Diagnosis and management of nutrient constraints in guava

C H A P T E R

48 Diagnosis and management of nutrient constraints in guava William Natalea,*, Danilo Eduardo Rozaneb, Ma´rcio Cleber de Medeiros Corr^eaa, Leon Etienne Parentc, Jose Aridiano Lima de Deusd a

Federal University of Ceara´, Fortaleza, Brazil Sa˜o Paulo State University, UNESP, Registro, Brazil c Department of Soil and Agri-Food Engineering, Universite Laval, Quebec, QC, Canada d Institute of Technical Assistance and Rural Extension of Parana´ (EMATER-PR), Curitiba, Brazil *Corresponding author. E-mail: [email protected] b

O U T L I N E 1 Introduction

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2 Guava production 2.1 Economic importance

712 712

3 Soils as growing media for guava production 3.1 Soil analysis 3.2 Leaf diagnosis

712 713 714

4 Lime requirement, liming, and liming materials 4.1 Liming before planting 4.2 Liming established orchards

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5 Fertilization 5.1 Fertilization at planting 5.2 Fertilization of young, nonbearing plants 5.3 Fertilization of established orchards 5.4 Alternative fertilizer sources: By-products of the guava processing agroindustry

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6 Evolution of guava nutrient diagnostic methods

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References

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Further reading

722

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1 Introduction Yield and quality of fruit crops are determined by several growth factors. Where growers maximize those factors, the plant can express its genetic potential, reaching economic profitability and environmental protection, avoiding problems associated with factor excess or misbalance. In tropical regions, infertile acid soils prevail due to advanced weathering. Soil capacity to meet plant nutrient demand is supported by liming and fertilization. According to Roberts (2009), up to 60% of the global food production results from the use of fertilizers. Fertilization, irrigation, and labor costs represent a large proportion of production costs in guava orchards. However, determining the nutritional requirements of a crop like guava remains a challenge. The right dosage of essential elements depends on cultivar, soil and climatic conditions, irrigation, production capacity, crop cycle, etc. With genetic improvement resulting in highly productive guava cultivars, it was necessary to improve management practices, adopting drastic pruning and irrigation and optimizing fertilization to achieve three harvests every 2 years. This chapter presents lime and fertilizer management from planting to orchard maturity for guava production at high-yield level.

A.K. Srivastava, Chengxiao Hu (eds.) Fruit Crops: Diagnosis and Management of Nutrient Constraints https://doi.org/10.1016/B978-0-12-818732-6.00048-4

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© 2020 Elsevier Inc. All rights reserved.

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48. Diagnosis and management of nutrient constraints in guava

2 Guava production 2.1 Economic importance Guava crop is one of the major fruit crops from tropical regions of the terrestrial globe, being known by many as the apple of tropics (Maity et al., 2006; Small, 2012) although its cultivation extends to subtropical regions. Besides, it is one of the cheapest, popular, and good source of ascorbic acid (Osman and Abd El-Rahman, 2009) and other important phytochemicals for human health (Rojas-Garbanzo, 2018) in countries with expressive cultivated area. According to data from the Food and Agriculture Organization of the United Nations (FAO, 2018) in 2016, the main guava producers in the world were India, China, Thailand, Mexico, and Indonesia. However, it is important to highlight that these data consider the group (mangoes, mangosteens, and guavas), because guava is considered as a minor tropical fruits. In particular, it is reported that India, Pakistan, China, Brazil, and Indonesia were the main producing countries between the years 2015 and 2017. India is ranked as the major guava producing country, accounting for an estimated 56% of total global output in 2017 (Altendorf, 2018). Fruticulture differs from other agribusiness activities in the country in three aspects. The first is social: fruit cultivation requires an enormous amount of labor from orchard planting to harvest. The second is economic: there is a strong demand for high-quality fruits, but the production must be viable to maintain fruit producers in rural areas. The third is environmental: cultivation of fruit plants allows managing soils once considered inadequate for conventional agriculture, thus contributing to improve soil quality from its initial infertile state. Although there is no consensus on its origin in tropical America, its center of origin covers Mexico and Central and South America (possibly from Mexico to Peru) where it is found cultivated and growing wild (Menzel, 1985; Small, 2012). It has high nutritive value and is consumed fresh or processed as candies, juices, jellies, etc. The literature provides extensive information about nutritional facts and qualitative properties such as taste, color, aroma, form, size, appearance, resistance to pests and diseases, and postharvest storage (Amorim et al., 2015a,b; Brunini et al., 2003; Quintal et al., 2017).

