Intensification and diversification increase land and water productivity and profitability of rice-based cropping systems on the High Ganges River Floodplain of Bangladesh

Field Crops Research 209 (2017) 10–26

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Intensification and diversification increase land and water productivity and profitability of rice-based cropping systems on the High Ganges River Floodplain of Bangladesh

MARK

⁎

M. Jahangir Alama, , E. Humphreysb,1, M.A.R. Sarkarc, Sudhir-Yadavd a

Regional Agricultural Research Station, Bangladesh Agricultural Research Institute, Jessore, Bangladesh Griffith, NSW 2680 Australia c Department of Agronomy, Bangladesh Agricultural University, Mymensingh, Bangladesh d International Rice Research Institute, DAPO 7777 Metro Manila, Philippines b

A R T I C L E I N F O

A B S T R A C T

Keywords: Conservation agriculture Rice equivalent yield Economics Irrigation Water productivity Protein

In the High Ganges River Floodplain of Bangladesh, rice-based cropping systems with lower tillage, labor and irrigation water requirement and higher productivity and profitability are needed. To explore options for achieving this, a replicated cropping system experiment was conducted at Jessore to evaluate cropping system intensification with varying degrees of tillage and rice residue retention. Four cropping systems/ establishment methods (CSE) were compared: CSE1: T.boro-T.aman (soil puddling and transplanting of both rice crops); CSE2: CTwheat-CTmungbean-T.aman (wheat and mungbean sown using a power tiller-operated seeder, PTOS, with full tillage (CT) and sowing in a single pass); CSE3: CTwheat-CTmungbean-CTDSaman (all crops sown using a PTOS with full tillage, dry seeded (DS) aman); CSE4: STwheat-STmungbeanSTDSaman (all sown using a PTOS with strip tillage (ST)). Two levels of aman residue retention (removed; partial retention) were compared in sub-plots. Water was ponded on the T.boro fields from transplanting until shortly before harvest, while all aman crops were grown using safe alternate wetting and drying (AWD) water management. System productivity (rice equivalent yield, REY) of all wheat-mungbean-aman systems was significantly higher than that of the T.boro-T.aman system in the first and fourth years and when averaged over the four years (by 10% or 1.3 t ha−1). This was due to higher prices paid to farmers for mungbean and wheat, which more than offset their lower grain yields in comparison with T.boro yield. Irrigation input was lower, by 62–83%, in the wheat-mungbean-aman systems than the T.boro-T.aman system. The wheat-mungbean-aman systems were also economically superior to the T.boro-T.aman system in terms of higher gross margin (by 26%), net return (double) and benefit cost ratio (1.1 vs 1.0) due to both higher returns and lower cost of production. The total labor requirement of all systems was similar; however, it was more evenly distributed throughout the year in the triple cropping systems. Productivity of the wheat-mungbean-aman systems with T.aman and DSaman was similar, despite significantly higher yield of wheat (by 10% or 0.4 t ha−1) following DSaman, as this was countered by a consistent trend (non-significant) for lower yield of the DSaman than T.aman. However, gross margin of the systems with DSaman was 5% higher than with T.aman due to lower cost of production of the former. Changing from puddling and transplanting to dry seeding of aman reduced total irrigation input to the triple cropping system by 238–879 mm (32–65%) over the four years. Establishment of wheat in 40 cm of standing aman residues using the PTOS was excellent with both full and strip tillage. Partial aman residue retention gave significantly higher (by 0.8–0.9 t ha−1) system yield than residue removal from the second year onwards, due to consistent trends for higher yields of all crops (significant in the case of wheat and mungbean). There were no significant differences between the use of CT and ST in the wheat-mungbean-aman system for any of the measured parameters. The results suggest that intensification from T.boro-T.aman to a wheat-mungbean-aman system can increase system productivity and profitability and reduce irrigation requirement, and that replacement of T.aman with DSaman in the triple cropping system can be done with reduced irrigation input, increased wheat yield, and little effect on rice yield. Furthermore, tillage for all three crops can be reduced to strip tillage with no adverse effects

⁎

1

Corresponding author. E-mail address: [email protected] (M.J. Alam). Former address: International Rice Research Institute, DAPO 7777 Metro Manila, Philippines.

http://dx.doi.org/10.1016/j.fcr.2017.04.008 Received 26 October 2016; Received in revised form 12 April 2017; Accepted 12 April 2017 0378-4290/ © 2017 Published by Elsevier B.V.

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on productivity or profitability. Long term studies are needed to determine the full impacts of the changes in crop intensification, establishment method, tillage and residue management on soil properties, irrigation requirement and crop performance.

led to lowering of ground water tables (Shamsudduha et al., 2009), land subsidence and formation of cracks and sinkholes. The lowering of the water table increases irrigation cost through higher cost of pumping, and the need to deepen tubewells and install more expensive pumps. Furthermore, in some areas such as south-western Bangladesh, high use of ground water has led to the accumulation of heavy metals in the ground water, especially arsenic (Dhar et al., 1997; Christopher and Haque, 2012; DPHE, 2000). As a result, a lot of arsenic is being brought into the food chain through irrigated (T.boro) rice cultivation (FAO, 2007; Rahman et al., 2008; Panaullah et al., 2009). Thus the rice–rice and rice-wheat systems as currently practised are not sustainable. Alternative practices are needed which will reduce the cost of production, increase land, labor, water and energy productivity, and reduce adverse environmental effects. One potential way of achieving this is to switch to conservation agriculture (CA) practices with reduced or zero tillage, residue retention and crop diversification (Hobbs et al., 2008). For rice-wheat systems, this could potentially be achieved by changing from: (1) puddled transplanted rice (PTR) to nonpuddled dry seeded rice (DSR), (2) continuously flooded rice to alternate wetting and drying (AWD) water management, (3) conventional to reduced tillage in wheat, (4) inclusion of a legume in the rotation, and (5) retention of crop residues. Inclusion of legumes in the rice-wheat rotation could also bring other benefits including disruption of cycles of weeds and diseases that occur in cereal monoculture (Chauhan et al., 2012), and soil fertility benefits (Bhuiyan, 2004; IFPRI, 2009) due to the potential of legumes to add nitrogen to the cropping system. It has been estimated that growing mungbean adds about 25–40 kg N ha−1 to the soil (Ali, 1992; Ahlawat et al., 1998), which can make a small contribution to the N requirement of high yielding rice-wheat cropping systems (Timsina and Connor, 2001). Given the above, a four-year cropping system experiment was implemented to evaluate the effects of changing from: (1) the conventional T.boro-T.aman system to a conventional practice wheat-mungT.aman system, and (2) changing from the conventional wheat-mungT.aman system to the same system using CA. The experiment was designed to enable separation of the effects of aman establishment method, tillage, and aman residue retention. This paper presents the findings on system performance in terms of yield, irrigation amount and its productivity, and profitability.

1. Introduction Rice is the staple food for the people of Bangladesh, contributing 95% of the total food grain consumed (BBS, 2011), about two-thirds of the total calorie supply and half of the total protein intake of an average person (Begum and D’Haese, 2010). About 75% of the total cropped area and over 80% of the total irrigated area is planted to rice. Wheat is the second most important cereal, and contributes 7% of the total output of food cereals (Hossain and Teixeira da Silva, 2013). The predominant cropping systems in Bangladesh are: (1) T.boro −T.aman (puddled transplanted winter rice, fully irrigated, followed by puddled transplanted monsoon rice, predominantly rainfed), and (2) wheat–T.aman, which occupy 2.4 and 0.5 Mha, respectively (Ladha et al., 2003; Dawe et al., 2004; Bhuiyan et al., 2004). In the past few decades, high food production growth rates (rice 2.3%p.a, wheat 3%p.a.) have kept pace with population growth as a result of the introduction of high yielding varieties and increased inputs, and the development of ground water irrigation which enabled a 5-fold increase in the area of T.boro production (BBS, 2013). However, yields of rice and wheat have now almost stagnated (Ahmed, 2004). With the population increasing at 1.47% p.a. (BBS, 2013), and the gradual decrease (0.08 Mha or 1% p.a.) in the area of cultivable land due to increasing industrialization and urbanization (Planning Commission, 2009), the challenge of ensuring future calorific food security continues. Malnutrition is also a major problem in Bangladesh; for example, 88% of the populations suffer from protein deficiency (Kabir et al., 2005). At present, only 0.25 Mha (3% of the total cultivable land area) are under pulse cultivation, producing 0.23 Mt p.a. Pulses such as mungbean have two and three times the protein content of wheat and rice, respectively. Mungbean also contains essential micronutrients, especially Zn, Fe, and essential amino acids (especially lysine), that are lacking in rice and wheat. Therefore, there is a need to intensify and diversify cropping systems by including legumes. The current T.boro-T.aman and wheat-T.aman cropping systems are not sustainable because of decreasing profitability due to increasing labor and tillage costs, increasing agricultural labor scarcity, groundwater depletion, and declining soil fertility. Production costs of the T.boro–T.aman system increased by about 55% during 1996–2006 (BRRI, 2007a,b), mainly due to increased input costs, especially labor and irrigation and comparatively low in seed, fertilizer, fuel and pesticides. The high tillage and labor requirements for rice production are due to the practices of puddling and transplanting. The soil is initially cultivated (usually 1–2 passes) under moist or dry conditions using a rotary tiller powered by a 2-wheel tractor (2-WT), and is then soaked with water and tilled while flooded (usually two passes), and then levelled. In addition to the high financial cost of burning fuel, large amounts of the greenhouse gas CO2 are generated. Bangladesh is one of the most vulnerable countries in the world to climate change and sea level rise because much of her territory is located on low lying deltas (IPCC, 2007; Sarwar, 2005; Alam, 1996). Transplanting is very labor intensive; labor for all operations from seedbed preparation to transplanting accounts for nearly one third of the total cost of production (Rashid et al., 2009). Furthermore, labor is often not available on time, resulting in late establishment and reduced yield of both rice and subsequent crops in the rotation. In addition, transplanting often leads to back damage in older farmers (Hussain, 2005). In the main T.boro producing areas of Bangladesh, farmers withdraw large amounts of ground water for T.boro cultivation which has

