Groundnut yield response to single superphosphate, calcitic lime and gypsum on acid granitic sandy soil

Phosphorus and calcium are the major nutrients limiting groundnut production. The objectives were to determine (a) optimum application levels of P and Ca, and (b) compare the effectiveness of calcitic lime (40% Ca, 4.5% Mg) and gypsum (22% Ca, 17% S) as sources of Ca for groundnut grown on sandy soils. Field experiments were established in smallholder farming areas using four levels of P (0, 8.5, 17 and 34 kg ha-1) combined factorially with calcitic lime (0, 200, 400 and 800 kg ha-1) to give 16 treatments. Similar levels of P were combined factorially with gypsum (0, 100, 200 and 400 kg ha-1) to give sixteen treatments. Experiments were laid in a randomized complete block design with three replications. Phosphorus had a significant effect on groundnut yield at the majority of the experimental sites. Application of P at 8.5 kg ha-1 gave the optimum groundnut yield response. The optimum application rates for calcitic lime and gypsum were 200 and 100 kg ha-1. Gypsum and calcitic lime were not significantly different as sources of Ca for groundnut. Soil chemical properties were significantly improved following application of P and Ca source