUEFTS) model originally to calculate maize yield as a function of N, P, and K supply from soil and fertilizer while accounting for interactions among the nutrients (N, P, and K). Using experimental data from Uganda, this static model was applied to East Africa highland bananas (AAA) with interesting results (Nyombi et al., 2010). With the developed model parameters, it is relatively easy to calculate the amount of fertilizer required for a target yield, provided moisture supply is not limiting. In South and Central America (Costa Rica and Honduras), N, P, and K apparent recovery fraction are estimated at 50%, 30%, and 75% (Lopez and Espinosa, 2000). Using these and other derived banana parameters, the QUEFTS model predicts that for a fresh banana yield of 70 Mg/ha, 426 kg N/ha + 55 kg P/ha + 1576 kg K/ha. These values are not so different from fertilizer application rates in high yielding plantations in the banana growing regions (Robinson, 1996). With the fertilizer amount determined, it is important to identify the sources of nutrients, methods of application, and when to apply. The types of fertilizers to use as sources of nutrients depend on availability, the soil pH, and the texture (sandy or clayey). However, to achieve the above yields, special attention must be taken for potassium, which is the most important nutrient for banana growth. The common sources of potassium are potassium chloride (KCl) (60% K2O and 45% Cl), potassium sulfate (50% K2O and 17%–18% S), and potassium magnesium sulfate (21%–22% K2O, 10%–11% Mg, and 21%–22% S). Potassium is susceptible to leaching losses in light textured (sandy) soils and fixation in clay soils; it is thus better to apply the granular form or to split applications. In most banana-producing regions, usually three six (six splits) per year are used for experimentation and are recommended to farmers. This improves the recovery efficiency of the applied fertilizer. Bananas are also produced on saline soils in drier environments (with irrigation) resulting into an increase in Na content in roots reducing K uptake and banana yield (Israeli et al., 1986). In the Canary Islands, the optimal value for the soil K:Na ratio is considered to be 2.5. For soils with high Na content, the combined application of gypsum, manure, and potassium ( Jeyabaskaran et al., 2000). Nitrogen sources include the following: calcium ammonium nitrate (CAN) (26% N, 3.5% CaO, and 4% MgO), urea (46% N), and ammonium sulfate (21% N and 24% S). Urea should be covered or applied in solution to minimize volatilization losses (Chan, 1986). Prasertsak et al. (2001) reported that 25% of applied N was lost from the system by runoff, leaching, ammonia volatilization, or denitrification in the wet tropics of Queensland, Australia (annual rainfall 1800–4000 mm and plant density 1300 mats/ha). Godefroy and Dormoy (1990) reported leaching losses from soils with a low cation exchange capacity in Martinique to be 165 kg N/ha/yr. Nitrogen must be applied in splits. CAN is preferred on acid soils to raise the pH. Urea and ammonium fertilizers are preferably used on soils with a high pH. Monoammonium phosphate (10%–12% N and 48%–61% P2O5) and diammonium phosphate (18% N and 46% P2O5) are also used. Other sources of phosphorus include the following: triple super phosphate (20% P) and single super phosphate (12%–18% P2O5, 18%–21% Ca, and 11%–12% S). Usually two applications per year are adequate. The other source of magnesium is magnesium sulfate (13%–16% Mg and 13% S). Micronutrient deficiencies are more common now (especially Zn and B). Zinc is supplied by application of zinc sulfate (22% Zn and 11% S) and boron through application of borax (11% B). Fertigation is more efficient with less losses, but it is only possible for large-scale farmers. For small scale farmers, fertilizers are applied per plant by hand.
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44. Diagnosis and management of nutrient constraints in bananas (Musa spp.)
8 Conclusions Bananas are and will remain an important source of income and nutrition to current and future generations. However, to increase the current yields and ensure future fruit supplies, the causes of low yields especially in Africa and Asia, where population increase is fast, must be addressed. Low yields are attributed to biotic (pests and diseases) and abiotic constraints (moisture stress and nutrients). Biotic constraints reduce the uptake and utilization efficiency of water and nutrients and should be controlled using the different methods as discussed in this chapter. Bananas take up large amounts of K, N, P, Mg, and Ca, if soil moisture is not limiting. Where the indigenous nutrient supply is low, these must be supplied from both organic manures and mineral fertilizers. Given the fact that nutrient deficiencies show a strong spatial and temporal variability in different banana systems due to soils, soil and foliar analysis are important if static models such as QUEFTS are to be successful applied to calculate fertilizer requirements for target yield levels. Balanced nutrition is important to minimize growth and postharvest physiological disorders. Variation in soils (cation exchange capacity), rainfall received, and the need to synchronize nutrient demand by the plant and supply dictate that fertilizers supplying the macronutrients are applied in splits. This reduces losses due to runoff, leaching, and volatilization, hence improving the recovery efficiency of the applied fertilizers. Owing to the perennial nature of banana plantations, micronutrients have gained importance, and these must be applied on foliage or in soil before deficiency symptoms are seen.
9 Future research Biotic constraints are a major yield reducing factor. Research should focus on identifying and inserting genes of resistance into bananas without changing the quality and taste of the different varieties. Such genes can be identified in other plants or in wild bananas. Since bananas are also grown by resource poor farmers in areas receiving about 1000 mm of rainfall per annum, research should focus on soil moisture conservation and assess the potential for rain water harvesting and irrigation. Investments in irrigation and rain water harvesting need cash that must come from new market opportunities, improved fruit quality, and value addition. Banana production systems may be susceptible to the impacts of climate change, due to the shallow rooting depth, rainfall seasonal changes, and the high LAI. The potential impacts of elevated temperatures, increased or reduced rainfall on the banana yield, must be fully understand, and mitigation and adaptation measures put in place in the different banana regions. Soil fertility management is still a major problem in Africa. The potential for banana-livestock integration needs to be thoroughly investigated. Some key questions must be answered; how many cows can adequately supply manure for 0.5 ha, and what are the sources of feed for livestock. This may improve productivity of the smallholder plantations (through supply of nutrients and moisture conservation), especially where farmers use little or cannot afford mineral fertilizers. A lot of research information has been generated over the past decades, but the yield is still low. Our scientific understanding of banana systems has greatly improved. It is thus imperative to put together all this systems knowledge and establish some banana trials. In such trials, pests and diseases are controlled adequate water and nutrients supplied. The costs and benefits can then be assessed. This may aid adoption of technologies fronted to the farmers.
