Prospect of dhaincha (Sesbania rostrata) intercropping with T. Aus in a T. Aus—T. Aman cropping pattern

Abstract

The beneficial effect of dhaincha (Sesbania) green manuring on soil N fertility and crop productivity has been adequately demonstrated. But the large-scale adoption of this green manuring practice by farmers has not been seen because of the competition with other main crops for land. Farmers, in general, are not willing to grow a green manuring crop by sacrificing a main crop. In order to evaluate the prospect of dhaincha intercropping with T. Aus with respect to biomass production and N-accumulation along with its subsequent impact on crop production, a field experiment was conducted in 1993 in a silty clay soil of the Bangladesh Rice Research Institute Farm following a T. Aus—T. Aman cropping pattern. Both T. Aus and T. Aman crops were grown with and without dhaincha under five rates of N (0, 30, 60, 90 and 120 kg N/ha). One-month-old dhaincha seedlings were transplanted between each two alternate rice rows with a spacing of 20 × 5 cm on the same day as Aus transplanting. Dhaincha plants were clipped twice during the Aus season and final incorporation was made prior to Aman planting.

Results show that dhaincha biomass production decreased with increasing levels of added N when intercropped with T. Aus rice. Total N accumulated until T. Aman was planted ranged from 138 to 209 kg/ha. Irrespective of N rates, dhaincha intercropping significantly decreased the grain and straw yield of T. Aus (BR21).

However, the highest grain yield of T. Aus was recorded at 60 kg N/ha with and without dhaincha intercropping. In the T. Aman season, on the other hand, the grain yield of BR22 increased by 0.8 t/ha due to dhaincha green manuring alone. Further addition of N to dhaincha green manuring progressively depressed the grain yield. Without dhaincha green manuring, the grain yield of T. Aman (BR22) increased to 60 kg N/ha. When the total grain yield of the T. Aus—T. Aman cropping pattern is considered, intercropped dhaincha green manure with 60 kg N/ha added for T. Aus but no added N for T. Aman produced 7.0 t/ha grain yield which is comparable to the grain yield obtained with 60 kg N/ha for T. Aus plus 30 kg N/ha for T. Aman without intercropped dhaincha green manure.