2. Materials and methods 2.1. Site description The experiment was conducted over four years on the experimental farm of the Regional Agricultural Research Station of Bangladesh Agricultural Research Institute at Jessore (23°11′ N, 89°14′ E and 16 m ASL). The climate in this region is subtropical monsoon with average annual rainfall at Jessore of 1590 mm, 90% of which falls from June to October (Fig. 1a), the period of growth of the aman crop. Monthly average maximum temperature ranges from 26 °C in January to 36 °C in April, while monthly average minimum temperature ranges from 11 °C in January to 24 °C in April (Fig. 1b). Monthly mean daily solar radiation ranges from 13 MJ m−2d−1 in January to 22 MJ m−2 d−1 in April/May (Fig. 1c). The soil at the experimental site was a calcareous brown clay loam of the High Ganges River Floodplain (BARC, 2012), with clay content declining from 38% in the topsoil to 26–28% at 60–120 cm (Table 1). Bulk density was 1.4–1.5 g cm−3 throughout the profile, apart from a slightly denser layer at 20–25 cm. The topsoil (0–15 cm) was slightly alkaline (pH 7.7) 11

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Fig. 1. (a) monthly mean rainfall (mm), (b) monthly mean maximum and minimum temperature, (c) monthly mean solar radiation during the four years in comparison to the long term (1981–2010) values at the Bangladesh Meteorological Department station at Jessore.

12

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Table 1 Soil physical and chemical properties of the experimental site. Depth (cm)

0–15 15–30 30–60 60–90 90–120

Bulk density (g cm−3)

1.52 (5–10 cm) 1.59 (20–25 cm) 1.41 (40–50 cm) 1.45 (70–80 cm) 1.47 (100–110 cm)

Soil texture

Textural class

pH (1:2.5 soil:water)

Organic C (g C kg−1)

Sand (%)

Silt (%)

Clay (%)

31.5

30.7

37.7

Clay loam

7.7

0.98

33.5

30.7

35.7

Clay loam

7.8

0.46

31.5

36.7

31.7

Clay loam

–

–

35.5

38.7

25.7

Clay loam

–

–

35.5

36.7

27.7

Clay loam

–

–

2.3.1. Wheat A pre-sowing irrigation (50 mm) was applied about a week before sowing each wheat crop. The wheat (BARI gom26, duration 104–110 d) was sown on 14–16 November each year, when soil moisture was optimum, at 120 kg seed ha−1, with a sowing depth of 3–5 cm and row spacing of 20 cm. The wheat was sown in exactly the same way, using the PTOS, in both the bare plots and the plots with 40 cm standing aman straw. There was no rice crop prior to the first wheat crop, so the +R plots were mulched with 3 t ha−1 rice straw after wheat sowing. Total fertilizer application was 100 kg N ha−1 as urea, 30 kg P ha−1 as triple superphosphate, 50 kg K ha−1 as muriate of potash, 20 kg S ha−1 as gypsum and 1 kg B ha−1 as boric acid. Two thirds of the N and all the P, K, S and B fertilisers were broadcast just before sowing, and the rest of the N was broadcast shortly before the first irrigation. Weeds were well-controlled by one hand weeding at 25–27 DAS each year, and there was no significant damage from pests and diseases in any wheat crop. The wheat received two post-sowing irrigations each season – at crown root initiation (18–20 DAS) and during grain filling (71–75 DAS). Irrigation water was applied until the average water depth on the surface of each plot reached 50 mm. At harvest (between 6 and 15 March over the years) the crop was removed by cutting the straw close to the soil surface.

and had low soil organic C content (1.0%). The depth to the groundwater was about 30 m and the salinity of the groundwater, which was used for irrigation, was low (0.67 dS m−1). The site had a long history of growing upland crops such as mungbean, chickpea and wheat, and had not previously grown rice. 2.2. Experimental design Four cropping system/establishment method treatments (CSE) were compared in main plots as follows: CSE1: T.boro-T.aman (control)

• both crops transplanted into puddled soil CSE2: CTwheat-CTmungbean-T.aman

• conventional tillage (CT) for wheat and mungbean which were sown

using a power tiller-operated seeder (PTOS) in a single pass with full tillage; aman transplanted into puddled soil CSE3: CTwheat-CTmungbean-CTDSaman

• conventional tillage (CT) for all crops including dry seeded (DS)

2.3.2. T.boro Sprouted seeds of BRRI dhan29 (duration 160 d) were broadcast on the seedbed between 11 November and 6 December each year. Sevendays before transplanting, the plots were soaked with water for 2 d and cultivated (four passes) using a 2-WT, followed by 2–3 ladderings (levelling with a ladder-like implement dragged by a 2WT). Forty five day-old seedlings were uprooted carefully from the seedbed and transplanted with 2 seedlings hill−1 and 20 cm × 20 cm hill spacing.Total fertilizer application was 170 kg N ha−1 as urea, 20 kg P ha−1 as triple superphosphate, 60 kg K ha−1 as muriate of potash, 10 kg S ha−1 as gypsum and 2 kg Zn ha−1 as zinc sulphate. All of the P, K, S and Zn fertilisers were broadcast before transplanting. Urea was broadcast in three equal splits at 10 d after transplanting (DAT), 40 DAT (4–5 tiller stage) and 55 DAT (7 d before panicle initiation). The plots were continuously flooded/saturated from the time of transplanting to about two weeks before harvest, by irrigating frequently (every 0.5–4 d as needed) to top up to 50 mm water depth. Weeds were well-controlled by two hand weedings at 30–35 and 60–65 DAT each year. There were several infestations of stem borer at variousgrowth stages in all treatments, and of rice bug during the grain filling stage. Good control of stem borer was achieved by applying fipronil 3G (Regent 3G®, BASF Bangladesh Limited) at 300 g a.i. ha−1 and flubendiamide (Belt 24WG®, Bayer Crop Science Bangladesh) @ 48 g a.i. ha−1. Application of malathion (Hilthion®, The Limit Agroproducts Limited Bangladesh) @ 570 g a.i. ha−1 and emidacloprid (Emifaf®, Auto Crop Care Limited, Bangladesh) @ 25 g a.i. ha−1gave good control of rice bug. The cropswereharvested between 11 and 15

aman, using a PTOS in a single pass with full tillage CSE4: STwheat-STmungbean-STDSaman

• as for CSE3 but using strip tillage(ST) for all crops Two levels of aman residue retention – removed at ground level (-R), and partial retention (+R, 40 cm of standing stubble)-were compared in sub plots. The experiment was a fully randomized split plot design with three replicates. The main plots were 22 m × 9.6 m and the sub plots were 11 m × 9.6 m. There was a 1.0 m wide drain between each replicate; each drain was connected to the farm drainage system. There was a 1.4 m wide buffer between adjacent main plots within each replicate. The experiment commenced with sowing of wheat and T.boro crops in November 2011. 2.3. Site and crop management Prior to establishment of the experiment there was a uniform mungbean crop on the site. After harvest of the pods, the residues were removed and the site was cultivated to a depth of about 10 cm and leveled using laser guidance. Earthen bunds approximately 15 cm high were formed around each subplot. An irrigation water delivery system (75 mm PVC pipeline) was constructed to enable delivery of water to every sub plot. All crops were managed using recommended practice (BARI, 2011; BRRI, 2011). 13

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duration 135 d) were broadcast on the seedbed within 0–3 d of the date of dry seeding each year. Twenty five day-old seedlings were uprooted carefully from the seedbed and transplanted with 2 seedlings hill−1 and plant spacing of 20 cm × 20 cm. Total fertilizer application was 90 kg N ha−1 as urea, 10 kgnP ha−1 as triple superphosphate, 25 kg K ha−1 as muriate of potash, 10 kg S ha−1 as gypsum and 2 kg Zn ha−1 as zinc sulphate. All P, K, S and Zn fertilizers were broadcast on the soil surface immediately before transplanting. Nitrogen was applied in three equal splits at 10 DAT, 30 DAT (4–5 tiller stage) and 50 DAT (7 d before panicle initiation). During the first two weeks after transplanting, irrigation water was applied to each plot daily (if needed) until average water depth was 50 mm. Thereafter, irrigation was applied wheneversoil water tension at 15 cm depth increased to 15 kPa as for DSaman. Weeds were well-controlled with two hand weedings at 15 and 35 DAT. Insect infestations occurred as for DSaman, and good control was achieved using the same procedures. The crops were harvested between 28 October and 5 November in the first three years, and on 27 November in 2015, leaving 40 cm high straw in the straw retained treatment as for DSaman.

May each year by cutting the plants close to the soil surface. 2.3.3. Mungbean Mungbean (BARI mung6, duration 60 d) was sown by PTOS between 12 and 20 March at 40 kg ha−1, sowing depth 3–4 cm and row spacing 30 cm. Total fertilizer application was 20 kg N ha−1 as urea, 20 kg P ha−1 as triple superphosphate and 30 kg K ha−1 as muriate of potash. All of the fertilizer was broadcast just before sowing. The mungbean was irrigated once during the first season (2 DAS), and twice in the other years (2013: 3 and 20 DAS; 2014:19 and 41 DAS; 2015:1 and 27 DAS). Irrigation water was applied until an average water depth of 50 mm was achieved. Weeds were well-controlled with one hand weeding 17–20 DAS each year. Thinning of the mungbean was done at the same time to achieve the recommended 10 cm distance between plants in the same row. Pod borer attack at the pod formation stage was well-controlled each year using deltamethron (Desis 2.5 EC®,Bayer Crop Science Bangladesh) sprayed @ 12.5 g a.i. ha−1. There were two pod pickings each year, between 11 and 20 May 2012, 23–30 May 2013, 24 May to 7 June 2014, and 10–25 May 2015. The mungbean residues were left in the field.