References Angeles, D.E., Sumner, M.E., Lahav, E., 1993. Preliminary DRIS norms for banana. J. Plant Nutr. 16, 1059–1070. Bagamba, F., 2007. Market Access and Agricultural Production. The Case of Banana Production in Uganda. PhD thesis, Wageningen University, The Netherlands. Baijukya, F.P., de Ridder, N., Masuki, K.F., Giller, K.E., 2005. Dynamics of banana based farming systems in Bukoba District, Tanzania: changes in land use, cropping and cattle keeping. Agric. Ecosyst. Environ. 106, 395–406. Beaufils, E.R., 1971. Physiological diagnosis—a guide for improving maize production based on principles developed for rubber trees. Fertil. Soc. S. Afr. J. 1, 1–28. Beaufils, E.R., 1973. Diagnosis and recommendation integrated system (DRIS) a general scheme for experimentation and calibration based on principle developed from research in plant nutrition. South Africa. Soil Sci. Bull. 1, 1–132. Chan, K.S., 1986. The simple open soil method of measuring urea volatilization losses. Plant Soil 92, 73–79. Delvaux, B., 1988. Constituents and Surface Properties of Soils Derived From Basalt Pyroclastic Materials in Western Cameroon-Genetic Approaches to Their Fertility. PhD thesis, University of Catholique de Louvain, Belgium.
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Delvaux, B., 1989. Role of constituents of volcanic soils and their charge properties in the functioning of the banana agrosystem in Cameroon. Fruits 44 (6), 309–319. Delvaux, B., Lassoudiere, A., Perrier, X., Marchal, J., 1987. A methodology for the study of soil-plant cultivation technique relations—results for banana-growing in Cameroon. In: Galindo, J.J. (Ed.), ACORBAT 85, pp. 351–357. Memorias VII Reunion. Delvaux, B., Dufey, J.E., Vielvoye, L., Herbillion, A.J., 1989. Potassium exchange behaviour in a weathering sequence of volcanic ash soils. Soil Sci. Soc. Am. J. 53, 1679–1684. FAO, 2017. Banana Statistical Compendium 2015–2016. Food and Agriculture organization, Rome, Italy. Godefroy, J., Dormoy, M., 1990. The dynamics of mineral fertilizers in a ferrisol in Martinique used for banana growing. Fruits 45, 93–101. Hallmark, W.B., Beverly, R.B., 1991. Review—an update in the use of the diagnosis and recommendation integrated system. J. Fertil. Issues 8, 74–88. Hallmark, W.B., Walworth, J.L., Sumner, M.E., de Mooy, C.J., Pesek, J., Shao, K.P., 1987. Separating limiting from non-limiting nutrients. J. Plant Nutr. 10, 1381–1390. Hanson, E.J., 1987. Fertilizer use efficiency: integrating soil tests and tissue analysis to manage the nutrition of highbush blueberries. J. Plant Nutr. 10, 1419–1427. Irizarry, H., Rivera, E., Rodriguez, J., 1988. Nutrient uptake and dry matter composition in the plant crop and first ratoon of the grand Naine banana grown on an Ultisol. J. Agrie. Univ. P.R. 72, 337–351. Israeli, Y., Lahav, E., Nameri, N., 1986. The effect of salinity and sodium absorption ratio in the irrigation water on growth and productivity of banana under drip irrigation conditions. Fruits 41, 297–301. Janssen, B.H., Guiking, F.C.T., Van der Eijk, D., Smaling, E.M.A., Wolf, J., Van Reuler, H., 1990. A system for quantitative evaluation of the fertility of tropical soils (QUEFTS). Geoderma 46, 299–318. Jeyabaskaran, K.J., Pandey, S.D., Laxman, R.H., 2000. Studies on reclamation of saline sodic soil for banana (cv. Nendran). In: Proceedings of the International Conference on Managing Natural Resources for Sustainable Agricultural Production in the 21st century, New Delhi, vol. 2, pp. 357–360. Jones, J.B., 1998. Plant Nutrition Manual. CRC Press, Boca Raton, FL. Kagezi, G.H., Kangire, A., Tushemereirwe, W., Bagamba, F., Kikulwe, E., Muhangi, J., Gold, C.S., Ragama, P., 2006. Banana bacterial wilt incidence in Uganda. Afr. Crop. Sci. J. 14 (2), 83–91. Karamura, D.A., 1998. Numerical Taxonomic Studies of the East African Highland Bananas Musa AAA-East Africa in Uganda. PhD thesis, University of Reading, England. Lahav, E., Turner, D.W., 1983. Fertilizing for High Yield—Banana. International Potash Institute, Berne, Switzerland, p. 62 Bulletin no. 7. Lahav, E., Turner, D.W., 1989. Banana Nutrition, Bull. 12. International Potash Institute, Worblaufen-Bern, Switzerland. Lopez, A., Espinosa, J., 2000. Manual on the Nutrition and Fertilization of Banana. National Banana Corporation and Potash and Phosphate Institute Office for Latin America, Limon, Costa Rica and Quito, Ecuador. Marschner, H., 2003. Mineral Nutrition of Higher Plants, second ed. Academic Press, London/San Diego, CA. Nyombi, K., 2010. Understanding Growth of East Africa Highland Bananas: Experiments and Simulation. PhD thesis, Wageningen University, Netherlands. Nyombi, K., 2013. Towards sustainable highland banana production in Uganda: opportunities and challenges. Afr. J. Food Agric. Nutr. Dev. 13, 7545–7561. Nyombi, K., van Asten, P.J.A., Corbeels, M., Taulya, G., Leffelaar, P.A., Giller, K.E., 2010. Mineral fertilizer response and nutrient use efficiencies of east African highland banana (Musa spp., AAA-EAHB, cv. Kisansa). Field Crop Res. 117, 38–50. Parent, L.E., Dafir, M., 1992. A theoretical concept of compositional nutrient diagnosis. J. Am. Soc. Hortic. Sci. 117, 239–242. Peet, M.M., 1992. Fruit cracking in tomato. Hortic. Technol. 2, 216–223. Prasertsak, P., Freny, J.R., Saffigna, P.G., Denmead, O.T., Prove, B.G., 2001. Fate of urea nitrogen applied to a banana crop in wet tropics of Queensland. Nutr. Cycl. Agroecosyst. 59, 65–73. Putra, E., Zakaria, W., Abdullah, N., Saleh, G., 2010. Weak neck of Musa sp. cv. Rastali: a review on it’s genetic, crop nutrition and post-harvest. J. Agrotechnol. 