Grain yield and system productivity for rice-wheat-mungbean and rice-wheat-maize sequences in northern Bangladesh

摘要

An experiment was conducted at the Wheat Research Center of the Bangladesh Agricultural Research Institute, Nashipur, Dinajpur, during four consecutive years from 1996-1997 to 1999-2000, with a view to sustaining the productivity of rice-wheat cropping systems by mung bean residue and fertilizer management. There were six treatment combinations, made up of three cropping patterns (rice-wheat-mungbean, with mungbean residues removed; rice-wheat-mungbean, with mungbean residues retained; rice-wheat-maize, with maize residues removed) and two fertilizer rates (based on soil-tests and on farmers' practices), and were tested with two fertilizer series. In one series, the complete fertilizer dose was added, in the other, N was omitted. Wheat yields across the years ranged from 1.77 to 3.40 t/ha in +N and 0.61 to 1.32 t/ha in -N treatments. The mungbean crop was severely affected by excess rainfall and thus yields were small, averaging from 0.33 to 0.64 t/ha across 4 years. Maize crops were also severely affected by excess rainfall in all the years, with grain yields ranging from only 0.85 to 3.80 t/ha. Rice yields were small in the first three years (2.75 to 4.09 t/ha) due to lodging at the grain-filling period, but were high in the fourth year (4.90to 5.90 t/ha) due to favourable weather conditions. There was a consistent effect of retention of mungbean residues grown without N on the following wheat crops every year. A slight positive effect of mungbean residues on the third and fourth crops of rice, especially in -N treatments was found. The total system productivity, expressed as equivalent yield, was greater for the soil-test-based than the farmers' fertilizer treatments, and was greater for rice-wheat-maize systems compared to rice-wheat-mungbean systems. Results reveal that total system productivity of the rice-wheat systems could be increased by applying fertilizers based on soil-tests and that there is a cumulative effect of retention of mungbean residues on the succeeding crops of rice and wheat.