2.4. Observations

2.3.4. Aman 2.3.4.1. Dry seeded (DS) aman. Glyphosate 41% S.L. (I.P.A. salt) @ 3 L ha−1 was sprayed two weeks before sowing to kill the mungbean plants. The rice (BRRI dhan49, duration 135 d) was sown between 18 June and 7 July with a target seed rate of 50 kg ha−1 at a sowing depth of 3–4 cm and row spacing 20 cm. In the first year the PTOS main shaft broke after sowing the full till DSaman, and the strip till aman (STDSaman) was sown by hand into furrows made using a sharpened iron rod. The actual seed rate was much higher than the target, and thinning was done at 15 DAS in both the CT and STDSaman to achieve a plant population of 350–400 m−2. Thinning was not performed in subsequent years when both CT and ST DSaman were sown using the PTOS, resulting in plant populations of (380–390 m−2). Total fertilizer application was 120 kg N ha−1 as urea, 10 kg P ha−1 as triple superphosphate, 25 kg K ha−1 as muriate of potash, 10 kg S ha−1 as gypsum and 2 kg Zn ha−1 as zinc sulphate. All of the P, K, S and Zn fertilizers were broadcast just before sowing. Urea was applied in four equal doses at 20, 40, 60 and 75 DAS. The urea was applied prior to irrigation when possible (when the plots were not flooded as a result of heavy rain).Safe alternate wetting and drying (AWD) water management (Lampayan et al., 2015) was used, with irrigation applied whenever soil water tension at 15 cm depth increased to 15 kPa. Weeds were well controlled by spraying the pre emergence herbicide pendimethalin (Panida 33 EC®, Auto Crop Care Limited, Bangladesh) at 850 g a.i. ha−1 at 2 DAS followed by the post emergence herbicide ethoxysulfuron (Sunrice 150 WG®, Bayer Crop Science Bangladesh) @ 20 g a.i. ha−1 at 21 DAS, and one hand weeding at 40 DAS. Each year, all treatments were infested by stem borer at various growth stages, and by blast and rice bug during grain filling. These infestations were well-controlled by applying emidacloprid (Emitaf®, Auto Crop Care Limited, Bangladesh) @ 25 g a.i. ha−1, carbofuran (Furadan 5G®, Padma Oil Company Limited Bangladesh) @ 500 g a.i. ha−1, and tebukonajol + triphoxystrobin (Nativo 75WG®, Bayer Crop Science Bangladesh) @ 300 g a.i. ha−1. In the second year the crop was also infested with sheath blight and blast, which were well-controlled by spraying tricyclazole (Trooper 75 WP®, Auto Crop Care Limited, Bangladesh) @ 370 g a.i. ha−1 and tebukonajol + triphoxystrobin (Nativo 75WG®, Bayer Crop Science Bangladesh) @ 300 g a.i. ha−1 at 80 DAS. The crops were harvested between 24 October and 14 November over the years. The rice was cut at ground level in the rice straw removed treatments, and 40 cm above the soil surface in the rice straw retained treatments (rice straw retention of 2 t ha−1).

2.4.1. Crop yield Grain yield was determined by harvesting a 16 m2 area for rice and wheat, and 15.6 m2 for mungbean, in the centre of each subplot. The grain was manually threshed and fresh grain weight was determined. Grain moisture content was calculatedfrom the average of three subsamples per subplot, determined using a grain moisture meter (Model: GMK-303RS, Korea) at the time of weighing for yield determination. Fresh grain yield was converted to grain yield (t ha−1) at 12% moisture content (wheat), 14% (rice) and 10% (mungbean).

2.4.2. System rice equivalent yield Rice equivalent yield (REY) of wheat and mungbean was calculated from the grain yield and price of each crop using the formula: REY (crop ᵪ) = Yᵪ (Pᵪ/Pr) where, Yᵪ is the yield of crop ‘x‘(t grain ha−1at the above moisture content for that crop), Pᵪ is the price of crop ‘x‘ (USD t−1) and Pr is the price of rice (Biswas et al., 2006). The prices of rice, wheat and mungbean used were USD 192, 256 and 641 t−1, respectively. These values werecalculated from the local market prices at Jessore in October 2013, in Bangladeshi Taka (BDT), which were converted to USD using 1 USD = 78.0 BDT (the average exchange rate from November 2013 to October 2015). System REY was calculated as the sum of the REY of each crop in the cropping system year (November to October).

2.4.3. Irrigation The volume of irrigation water applied to each subplot was determined at every irrigation using a propeller flow meter installed in a straight section of the pipeline downtream from the tubewell outlet. Each subplot was irrigated one at a time, and the amount of water applied (mm) was calculated from the initial and final flow meter readings divided by the area of the subplot.

2.4.4. Irrigation water productivity Water productivity with respect to irrigation (WPI) was calculated fromgrain yield (14% moisture content for rice, 12% for wheat, 10% for mungbean) and irrigation input as follows:

Grain WPI (kg ha−1 mm−1)= 2.3.4.2. Puddled transplanted (T.) aman. Sprouted seeds (BRRI dhan49, 14

Grain yield (kg ha−1) Total irrigation amount (mm)

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where, TVC = total variable cost investment i = annual interest rate (10%, Rahman, 2014); and t = length of the crop production period in months (as above). Gross return for each crop was calculated from the amount of grain and straw harvested (t ha−1) and their farm gate prices. The prices of rice, wheat and mungbean grain and rice straw were 192, 256, 641 and 19 USD t−1, respectively. Wheat straw does not have any monetary value in the market at Jessore, and mungbean residues were retained in the field. Gross margin for each crop was calculated as the difference between total (gross) return and total variable cost. Net return was calculated as the difference between gross return and total cost. The benefit cost ratio (BCR) was calculated from the gross return divided by the total cost. Annual system economic performance was calculated from the sum of the returns and the sum of the costs for each crop in each one-year cycle.

2.4.5. System protein output System protein output was calculated from the sum of the protein output in the grain of each crop, which was estimated using the following formula:

Protein output (kg ha−1)

Protein% × Dry grain yield (t ha−1) × 1000 100

The protein content used for rice, wheat and mungbean was 8.8, 12.1 and 20.9% (dry grain yield), respectively (Timsina et al., 2006; BARI, 2011). 2.5. System economic performance Total production cost was calculated as the sum of variable (operating) and fixed costs. Prices of inputs and outputs were determined in BDT based on prices in the local (Jessore) market in 2013. Prices were converted to USD using an exchange rate of 1USD = 78.0 BDT as above. The variable costs used in the analysis were the costs of tillage, seed, sowing, rice seedling raising, transplanting, fertilizers, biocides, irrigation, harvesting and threshing (Tables 2a and 2b). These were based on information provided by local farmers and the data of Rahman (2014). The costs of tillage, mechanical sowing and irrigation were based on the charges of local service providers. Fixed costs are those costs which do not change with change in the volume and type of production, such as the rental value of land, depreciation of machinery and interest on operating capital. In this analysis, depreciation of machinery was not considered as this is included in the charges of service providers. Land rental value was the rental cost for one year based on information provided by local farmers. Rental coast was assigned to each crop according to the duration of the crop. For the T.boro-T.aman system, durations of 6.5 and 5.5 months, respectively, were used. For the wheat-mung-aman systems the breakdown was 4, 3 and 5 months, respectively. Interest on operating capital (IOC) was calculated using the following equation:

2.6. Weather data Daily maximum and minimum temperature, rainfall and sunshine hours during the experimental period were collected from the Bangladesh Meteorological Department (Jessore) weather station located about 5 km from the experimental site. Long term weather records (1981to 2010) were also acquired from the same weather station. Solar radiation was calculated from daily sunshine hours using the Angstrom Formula (Sys et al., 1991).

2.7. Statistical analysis Data were analyzed byANOVA (using Crop Stat 7.2) to evaluate differences between treatments, and the means were separated using least significant difference (LSD) at the 5% level of significance (p < 0.05).

IOC = TVC*i*t/(100*12) Table 2a Costs of wheat and mungbean production used in the economic analysis. Wheat

Mungbean −1

Variable costs Seed (kg) Sowing by PTOS (full and strip tillage) Human-labor (Man-day) Seeding Fertilizer Irrigation Insecticide Weeding Harvesting and threshing Total labor

• • • • • •

Fertilizer Urea (kg) TSP (kg) MoP (kg) Gypsum (kg) B (kg) Irrigation (per crop) Threshing by machine Insecticide Total variable cost Fixed costs Interest on OC (%) Land rental value Total fixed cost Total cost

• • • • •

Quantity ha

Unit price (USD)

Total (USD)

Quantity ha−1

Unit price (USD)

Total (USD)

120 1

0.6 48.1

76.9 48.1

40 1

1.0 48.1

41.0 48.1

2 2 6

3.8 3.8 3.8

7.6 7.6 22.8

23 27 60

3.8 3.8

87.4 102.6 228

2 2 5 6 24 30 69

3.8 3.8 3.8 3.8 3.8 3.8

7.6 7.6 11.4 22.8 98.8 114.0 262.2

210 150 100 125 6 1 1

0.2 0.3 0.2 0.4 2.1 138.5 25.6

43.1 48.1 19.2 48.1 12.3 138.5 25.6

43 100 60

0.2 0.3 0.2

8.8 32.1 11.5

1

80.8

80.8

1

47.5

47.5 532

0.1 1

480

688 0.1 1

23 160 183 871

480

15

13 120 133 665

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Table 2b Costs of rice production used in the economic analysis. T.boro Quantity ha−1

Variable costs Seedbed (all labor and inputs for seedling raising) Seed Sowing by PTOS (full and strip tillage) Land preparation/Tillage Human-labor (man-day) Seed sowing Seedling raising Seedling uprooting Transplanting Herbicide Fertilizer Irrigation Weeding Insecticide Harvesting and threshing Total labor (not including seedling raising)