9 (2), 45–51. Raghupathi, H.B., Reddy, B.M.C., Srinivas, K., 2002. Multivariate diagnosis of nutrient imbalance in banana. Commun. Soil Sci. Plant Anal. 33, 2131–2143. Risede, J.M., Chabrier, C., Dorel, M., Dambas, T., Achard, R., Queneherve, P., 2010. Integrated Management of Banana Nematodes: Lessons from a Case Study in the French West Indies. CIRAD, France. Robinson, J.C., 1996. Bananas and Plantains. CAB International, England. Rukazambuga, N.D.T.M., Gold, C.S., Gowen, S.R., 2002. The influence of crop management on banana weevil, Cosmoplites sordidus (Coleoptera: Curculionidae) populations and yield of highland banana (cv. Atwalira) in Uganda. Bull. Entomol. Res. 92, 413–421. Smithson, P.C., McIntyre, B.D., Gold, C.S., Ssali, H., Kashaija, I.N., 2001. Nitrogen and potassium fertilizer vs. nematode and weevil effects on yield and foliar nutrient status of banana in Uganda. Nutr. Cycl. Agroecosyst. 59, 239–250. Sseguya, H., Semana, A.R., Bekunda, M.A., 1999. Soil fertility management in the banana-based agriculture of Central Uganda: farmer’s constraints and opinions. Afr. Crop. Sci. J. 7, 559–567. Stover, R.H., Simmonds, N.W., 1987. Bananas, third ed. Longman Scientific and Technical, Harlow Essex. Taulya, G., van Asten, P.J., Leffelaar, P.A., Giller, K.E., 2014. Phenological development of east African highland banana involves trade-offs between physiological age and chronological age. Eur. J. Agron. 60, 41–53. Turner, D.W., 1987. Nutrient supply and water use of bananas in a subtropical environment. Fruits 42, 89–93. Turner, D.W., Korawis, C., Robson, A.D., 1989. Soil analysis and its relationship with leaf analysis and banana yield with special reference to a study of Carnarvan, Western Australia. Fruits 44, 193–203. Wairegi, L.W.I., van Asten, P.J.A., 2011. Norms for multivariate diagnosis of nutrient imbalance in east African highland cooking banana (Musa spp. AAAEA). J. Plant Nutr. 34 (10), 1453–1472. Walworth, J.L., Sumner, M.E., 1987. The diagnosis and recommendations integrated system (DRIS). Adv. Soil Sci. 6, 149–188. Wortmann, C.S., Bosch, C.H., Mukandala, L., 1994. Foliar nutrient analysis in bananas grown in the highlands of East Africa. J. Agron. Crop Sci. 172, 223–226.
44 Diagnosis and management of nutrient constraints in bananas (Musa spp.) Kenneth Nyombi* Makerere University, College of Agricultural and Environmental Sciences, Kampala, Uganda *Corresponding author. E-mail: [email protected] O U T L I N E 1 Introduction
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2 Classification, geographical distribution, and major cultivars
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3 Biotic production constraints and yields
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4 Major soil types and nutrient requirements for banana production
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5 Diagnosis of banana nutrient constraints (nutrient deficiency symptoms, soil fertility norms for
different banana cultivars used globally, and leaf nutrient standards)
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6 Physiological disorders due to nutritional and environmental constraints
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7 Management of nutrient constraints
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8 Conclusions
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9 Future research
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References
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1 Introduction Bananas (Musa spp.) are major food crop globally, ranking fourth in the world after rice, wheat, and maize (FAO, 2017). They are large perennial herbs growing to a height of 2–9 m at maturity depending on variety. Native to the Indo-Malaysian, Asian, and Australian tropics, bananas are currently grown throughout the tropics and subtropics between latitudes 33°N and 33°S (Stover and Simmonds, 1987). They have developed secondary loci of genetic diversity in Africa (the great Lakes region), Latin America, and the Pacific (Papua New Guinea and the Solomon Islands). Bananas grow in a wide altitude range from 0 to 2000 m.a.s.l., but lower temperatures at high altitudes reduce the rate of leaf emergence or the growth in leaf area index (LAI), the rate of fruit growth, and length of the crop cycle duration. With increasing altitude from 1174 to 1405 m.a.s.l, Taulya et al. (2014) noted that phenological development of East Africa highland bananas (Musa AAA-EA) involved trade-offs between physiological and chronological age. Generally, bananas require a base temperature of 14°C and the temperate range for optimal growth is 25°C–30°C (Stover and Simmonds, 1987). Under good growth conditions (if soil moisture and nutrients are not limiting), the net assimilation rate (NAR) depends on the total photosynthetically active radiation (PAR), but shading up to 50% in tropical regions may not reduce yields. At higher shading such as in plantations with leaf area index (LAI) greater than 4, growth of ratoon crops is delayed by a couple of months due to the low PAR penetration. Bananas take up large amounts of water owing to the large broad leaves and high leaf area index. Water use is a function of supply, demand (potential evaporation), and soil water holding capacity (Lahav and Turner, 1989). In the tropics, bananas are produced in areas receiving about 1000 mm of rainfall per annum, with no irrigation resulting into moisture stress, reduced nutrient uptake during the dry months, and consequently low yields. In the Caribbean, rainfall may exceed