3 Soils as growing media for guava production Fruticulture is an important activity on ferralsols (oxisols) and acrisols (ultisols) (IUSS Working Group WRB, 2015; Soil Survey Staff, 2010) that are deep and permeable, an ideal soil condition for the deep rooting system of perennial plants. However, ferralsols have a strong acid reaction and are infertile, requiring both liming and fertilization to sustain fruit production. However, perennial crops respond to liming and fertilization differently from annual crops. The reasons are many and varied, as follows (adapted from Gros, 1974): (a) Roots of perennial plants such as guava explore a large volume of soil that increases with plant age, but little is known about reserves of plant-available nutrients in deeper soil layers. (b) The perennial plant is a substantial reservoir of nutrients. Hence, the tree does not immediately suffer from nutrient deficiencies detected by soil analysis and responds slowly to correcting measures. (c) Regular pruning makes it difficult to set apart the effects of liming and fertilization from that of pruning that restricts vegetative growth. Pruning is essential because “hunger for light” is as harmful as “hunger for nutrients.” (d) Liming and fertilization are important not only for vegetative development and fruiting but also to sustain future harvest by forming new fruit branches for future harvesting and building reserves of nutrients in belowground and aboveground organs for the next fruiting stages. Some fruit crops, especially those native to tropical regions such as guava, were considered as rustic plants, as is still the case in some countries, like Pakistan, which are observed: limited of superior varieties, low implementation of good cultivation practices, less developed technology, and resistance to follow recommendations made by technics (Khushk et al., 2009; Hassan et al., 2012). For this reason, they were grown regardless of soil and climate conditions. However, it is not possible to imagine that a soil can be mined indefinitely by a crop without replacing exported nutrients. Due to the specific growth patterns of perennial fruit plants, it remains difficult to implement long-term experimentation. In the short run, soil and plant tissue analyses

3 Soils as growing media for guava production

713

allow detecting growth-limiting nutrients. Rational liming and fertilization programs can then be elaborated to optimize the efficient use of nutrients, increase fruit yield and quality, and minimize economic costs and environmental risks.

3.1 Soil analysis There is large variation in soil capacity to supply nutrients. Soils are highly complex and interactive systems. Most soils, especially those located in tropical regions, cannot supply adequate amounts of nutrients to meet the demand of fruit crops. Soil chemical analysis can assess soil fertility status to assist quantifying fertilizer and lime requirements by cropping systems. Soil analyses are easy to perform, standardized, rapid and inexpensive, executable at any moment, and reproducible. Although there is a consensus that soil chemical analysis is the most practical way to evaluate soil fertility, its value as decision tool depends on representative sampling. In perennial crops, such as fruit crops, there is little consensus on soil sampling procedures. While some bulletins recommend sampling the whole area, research revealed closer relationship between soil nutrients in the inter row and leaf and fruit nutrient contents (Natale et al., 2007; Prado and Natale, 2008). This is due to the large and efficient root system of fruit crops. If soil samples are collected either in the fertilized area within canopy projection or in inter rows, then sample from which location should lead to recommendations? Another very controversial issue is sampling depth, considering the large soil volume explored by the root system. Finally, should the soil be sampled the same way before planting and in established orchards? Before planting guava orchards, soil sampling should be performed randomly by collecting 15–20 subsamples in representative areas that are uniform in terms of color, slope, topographic position, soil type and management, etc. Because the deep and extensive root system of guava explores the same volume of soil for many years, soils are sampled separately in the top (0–20 cm) and subsurface (20–40 cm) layers to identify growth factor limitations. After compositing and mixing soil subsamples, an approximate amount of 300 g is sent to a registered laboratory well before planting for in-time interpretation of the results, lime and fertilizer recommendation, and input purchase, application, and incorporation into soil before planting. In established guava orchards, soil samples are collected in strips within fertilized areas that are uniform in plant age, cultivar, yield potential, soil type, fertilization regime, crop management, etc. (Fig. 48.1). The most adequate period for soil sampling is close to the end of the harvest season, allowing enough time between the last and the next fertilization operation and allowing liming as required. Soil in inter rows should be analyzed every 2–3 years in the 0–20-cm and 20–40-cm layers. Based on a wide database, the interpretation of soil chemical analyses against expected yield has been facilitated by the development of a software to establish liming and fertilization programs, for example, the Fert-Goiaba software (Silva et al., 2009) developed by Brazilian researchers that can be accessed for free at http://www.registro.unesp. br/#!/sites/cnd/. Row

