Screening of cassava effluent- a proposed weed biocontrol agent for its effect on soil nutrients and microbial population

Weed management in crop production has the objective of reducing plant nutrient competition with minimal effect on soil microbial load. Hence, it is important to investigate the effect of botanicals used for weed management in this regard. The effect of cassava effluent (CE) concentrations of 60, 120, 180 and 240 μg CN/kg (CN is a universal chemical symbol for cyanide) soil that were applied one, two, three and four times, was evaluated on soil nutrients and microbial load in a 4 x 4 factorial arrangement. Control treatment (without CE) was incorporated into the experiment in an incomplete factorial design. This was laid out in completely randomized design in the screen-house. Results showed that CE concentration and frequency of application altered the C, Ca, Mg, Na, K, Cu, Fe, Mn and Zn contents of the soil. CE concentration and frequency of application had significant interaction (p<0.05) on all the plant nutrients analysed. CE concentration of 60 and 120 μg CN/kg soil applied one to four times had available P concentrations lesser than the control treatment. Contrarily, P increased by 45% when CE of 240 μg CN/kg soil was applied three times. Significant (p<0.05) interaction between CE concentration and application frequency markedly decreased culturable bacterial population, while fungal population was increased by some interactions. The study concluded that application of CE for weed control has moderating effect on soil nutrients and microbial load. Hence, its adoption for weed control requires the understanding of its influence on chemical and biological properties of soil.