A.K. Srivastava, Chengxiao Hu (eds.) Fruit Crops: Diagnosis and Management of Nutrient Constraints https://doi.org/10.1016/B978-0-12-818732-6.00044-7
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2000 mm per annum, which coupled intensive mineral fertilizer and pesticide use results into leaching and pollution (Godefroy and Dormoy, 1990). Global banana production is estimated at 120 million tons per year (FAOSTAT). Most of the export bananas are desert bananas—Cavendish (AAA)—and export volumes are estimated at 16.741 million tons per year (FAO, 2017), generating about USD 8 billion per year. Latin America and the Caribbean export 84%, Asia 12%, and Africa 4%. The main banana exporters are Ecuador (33%), the Philippines (14%), Costa Rica (12%), Guatemala (11%), and Colombia (11%), with organic bananas mainly exported by Colombia, Peru, and the Dominican Republic. Export destinations are the North American markets, Western Europe, Japan, Russia, and the Asian market, which mainly takes exports from the Philippines. The rest (about 85% of total production) is consumed locally, most especially in large producing countries such as India, China, Brazil, the Philippines, and in some African countries such as Uganda and Rwanda, where per capita consumption exceeds 200 kg of banana. Bananas provide potassium (358 mg/100 g), vitamin B6 (20%), and vitamin C. Potassium reduces the risk of heart disease and lowers blood pressure. Ripe bananas provide up to 90 cal, 12 g of sugars (mainly sucrose, fructose, and glucose), 0.3 g of fat, and 2.7 g of fiber per 100 g. Its nutritional content, health benefits coupled with increasing global population, have kept the banana demand strong.
2 Classification, geographical distribution, and major cultivars There are over 1000 varieties of bananas produced globally, which are grouped according to the ploidy levels and the uses (cooking and desert). Ploidy level refers to the number of chromosome sets and the relative proportion of Musa acuminata (A) and M. balbisiana (B) in their genome (Karamura, 1998). The common cultivated cultivars globally are triploid hybrids: AAA (Cavendish, East Africa highland banana), AAB (Silk, Mysore), ABB (Saba, Bluggoe, Monthan, Simoi), and BBB (Saba). Diploids AA, AB (beer bananas), and BB, which are starchier, are also grown. Tetraploids AAAA (FHIAs), AAAB (PA12.03 and SH-3640), AABB (FHIA03), and ABBB are grown but are not so common. In Southeast Asia, cooking bananas (ABB) and dessert bananas (AAB) are common. In central and South America and China, Cavendish banana (AAA) are grown in commercial plantations and account for about 47% of global production (FAO, 2017). This is attributed to their dwarf stems, implying reduced damage to storms and the ability to recover quickly from natural disasters. In Africa, there are over 200 cultivars of East African highland cooking bananas (AAA-EA) grown in the great Lakes region for home consumption with surplus sold to urban centers. In this region, a number of beer cultivars (AB, ABB, and AAA) and desert types (AAA and AB) are grown. Plantains (AAB) are starchier and are common in West and Central Africa and Central and South America (Stover and Simmonds, 1987).
3 Biotic production constraints and yields The major biotic constraints to banana production, which differ from one region to another (given the soils, temperature, altitude, management, and production orientation), are pests: weevil (Cosmopolites sordidus), nematodes (burrowing nematode, Radopholus similis; root lesion nematode, Pratylenchus goodeyi; spiral nematode, Helicotylenchus multicinctus; reniform nematode, Rotylenchulus reniformis; stunt nematode, Tylenchorhynchus spp.; and ring nematode, Criconemoides sphaerocephalum), moths (scab moth, Nacoleia octasema), and diseases (black Sigatoka, Mycosphaerella fijiensis; bunchy top, banana bunchy top virus (BBTV); Panama disease or Fusarium wilt, Fusarium oxysporum; anthracnose, Colletotrichum musae; and banana bacterial wilt, BBW). The banana weevil is the best known banana insect pest in the great Lakes region. In Uganda, it was first reported in 1908 and mainly affects bananas at altitudes below 1600 m.a.s.l. (Sseguya et al., 1999). The feeding larva eats through the rhizome reducing water and nutrient uptake. Commonly reported yield losses due range between 14% and 20% (Rukazambuga et al., 2002), but heavy attack can lead to 100% yield loss. It is controlled through field sanitation, better agronomic practices, and the use of chemicals (organophosphates and carbamates). Nematodes are a major yield reducing factor in all banana-producing regions, and their populations increase with age of the plantation, if not controlled. They attack roots and rhizomes causing necrosis of root tissues and corm, thus impeding water and nutrient uptake. R. similis is common at altitudes below 1500 m.a.s.l, while the root lesion nematodes are common at altitudes higher than 1500 m.a.s.l. Nematodes are controlled through cultural practices, using nematode-free planting materials, soil treatment before planting or fumigation, crop rotation, fallowing, varietal resistance, and nematicides (Risede et al., 2010). The scab moth larvae enter the banana flower and destroy the growing fruits, causing scars and deformed fingers. It is common in the Southwest Pacific and is controlled by injecting the banana flower after it emerges with an insecticide.
