Effect of intercropping on biomass of weeds and the associated crops.

To study the effect of intercropping on biomasses of maize, the intercrops i.e. mungbean, cowpea and sesbania, and weeds. The experiments were conducted at the New Developmental Farm of the University of Agriculture Peshawar. The experiments were laid out in randomized complete block design with split plots arrangements in such a way that the herbicidal and non herbicidal treatments were kept in the main plots; whereas the subplots comprised of 10 treatments of intercropping including 1-row-maize : 1-row-cowpea, 1-row-maize : 1-row-mungbean, 1-row-maize : 1row-sesbania, 1-row-maize : 2-rows-cowpea, 1-row-maize : 2rows-sesbania, 1-row-maize : 2-cowpea, sole maize (M), sole cowpea (C), sole sesbania and sole mungbean. The years, herbicide use, intercropping and their interactions all significantly affected the maize biomass, weed fresh biomass, mungbean biomass, sesbania biomass and cowpea biomass (kg ha -1 ). The mean weed biomass in 2013 was higher than 2012. In contrary, the biomasses of maize, mungbean, cowpea and sesbania were higher in 2012. For the effect of the herbicide use, the weed biomass was lower in the herbicidal treatments during both the years. However, the biomasses of the associated crops were higher in the plots treated with the herbicide pendimethalin as pre-emergence. As far as the intercropping effect is concerned, the weed biomass was highest in the sole crops as compared to the plots where intercropping was done. Minimum weed biomass was obtained in plots where 10 rows of mungbean were intercropped with six rows of maize. The sole treatments had the highest respective crop biomass i.e. maize, mungbean, cowpea and sesbania had their highest biomasses in their sole treatments. In conclusion, the weed biomass is reduced by increasing the crop population and diversity and also by the use of pendimethalin. In addition, the crop biomass is better when the intercropping is done with a ratio of one maize row and one row of the intercrop. Therefore, the integration of the pre-emergence herbicide (pendimethalin) with the intercropping of legumes with maize in a 1:1 will be an effective approach for weed suppression, and higher crop biomass.