Row

Inter row

Row

Inter row

FIG. 48.1 Examples of collection points for soil sampling in strips within fertilized areas (rows) and inter row.

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48. Diagnosis and management of nutrient constraints in guava

3.2 Leaf diagnosis Because soil chemical (acidity) or physical (compaction) impediments may limit rooting volume of perennial crops beyond soil sampling depth, the only practical way to assess the overall benefits of liming and fertilization is to “ask the plant” through leaf analysis. Nutritional status monitoring of fruit crops using foliar analysis allows fine adjustment of the mineral nutrition across several nutrients to reach high fruit yield with fertilizers and liming materials (Anjaneyulu et al., 2008). In this matter, soil and plant diagnoses are complementary. The cost of soil and plant analyses is low compared with expected yield increase after rebalancing fertilization. Saving of 30 kg/ha/yr of fertilizer (from over 1400 kg applied) or yield increase of about 100 kg/ha/yr of guava (from over 60,000 kg produced) is sufficient (e.g., in Brazil) to cover the cost of leaf analysis. The choice of the diagnostic tissue is based on the assumption, confirmed by research, that a key tissue is a representative of carbon assimilation. Because leaves can elaborate substances for growth and fruiting, their nutrient content must reflect the general nutritional status of plants. The diagnostic leaf is a well-defined organ sensitive to change in nutrient concentration and photosynthetic capacity. Leaf diagnosis compares leaf sample analytical results with nutrient standards defined from a “normal” plant or group of plants where all nutrients are in quantities and proportions thought to be adequate to achieve high yields. The interpretation of leaf analytical results is based on causal relationships between leaf nutrient concentrations, on the one hand, and fertilization or liming, on the other, that impact crop productivity. In the specific case of guava, recently mature leaves (third pair from the tip of the branch), including petiole (Fig. 48.2), is collected at full bloom around the tree, approximately 1.5 m high from soil surface (Natale et al., 2002). Full bloom stage allows enough time for possible correction. Sampling is conducted by grouping areas similar in terms of cultivar, age, yield, management, soil, and fertilization regime. Four pairs of undamaged diagnostic leaves are collected from 20 guava trees in irrigated areas and 40 pairs in rainfed areas (Rozane et al., 2009b). Leaves are collected at least 30 days after the last spraying to minimize contamination, placed in paper bags, and sent to the laboratory within a maximum of 2 days. If longer time is necessary, leaves are placed in a refrigerator at
5°C (Souza et al., 2010). Nutrient budgets compare nutrient removal through harvest with nutrient inputs. It is frequently recommended to fertilize using a “replacement” concept, which is a serious mistake because nutrients necessary to form guava shoots after pruning and the natural renewal of the root system and soil fertility level are not taken into account. In addition, the order of importance of nutrients for fruits is rarely the same as for the whole plant (Amorim et al., 2015a,b). Another aspect to consider is that nutrient-use efficiency of use of the nutrients is generally low in the tropics, despite adequate management techniques, corresponding to 50%, 10%, and 40% for N, P, and K, respectively (Baligar and Bennett, 1986a,b) (Table 48.1). The nutrients exported per ton of fruit and leaf nutrient concentrations is considered as adequate for cultivar “Paluma” (Natale et al., 2002).