4 Major soil types and nutrient requirements for banana production
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Globally, black sigatoka is the most important fungal banana disease. An attack leads to the development of lesions on leaves significantly reducing the number of green leaves, leaf area to intercept radiation, and the bunch yield (Stover and Simmonds, 1987). Usually, a combination of cultural practices (field sanitation, canopy aeration, pruning, cutting off affected leaves, and resistant varieties) and chemicals (fungicides) are important for controlling this disease. The bunchy top disease is a major problem for banana plantations in Hawaii and the Pacific. It is controlled by using clean planting materials and disinfecting tools used on plantations. The panama disease caused by a soil borne fungus is a major banana disease worldwide. Fungal attack results into stem, root, and rhizome necrosis. Plant death mainly occurs at or during flowering and periods of soil moisture stress. Since the fungus lasts long in soil, control is largely preventive, through planting resistant varieties or clean materials in clean soil. Banana anthracnose disease mainly damages fruits and is controlled by removing affected leaves that are close to the bunches. Banana bacterial wilt (BBW) devastated banana plantations in the great Lakes region, with yield losses up to 100% (Kagezi et al., 2006). Affected plants wilt when the leaves are green and die off. It is controlled by sanitation (planting disease free materials, disinfecting farm tools, and removing male buds). Yields on banana farms are a complex interaction of both the biotic and abiotic (soil moisture stress and soil fertility) constraints. The biotic constraints and moisture stress reduce the recovery efficiency of applied fertilizer and the fertilizer-use efficiencies for farmers who use fertilizers. In Africa, banana production is mainly by smallholder farmers on fields <0.5 ha, with medium size commercial farms (>3 ha) gaining prominence due to increasing demand. In the great Lakes region, actual banana yields on smallholder farms are low (5–20 Mg/ha/yr FW) due the constraints mentioned earlier, far below the estimated potential yield (100 Mg/ha/yr FW) (Nyombi, 2010). Under average farmer management, Smithson et al. (2001) reported yields of 67 Mg/ha FW from Southwestern Uganda. This shows that the yield gap can actually be reduced with proper management. For example, Costa Rica, a leading banana producer and exporter have been able to increase yields from 10 to 20 Mg/ha/yr FW before 1960 to 50–80 Mg/ha/yr FW today for Cavendish (AAA) through better agronomic management and cultivar choice (Stover and Simmonds, 1987). In general, commercial production of the Cavendish variety gives yields ranging 40–60 Mg/ha FW in other regions (India and China), while small producers report yields of about 30 Mg/ha FW. In the Philippines, actual yields are low, with varieties such as Saba (cooking—ABB) and Lakatan (dessert—AAA), yielding 11–20 Mg/ha FW. It is important to note that yields are generally low for locally consumed bananas. Population growth coupled with increasing demand, improved infrastructure, market access, and value addition are likely to increase prices, and compel farmers invest more into management thus raising yields (Bagamba, 2007).
4 Major soil types and nutrient requirements for banana production Globally, bananas are grown on a wide range of soils from the fertile and young Inceptisols (with a large capacity for stocking potassium) and Andisols, moderate K releasing capacity (Delvaux et al., 1987, 1989; Delvaux, 1989) to the old and low fertility Ferralsols and Acrisols (Fig. 44.1). In many areas especially in Africa, banana production systems are built on old soils with soil pH, extractable phosphorus (P), calcium (Ca), and potassium (K) below critical levels and nutrient availability largely depends on mineralization of soil organic matter. Generally, soils must be deep, free draining loams, or light clays, because bananas can’t tolerate extreme water logging especially for clay soils (>60% clay). Rooting depth of bananas determines the ease of root movement through the soil; however, maximum rooting depth of 1.5 m has been reported (Lahav and Turner, 1989). A higher clay content >50% depresses yields due to compaction, poor root movement, and reduced available water (Robinson, 1996) resulting poor emergence of fruit (Fig. 44.2). The best pH range for good banana growth is 5.5–8.0. Low pH (4.5) reduces yield by 50% as compared with the optimal range due to low availability of important nutrients such as phosphorus especially in P-fixing old tropical soils. For acid soils, 600–750 kg of lime per hectare can be plowed into soil at land preparation to raise the pH. Bananas are heavy feeders ( Jones, 1998). Nutrient requirements are in order as follows: potassium > nitrogen > phosphorus (Nyombi et al., 2010). In addition, bananas take up significant quantities of other nutrients such as calcium and magnesium. Typical N, P, and K uptake levels amount to 388, 52, and 1438 kg/ha in a crop cycle for AAA Cavendish dessert banana plants yielding 50 Mg/ha FW at a density of 2400 plants/ha (Lahav and Turner, 1983). Due to the large quantities of potassium taken up by bananas, apparent K recovery fractions are high (75%) as reported by Lopez and Espinosa (2000), if soil moisture is not limiting. Potassium plays a crucial role in regulating the transfer of nutrients to the xylem, regulating water in the plant and the functioning of the stomata. When potassium supply is low, the transfer of nitrogen, phosphorus, calcium, magnesium, and other nutrients across the xylem is restricted
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44. Diagnosis and management of nutrient constraints in bananas (Musa spp.)
FIG. 44.2 Moisture stress from the floral initiation stage to flowering often results into choked bunches and flower abortions in East Africa highland bananas (Musa AAA-EA).
FIG. 44.1
A soil profile pit dug on a haplic ferralsol in central Uganda showing the shallow A horizon, the iron and aluminum oxide-rich B horizon and the stone layer.
(Turner, 1987). Low potassium supply reduces total dry matter production and its allocation within the plant, most especially the bunch. This attributed to the reduced photosynthesis, respiration, and total green leaf area of the plant (Fig. 44.3). Potassium deficiency also impairs protein synthesis, sugar transportation, and N utilization leading to N accumulation in plants (Nyombi et al., 2010). Potassium deficiency also leads into shortening of internodes, delayed flower initiation, choking of bunches, and stunted growth. Nitrogen is component of enzymes and chlorophyll and give leaves a green color. It is very important in green leaf area formation, photosynthetically active radiation interception, and determining its use efficiency (Marschner, 2003). Low nitrogen supply results into pale green leaves, with midribs, leaf sheaths, and petioles turning pink. Phosphorus is crucial for root growth, energy transfer, and fruit formation. Good root growth is important due to the large fresh mass (stem and leaves) and to support the bunch after flowering. Low P supply leads to curling of leaves, and a bluish green color on young leaves. Magnesium uptakes in banana plants can be as high as 55 kg/ha/yr for Grand Naine on an Ultisol (Irizarry et al., 1988). Low magnesium supply results into yellow discoloration of midblade and midrib portion and purple mottling of the petioles and marginal necrosis. Calcium is important in cell wall structure and ensuring the integrity of the banana peel during ripening. Calcium deficiency results into the thickening of veins and the deformation of the leaf lamina. Sulfur is a component of chlorophyll molecule and is crucial for protein synthesis. Sulfur deficiency results into white or yellow patches on young leaves and on leaf margins, thickening of veins, and reduced bunch size. Copper deficiency results into chlorosis of leaves. Zinc deficiencies mostly occur in limed or alkaline soils. FIG. 44.3
Potassium deficiency in a newly established banana plantation on a Lixic Ferralsol at Ntungamo, Southwestern Uganda. Potassium-deficient old leaves turn orange-yellow in color due to K relocation to the young leaves; show scorching along the margins, later curl inward; and die resulting into a reduction in total leaf area.
