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Wheat–maize–rice Cropping on Permanent Raised Beds in Bangladesh

A.S.M.H.M. Talukder
Senior Scientific Officer (Agronomy), Wheat Research Centre, BARI, Nashipur, Dinajpur-5200

C.A. Meisner
Cornell University International Adjunct Professor, Road 68, House 14B, Apt 5, Gulshan-2, Dhaka-1212

M.E. Baksh
Senior Scientific Officer (Agricultural Economics), Wheat Research Centre, BARI, Nashipur, Dinajpur-5200

S.R. Waddington
Regional Agronomist, CIMMYT, PO Box 6057, Gulshan, Dhaka-1212, Bangladeh

Abstract/ Executive Summary:

Rice–wheat (RW) cropping systems are critical to food security of the increasing population in Bangladesh. However, the sustainability of RW systems is threatened by productivity decline and environmental sustainability. Crop production on permanent raised beds (PRB) is expanding worldwide as a way to increase system productivity, diversify cropping and improve the efficiency of resource use, especially water. When coupled with raised beds, straw retention can improve soil moisture retention, soil health and crop productivity. A 3-year study was conducted at the Wheat Research Centre, Dinajpur, Bangladesh, to compare the effects of four N fertiliser rates (0%, 50%, 100% and 150% of the recommended rate) and four straw retention (SR) / tillage treatments (100% SR of all crops + permanent raised beds (PRB), 50% SR + PRB, 0% SR + PRB and 0% SR + conventional tillage on the flat (CTF)) in a RW–maize cropping system. Permanent beds with straw retention produced the highest grain yields for all three crops in the sequence. Within each N rate the total system (rice+wheat+maize) productivity was greatest with 50–100% SR on PRB and least in CTF with zero straw retention. At 100% of recommended fertiliser N rate, mean annual system productivity was 17.9–19.7 t/ha for PRB with 50–100% SR, 15.7 t/ha with PRB without SR and 14.1 t/ha with CTF without straw. For all three crops, yields of PRB with 50% and 100% SR were similar. These benefits from straw retention with PRB were established within 2–3 years. Yield in N-unfertilised plots increased when straw was retained due to increased supply and uptake of N. The results suggest that N fertiliser rates can be reduced when straw is retained. Soil organic matter in surface soil layers of the PRB had increased by 13–41% after 4 years (ie four rice+wheat+maize crop cycles) with straw retention, with a greater increase with 100% SR than 50% SR. Soil organic C in PRB without SR was similar to the initial organic C prior to bed formation. Straw retention is an important component of soil management and may have long-term positive impacts on soil quality. Compared with conventional tillage on the flat with all crop residues removed, the combination of PRB with residues retained appears to be a very promising technology for sustainable intensification of RW systems in Bangladesh.

Keywords: Wheat–maize–rice cropping pattern, Raised beds, Bangladesh

Location: Bangladesh

Start Date:

End Date:

Program Area: Crop-Soil-Water Management

Commodity: Cropping pattern

Objectives:

• evaluate yields of intensive multicrop wheat– maize–rice sequences on PRB compared with those grown on conventionally tilled flat systems • assess the effect of mulching on crop performance and soil properties on PRB • assess N level effects on yield and estimate N use efficiency • study the changes in soil properties over time.

Methodology:

