Production potential and economics of maize intercropped with legumes as influenced by weed control

Abstract

Field trials were carried out at the New Developmental Farm of The University of Agriculture Peshawar Pakistan during the years 2012 and 2013 on intercropping of mungbean, sesbania and cowpea with maize crop. These trials were laid out in a Randomized Complete Block (RCB) design, with split-plot arrangement keeping three replications. In these experiments there were two main plots (herbicide vs no herbicide). The subplots comprised of 10 treatments including sole maize with 6 rows each 80 cm apart, sole mungbean with 15 rows each 30 cm apart, sole cowpea with 15 rows each 30 cm apart, sole sesbania with 15 rows each 30 cm apart, 5-rows-mungbean : 6-rows-maize, 5-rows-cowpea : 6-rows-maize, 5-rows-sesbania : 6-rows-maize, 10-rows-mungbean : 6-rows-maize, 10-rows-cowpea : 6-rows-maize and 10-rows-sesbania : 6-rows-maize. Maize was cultivated as the main crop and sesbania was intercropped as green manure, cowpea as fodder and mungbean as the grain purpose crops. The plots where herbicides were applied had significantly lower weed density, fresh and dry weed biomass during 2012 and 2013. The average weed density, fresh and dry weed biomass were lower in 2012 than in 2013. The weed density fresh and dry weed biomass were higher in sole maize plots among the intercropping treatments. The maize plant height was higher in plots of no herbicide use during both the years of study. It was lowest in sole maize plots in the two years study and highest in the plots of 10 rows mungbean intercropped with six row maize. The other maize parameters like number of grains ear-1, thousand grain weight, grain yield, biological yield, harvest index and maize grains protein content were higher in plots where herbicides were applied during both 2012 and 2013. Similarly, among the intercropping treatments, the number of grains ear-1, thousand grain weight, grain yield, biological yield, harvest index and maize grains protein content were highest in sole maize plots. Among the legume intercrops the performance of maize was best with cowpea followed by sesbania and mungbean. For mungbean crop, the number of seeds pod-1, thousand grain weight, grain yield, biological yield and harvest index were higher in herbicide applied plots in both of the years. The number of seeds pod-1, thousand grain weight, grain yield, biological yield and harvest index of mungbean were highest in the sole mungbean plots among the intercropping treatments in 2012 as well as in 2013. The grain yield, biological yield and harvest index of mungbean were lowest in the plots of 5 rows mungbean intercropped with 6 rows of maize in both the years’ trials. For the cowpea crop, the plant height and fresh weed biomass were significantly higher in plots of herbicide application during 2012 and 2013. Among the intercropping treatments, the plant height and fresh biomass of cowpea were highest in sole cowpea plots. For sesbania crop, the plant height, fresh and dry biomasses were significantly higher during 2012 and 2013 in plots where herbicides were applied. The plant heights, fresh and dry biomass of sesbania were highest in sole sesbania plots among the intercropping treatments in both of the trials conducted in 2012 and 2013. The total soil nitrogen and total organic matter were significantly higher during either years of study in herbicidal plots. Similarly, for the effect of intercropping the total soil nitrogen and organic matter were highest in sole mungbean plots during both years. The highest LER of 1.49 during 2012 was calculated for 10 rows sesbania intercropped with 6 rows maize. The LER trend in 2013 was similar to that in 2012. The cost benefit ratio ranged between 1.67 - 3.90 in the average yields of the two years in which the lowest CBR was computed for sole mungbean and the highest for 5 row mungbean intercropped with 6 rows maize. The aggressivity for all the intercropping treatments ranged between 0.1492 to 1.1545 with the minimum aggressivity in 5 rows mungbean intercropped with 6 rows maize and maximum in 10 row cowpea intercropped with 6 rows maize. The partial aggressivity for maize was higher than the legume intercrops in all the intercropping combinations. The competitive ratios for the intercropping treatments were in the range of 2.07-4.53 with the lowest competitive ratio for 5 rows sesbania intercropped with 6 rows maize and highest for 10 row cowpea intercropped with 6 rows maize. The partial competitive ratios for maize were also higher than the partial competitive ratio values for the intercrops in all the intercropping treatments. In conclusion, the use of herbicide in maize crop in integration with intercropping of legumes such as mungbean, cowpea or sesbania in alternate rows is a mean of achieving good weed control, improving soil fertility, attaining higher LERs, and often providing greater income to farmers.