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5 Diagnosis of banana nutrient constraints
Leaves show a high amount of anthocyanin on the underside, with fruits small and twisted. Manganese deficiency results into light greening of leaf margins of younger leaves. Deficiency of boron results into thickening of secondary veins, delayed flowering, curling of leaves, and lamina deformation. Potassium is sensitive to cation balance, and the assessment of soil K critical levels is dependent on the K/Ca/Mg balance. Therefore, soil analysis is important for monitoring K fertilization to determine the relationship between crop response to the added K, K concentration in soil, and the K/Ca/Mg balance. Soil critical K content was reported at 1.4 meq/100 g of soil, with a K/Mg ratio of 0.28 (Lahav and Turner, 1989). Optimal calcium absorption would require a soil balance K:Mg:Ca of 1:3.5:10.7 (Turner et al., 1989).
5 Diagnosis of banana nutrient constraints (nutrient deficiency symptoms, soil fertility norms for different Banana cultivars used globally, and leaf nutrient standards) Plant nutrient deficiencies are diagnosed using foliar analysis (Hallmark and Beverly, 1991), which helps to accurately assess the need for fertilization. Foliar analysis is based on the assumption that there is always a positive relationship between the quantities of nutrient applied, leaf nutrient status, and consequently the yield. This assumption however may not hold if pests and moisture supply limit uptake of the applied fertilizers. Timely leaf analysis helps to prevent deficiencies rather than correcting them. In most banana-producing countries, not only laminar structure of third leaf is sampled, but also samples of the central vein of third leaf and the petiole of seventh leaf can also be used. Usually, a strip of tissue 10-cm wide, on both sides of the central vein, is taken (Lopez and Espinosa, 2000) and analyzed using standard laboratory methods for assessing leaf nutrient contents. The critical levels of foliar nutrients of Dwarf Cavendish (AAA) dessert banana are presented in Table 44.1. However, as already discussed, nutrient uptake and distribution are affected by interactions within the plant; therefore, multinutrient approaches have been derived. There are two common methods used to diagnose nutritional imbalances: diagnosis and recommendation integrated system, DRIS (Walworth and Sumner, 1987) and compositional nutrient diagnosis, CND (Parent and Dafir, 1992). DRIS norms are considered as best and are commonly used. They envisage that the ratios N:P, N:K, P:K, Ca:Mg, and their reciprocals remain constant in the leaf irrespective age. Therefore, nutrient concentration ratios rather than concentrations of single nutrients themselves are used (Beaufils, 1971, 1973) to identify the imbalances. These norms are usually developed for specific locations (climate and soils), cultivar, and under a given crop and soil management regime. For example, Wortmann et al. (1994) developed DRIS norms for AAA-EA cooking banana cultivars in the Kagera region of Northwest Tanzania as N (3.15), P (0.25), K (3.04), and Ca (1.13). Wairegi and van Asten (2011) using foliar analysis data from different banana growing zones in Uganda for similar cooking bananas reported that foliar N, P, K, Ca, and Mg ranged between 1.35%–3.89%, 0.10%–0.38%, 1.54%–5.83%, 0.23%–1.74%, and 0.25%–0.85%. This shows that on average, Wortmann et al. (1994) had higher N (3.15% vs 2.79%), P (0.25% vs 0.21%), Ca (1.13% vs 0.91%), and lower K (3.04% vs 3.84%) as compared with the findings of Wairegi and van Asten (2011). Smithson et al. (2001) in a study at Rubale, Southwest Uganda, suggested that the norm for K in AAA-EA cooking banana was lower than the 4.49 suggested by Angeles et al. (1993) but higher than 3.04 obtained by Wortmann et al. (1994). This emphasizes the TABLE 44.1 Critical levels of foliar nutrients of Dwarf Cavendish (AAA) dessert banana.
Nutrient
Leaf 3 Lamina %
Leaf 3 Central vein %
Leaf 7 Petiole %
Nitrogen
2.6
0.65
0.4
Phosphorus
0.2
0.08
0.07
Potassium
3.0
3.0
2.1
Calcium
0.5
0.5
0.5
Magnesium
0.3
0.3
0.3
Sodium
0.005
0.005
0.005
Sulfur
0.23
–
0.35
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44. Diagnosis and management of nutrient constraints in bananas (Musa spp.)
TABLE 44.2 Diagnosis and recommendation integrated system (DRIS) and critical nutrient levels in the 3rd leaf lamina. Nutrient (%)
DRIS
Critical value range
Average of published values
Nitrogen
3.04
1.81–4.00
3.03
Phosphorus
0.23
0.12–0.41
0.22
Potassium
4.49
1.66–5.40
3.40
Critical levels of micronutrients: boron (10 mg/kg), iron (100 mg/kg), manganese (160 mg/kg), zinc (20 mg/kg), and copper (9 mg/kg). Based on Angeles, D.E., Sumner, M.E., Lahav, E., 1993, Preliminary DRIS norms for banana. J. Plant Nutr. 16, 1059–1070.
location and management specificity of DRIS norms even for the same cultivar. Angeles et al. (1993) reported higher K (4.49%), N (3.04%), and P (0.23%) in a high yielding banana plantation—70 Mg/ha (Table 44.2).
