Abstract
Six experiments were carried out at the Regional Agricultural Research Station of the Bangladesh Agricultural Research Institute, Jamalpur during 2004-2007. Initially, six different types of maize hybrids (Single cross, three-way cross and double cross) were planted at different dates in rabi seasons of 2004-05 and 2005-06 to find out the optimum planting time in AEZ-9. Results indicated that the hybrids Pacific-11, Pacific-60 and 900 M were better in terms of growth and yield at November 14 planting in both the years. BHM-3 showed better performance at October 29 planting but it was also a good variety at November 14 planting in both the years. Among the planting times, November 14 planting gave the highest grain yield followed by October 29 planting while DM production and stover yield were found highest at December 29 planting in both the years. After November 14 planting, the grain yield decreased by 24%, 35% and 44% when planted on November 29, December 14 and December 29, respectively. Decreased grain yield at late planting was associated with lower cobs plant', lower grains cob1 and lower 1000-grain weight which might have occurred due to forced ripening at high temperature and high rainfall both the years and also due to lower dry matter partitioning in reproductive parts during later stage. The late plantings resulted in high crop growth rates during the vegetative period because of high radiation use efficiency (RUE), high percentage radiation interception (RI) but low crop growth rates during grain filling because of low RUE and low RI. After identifying of optimum planting time, F2 population was studied in respect of fertilizer management and plant density to find out the optimum fertilizer dose and plant density in 2005-06 in order to compensate the yield loss in F2 population. It was found that all the growth parameters, yield components and yield varied significantly due to variable fertilizer doses. Fertilizer dose as recommended for F, hybrids and 33% higher than that of recommended dose were found identical in respect of grain yield in F2 populations. Grain yield decreased by 21% and 44% due to reduction of fertilizers by one-third and one-half of the recommended doses, respectively. Plant to plant spacing 20 cm - 25 cm was found better in respect of grain yield. Grain yield decreased by 9% due to decrease plant spacing from 75 cm x 20 cm to 60 cm x 20 cm. In both the experiments, F2 populations of Pacific-11 and Pacific-60 produced higher grain yield than other F2 populations under study. When planting time, fertilizer dose and population density were identified, three F, hybrids were compared with their F2 populations and one open pollinated (OP) maize (BM- 7) during rabi season of 2006-07. Three F, hybrids Pacific-11, Pacific-60 and BHM-3 gave identical grain yield while their F2 population produced 15%, 17%, 23% lower grain yield compared to their original hybrids, respectively. OP maize BM-7 gave identical or lower grain yield than three F2 populations. From the economic point of view, F, hybrids required 15% higher costs of cultivation than F2 of which 12% was only for purchase of F, hybrid seeds. Gross return obtained from F, hybrids was 14% higher than F2 while F2 population produced 10% higher gross return than OP population. Net return was found 23% higher in F, hybrids than F2 while F2 population gave 16% higher net return than OP populations. Purchase of F, hybrid seed is more costly than F2 seed. Therefore, many resource poor farmers will tend to cultivate F2 population although the return would be to some extent lower than F, hybrids.