Abstract
Two series of experiments involving eleven individual trials were conducted at the Bangladesh Rice Research Institute (BRRI). Regional Station. Rajshahi, to evaluate the agro-economic productivity and profitability of dry seeded Aman rice-maize-mungbean system. The first main experiment with six tillage and five weed management options was conducted over two seasons (2010-2012) in Aman rice to evaluate the effect of weed management options in rice under conservation tillage system. The tillage options viz. zero tillage (ZT), strip tillage (ST) using a power tiller operated seeder (PTOS), minimum tillage (MT) using a PTOS. permanent bed (PB) using a bed planter, fresh bed (FB) using a bed planter and conventional tillage (CT) were allocated in the main plots and five weed management options viz. weed free (W1). post emergence herbicide (Bispyriac Na+) + hand weeding (1HW), pre emergence herbicide (Pandimethylin) + post emergence herbicide, post emergence herbicide and weedy condition (control) were given in sub plots under split plot design. The second main experiment under rice-maize-mungbean cropping system was conducted in three seasons (2010-13) with each of three crops to identify the effect of conservation tillage and crop residue management on the productivity and profitability of the system. The main plot treatments were six tillage viz. ZT, ST using a PTOS, MT using a PTOS, PB using a bed planter. FB using a bed planter and CT. The sub plot treatments were residue management options viz. 0% previous crop residue return (CR), 50% previous crop residue return (CR50) and 100% previous crop residue return (CR100). In first sets of experiments, although the CT. PB and FB produced similar rice yields (P<0.05), gross margin was remained higher (7-10%) in beds due to less cost involvement. Similarly, post emergence herbicide (Bispyric Na+) plus by one hand weeding (1HW) and weed free treatments achieved at par grain yields although the gross margin remained higher (9%) in Bispyribac + 1HW treatment. In the 2nd sets of experiments, all the conservation tillages especially PB and FB had significantly higher grain yields of maize compared to CT. The gross margin of maize was also higher (11 to 28%) in all the conservation tillage options. In rice and mungbean, PB and FB produced at par grain yields with CT. Compared with CT, the rice equivalent yield (REY) remained higher in PB (6%) followed by FB (4%). The other tillage options such as ZT, ST and MT also gave comparable effects with CT in terms of REY. Organic matter (9 to 15%) and total N (12 to 24%) content of soil also remained higher in all conservation tillage treatments. In case of residue management options, the REY influenced significantly in 2nd year and onwards due to returning of 50% crop residues. Soil organic matter content of soil also increased (9%) significantly in CR50 treatment. The total N, available P and S content of soil increased statistically due to 100% crop residue incorporation. Thus, the results suggest that there is a potentiality of all conservation tillages particularly PB and FB for greater productivity and profitability in dry seeded Aman rice-maize-mungbean system.