Weed Suppression and Yield Performance of Maize + Legume Intercropping Systems

Four experiments were carried out at the Bangladesh Agricultural Research institute, Joydebpur, Gazipur during 2009 to 2011 to identify suitable legume crops with maize and to select the best planting arrangement in maize+legume intercropping systems for better weed suppression, productivity and economic benefits in Rabi and Kharif seasons. In the first two experiments, there were 17 treatments of which two sole crop of hybrid maize (Zea mays) (weed free and no weeding), three weed free sole crops of pea, bushbean and cowpea in Rabi season, three weed free sole crops of mungbean, soybean and blackgram in Kharif season, and their intercropping treatments. Twelve intercropping systems with varying weeding regimes (no weeding, one hand weeding at 20 days after emergence (DAE), one hand weeding at 40 DAE and two hand weeding at 20 and 40 DAE of maizelegume intercropping under normal row (75 cm × 25 cm) and two rows of legumes in between two rows of maize were used in the first and second experiments. In the third and fourth experiments, five maize+legume (maize+ pea in Rabi and maize+mungbean in Kharif) intercropping systems involving five spatial arrangements and densities of each component along with sole cropping of maize and legumes constituted the treatment combinations. In intercrop situation the population density of maize was maintained same as that of the sole crop of maize but it varied for legumes (33.33%, 66.67%; 26.67%. 40.0% and 53.33% of sole crop). The treatments were arranged in randomized complete block design with three replications. Data on plant morphology, light interception, yields and yield attributes of maize and legumes were recorded. Leaf area index, crop growth rate, relative yield total (RYT) and land equivalent ratio (LER) were calculated. Data on number of weed species, weed dry weights m-2 were also recorded and weed control efficiency of different treatments and competitive ratio of maize under different legumes were calculated. Benefit-cost ratio of the intercropping treatments was also estimated. Among all intercropping systems, maize-pea in Rabi and maize+mungbean in Kharif with two hand weedings at 20 and 40 DAE gave the lowest weed dry weight and the highest weed control efficiency (86%). Photosynthetically active radiation interception was also higher (95%) in maize+pea and maize+mungbean with two hand weedings situations. The values of leaf area index, total dry matter and crop growth rate were found higher in those intercropping systems. These two intercropping systems gave higher productivity, resource complementarity and profitability (in Rabi: RYT = 1.80, LER = 1.80, BCR = 5.28 and in Kharif: RYT = 1.81, LER = 1.81, BCR = 2.61). In case of planting arrangements, two rows of pea in Rabi and two rows of mungbean in Kharif intercropped within two normal rows of maize (75 cm x 25 cm) exhibited maximum complementarity in resource use (LER = 1.46 in Rabi and 1.59 in Kharif), gave the highest productivity (RYT = 1.46 in Rabi and 1.59 in Kharif) and profitability (BCR = 5.36 in Rabi and 3.63 in Kharif). Weed dry weights were lower under these treatments (83.74% reduction in Rabi and 91% reduction in Kharif) than other spatial arrangements. Intercropping of two rows of pea in Rabi season and two rows of mungbean in between two rows of maize with two hand weedings at 20 and 40 DAE should be practiced as most weed-suppressive and profitable maize+legume intercropping practice.