Phosphorus Fertilization Under Different Land Preparation Methods and Performance of Groundnut (Arachis hypogea L.) in Rainforest Zone of Southern Nigeria.

A field experiment was conducted on an Arenic paleudult in the rainforest zone of Southern Nigeria to determine the response of an improved variety of peanut (Arachis hypogea L. var. Samnut 23) to phosphorus, under different land preparation methods. Selected land preparation methods were “slash and burn” (SB) and “slash and mulch” (SM), and the phosphate fertilizer rates were 0, 30, 60, 90 and 120 kg P/ha. The experiment was laid out as a Randomized Complete Block Design. Each land preparation was divided into plots. Macro- and micro nutrient contents of peanut plants were determined, and the growth and yield components were also assessed. Results showed that the pre-plant soil analysis for the SB management had a pH of 5.77, 1.8 g kg^-1 of  N, 2.05 mg kg^-1 of  P and 0.11cmol (+) kg^-1 of K; while that of the SM had a pH of 5.95, 0.9 g kg^-1 of N, 0.86 mg kg^-1of P and 0.07cmol(+) kg^-1 of K. Plant height was not significantly different (p≤ 0.05) between the land preparation methods, but leaf area was significantly different. However, plant height and leaf area responded better in SB treatment at a rate of 90 kg P/ha than the SM treatment at the same rate. Also the seed weight was significantly different (p≤ 0.05) between the land preparation methods. SB had the highest seed weight of 151.7 g and this was obtained at 60 kg P/ha, but for the SM treatment, the highest seed weight was142.7 g, obtained at 90 kg P/ha. Pod weight of 909 kg/ha was obtained at 60 kg P/ha under the SB treatment, while pod weight of 495 kg/ha was measured at P rate of 120kg/ha under the SM treatment. Significant differences were also observed in the nutrient concentrations of leaves and roots. Highest leaf phosphorus content (3.502 mg/kg) was recorded at 90 kg P/ha in the SM treatment while the highest nutrient content of P in the roots (0.272 mg/kg) was recorded at 30 kg P/ha also in the SM treatment. However, the SB treatment recorded the highest peanut seed pods/shell at 60 kg P/ha. Generally, phosphorus fertilization under the SB management practice gave better results than the SM management practice.