6 Physiological disorders due to nutritional and environmental constraints In most fruit crops, physiological disorders associated with micronutrients as compared with macronutrients are more common given their perennial nature and the focus mainly on macronutrients (N, P, and K) during fertilizer applications (Hanson, 1987). In bananas, high K:Mg ratios above 0.6–0.7 induce typical mottling of the petiole (blue), which reduces crop yields. For example, Delvaux (1988) working on an old and highly leached acid Ultisols in Cameroon reported that a K:Mg ratio of over 0.7 induces blue, only when root depth is shallow (<20 cm) and when both exchangeable Mg concentration and total Mg soil reserve are below 1.3 and 45 meq/100 g of soil, respectively. However, blue can also be associated with a low K:Mg ratio in the field caused by potassium deficiency and was not related to high magnesium supply. Micronutrient deficiencies (Zn, Mn, and B) are more common in banana (Robinson, 1996), and these must be detected before the visual symptoms and addressed to reduce their effect on yields and fruit quality. These are also attributed to expansion of banana production to poor soils, limited use of organic manures, imbalanced NPK fertilizers, and high intensity crop production (>2500 plants/ha). To correct the micronutrient deficiencies, appropriate foliar, and soil nutrient applications are necessary. Disorders caused by micronutrient deficiencies include the following: bronzing (the development of bronze or copper color on leaves), chlorosis (the loss of green color resulting into pale yellow tissues), tip dieback (collapse and death of the growing tip or the younger leaves), lesions (small wounds on the leaf or stem tissue followed by discoloration), and necrosis or death of plant tissues. Under field conditions, disturbances in the plant metabolic and physiological activities can occur resulting from an excess or deficit of environmental variables like temperature, light, and aeration, coupled with micronutrient deficiencies. Banana choke throat is due to low temperature, which turns the leaves yellow and in severe cases, lead to tissue necrosis. At flowering, the bunch is unable to emerge from the pseudostem properly and is deformed, and bunch maturity is delayed by 1–2 months. Tree shelter belts can be planted in the wind direction, or low-temperature tolerant cultivars can be planted at that location. Another common disorder is chilling injury. This occurs when preharvest or postharvest temperatures fall below 14°C for various time periods. Banana peels become dark, and the fruits do exhibit uneven ripening. In the commercial Cavendish and Gros Michel banana, chilling injury manifests its self at temperatures below 12.5°C. To avoid this problem, the major banana exporting companies ship bananas at a controlled temperature of 13–14°C. Other physiological disorders happen during ripening, thus reducing postharvest fruit quality, quantity, and marketability. Peel cracking is common disorder, but it largely depends on genetic, environmental, and physiological factors before harvest and environmental conditions of storage after harvest. This exposes the banana pulp to pathogen infections. Peel cracking can be controlled by managing the humidity levels in the ripening, storage, and transportation chambers. Peet (1992) argued that splitting may also be attributed to preharvest conditions, as calcium and potassium deficiency. Most of the export bananas are sold as clusters of fingers in supermarkets. Finger drop usually occurs during ripening, with individual fingers dropping off from the cluster, reducing market value, and increasing susceptibility to pathogens. A weak finger neck may have three possible causes: genetics, nutrition, and postharvest conditions. Balanced banana nutrition is very important to deter neck breakage. Usually, the application of boron, calcium, magnesium, or silicon enforces cell structure and deters this disorder (Putra et al., 2010). It is important to ensure balance nutrition to have good quality banana fruits (Raghupathi et al., 2002).
7 Management of nutrient constraints
657
7 Management of nutrient constraints In Africa, few banana farmers use fertilizers; therefore, nutrient supply largely depends on the mineralization of soil organic matter, but the size the active pool is always small. Organic fertilizers (grasses, composts, crop residues, and animal manures) were proposed as the first line remedy to soil fertility decline from the 1930s in Africa. In the great Lakes region, research done in the 1940s and 1950s focused on the quantification of organic fertilizers applied and yield data collection on farms. But the yield increases above the control reported were low—<10 Mg/ha/yr (Nyombi, 2013). In the Americas and the Caribbean, from the 1960s, the focus was on integrated pest management and the use of mineral fertilizers to increase banana yield to meet the growing demand for the fruits. These efforts have largely paid off with yields of more than 70 Mg/ha FW in high yielding banana plantations today. In Africa, from the 1980s, studies focused principally on diagnosing plant nutrition status, the use of mineral fertilizers, and the combined application of organic and mineral fertilizers. The integrated plant nutrition approach was advocated for giving the range of nutrients from organic materials and other benefits such as soil structure improvement and soil water retention. But increasing land pressure and shrinking farm sizes have reduced farmers capacity to obtain off-farm organic resources from communal areas (Baijukya et al., 2005), with additional supply of N, P, and K expected to come from mineral sources (Hallmark et al., 1987). Increasing commercialization of banana trade from the Americas from the 1960s led to increases in mineral fertilizer use and efforts to make production more efficient and profitable to maintain and attract new markets. Today, these efforts have led to a number of companies that are famous for trade in banana such as Chiquita, Del Monte, Dole Foods, and Fyffes, with a net worth valued at billions of dollars. Science has played a crucial role to determine the optimal amount of fertilizer or fertilizer amounts to apply for a target yield. Janssen et al. (1990) developed the quantitative evaluation of the fertility of tropical soil (QUEFTS) model originally to calculate maize yield as a function of N, P, and K supply from soil and fertilizer while accounting for interactions among the nutrients (N, P, and K). Using experimental data from Uganda, this static model was applied to East Africa highland bananas (AAA) with interesting results (Nyombi et al., 2010). With the developed model parameters, it is relatively easy to calculate the amount of fertilizer required for a target yield, provided moisture supply is not limiting. In South and Central America (Costa Rica and Honduras), N, P, and K apparent recovery fraction are estimated at 50%, 30%, and 75% (Lopez and Espinosa, 2000). Using these