FIG. 48.2 Example the diagnostic leaf for sampling (third pair from the tip of the branch). From Natale, W., Rozane, D.E., 2018. Análise de solo, folhas e adubac¸ão de frutíferas. UNESP, Registro.

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4 Lime requirement, liming, and liming materials

TABLE 48.1 Quantity of macro- and micronutrients exported per ton of fresh fruits and contents of leaf macro- and micronutrients considered as adequate for the guava cultivar “Paluma,” Brazil. Nutrients

N

P

K

Ca

Mg

S

B

Cu

Fe

Mn

Zn

121

1554

94

107

107

0.67

1.34

1.88

1.88

1.88

20–40

60–90

40–80

25–35

g/t a

Export

1179 g/kg

Adequate content

20–23

mg/kg 1.4–1.8

14–17

7–11

3.4–4.0

2.5–3.5

20–25

a

Considering mean yield of 52,475 kg/ha. Dry matter represented, on average, 13.8% of the fresh matter. Data from Natale, W., Coutinho, E.L.M., Pereira, F.M., Boaretto, A.E., 2002. Nutrients foliar content for high productivity cultivars of guava in Brazil. Acta Hortic. 594, 383–386. https://doi.org/10.17660/ActaHortic.2002.594.48.

4 Lime requirement, liming, and liming materials 4.1 Liming before planting Soil acidity is a useful concept relating to pH, aluminum toxicity, base saturation of cation exchange capacity, cationic ratios, lime requirement, and nutrient availability that impact crop yield in tropical regions. Because the roots of fruit trees explore the same volume of soil during most of their lifetime, a uniform and deep incorporation of limestone to at least 30 cm could provide a suitable root environment for rapid plant establishment and efficient use of water and nutrients. Orchard planting offers a unique opportunity to incorporate limestone deeply into soil to facilitate rooting, promote plant development, and foster early fruit production. Before planting seedlings, it is recommended to apply evenly and incorporate 90 days before planting limestone of coarse particle size in the 0–20-cm or 0–30-cm layers to increase soil base saturation (V) to 65%. Where lime requirements exceed 4 t/ha, it is recommended to apply half rate before plowing, followed by cross harrowing, and then apply the other half, repeating both operations. Before planting new orchards, the best liming strategy is to select a limestone with long residual effect in terms of grain size distribution and mineral composition. The Brazilian legislation, for example, allows commercializing limestone with low total relative neutralizing power (TRNP) of at least 45% that contains coarse limestone particles (100% particles passing through of a sieve with 2-mm openings) and have long-lasting effects. If a liming material with 45% TRNP is incorporated into acid soil, a proportion 45% reacts within 90 days leaving the residual proportion of 55% for acid neutralization in future years. Limestone dosage requires not only the TRNP value but also mineral composition enabling to reach the proper cationic base saturation level. The liming material should be incorporated as deep as possible due to its low solubility and slow mobility across the soil profile. Application and incorporation into the 0–30-cm layer is generally sufficient, allowing for rapid establishment and early production of guava trees (Natale et al., 2012). Note that limestone dosage for incorporation down to 30 cm must be enhanced by 50% compared with dosage recommended for incorporation down to 20 cm. Natale et al. (2007) measured the effect of liming on soil fertility and guava nutrition and yield in Brazil. The soil was a ferralsols (oxisols) with clay texture and initial base saturation of 26% in the 0–20-cm layer. Liming material was applied manually, half before incorporation with a moldboard plow down to 0–30 cm and the other half surface incorporated with a disk harrow. Lime doses were 0, 1.85, 3.71, 5.56, and 7.41 t/ha. Soil chemical analyses were monitored for 78 months following lime application. Nutritional status and yield of guava trees were evaluated across five agricultural harvests. Liming increased pH, Ca, Mg, sum of bases (SB), and base saturation (V), besides decreased potential acidity (H + Al) down to 60 cm. Highest cumulative fruit production was obtained where V was close to 50% in the row and to 65% in the inter row in the 0–20-cm layer. During the first years after planting, there were generally close correlations between Ca and Mg concentrations in leaf and in inter row and on-the-row soils. Yield increased linearly or nonlinearly with limestone dose during the experimental period (2002–06). The Ca and Mg supply by liming increased Ca and Mg concentrations in the soil and the leaf. Cumulative fruit production showed a quadratic relationship with leaf Ca and Mg. Leaf Ca/Mg ratio close to 4:1 led to largest fruit production.