• • • • • • • • • •

Fertilizer Urea (kg) TSP (kg) MoP (kg) Gypsum (kg) ZnSO4 (kg) Irrigation (per crop) Pesticide Herbicide Threshing by machine Total variable Cost Fixed cost Interest on OC (%) Land rental value Total fixed Cost Total cost

• • • • •

T.aman Unit price (USD)

Total (USD)

Quantity ha−1

DSaman Unit price (USD)

27.7

Total (USD)

Quantity ha−1

27.0

–

40

0.4

16.0

35

0.4

13.5

1

76.9

76.9

1

76.9

76.9

3.8 3.8 3.8

11.4 41.8 114.0

3.8 3.8 3.8

7.6 30.4 83.6

3.8 3.8 3.8 3.8 3.8 3.8

11.4 22.8 114.0 7.6 121.6 445

3.8 3.8 3.8 3.8 3.8

11.4 7.6 95.0 7.6 102.6 346

0.2 0.3 0.2 0.4 1.9 480.8 66

73.8 30.0 24.0 25.2 11.4 480.8 66.0

0.2 0.3 0.2 0.4 1.9 96.2 102.1

40.0 16.0 9.6 24.2 11.5 96.2 102.1

58.1

58.1 1335

35.9

35.9 799

– 3 11 30 – 3 6 30 2 32 117

369 100 120 63 6 1 1 – 1

0.1 1

480

72.3 260 332 1667

– 2 8 22 – 3 2 25 2 27 91

195 50 50 63 6 1 1 – 1

0.1 1

480

36.6 220 257 1056

Unit price (USD)

Total (USD)

50 1

0.4 48.1

19.2 48.1

2

3.8

7.6

4 3 3 28 4 31 75

3.8 3.8 3.8 3.8 3.8 3.8

15.2 11.4 11.4 106.4 15.2 117.8 285

260 50 50 63 6 1 1 1 1

0.2 0.3 0.2 0.4 1.9 96.2 102.1 37.2 35.9

53.3 16.0 9.6 24.2 11.5 96.2 102.1 37.2 35.9 738

0.1 1

480

30.8 200 231 969

3. Results

similar each year, except for lower values in April 2015. (Fig. 1c).

3.1. Weather

3.1.3. Mungbean Each year there was a relatively dry start to the mungbean cropping period, which ran from mid March to late May. Total rainfall and its distribution were quite different during the four years of experimentation (Figs. 1 a, 2 a–d). Total rainfall ranged from 123 mm, (16 rainy days) in 2012 to 372 mm (22 rainy days) in 2013, compared with the long term average of 256 mm from mid March to the end of May. In 2012 and 2015 there were 60–70 mm rain over 2d in early April (early vegetative stage) and further rains in late April/early May (grain filling stage). In 2013, there was heavy rain in mid April, with little rain thereafter. In 2014, there was little rain during the vegetative stage (April) but heavy rain during pod harvesting. Monthly mean daily minimum temperatures were similar each season, and similar to the long term average, except for higher values in April 2014. Mean monthly maximum daily temperatures were similar in March, but higher in April 2014 (flowering stage) than the long term average, by ∼2 °C, and higher in May 2012 and 2014 than the long term average (pod formation and grain filling stages)(Fig. 1b). Mean monthly daily solar radiation was similar in March each year, lower in April 2014 than the other three years, and in May was highest in 2012 and least in 2014 (Fig. 1c).

3.1.1. Wheat Rainfall was low during the first three wheat crops (mid November to early March), with totals of 36, 23, 19 mm, respectively, and exceeded the long term average by 66 mm in 2015-15 due to high rainfall towards the end of the grain filling period (Figs. 1 a, 2 a–d ). Monthly mean daily maximum and minimum temperatures during each wheat crop were usually slightly lower than the long term averages, and the 2012–13 season was particularly cool in January, with several frost days and mean minimum temperature about 3 °C lower than in other years and the long term average (Fig. 1b). Monthly mean daily solar radiation was similar each year throughout the wheat season (Fig. 1c). 3.1.2. T.boro The period of growth of the T.boro crops coincided with that of the wheat crops, but continued on until early May. As for wheat, the total amount of rainfall during the first three T.boro crops was also lower than the long term average (240 mm), but higher in 2014–15. Rainfall distribution during the T.boro crops was poor, ranging from 47 mm (12 rainy days) in 2012–13 to 356 mm (23 rainy days) in 2014–15 (Fig. 2a–d). Each year, most of the rain fell during the grain filling stage. Monthly mean daily maximum and minimum temperatures during each T.boro crop were lower than or similar to the long term average (Fig. 1b). The 2012–13 season was generally cooler than the other three seasons. Monthly mean daily solar radiation was generally

3.1.4. Aman Rainfall during the aman crops ranged from 1055 mm in 2014 to 1366 mm in 2015, compared with the long term average (mid June to early November) of 1160 mm. In 2012, the full onset of the monsoon 16

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Fig. 2. Distribution of rainfall at the experimental site in (a) 2011–12, (b) 2012–13, (c) 2013–14, and (d) 2014–15. Horizontal bars should the growth period of each crop.

20–24 rainy days) (Fig. 2a–d). However, in those three years there were only a few rainy days from mid September to the time of harvest in early November. Monthly mean daily maximum and minimum temperatures were generally close to the long term average except for unusually hot weather in June 2012 (Fig. 1b). Maximum temperature in October 2012 was also a few degrees lower than in the next three years

started in mid June, whereas in 2013 and 2014 the monsoon rains started earlier (mid-late May) (Fig. 2a–c). In 2015 there was considerable pre-monsoon rain in April and May, and the full onset of the monsoon started in mid June (Fig. 2d). Rainfall was well distributed throughout the duration of the 2013 aman crop (88 rainy days), and during the first three months after sowing in the other three years (total

Table 3 In-field duration of wheat, mungbean, boro and aman crops, and of total (annual) cropping system. Crop year

2011–12 2012–13 2013–14 2014–15

Wheat

112 119 119 112

T.boro

130 145 129 116

Mungbean

69 70 79 74

T.aman

115 114 110 112

DSaman

129 133 129 130

Total systema CSE1

CSE2

CSE3/4

245 259 239 228

296 303 308 298

310 322 327 316

a CSE1 = T.boro-T.aman; CSE2 = CTWheat-CTMungbean-T.aman; CSE3 = CTWheat-CTMungbean-CTDSaman; CSE4 = STWheat-STMungbean-STDSaman; T = puddled transplanted, CT = conventional tillage using power tiller operated seeder (PTOS) and seeding in a single pass; ST = strip tillage using PTOS and seeding in a single pass.

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6–10%. Yield declined from 4.3 t ha−1 in the first year to 3.5–3.6 t ha−1 in subsequent years in the system with T.aman, and to 3.9–4.0 t ha−1 in the systems with DSaman.

and the long term average. There was considerable variation in mean monthly solar radiation across the four years (Fig. 1c). 3.2. Crop duration

3.3.1.2. Irrigation. Irrigation input to wheat ranged from 189 to 328 mm over treatments and years, and was never affected by CSE (Table 5). However, there was a very small but significant reduction in irrigation input with aman residue retention of 15–25 mm in years 2–4.

The duration of the wheat crops (sowing to harvest) ranged from 112 to 119 d over the four years (Table 3). The duration of mungbean was about two thirds that of the wheat. The in-field duration of T.aman was similar to that of wheat, while that of DSaman was 14–19 d longer. The in-field duration of T.boro ranged from 116 d for the crop sown on 6 December 2014 to 145 d for the 2012–13 crop which was sown almost three weeks earlier, and which experienced much cooler weather during the first three months after sowing than in other years (Fig. 1b). Thus the total in-field duration of crops in the T.boro-T.aman system (228–259 d) was much less than that of the wheat-mung-T.aman system (296–308 d), while the wheat-mung-DSaman system was 14–19 d longer.

3.3.1.3. Irrigation water productivity. Grain WPI of wheat ranged from 8.9 to 23.3 kg ha−1 mm−1 over treatments and years. Grain WPI of wheat was significantly higher following DSaman than T.aman, by 16–18% (Table 6), due to higher yield. Grain WPI with aman residue retention was significantly higher than without retention in all four years, by 16–18%, due to higher yield and lower irrigation input. 3.3.2. T.boro 3.3.2.1. Grain yield. Yield of T.boro ranged from 7.5 to 8.7 t ha−1 over treatments and years. There were no significant effects of aman straw retention on T.boro yield in any year (Table 4). Yield was highest in 2011–12 (mean 8.5 t ha−1), and similar in the other three years (7.9–8.1 t ha−1).

3.3. Crop yield, irrigation input and water productivity The interaction between CSE and aman residue management on grain yield, irrigation input and irrigation water productivity was never significant for any crop. Therefore, only the main treatment effects are presented in the following sections. In the wheat-mung-DSaman systems (CSE3,4), there were no significant differences between full and strip tillage for any parameter for any crop.

3.3.2.2. Irrigation. There were no significant effects of aman straw retention on irrigation input to T.boro in any year (Table 5). Irrigation input declined progressively and by large amounts over the years, from 5960 mm to the 1st T.boro crop to 1890 mm to the 4th T.boro crop (7th puddled transplanted rice crop).Irrigation input to T.boro declined linearly and significantly (R2 = 0.99, p < 0.0001) with increase in the number of puddled transplanted crops, at an average of 686 mm per puddled transplanted crop.