and other derived banana parameters, the QUEFTS model predicts that for a fresh banana yield of 70 Mg/ha, 426 kg N/ha + 55 kg P/ha + 1576 kg K/ha. These values are not so different from fertilizer application rates in high yielding plantations in the banana growing regions (Robinson, 1996). With the fertilizer amount determined, it is important to identify the sources of nutrients, methods of application, and when to apply. The types of fertilizers to use as sources of nutrients depend on availability, the soil pH, and the texture (sandy or clayey). However, to achieve the above yields, special attention must be taken for potassium, which is the most important nutrient for banana growth. The common sources of potassium are potassium chloride (KCl) (60% K2O and 45% Cl), potassium sulfate (50% K2O and 17%–18% S), and potassium magnesium sulfate (21%–22% K2O, 10%–11% Mg, and 21%–22% S). Potassium is susceptible to leaching losses in light textured (sandy) soils and fixation in clay soils; it is thus better to apply the granular form or to split applications. In most banana-producing regions, usually three six (six splits) per year are used for experimentation and are recommended to farmers. This improves the recovery efficiency of the applied fertilizer. Bananas are also produced on saline soils in drier environments (with irrigation) resulting into an increase in Na content in roots reducing K uptake and banana yield (Israeli et al., 1986). In the Canary Islands, the optimal value for the soil K:Na ratio is considered to be 2.5. For soils with high Na content, the combined application of gypsum, manure, and potassium ( Jeyabaskaran et al., 2000). Nitrogen sources include the following: calcium ammonium nitrate (CAN) (26% N, 3.5% CaO, and 4% MgO), urea (46% N), and ammonium sulfate (21% N and 24% S). Urea should be covered or applied in solution to minimize volatilization losses (Chan, 1986). Prasertsak et al. (2001) reported that 25% of applied N was lost from the system by runoff, leaching, ammonia volatilization, or denitrification in the wet tropics of Queensland, Australia (annual rainfall 1800–4000 mm and plant density 1300 mats/ha). Godefroy and Dormoy (1990) reported leaching losses from soils with a low cation exchange capacity in Martinique to be 165 kg N/ha/yr. Nitrogen must be applied in splits. CAN is preferred on acid soils to raise the pH. Urea and ammonium fertilizers are preferably used on soils with a high pH. Monoammonium phosphate (10%–12% N and 48%–61% P2O5) and diammonium phosphate (18% N and 46% P2O5) are also used. Other sources of phosphorus include the following: triple super phosphate (20% P) and single super phosphate (12%–18% P2O5, 18%–21% Ca, and 11%–12% S). Usually two applications per year are adequate. The other source of magnesium is magnesium sulfate (13%–16% Mg and 13% S). Micronutrient deficiencies are more common now (especially Zn and B). Zinc is supplied by application of zinc sulfate (22% Zn and 11% S) and boron through application of borax (11% B). Fertigation is more efficient with less losses, but it is only possible for large-scale farmers. For small scale farmers, fertilizers are applied per plant by hand.
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44. Diagnosis and management of nutrient constraints in bananas (Musa spp.)
8 Conclusions Bananas are and will remain an important source of income and nutrition to current and future generations. However, to increase the current yields and ensure future fruit supplies, the causes of low yields especially in Africa and Asia, where population increase is fast, must be addressed. Low yields are attributed to biotic (pests and diseases) and abiotic constraints (moisture stress and nutrients). Biotic constraints reduce the uptake and utilization efficiency of water and nutrients and should be controlled using the different methods as discussed in this chapter. Bananas take up large amounts of K, N, P, Mg, and Ca, if soil moisture is not limiting. Where the indigenous nutrient supply is low, these must be supplied from both organic manures and mineral fertilizers. Given the fact that nutrient deficiencies show a strong spatial and temporal variability in different banana systems due to soils, soil and foliar analysis are important if static models such as QUEFTS are to be successful applied to calculate fertilizer requirements for target yield levels. Balanced nutrition is important to minimize growth and postharvest physiological disorders. Variation in soils (cation exchange capacity), rainfall received, and the need to synchronize nutrient demand by the plant and supply dictate that fertilizers supplying the macronutrients are applied in splits. This reduces losses due to runoff, leaching, and volatilization, hence improving the recovery efficiency of the applied fertilizers. Owing to the perennial nature of banana plantations, micronutrients have gained importance, and these must be applied on foliage or in soil before deficiency symptoms are seen.
9 Future research Biotic constraints are a major yield reducing factor. Research should focus on identifying and inserting genes of resistance into bananas without changing the quality and taste of the different varieties. Such genes can be identified in other plants or in wild bananas. Since bananas are also grown by resource poor farmers in areas receiving about 1000 mm of rainfall per annum, research should focus on soil moisture conservation and assess the potential for rain water harvesting and irrigation. Investments in irrigation and rain water harvesting need cash that must come from new market opportunities, improved fruit quality, and value addition. Banana production systems may be susceptible to the impacts of climate change, due to the shallow rooting depth, rainfall seasonal changes, and the high LAI. The potential impacts of elevated temperatures, increased or reduced rainfall on the banana yield, must be fully understand, and mitigation and adaptation measures put in place in the different banana regions. Soil fertility management is still a major problem in Africa. The potential for banana-livestock integration needs to be thoroughly investigated. Some key questions must be answered; how many cows can adequately supply manure for 0.5 ha, and what are the sources of feed for livestock. This may improve productivity of the smallholder plantations (through supply of nutrients and moisture conservation), especially where farmers use little or cannot afford mineral fertilizers. A lot of research information has been generated over the past decades, but the yield is still low. Our scientific understanding of banana systems has greatly improved. It is thus imperative to put together all this systems knowledge and establish some banana trials. In such trials, pests and diseases are controlled adequate water and nutrients supplied. The costs and benefits can then be assessed. This may aid adoption of technologies fronted to the farmers.
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