4.2 Liming established orchards Limestone incorporation is not recommended in established orchards, due to potential phytosanitary problems resulting from root injury. Considering low limestone solubility; root injury and reduced rooting; risk of infecting the whole orchard; pest invasion, especially nematodes; and loss in soil physical quality, neutralizing soil acidity in the root zone is challenging.

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48. Diagnosis and management of nutrient constraints in guava

In orchards already established, ammonium-based fertilizers applied within canopy projection contribute to soil acidity, requiring regular soil analyses (0–20-cm and 20–40-cm layers). Sampling is usually performed in the 0–20-cm layer. It is also important to assess calcium and aluminum concentrations in deeper layers. Limestone applied to correct acidity in the arable layer (0–20 cm) moves slowly to the subsurface layer (20–40 cm) depending on soil type, rainfall and irrigation, dosage, elapsed time, and subsequent fertilization. An experiment carried out in Brazil evaluated doses and types of surface-applied limestone on soil fertility, plant nutrition, and guava yield in an established orchard (Corr^ea et al., 2018). There were two types of limestone (common, 80% TRNP, and calcined, 131% TRNP) surface applied at 0, 0.5, 1.0, 1.5, and 2.0 times the recommended dosage to elevate V (%) to the value recommended for guava. Soil acidity was reduced proportionally to lime dosage in the 0–10-cm and 10–20-cm layers. The 20–40-cm and 40–60-cm layers were not affected by liming 24 months following lime application. Common limestone and calcined limestone reduced soil acidity in the 10–20-cm layer, respectively, 24 months and 6–12 months after liming. Leaf and fruit mineral composition and guava yield were impacted 14 and 20 months, respectively, following liming. Hence, surficial liming established orchards could correct soil acidity in the 0–20-cm layer within 24 months. Calcined limestone produced similar effects in orange orchards 12–24 months following surficial liming (Silva et al., 2007). It is recommended to sample soil every year in planting rows below canopy projection and apply limestone in strips, that is, in within fertilized areas (rows). Agricultural implements used for limestone application have devices that adapt to strip application, but the rate must be adjusted to strip area because recommended dosage is per hectare. Maintenance is performed by applying limestone of fine particle size to raise V to 50% in the row and to 65% in the inter row where V (%) is below 40% and 55%, respectively (Natale et al., 2007). In high-yielding orchards, annual limestone applications in the planting row (up to 1 t/ha) every 2–3 years in the inter row are based on soil analysis. Where soil Mg concentration is less than 9 mmolc/dm3, dolomitic limestone requires MgO concentration above 12%. Lime requirement is calculated by using the base saturation method as follows (van Raij et al., 1997): LR ¼