3.3.1. Wheat 3.3.1.1. Grain yield. Wheat yield ranged from 3.3 to 4.4 t ha−1 across treatments and years. Grain yield was significantly affected by both CSE and aman straw retention from the second wheat crop onwards (Table 4). In years 2–4, yield of wheat in the systems with DSaman was significantly higher than in the systems with T.aman, by 9–13%, while rice straw retention significantly increased wheat yield by

3.3.2.3. Irrigation water productivity. Grain WPI of T.boro ranged from 1.3 to 4.0 kg ha−1mm−1over treatments and years, and was not

Table 4 Effect of cropping system/establishment method (CSE) and rice residue management on grain yield (t ha−1) of individual crops and on annual cropping system rice equivalent yield (REY, t ha−1) during 2011–12 to 2014–15, and averaged over the four years. Cropping system establishment methoda

Crop/system

CSE1 c

d

Aman residue managementb

CSE2

CSE3

CSE4

LSD0.05 for CSE

(−R)

(+R)

LSD0.05 for R

Wheat (2011/2) T.boro(2011/2) Mung (2012) Aman (2012) System REY (2011/2)

NA 8.49 NA 5.24 13.7

4.29 NA 1.41 5.28 15.7

4.26 NA 1.24 5.01 14.8

4.26 NA 1.27 5.07 15.0

NA NA n/s n/s 1.3

4.19 8.29 1.32 5.09 14.7

4.35 8.70 1.29 5.21 15.0

n/s n/s n/s n/s n/s

Wheat (2012/3) T.boro (2012/3) Mung (2013) Aman(2013) System REY(2012/3)

NA 7.95 NA 5.18 13.1

3.59 NA 1.29 5.22 14.3

4.03 NA 1.24 4.91 14.4

3.93 NA 1.24 4.94 14.3

0.3 NA n/s n/s n/s

3.67 7.51 1.22 5.03 13.6

4.03 8.38 1.29 5.10 14.5

0.2 n/s 0.1 n/s 0.5

Wheat (2013/4) T.boro (2013/4) Mung (2014) Aman(2014) System REY(2013/4)

NA 8.00 NA 5.09 13.1

3.51 NA 1.26 5.08 13.9

4.00 NA 1.22 4.89 14.3

3.92 NA 1.24 4.93 14.3

0.3 NA n/s n/s n/s

3.63 7.75 1.20 4.95 13.5

3.99 8.25 1.28 5.04 14.3

0.2 n/s n/s n/s 0.2

Wheat (2014/5) T.boro (2014/5) Mung (2015) Aman(2015) System REY(2014/5) Mean system REY

NA 8.07 NA 5.56 13.6 13.4

3.59 NA 1.40 5.53 15.0 14.7

3.94 NA 1.26 5.38 14.8 14.6

3.92 NA 1.32 5.32 14.9 14.6

0.2 NA n/s n/s 1.0 0.6

3.70 7.79 1.28 5.39 14.2 14.0

3.93 8.36 1.37 5.50 15.0 14.7

0.2 n/s 0.1 n/s 0.3 0.2

a CSE1 = T.boro-T.aman; CSE2 = CTWheat-CTMungbean-T.aman; CSE3 = CTWheat-CTMungbean-CTDSaman; CSE4 = STWheat-STMungbean-STDSaman; T = puddled transplanted, CT = conventional tillage using power tiller operated seeder (PTOS) and seeding in a single pass; ST = strip tillage using PTOS and seeding in a single pass. b −R = aman residues removed at ground level; +R = partial retention of aman residues (40 cm of standing stubble). c The were no CSE treatments in the first wheat crop, which was sown following tillage of the whole site and land levelling. d NA = not applicable.

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Table 5 Effect of cropping system/establishment method (CSE) and rice residue management on annual system irrigation input (mm) during 2011–12 to 2014–15 and averaged over the 4 years. Cropping system establishment methoda

Crop/system

Wheat (2011/2)c T.boro (2011/2) Mung (2012) Aman (2012) System total

Aman residue managementb

CSE1

CSE2

CSE3

CSE4

LSD0.05 for CSE

(−R)

(+R)

LSD0.05 for R

NAd 5956 NA 1328 7284

209 NA 63 1284 1556

204 NA 60 827 1091

204 NA 64 775 1043

NA1 NA n/s 103 410

218 6127 64 1067 2809

194 5785 61 1040 2677

12 n/s n/s n/s n/s

231 NA 262 679 1172

221 NA 254 649 1123

n/s NA n/s 81 203

240 4990 267 1058 2686

223 4553 258 1002 2501

10 n/s 7 n/s 179

Wheat (2012/3) T.boro (2012/3) Mung (2013) Aman (2013) System total

1441 6212

243 NA 271 1352 1866

Wheat (2013/4) T.boro (2013/4) Mung (2014) Aman (2014) System total

NA 2957 NA 1417 4375

317 NA 219 1357 1893

320 NA 199 497 1016

295 NA 194 458 948

n/s NA n/s 84 207

318 3054 211 952 2112

303 2861 197 913 2003

13 n/s 7 n/s 86

Wheat (2014/5) T.boro (2014/5) Mung (2015) Aman (2015) System total Mean system total

NA 1888 NA 759 2648 5130

295 NA 141 743 1180 1624

284 NA 135 513 932 1053

268 NA 130 498 895 1002

n/s NA n/s 177 300 220

295 1961 142 644 1462 2267

270 1816 129 612 1365 2137

20 n/s 12 n/s 72 107

4771

a CSE1 = T.boro-T.aman; CSE2 = CTWheat-CTMungbean-T.aman; CSE3 = CTWheat-CTMungbean-CTDSaman; CSE4 = STWheat-STMungbean-STDSaman; T = puddled transplanted, CT = conventional tillage using power tiller operated seeder (PTOS) and seeding in a single pass; ST = strip tillage using PTOS and seeding in a single pass. b −R = aman residues removed at ground level; +R = partial retention of aman residues (40 cm of standing stubble). c The were no CSE treatments in the first wheat crop, which was sown following tillage of the whole site and land levelling. d NA = not applicable.

Table 6 Effect of cropping system/establishment method (CSE) and rice residue management on system irrigation WPI (kg ha−1 mm−1) during 2011–12 to 2014–15, and averaged over the 4 years. Cropping system establishment methoda

Crop/system

CSE1

Aman residue managementb CSE2

CSE3

CSE4

LSD0.05 for CSE

(−R)

(+R)

LSD0.05 for R

NA 1.43 NA 3.95 1.89

20.5 NA 22.4 4.11 10.1

20.9 NA 20.8 6.06 13.6

20.9 NA 19.8 6.54 14.4

NA1 NA n/s 0.6 1.2

19.3 1.35 20.8 4.77 9.74

22.4 1.50 21.3 5.01 10.2

1.0 n/s n/s n/s 0.4

Wheat (2012/3) T.boro (2012/3) Mung (2013) Aman (2013) System WPI

NA 1.67 NA 3.59 2.11

14.8 NA 4.76 3.86 7.66

17.5 NA 4.72 7.23 12.3

17.8 NA 4.88 7.62 12.7

2.1 NA n/s 0.9 1.0

15.3 1.51 4.57 4.75 8.29

18.1 1.84 4.99 5.09 9.14

1.2 n/s 0.3 n/s 0.4

Wheat (2013/4) T.boro (2013/4) Mung (2014) Aman (2014) System WPI

NA 2.71 NA 3.59 2.99

11.1 NA 5.75 3.75 7.37

12.5 NA 6.14 9.84 14.1

13.3 NA 6.36 10.8 15.1

0.9 NA n/s 1.7 1.1

11.4 2.54 5.72 6.77 9.38

13.2 2.89 6.47 7.21 10.4

0.7 n/s 0.6 n/s 0.7

Wheat (2014/5) T.boro (2014/5) Mung (2015) Aman (2015) System WPI Mean system WPI

NA 4.29 NA 7.32 5.15 2.61

12.2 NA 9.94 7.43 12.7 9.07

13.9 NA 9.34 10.5 15.9 13.9

14.7 NA 10.2 10.7 16.7 14.6

1.9 NA n/s 2.4 3.2 0.9

12.6 3.97 9.04 8.64 11.9 9.59

14.6 4.60 10.7 9.34 13.4 10.5

1.0 n/s 1.0 0.5 0.6 0.4

Wheat (2011/2) T.boro (2011/2) Mung (2012) Aman (2012) System WPI

c

d

a CSE1 = T.boro-T.aman; CSE2 = CTWheat-CTMungbean-T.aman; CSE3 = CTWheat-CTMungbean-CTDSaman; CSE4 = STWheat-STMungbean-STDSaman; T = puddled transplanted, CT = conventional tillage using power tiller operated seeder (PTOS) and seeding in a single pass; ST = strip tillage using PTOS and seeding in a single pass. b −R = aman residues removed at ground level; +R = partial retention of aman residues (40 cm of standing stubble). c The were no CSE treatments in the first wheat crop, which was sown following tillage of the whole site and land levelling. d NA = not applicable.

3.3.3. Mungbean 3.3.3.1. Yield. Mungbean yield ranged from 1.2 to 1.5 t ha−1 over treatments and years. There were no significant effects of CSE on mungbean yield (Table 4). Aman residue retention resulted in very

affected by aman residue retention (Table 6). Grain WPI increased over time due to the reduction in irrigation input, which more than offset the decrease in grain yield between the first and subsequent years.

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retention gave slightly but significantly higher (by 8%) grain WPI in 2015 than residue removal, but there was no effect in the first three years.

small but significant increases in yield in years 2 and 4, by 6 and 7%, respectively. Average yields were similar each year, at 1.2–1.3 t ha−1. 3.3.3.2. Irrigation. Irrigation input to mungbean varied from 59 mm in 2012 to 276 mm in 2013. There were no significant effects of CSE on irrigation input to mungbean (Table 5). However, aman residue retention resulted in very small but significant reductions in irrigation input in years 2–4, by 9–14 mm.

3.4. Total system As for each component crop, there were no significant interactions between CSE and aman residue management on system yield, irrigation input, WPI or protein output, so only the results of main treatment effects are presented below. Similarly, there were no significant differences between full tillage and strip tillage in the wheat-mungbean-DSaman systems. Furthermore, there were no significant CSE × R × Year interactions, therefore, it is valid to compare the system treatment means averaged over the four years.

3.3.3.3. Irrigation water productivity. Grain WPI of mungbean ranged from 4.5 to 23.1 kg ha−1mm−1over treatments and years, with much higher values in 2012 than in other years (Table 6) due to much lower irrigation input. There was no effect of CSE on WPI, however aman residue retention resulted in significantly higher WPi in years 2–4, by 9–18%.

