THE INFLUENCE OF FERTILIZER PLACEMENT ON MAIZE YIELD AND GROWTH OF WEEDS

Abstract

Three field experiments were conducted in two seasons in Zimbabwe to study the effects of rate and method of placement of NPK fertilizer on productivity of maize and the emergence and growth of weeds. Compound D (8% N, 14% K2O, 7% P2O5, 6,5% S) was applied at 75, 150 and 225 kg hað€€€1 using three placement methods viz. spot placement, banding and broadcasting in Experiment 1. The three placement methods were combined with four weed-free period and weedy periods in Experiment 2 and 3. Maize yield was highest at 150 kg hað€€€1 of compound D in Experiment 1. Banding consistently attained the highest maize grain yield, followed by spot placement and broadcasting. Early maize growth and grain yield data suggested that spot placement may reduce the yield response of the maize to fertilizer in water limited environments by predisposing maize plants to higher levels of moisture stress, when compared to banding. Spot and band placement increased radiation interception and early growth of maize and reduced the emergence, growth and seed production of weeds, compared to broadcasting; however the effects of fertilizer placement on weeds did not significantly affect the duration of critical period for weed control required to avert yield loss in maize. Our results suggest that smallholder farmers may maximize the benefits, of increased yield and suppression of weeds, derived from scarce fertilizer/manure resources by using precise methods of placement, more so with banding than spot placement.