A cool season wheat (Triticum aestivum) – spring maize (Zea mays) – monsoon rice (Oryza sativa) cropping pattern was implemented over 5 years, starting with maize sown in April 2002, at the Wheat Research Centre, Nashipur, Dinajpur, Bangladesh (25o38'N, 88o41'E, 38.2 m above sea level). The site has a subtropical climate and is located in Agroecological Zone 1 (Old Himalayan Piedmont Plains) on flood-free high land, with course-textured, highly permeable soil (BARC 1997). The area receives 1,757 mm mean annual rainfall, about 97% of which occurs from April to October. Total rainfall was highest during the maize season and lowest in the wheat season in all years. Mean minimum and maximum temperatures during the rice season (July to November) were 22.6 °C and 31.3 °C, during the wheat season (November to March) 13 °C and 27 °C, and for the maize season (April to July) 23 °C and 33 °C. Monthly distribution of rainfall, and minimum and maximum temperatures for the experimental period (April 2004 to March 2007) are shown in Figure 1. The soil at the experimental site was a non-calcareous brown sandy loam Haplaquept with moderate acidity (pH 5.5), low organic matter (0.8%) and low nitrogen (mineral N 35 µg/g soil). The trial involved a three-crop (rice–wheat–maize (RWM)) annual rotation planted on raised beds or cultivated flats. Rice was transplanted (one 15-dayold seedling per hill) with hill-to-hill spacing of 15 cm and line-to-line spacing on the beds of 30 cm in late July and harvested in late November by hand. Wheat was planted at the nationally recommended seeding rate of 100 and 120 kg/ha for beds and conventional layout, respectively, in late November and harvested in late March. Intercropped maize and mungbean (Vigna radiata) were planted at the same time at the nationally recommended seeding rate of 35 kg/ha for maize and 10 kg/ha for mungbean in early April and harvested in mid July for both beds and conventional layout. The trial was originally established as a PRB experiment with three straw management practices (main plots—100% straw retention (SR), 50% SR and 0% SR) and four N levels (subplots—0%, 50%, 100% and 150% of recommended). The area of each subplot was 15 m2 (5 × 3 m;). After completion of two crop cycles (2002 maize to 2003–04 wheat), the experiment was modified by the introduction of conventional tillage on the flat with no straw retention (CTF + 0% SR), starting with 2004 spring maize. This treatment was applied to three new plots adjacent to the original experiment. Thus, the modified experiment consisted of 16 subplots with four tillage/straw treatments (100% SR + PRB, 50% SR + PRB, 0% SR + PRB and 0% SR + CTF) and four N levels (0%, 50%, 100% and 150% of recommended) with three replicates. After planting the wheat, maize or rice, straw from the preceding cereal crop was returned as a mulch to the plot from which it had been removed at harvest. After harvesting and threshing, the rice and wheat straw were returned without chopping. The maize stems were cut into ~20-cm-long pieces using a knife before returning them to the field. A spade was used to clean out the furrows and reshape the beds once a year, prior to sowing wheat.

Source of Information: ACIAR PROCEEDINGS No.127 pp111-123

Article Link (Online Journal):

Funding Source:

1.

Budget:

Total Budget (Tk.) :

Achievement/Findings:

Retention of at least 50% of crop residues together with zero-till permanent bed soil systems offer an important soil restorative management strategy likely to have a long-term positive impact on soil quality and crop productivity in intensive rice–wheat–maize (RWM) cropping systems in Bangladesh. Lignified residual straw and roots added more organic matter and nutrients into the soils under PRB, resulting in increased nutrient uptake by the crops. Crop yields on beds with 50% straw retention rose by about 7% for rice, 12% for wheat and 18% for maize at 100% N rates over a 3-year cycle of the RWM cropping pattern compared with 0% SR + PRB at the same N rate. Compared with conventional tillage on the flat, crop yields on PRB with 50% straw retention rose by 17%, 22% and 35% for rice, wheat and maize crops, respectively, at 100% N rates over a 3-year cycle of the RWM cropping pattern. Yield in N-unfertilised rice, wheat and maize increased when straw was retained, and this appeared to be due to an increased uptake of N. This increase in soil N supply led to a reduction in N use efficiency in the N-fertilised plots, suggesting that N fertiliser application rates can be reduced when straw is retained. Retention of crop residues as a mulch reduced moisture depletion and increased SOM content over relatively short periods of time. Fertiliser use efficiency may be increased by implementing permanent bed management in addition to reducing weed and crop lodging problems. Permanent raised beds will also help ameliorate the adverse effects of tillage on soil structure, which lead to waterlogging under excess water conditions and hamper establishment, growth and development of most crops including maize. The use of PRB reduced the overall cost of production and long turnaround time (data not presented). Thus, our results showed that PRB with straw retention can help to sustainably intensify RW systems to RWM systems under high degrees of management on research stations in Bangladesh. Further on-farm adaptive research with farmers now appears warranted.

Knowledge Management: Report/Proceedings