ðV2  V1 Þ  CEC TRNP  10

where LR is lime requirement (t/ha), V2 is ideal base saturation for the crop (%), V1 is base saturation of the soil (%), CEC is cation exchange capacity (mmolc/dm3) computed as the sum of exchangeable cations (K, Ca, and Mg) and acidity (H+ + Al3+), and TRNP is total relative neutralizing power, considering carbonate concentration and particle size of the liming material (%). Total acidity (H+ + Al3+) is quantified using the SMP buffer pH method (Shoemaker et al., 1961) converted into mmolc (H+ + Al3+)/dm3 as follows (Quaggio et al., 1985):
H + + Al3 + ¼ 107:76 + 1:053pHSMP Gypsum application is an interesting alternative when the objective is to increase the Ca/Al ratio, neutralize toxic Al, and increase the concentrations of calcium and sulfur in subsurface layers, given the greater mobility of gypsum compared with limestone. The presence of Ca and elimination of toxic Al improve root system development in a larger soil volume. Gypsum alters soil pH by no more than 0.3 units at normal to high dosage because its reaction in soil does not release hydroxyl or carbonate ions (Meurer, 2012). The SO4 2 anions move downward with accompanying cations such as Ca2+, Mg2+, and K+. Gypsum is indicated for crops in general and fruit crops in particular where soil analysis of the 20–40-cm layer shows Ca concentrations less than 4 mmolc/dm3, Al3+ concentrations more than 5 mmolc/dm3, or aluminum saturation (%) exceeding 40%. Gypsum requirement is estimated as follows (van Raij et al., 1997): GR ¼ 6  clay where GR is gypsum requirement (kg/ha) and clay is clay content (g/kg). An alternative product is single superphosphate that contains large amount of gypsum, providing both calcium and sulfur to the crop and neutralizing toxic aluminum.

5 Fertilization 5.1 Fertilization at planting Phosphate fertilization depends on soil test P using the resin method (Table 48.2). Due to low P mobility in soils, phosphate fertilizers should be dropped in pits or furrows 1 month before planting. Pits are 60  60  60 cm3 in size for standard tree spacing of 7  5 m. Pits are filled with 20–30 L of composted cattle manure or 7–10 L of composted poultry manure besides phosphate fertilizer and mixed with excavated soil before filling (Table 48.2). Furrows about 50 cm

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5 Fertilization

TABLE 48.2 Phosphorus dose at planting of guava seedlings based on soil test P. Fertility classes

P2O5 gram per pit or furrow

Very low

270

Low

230

Medium

180

High

140

Obs.: Preferentially use magnesium thermal phosphate + B and Zn or single superphosphate + B and Zn.

TABLE 48.3 Recommendation of fertilization with nitrogen, phosphorus, and potassium for young guava trees cv. “Paluma,” according to soil analysis and plant age. Phosphorus

Potassium

Fertility classes

Fertility classes

Age Years

Nitrogen N (g/plant)

Very low Low P2O5 (g/plant)

Medium

High

Very low Low K2O (g/plant)

Medium

High

0–1

100

0

0

0

0

200

150

100

50

1–2

200

150

100

50

30

250

200

150

100

2–3

400

200

150

100

50

300

250

200

150

deep are filled with the same mixture (phosphorus, manure, and surface soil). Liming material must not be mixed to avoid phosphate immobilization. If soil analysis shows boron concentration less than 0.21-mg B/dm3 using hot water extraction and colorimetric determination, and zinc concentration less than 0.80-mg Zn/dm3 using DTPA extraction and quantification by atomic absorption spectrophotometry, 2.0 g of boron and 5.0 g of zinc are applied per pit or in furrow, and 3.0-kg B/ha and 6.0-kg Zn/ha are applied broadcast.

5.2 Fertilization of young, nonbearing plants Between guava planting and 3 years of age, fertilizer recommendations for cv. “Paluma” depend on soil test P (resin method) or K (exchange resin) (Table 48.3). Fertilizers are applied annually under canopy projection around the plant (Fig. 48.1), within a radius of 0.3 m, increasing up to 0.6 m with age. Fertilizers should be time-split into at least six applications at 30-day intervals during the rainy period. Where possible, especially on sandy soils, 25 L of cured cattle manure/plant/yr or 8 L of poultry manure/plant/yr are applied. Where boron concentrations is less than 0.21-mg B/dm3 and zinc concentrations less than 0.8–mg Zn/dm3, it is recommended to apply 2-g B/plant and 5-g Zn/plant along with manure application.