3.4.1. System rice equivalent yield System yield ranged from 12.6 to 16.0 t ha−1 over treatments and years. There was a consistent trend for higher REY of the three wheatmungbean-aman systems than of the T.boro-T.aman system, with significant differences in years 1 and 4, and when the data were pooled over the four years (Table 4). There was also a trend for higher system yield with aman residue retention, with significant differences in years 2–4 and when averaged over the four years.

3.3.4. Aman 3.3.4.1. Grain yield. Yield of the aman crops ranged from 4.9 to 5.7 t ha−1over treatments and years. There were no significant effects of CSE or aman residue retention on grain yield of aman in any year (Table 4). Average yield was highest in 2015 (5.4 t ha−1) and least in 2014 (5.0 t ha−1). 3.3.4.2. Irrigation. Irrigation input to DSaman ranged from 440 to 847 mm, compared with amounts of 731–1517 mm to T.aman. Irrigation input to DSaman was significantly lower than to T.aman each year, by 33–66% (Table 5). Irrigation input to DSaman in 2012 (mean 801 mm) was higher than in the other three years (478–664 mm) due to lower rainfall and poorer rainfall distribution (Fig. 2a–d).

3.4.2. System irrigation input There was a highly significant (p < 0.0001) effect of CSE on system irrigation water input each year due to the much higher input to the T.boro-T.aman system, which was in turn due to the very high input to the continuously flooded T.boro crops (Table 5). Irrigation input to the wheat-mungbean-DSaman systems was significantly lower than to the same system with T.aman each year, by about 200–900 mm, the size of the difference decreasing as rainfall increased during the aman season. Aman residue retention significantly reduced system irrigation input in years 2–4 by about 100 mm (∼7%) each year.

3.3.4.3. Irrigation water productivity. Grain WPI ranged from 2.9 to 10.1 kg ha−1mm−1 over treatments and years. Grain WPI of DSaman was significantly higher than that of T.aman, by factors of 2.2–6.6 (Table 6), due to lower irrigation input to DSaman. There were no significant effects of tillage on grain WPI of DSaman. Aman residue

Table 7 Effect of CSE and rice residue management on annual cropping system grain protein output (kg ha−1) during 2011–12 to 2014–15, and averaged over the 4 years. Cropping system establishment methoda

Crop/system

CSE1

Aman residue managementb CSE2

CSE3

CSE4

LSD0.05 for CSE

(−R)

(+R)

LSD0.05 for R

d

NA 643 NA 397 1039

456 NA 265 400 1121

453 NA 234 383 1070

454 NA 240 397 1091

NA1 NA NS NS NS

446 627 249 401 1079

463 658 244 388 1082

NS NS NS NS NS

Wheat (2012/3) T.boro (2012/3) Mung (2013) Aman (2013) System total

NA 601 NA 392 994

382 NA 245 395 1022

429 NA 216 372 1017

418 NA 219 374 1011

29.0 NA 16.0 NS NS

391 568 225 381 985

429 634 228 386 1037

22.9 NS NS NS 51.9

Wheat (2013/4) T.boro (2013/4) Mung (2014) Aman (2014) System total

NA 606

373 NA 237 385 995

426 NA 230 370 1026

417 NA 233 373 1023

35.0 NA NS NS NS

386 587 226 375 981

424 625 240 381 1036

18 NS NS NS 14.8

382 NA 264 418 1064 1072

420 NA 237 407 1064 1043

418 NA 249 402 1069 1051

22.0 NA NS NS NS NS

394 589 241 408 1032 1033

419 632 259 416 1083 1059

20 NS 12 NS 18.7 NS

Wheat (2011/2) T.boro (2011/2) Mung (2012) Aman (2012) System total

c

Wheat (2014/5) T.boro (2014/5) Mung (2015) Aman (2015) System total Meansystem total

385 991 611 420 1031 1019

a CSE1 = T.boro-T.aman; CSE2 = CTWheat-CTMungbean-T.aman; CSE3 = CTWheat-CTMungbean-CTDSaman; CSE4 = STWheat-STMungbean-STDSaman; T = puddled transplanted, CT = conventional tillage using power tiller operated seeder (PTOS) and seeding in a single pass; ST = strip tillage using PTOS and seeding in a single pass. b −R = aman residues removed at ground level; +R = partial retention of aman residues (40 cm of standing stubble). c The were no CSE treatments in the first wheat crop, which was sown following tillage of the whole site and land levelling. d NA = not applicable.

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3.5. Crop and system economic performance

3.4.3. System irrigation water productivity In all years, CSE had a very large effect on system WPI, with highest values (12–17 kg ha−1 mm−1) for the wheat-mungbean-DSaman systems, followed by the same system with T.aman (7–13 kg ha−1 mm−1), and with by far the lowest WPI in the T.boro-T.aman system (2–5 kg ha−1 mm−1)(Table 6). Partial aman residue retention gave significantly higher system WPI over no residue retention each year due to a consistent trend for higher system yield and lower system irrigation input.

All crops were profitable, with positive gross margin and net return, and BCR > 1, regardless of the amount of labor costed in the analysis (Table 8). Gross margin of T.boro crops was 12–36% higher than that of the other crops due to the high yield of T.boro. However, with 100% of labor costed, the total cost of T.boro production was also 50–90% higher, mainly due to higher irrigation and labor costs (Tables 2a and 2b). The net result was similar gross margins (means USD340–360 ha−1) for T.boro, T.aman and DSaman crops, slightly lower gross margins for wheat (mean USD322 ha−1), and lowest gross margin for mungbean (mean USD289 ha−1). Net return was highest for mungbean (mean USD156 ha−1), almost double that of T.aman, while net return of wheat and DSaman were similar and intermediate in value.Net return of T.boro was low at USD25 ha−1 when 100% of labor was costed. Mean BCR was highest for mungbean and least for T.boro. All cropping systems were also profitable (Table 9). Differences in gross return (range USD2830–2970 ha−1) and total cost (USD2600–2730) were relatively small. With 100% of labor costed, gross margin ranged from USD689–868 ha−1, while net return ranged from USD100–320 ha−1 and BCR from 1.04–1.12. Gross margin of the triple cropping systems was USD170–180 ha−1 (25%) higher than that of the T.boro-T.aman system, while net return was USD180–220 ha−1

3.4.4. System protein output There was no significant effect of CSE on system protein output in any year (Table 7). In years 2–4, protein output of wheat in the system with T.aman was significantly lower than in the systems with DSaman. However, this was compensated for by higher protein output of mungbean in the system with T.aman. In years 2–4, partial aman rice residue retention increased system protein output slightly but significantly (by 5–6%) due to an increase in wheat protein output (years 2–4) and in mungbean in the fourth year. However, when averaged over the four years, the effect was not significant, with an average protein output in the grain of 1046 kg ha−1.

Table 8 Economics of the four crops grown in the cropping systems. Data are mean ± standard error in USD (1USD = 78.0 BDT). Economic parametera

Wheat

Mungbean

T.boro

Aman

Mean

Mean

Mean

T.aman Mean

DSaman Mean

A. Gross return Activity 0–100%

1009 ± 27

822 ± 14

1692 ± 41

1141 ± 31

1090 ± 32

B. Total Activity Activity Activity Activity Activity

688 631 574 517 460

532 466 401 335 270

1335 1223 1112 1001 890

799 712 626 539 453

738 667 596 525 453

C. Total fixed cost Activity 100% Activity 75% Activity 50% Activity 25% Activity 0%

183 181 179 177 175

133 132 130 128 127

332 326 320 314 308

257 253 249 245 241

231 228 225 222 219

D. Total costs (B + C) Activity 100% Activity 75% Activity 50% Activity 25% Activity 0%

871 812 753 694 635

665 598 531 463 397

1667 1549 1432 1315 1198

1056 965 875 784 694

969 895 821 747 672

E. Gross margin (A–B) Activity 100% Activity 75% Activity 50% Activity 25% Activity 0%

321 378 435 492 550

± ± ± ± ±

33 33 33 33 33

289 355 420 486 551

± ± ± ± ±

15 15 15 15 15

358 469 580 691 802

Activity Activity Activity Activity Activity

139 198 257 316 375

± ± ± ± ±

33 33 33 33 33

156 223 290 357 424

± ± ± ± ±

15 15 15 15 15

1.16 1.24 1.34 1.45 1.59

± ± ± ± ±

0.04 0.04 0.04 0.05 0.05

1.23 1.37 1.55 1.77 2.07

± ± ± ± ±

0.02 0.02 0.02 0.03 0.03

variable cost 100% 75% 50% 25% 0%

100% 75% 50% 25% 0%

G. BCR (undiscounted) (A/D) Activity 100% Activity 75% Activity 50% Activity 25% Activity 0% a

Activity% is the% of total labor requirement costed in the analysis.

21

± ± ± ± ±

31 31 31 31 31

352 423 494 565 637

± ± ± ± ±

32 32 32 32 32

25 ± 41 142 ± 41 260 ± 41 377 ± 41 494 ± 41

86 ± 31 176 ± 31 267 ± 31 357 ± 31 447 ± 31

121 195 269 344 418

± ± ± ± ±

32 32 32 32 32

1.02 1.09 1.18 1.29 1.41

1.08 1.18 1.30 1.46 1.64

1.12 1.22 1.33 1.46 1.62

± ± ± ± ±

0.03 0.04 0.04 0.04 0.05

± ± ± ± ±

41 41 41 41 41

0.02 0.03 0.03 0.03 0.03

342 429 515 602 688

± ± ± ± ±

± ± ± ± ±

0.03 0.03 0.03 0.04 0.04

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fitting wheat and mungbean crops with dry seeded aman has not previously been reported in this region. The results show that such a system is feasible using available varieties, and that it is possible to plant all crops at the optimum time and achieve good yields. The average duration of the fallow period between crops in the dry seeded aman system ranged from 18 to 22 d, suggesting ample time for turnaround between crops. However, planting each crop at the optimum time allowed a gap of only 5–7 d between wheat harvest and mungbean sowing, while the gap between sowing and harvest of all other crops in the triple cropping system ranged from 10 to 28 d. Relay sowing of the mungbean could be another option for ensuring timely establishment.

