Abstract
Cropping systems in the High Ganges River Floodplain of Bangladesh are highly diverse, but
usually include puddled transplanted rice (PTR) during the rainy season. Establishment costs of
PTR are high due to intensive tillage and high labour requirement for transplanting. Furthermore, puddling damages soil structure for non-rice crops, and groundwater levels are declining due to large amount of pumping for boro rice crop. Therefore, improved systems are needed which reduce tillage, labour and water requirement while increasing productivity to
feed the growing population. To address these concerns, a replicated cropping system
experiment was conducted to evaluate cropping system intensification with varying degrees of tillage and labour requirement. The experiment was conducted on a clay loam soil at Regional
Agricultural Research Station, Bangladesh Agricultural Research Institute, Jessore during 2011-2013.
Four cropping systems/establishment methods (CSE) were compared: CSE1: T. Boro rice-T. Aman rice
(control), CSE2: Wheat-Mungbean-T. Aman rice (wheat and mungbean sown using a power
tiller-operated seeder, PTOS, with full tillage and sowing in a single pass; puddled transplanted aman), CSE3: Wheat-Mungbean-DS Aman rice (dry-seeded rice (DSR), wheat, and mungbean all
sown using a PTOS with full tillage), and CSE4: Wheat-Mungbean-DS Aman rice (all sown
using a PTOS with strip tillage). Two levels of Aman residue retention (removed; partial
retention - 40 cm of standing stubble) were compared in sub plots. Rice water management was
continuous flooding in both crops in CSE1, and safe alternate wetting and drying (AWD) in
CSE2-4. System productivity (rice equivalent yield, REY) of all Wheat-Mungbean-Aman systems
(CSE2-4) was significantly higher than that of T. Boro rice-T. Aman rice (CSE1) in the first year,
and when averaged over the first two years (by 10% or 1.4 t ha-¹). This was due to higher prices
paid to farmers for mungbean and wheat, which more than offset the lower grain yield in
comparison with Boro rice yield. Profitability of the Wheat-Mungbean-Aman systems was 54%
higher than that of T. Boro rice-T. Aman rice system due to both higher returns and lower cost of
production. Productivity of the Wheat-Mungbean-Aman systems with PTR (CSE2) and DSR
(CSE3, 4) was similar despite significantly higher yield of wheat (by 10% or 0.4 t ha-1) following
DSR than PTR, due to a consistent trend (non-significant) for lower yield of DSR than PTR.
However, profitability of the systems with DSR was 5% higher than with PTR due to lower cost
of production. 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 system yield than residue removal in the second year, and when averaged over the 2
years (by 0.6 t ha-¹) due to consistent trends for higher yields of all crops (significant in the case
of wheat and mungbean in the second year). The flooded T. Boro rice-T. Aman rice cropping
system used much more irrigation water than the other systems. Changing from puddling and
transplanting (CSE2) to dry seeding (CSE3,4) reduced total system irrigation input by an
average of 46% (619 mm). After two years, there was no effect of CSE or partial aman residue
retention on bulk density of the top soil nor on ponded infiltration rate. The results suggest that
intensification from T. Boro rice-T. Aman rice to a Wheat-Mungbean-Aman system can increase
system productivity and profitability and reduce irrigation requirement. The results also
suggest that replacement of puddled transplanted Aman rice with dry seeded Aman rice can be
done with no yield loss, reduced irrigation input and benefits for wheat grown in the rotation.
Furthermore, tillage for all three crops can be reduced to strip tillage with no adverse effects on
productivity, and slightly reduced production cost. Longer term studies are needed to
determine the full impacts of the changes in crop intensification, establishment method, tillage
and residue management.