5.3 Fertilization of established orchards A modified fertilization program is recommended from the third year after planting when guava trees reach full production. Fertilization must meet crop nutrient requirements to sustain orchard productivity and offset nutrient removal by fruits while maintaining nutrient balance and fruit quality. Nutrient requirements are assessed from soil and leaf analyses, considering plant age, crop management, and expected yield (Table 48.4). Fertilizer dosage is adjusted in intensively exploited orchards under irrigation managed with drastic pruning and three harvests every 2 years. Fertilizers should be applied every season below canopy projection and around the plant within a radius of 0.6 m from stem. There are at least four applications of equal doses, at pruning, at full bloom, about 30 days later when the fruits reach 1.5 cm in diameter, and about 60 days after flowering when the fruits reach about 2.5–3.0 cm in diameter. Whenever possible, especially in sandy soils, add 25 L of cured cattle manure/plant/yr or 8 L of poultry manure/ plant/yr. Considering frequent shortage of boron and zinc and their removal by fruits, foliar application of

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48. Diagnosis and management of nutrient constraints in guava

TABLE 48.4 Fertilizer recommendation for nitrogen, phosphorus, and potassium in established orchards of cv. “Paluma” according to soil (and leaf ) analysis and yield classes. Phosphorus

Potassium

Fertility classes

Fertility classes

Production classes

Nitrogen

High

Very low Low K2O (g/plant)

Medium

High

N (g/plant)

Very low Low P2O5 (g/plant)

Medium

t/ha <-50

800

200

150

100

50

800

600

400

200

50–60

1000

250

200

150

100

1000

800

600

400

1200

a

150

a

1000

800

600

1400

a

200

a

1200

1000

800

60–70 >70

250 300

200 250

a

It is hardly possible to reach such production class with such low level of phosphorus or potassium. Obs. 1: Where N leaf concentration exceeds 23-g N/kg, reduce N fertilization regardless of last application. Obs. 2: Where K leaf concentration exceeds 17-g K/kg, reduce K fertilization regardless of last application.

B and Zn is recommended in fruit-bearing orchards. Each 1 L of liquid mixture should contain 0.6 g of boric acid and 5.0 g of zinc sulfate. Boron and zinc are monitored by leaf analysis to avoid overreaching the narrow nutrient ranges between deficiency and excess. Plants should be sprayed once at early vegetative development and at flowering. It is advisable to take advantage of phytosanitary treatments performed during these periods, combining pesticides and micronutrients in a single operation.

5.4 Alternative fertilizer sources: By-products of the guava processing agroindustry The increasing activity of fruit processing generates large amounts of wastes as by-products. Lack of scientific information based on long-term field experiments prevented disposing by-products as fertilizers. By-products can be recycled to sustain the guava production systems viable both environmentally and economically. By-products are composed primarily of guava seeds, which are a “clean” waste. This by-product represents on average 8% of fruit fresh weight and is high in nitrogen and other nutrients (Souza et al., 2014a,b, 2016). A long-term field experiment was conducted in Brazil, applying different doses of guava by-product to measure their effect on soil, plants, and fruit production in a commercial guava orchard (Souza et al., 2014a,b, 2016). The by-product improved soil fertility; leaf N, Mg, and Mn concentrations; and crop production. By-product dosage between 18 and 27 t/ha applied annually was sufficient to maintain leaf N contents at adequate levels. 5.4.1 Contribution pruning to nutrient cycling Being a perennial plant guava has some peculiarities that make it react differently to liming and fertilization compared with annual crops (Natale et al., 2012). The soil exploration volume is large, and the nutrient vertical distribution is highly variable. There is also a large nutrient reserve in roots, branches, trunk, and leaves. Mobile nutrients can be translocated, preventing or slowing down the occurrence of nutritional deficiencies (Epstein and Bloom, 2005). The biogeochemical cycle that transfers nutrients from soil to plant and from plant to soil is accelerated by drastic pruning of the trees, slowing down plant reaction to lime and fertilizers, and their ensuing effects on plant nutrient status (Hernandes et al., 2012). In guava orchards, correctly performed pruning requires deep understanding of plant physiology (Simão, 1998). Reducing the number of leaves by pruning weakens the photosynthetic capacity of the plant. However, the more drastic and well conducted is the pruning, the greater is the plant vigor because pruning stimulates sap circulation and plant vegetative development. The vigor of the buds depends on their position and their number of branches. When the plant reaches its maturity, fruiting pruning will be carried out as it favors the production of fruiting branches. The fruiting is a consequence of the accumulation of carbohydrates, which tends to be greater in new branches with smaller diameter, compared with old and larger branches (Piza Júnior, 2002). Thus, to conduct pruning operations correctly (Fig. 48.3), knowledge about plant vigor, phenological phase, sap flow, canopy relationship, and root system, among others, is mandatory, as outlined by Rozane et al. (2009a): - Eliminate parts attacked by pests and diseases to keep plants healthy; - Increase insolation inside the canopy to reach high photosynthetic activity;

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6 Evolution of guava nutrient diagnostic methods

FIG.