Table 9 Economics of the four cropping system/establishment method CSE) treatments evaluated in the field experiment. Data are mean ± standard error in USD (1USD = 78.0 BDT). Economics

CSE1 Mean

CSE2 Mean

CSE3 Mean

CSE4 Mean

2833 ± 49

2972 ± 53

2920 ± 54

2920 ± 54

2113 1901 1690 1478 1267

2052 1855 1659 1463 1267

2052 1855 1659 1463 1267

573 565 558 550 543

547 540 534 527 521

547 540 534 527 521

D. Total costs (B + C) Activity 100% 2733 Activity 75% 2523 Activity 50% 2313 Activity 25% 2103 Activity 0% 1893

2686 2467 2247 2028 1809

2599 2396 2193 1991 1788

2599 2396 2193 1991 1788

E. Gross margin (A–B) Activity 100% 689 ± 49 Activity 75% 889 ± 49 Activity 50% 1089 ± 49 Activity 25% 1289 ± 49 Activity 0% 1489 ± 49

859 ± 53 1071 ± 53 1282 ± 53 1494 ± 53 1705 ± 53

868 ± 54 1065 ± 54 1261 ± 54 1457 ± 54 1653 ± 54

868 ± 54 1065 ± 54 1261 ± 54 1457 ± 54 1653 ± 54

F. Net return (A–D) Activity 100% Activity 75% Activity 50% Activity 25% Activity 0%

286 ± 53 505 ± 53 725 ± 53 944 ± 53 1163 ± 53

321 ± 54 524 ± 54 727 ± 54 929 ± 54 1132 ± 54

321 ± 54 524 ± 54 727 ± 54 929 ± 54 1132 ± 54

1.11 1.20 1.32 1.47 1.64

1.12 1.22 1.33 1.47 1.63

1.12 1.22 1.33 1.47 1.63

A. Gross Return Activity 0–100% B. Total Activity Activity Activity Activity Activity

variable cost 100% 2144 75% 1944 50% 1744 25% 1544 0% 1344

C. Total fixed cost Activity 100% Activity 75% Activity 50% Activity 25% Activity 0%

589 579 569 559 549

100 310 520 730 940

± ± ± ± ±

49 49 49 49 49

G. BCR (undiscounted) (A/D) Activity 100% 1.04 ± 0.02 Activity 75% 1.12 ± 0.02 Activity 50% 1.22 ± 0.02 Activity 25% 1.35 ± 0.02 Activity 0% 1.50 ± 0.03

± ± ± ± ±

0.02 0.02 0.02 0.03 0.03

± ± ± ± ±

0.02 0.02 0.02 0.03 0.03

4.2. Effect of cropping system/establishment (CSE) method on crop and system yield

± ± ± ± ±

4.2.1. DSaman vs T.aman in the wheat-mungbean-aman system The adverse effect of puddling for the aman crop on other crops in the wheat-mungbean-aman system commenced after the first year of puddling. This is consistent with the findings on soils with a history of puddling (converse to the situation in the present study), where replacement of puddling and transplanting with dry seeding of rice resulted in higher yield of wheat starting with the second or third wheat crop (e.g. Kumar et al., 2008; Gathala et al., 2011; Jat et al., 2014). In the present study, the relative decline in wheat yield following T.aman in comparison with DSaman did not increase as the number of puddled transplanted crops increased, also the case in a 7-year experiment on a clay loam in Bihar, India (Jat et al., 2014). However, in the latter study, the relative yield increase following DSR was usually much larger than in our experiment at Jessore. In contrast to our study and that of Jat et al. (2014), Gathala et al. (2011) found a trend for increasing relative yield of wheat following DSR compared with PTR over the years. The reasons for the different findings are not known. The higher yield of wheat grown after DSaman than after T.aman is likely to be due to improved soil structure (Gathala et al., 2011; Dhiman et al., 1998; Gangwar et al., 2008). In contrast to wheat, there was no effect of CSE on yield of mungbean or rice in all four years. The effect of rice tillage/establishment on the performance of mungbean in rice-wheat-mungbean systems has not previously been reported to our knowledge. In systems with PTR, the effect of tillage method for mungbean was variable (Alam et al., 2014; Islam et al., 2014; Kader et al., 2014). Reports on the grain yield of well-managed DSR relative to that of PTR show variable results (Kumar and Ladha, 2011). In our study, the grain yield of DSaman and T.aman were similar each year, consistent with the findings of Sudhir-Yadav et al. (2011a), Bhushan et al. (2007) and Singh et al. (2009) on a range of soil types (sandy loam, silty loam, clay loam). Importantly, the same water management (safe AWD) was used for both establishment methods in those three studies, as in our study. In contrast, other studies in the northwest Indo-Gangetic Plain (IGP) often show a yield penalty with DSR (Ladha et al., 2009; Gathala et al., 2011; Jat et al., 2009; Saharawat et al., 2009). Poor performance of DSR relative to PTR could be due to factors such as sub-optimal water, nutrient and weed management (Johnson and Mortimer, 2005; Sudhir-Yadav et al., 2011a,b), iron deficiency (Sudhir-Yadav et al., 2011a) and problems with soil pathogens (Kumar and Ladha, 2011). The higher wheat yield in the systems with DSR did not translate into higher annual system REY, as this was compensated for by a consistent trend (not significant) for higher yield of T.aman than DSaman.

0.02 0.02 0.02 0.03 0.03

1 CSE1 = T.boro-T.aman; CSE2 = CTWheat-CTMungbean-T.aman; CSE3 = CTWheatCTMungbean-CTDSaman; CSE4 = STWheat-STMungbean-STDSaman; T = puddled transplanted, CT = conventional tillage using power tiller operated seeder (PTOS) and seeding in a single pass; ST = strip tillage using PTOS and seeding in a single pass

higher. The higher profitability of the triple cropping systems was due to slightly higher returns (more so CSE2), and lower variable costs (more so CSE3,4). Gross and net returns and BCR of the triple cropping systems with DSaman and T.aman were similar. Profitability was strongly affected by the proportion of labor costed in the analysis, but the effect on relative profitability of the four systems was much less (Table 9). For example, with 75% of labor costed, both gross margin and net return of all systems increased by about USD200 ha−1 compared with these values when 100% of labor was costed, while BCR increased from 1.1 to 1.2. The effect of reducing the proportion of labor costed in the analysis was almost entirely due to lower variable costs. 4. Discussion 4.1. Feasibility of a dry seeded rice-wheat-mung system

4.2.2. T.boro-T.aman versus wheat-mung-aman The higher REY of the wheat-mung-aman systems than the T.boroT.aman system was due to the higher price received by farmers for mungbean and wheat than for rice, which more than compensated for their much lower yields in comparison with T.boro. The similar grain

The feasibility of intensifying and diversifying the puddled transplanted aman-wheat system by adding mungbean is well established in the High Ganges River Floodplain and other parts of Bangladesh (Hossain et al., 2016; BARC, 2012). However, the feasibility of annually 22

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(25–40 DAS) (also shown by Sudhir-Yadav et al., 2011b), and to finish the crops as a result of low rainfall in September combined with the later maturity of the T.aman crops (Table 11). Sometimes the soil cracked between irrigations, and the cracks appeared to be larger in the PTR. The greater cracking in PTR may have increased the rate of soil drying and thus contributed to the higher irrigation requirement of PTR, as found by Sudhir-Yadav et al. (2011b). In the last year, due to high rainfall, there was little irrigation requirement until the grain filling period, and thus a much smaller difference in irrigation requirement of T.aman and DSaman crops than in the other three years. The irrigation water input for puddling varied from 60 to 210 mm over the years, reflecting variability in rainfall prior to puddling. The irrigation requirement for puddling was generally of similar magnitude to that for establishment of the DSaman between sowing and the time of transplanting. However, this could vary depending on the incidence and amount of rainfall. Over the whole season, Sudhir-Yadav et al. (2011b) found a 30% irrigation reduction with DSR compared with PTR with the same safe AWD water management, compared with a 33–66% reduction in the present study. Whether such large reductions would be achieved in farmers’ fields is questionable, as seepage from small plots is disproportionately high due to the large perimeter to area ratio (Humphreys et al., 2008). The variation in irrigation water savings with DSR in our study was associated with rainfall variability.

protein yield of both systems was a result of the higher yield of T.boro which compensated for its lower protein content. While both systems had the same protein output, a much larger quantity of rice (2.4 kg) or wheat (1.7 kg) would need to be consumed to achieve the same level of protein consumption as 1 kg of mungbean. Furthermore, rice and wheat are lacking in some of the essential amino acids found in mungbean, which also provides better mineral nutrition. 4.3. Effect of aman residue retention on crop and system yield The improved wheat crop performance with rice straw retention could be due to higher topsoil water content and its influence on tiller density. Tensiometer data (not presented) showed a trend for the topsoil to dry more slowly after irrigation, consistent with the findings of other studies in the region (e.g. Rahman et al., 2005; Sidhu et al., 2007; Balwinder-Singh et al., 2011a). The higher soil water content with surface residue retention is due to suppression of soil evaporation by the mulch (Balwinder-Singh et al., 2011a,b). In the present experiment, a considerable amount of straw remained on the surface when wheat was sown into the standing residues using both strip and full tillage with the PTOS. The trend for higher spike density (Table 10) in the straw retained treatment was a result of lower tiller mortality (data not presented), as also suggested by Gupta et al. (2016). The significant response of mungbean to aman straw retention in years2 and 4 cannot be explained with the available data. By the time of mungbean sowing, there was little undecomposed rice straw remaining on the soil surface. There was no effect of aman straw retention on yield of either T.aman or DSaman in any system, nor on yield of T.boro. Other studies in rice-wheat systems in north west India found that yield benefits of rice straw incorporation did not appear in rice until the fourth crop (Verma and Bhagat, 1992), or that the benefits were small during the first six years (Yadvinder-Singh et al., 2005). In those studies, the amounts of straw retained (2.2–6.0 t ha−1) were usually much larger than in our experiment (∼2 t ha−1). The net result of aman residue retention in the present experiment was significantly higher system REY from the second year onwards, and averaged over the four years (by 0.7 t ha−1). This was mostly due to higher wheat yield.