48.3 Example

the

pruning

technique

in guava.

- Sustain high plant productivity with adequate architecture of the canopy by balancing vegetative and fruiting branches; - Stabilize the production, avoiding alternate bearing and improving fruit distribution and quality (size, color, and weight). It’s important to highlight that the correct time for guava crop pruning differs to different regions of the world due to the geographic location of the area directly influence the plant phenology and flowering cycles (Singh et al., 2001).

6 Evolution of guava nutrient diagnostic methods Plant mineral nutrition has evolved a lot since the 19th century, where the essentiality of nutrients was demonstrated and the foundations of agricultural chemistry were established based on Sprengel’s law of minimum followed by Liebscher’s law of optimum stating that production factors perform best where other factors are close to their optimum (De Wit, 1992). The beginning of the 20th century, the idea of using leaf mineral content as criterion for assessing plant nutritional status emerged. The chemical analysis of diagnostic tissues is now an essential tool to determine the nutrient status of perennial crops after reaching nutritional stability. In India, Hundal et al. (2007) checked that monitoring nutrient status of guava was equally effective by Diagnosis and Recommendation Integrated System (DRIS) and sufficiency range for diagnosing deficiencies of nitrogen, phosphorus, potassium, calcium, sulfur, manganese, zinc, and copper. However, researchers acknowledged that maximum yield depends not only on nutrient concentrations but also on balances between nutrients defined as ratios. Due to myriads of nutrient interactions (Parent, 2011), optimum nutrient concentration ranges taken in isolation are far from sufficient to achieve high yield. Nutrients must be combined in a system approach (Nowaki et al., 2017). Compositional data are intrinsically multivariate, influencing each other in a system close to the unit of measurement (e.g., kilogram of leaf dry matter). Multivariate analysis has been applied to guava crop databases elaborated over the last 25 years to diagnose nutrients interactively and globally. To facilitate the execution of computations and the interpretation of the results, a team of researchers developed the program “CND-Goiaba” (Rozane et al., 2013) that evaluates the nutritional status of guava based on the compositional nutrient diagnosis (CND) method (Parent and Dafir, 1992; Parent, 2011). Based on leaf analysis, this tool allows fruit growers to assess nutrient adequacy, deficiency, or excess accounting for their interactions (Rozane et al., 2012). The program is available for free at https:// web.registro.unesp.br/sites/cnd_goiaba/. Fig. 48.4 presents how leaf mineral composition is diagnosed, interpreted, and transcribed using the program “CND-Goiaba.” Needless to say, the efficiency of computational tool depends on

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48. Diagnosis and management of nutrient constraints in guava

FIG. 48.4 Diagnosis of leaf nutrient composition transcribed and calculated by the program “CND-Goiaba.”

the robustness, size, and quality of the database to integrate a progressively larger number of interacting factors, and this requires constant research efforts. Guava is a very important crop for producing countries. It is a perennial crop that explores a large volume of soil. Because the orchard is established for several decades, the soil must be properly characterized chemically, morphologically, and physically before planting the orchard, and corrective measures must be implemented immediately. Trees must be pruned regularly to maintain its vigor. In this chapter, we describe and quantify liming, fertilization, and pruning operations from tree planting to orchard maintenance. Nutrient diagnosis is required to adjust the fertilization regime after accounting for soil and plant reserves and for the contribution of pruned branches.

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Further reading Natale, W., Rozane, D.E., 2018. Análise de solo, folhas e adubac¸ão de frutíferas. UNESP, Registro.