4.4.3. System irrigation input The much higher total irrigation input to the T.boro-T.aman system (2600–7300 mm) than all other cropping systems (900–1900 mm) was due to the very high irrigation input to the T.boro. This probably reflected the fact that the site had not previously grown PTR, together with the fact that the T.boro crops were kept flooded. The input to T.boro declined linearly from 5960 mm in the first crop to 1888 mm in the fourth T.boro crop (7th puddled transplanted crop). The first T.boro crop had to be irrigated daily (and twice daily in early stages) to try and maintain ponding/soil saturation, compared with every second day in the second T.boro crop, every 2–3 d in the third T.boro crop, and every 3–4 d in the fourth T.boro crop, suggesting a reduction in infiltration rate due to the gradual development of a plow pan with successive PTR crops. Irrigation input to the wheat-mungbean-T.aman system was significantly higher (by 265–900 mm) than to the same systems with DSaman due to the higher irrigation input to T.aman than DSaman, as discussed above.

4.4. Effect of cropping system/establishment method (CSE) and aman straw retention on irrigation input

4.5. Economics

4.4.1. Wheat Aman residue retention reduced irrigation input slightly (by ∼20 mm), much less than the reduction commonly observed in studies in northwest India (e.g. Balwinder-Singh et al., 2011a; Gupta et al., 2016). While surface residue retention in our study had a small effect on soil water content in the topsoil, it had negligible effect deeper in the root zone (data not presented), in contrast with the findings of Yadvinder-Singh et al. (2008) and Balwinder-Singh et al. (2011a) where soil water content was affected to a depth of 40 cm. These differences with our study may reflect the higher level of rice residue retention (6–8 t ha−1), and longer duration (∼160 d) and greater growth of the wheat varieties grown in northwest India. The effect of surface residue retention on irrigation requirement also depends on seasonal weather conditions. In northwest India, with irrigations scheduled when soil water deficit increased to 50% of plant available water capacity, the number of irrigations was reduced by one in about 50% of years (Balwinder-Singh et al., 2016). In our study, the crops were irrigated according to growth stage, so there was no effect of aman residue retention on the number of irrigations.

All crops and cropping systems were profitable; however, all three triple cropping systems were more profitable than the T.boro-T.aman system. The economic performance of the three triple cropping systems was always similar in terms of gross margin, net return and BCR, regardless of the method of rice establishment. Gross margin of the triple cropping systems was higher by an average of USD180–190 ha−1, while net return was higher by USD190–220 ha−1, than of the T.boroT.aman system. The reduction in the cost of production in switching from T.aman to DSaman in the wheat-mungbean-aman system was ∼USD15–63 ha−1, within the range (USD9–125 ha−1) of the findings of the review of Kumar and Ladha (2011). The main reasons for the cost Table 10 Effect of aman residue management on spike density (no. m−2) of wheat.

4.4.2. Aman The main reasons for the higher irrigation input to T.aman than DSaman were the water requirement for ponding for the first 15 DAT

Aman residue managementa

2011–12

2012–13

2013–14

2014–15

−R +R Lsd0.05

378 388 NS

301 333 17

302 330 27

290 314 7

a −R = aman residues removed at ground level; +R = partial retention of aman residues (40 cm of standing stubble).

23

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Table 11 Total amount of irrigation and rainfall received during different crop stages of T.aman and DSaman during 2012–2015. Number of irrigations in parentheses. Crop stagea

2012

2013

Irrigation (mm) PTR Sowing to 25 DAS Puddling 25 to 40 DAS 40–80 DAS 80 DAS to PM Total a

Rainfall (mm)

DSR

104 263 281 801

Irrigation (mm) PTR

153 (3) 147 (3) 438 (9) 428 (8) 293 (4) 1306 (24)

(2) (5) (5) (15)

261 138 337 148 884

2014 Rainfall (mm)

DSR

123 218 186 664

Irrigation (mm) PTR

137 (2) 209 (3) 486 (9) 362 (6) 340 (5) 1397 (23)

(2) (4) (3) (11)

2015

DSR

163 120 365 348 996

Rainfall (mm)

Irrigation (mm) PTR

DSR

495 59 (1) 438 (8) 258 (3) 632 (10) 1387 (22)

Rainfall (mm)

556 100 (2)

64 (1) 54 (1) 360 (8) 478 (10)

114 282 144 1035

95 (2) 556 (9) 751 (13)

152 (3) 353 (7) 505 (10)

80 363 44 1043

DAS = days after sowing, PM = physiological maturity.

margin, net return and BCR when considering 100% of the cost of labor (close to the case for large farmers (> 3 ha)). This was still the case when it was assumed that some or much of the labor was provided by the farmer and family and not costed, as in the case of marginal farmers (almost all labor provided by the farmer and family), and small farmers (about 75% of the labor provided). Most farmers in this region are small (38% with 0.01–1 ha) or marginal (30% with < 0.01 ha)(Personal communication, Regional Office of the Department of Agricultural Extension, Jessore). The effects of rice establishment and tillage methods on REY and profitability of the triple cropping systems were negligible. Total labor requirement of the triple cropping system with DSaman (204 man-days) was similar to that of the T.boro-T.aman system (208 man-days), while that of the triple cropping system with T.aman (220 man-days) was slightly higher. However, the labor requirement was spread more evenly across the year in the triple cropping systems, reducing the demand at peak periods (especially transplanting and harvesting) and providing more continuous employment opportunities for farm laborers.

reduction with DSaman were the high tillage cost for puddling, and the high labor requirement for uprooting, hauling and transplanting the seedlings for PTR. As a result, the total system cost increased slightly with the number of PTR crops per year (none in CSE3,4, one in CSE2 and two in CSE1), by an average of USD130 when going from CSE3,4 to CSE1. The cost of irrigation of the T.boro crops (supply of water and labor) also contributed greatly to the higher production cost of CSE1.

4.6. Tradeoffs and optimum cropping system/establishment method The results clearly demonstrate the biophysical and economic feasibility of all four cropping systems evaluated. There was good yield stability of individual crops and the total system over the wide range of weather conditions experienced by each crop over the four years, demonstrating that all systems are suited to this environment. However, successful implementation of the wheat-mungbean-DSaman system is more demanding than the other systems due to the need for timely establishment and harvest of each crop, whereas there is more flexibility with the T.boro-T.aman system. For example, transplanting of the T.boro crop will not be affected even if the aman crop is not harvested until December, whereas the optimum time for planting wheat is mid November, which in turn enables seeding of mungbean and DSaman to take place at the optimum times. Where labor shortage and cost are issues for establishment of the aman crop, dry seeding provides the advantage of greatly reduced labor cost for crop establishment, together with more timely and rapid planting. The studies of Ahmed et al. (2014) indicate that late May/ early June is the optimum time for dry seeding in this region, prior to the onset of the monsoon rains, thus reducing the risk of the soil being too wet for dry seeding and the risk of establishment failure from rains shortly after sowing. While in theory it would also be possible to have a dry seeded boro-dry seeded aman system to reduce labor requirement and establishment costs, this is not a good option with current boro varieties. Ahmed et al. (2016) found that dry seeding from early November to late January is too risky in Jessore and other major boro regions because of cold damage during crop establishment. Dry seeding of the aman crop also brings the advantage of reduced irrigation requirement in comparison with puddling and transplanting. Reduced irrigation requirement is also a big advantage of the triple cropping system in comparison with the T.boro-T.aman system. The main benefit to farmers is reduced labor requirement for irrigation, as the price farmers pay for irrigating the crop is currently not related to the amount of water applied. In the Jessore region, farmers usually pay a fixed amount (USD577 ha−1) to tubewell owners for irrigation water for the T.boro crop. The high cost reflects the high irrigation requirement for puddled transplanted boro grown with continuous flooding/ soil saturation. On the other hand, for aman, wheat, mungbean and other crops they usually pay an hourly pumping rate (USD1.3–1.5 h−1). The triple cropping systems had higher REY (by an average of 9% or 1.2 t ha−1) than the T.boro-T.aman system, and much higher gross

5. Conclusions This study has shown that, in terms of economics and labor and irrigation water requirements, the wheat-mungbean-aman systems were superior to the T.boro-T.aman system. Furthermore, while total protein output in the grain from each system was similar, the quality of the protein was better in the triple cropping systems, and with much greater diversity in terms of grain type and potential uses. However, these benefits came at the expense of reduced rice production, from an average of about 13 t ha−1 yr−1 to 5 t ha−1 yr−1. Furthermore, in lower lying, poorly drained parts of the landscape, timely establishment of wheat after aman harvest may not be feasible. Therefore, implementation of the triple cropping system should only be recommended for well-drained lands. The triple cropping systems with DSaman were superior to the system with T.aman in terms of lower labor and irrigation requirements, and with negligible differences between the use of full and strip tillage to establish all crops. In view of the considerable malnutrition in Bangladesh, diversifying from the puddled transplanted T.boro-T.aman system to more diverse triple cropping systems such as the wheat-mungbean-aman system should be promoted on lands suited to this cropping system. For maximum wheat and mungbean productivity and reduced irrigation requirement, dry seeding of the aman crop should also be promoted. Acknowledgements We acknowledge the support of the International Fund for Agricultural Development (IFAD) though the IRRI-led project C-ECG46 ‘Accelerating resource-conserving technology (RCT) adoption to improve food security and rural livelihoods while reducing adverse environmental impacts in the Indo-Gangetic Plains (IGP)’, and the 24

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