Response of Two Groundnut (Arachis hypogaea L.) Varieties to Sowing Date and NPK Fertilizer Rate in a Semi-Arid Environment: Yield and Yield Attributes

In order to determine the optimum sowing date and NPK fertilizer rate for two groundnut (Arachis hypogaea L.) varieties for best yield performance and to improve their production, field trials were conducted during the 2004 and 2005 cropping seasons at Samaru, Nigeria. The treatments were composed of factorial combinations of three sowing dates (mid-June, end-June and mid-July), three NPK fertilizer rates (10 kg N+13 kg P+13 kg K ha-1, 20 kg N+26 kg P+26 kg K ha-1 and 30 kg N+39 kg P+39 kg K ha-1) and two varieties (SAMNUT-22 and SAMNUT-23). Fertilizer rates x sowing dates constituted the main plot while varieties were assigned to the sub-plot as the experiment was laid out in split-plot design with four replications. Delaying of groundnut sowing till mid-July caused a 27.3% decline in number of pods per plant. When sowing was delayed until end of June or mid-July, pod, seed and haulm yields declined 44.9, 45.2 and 23.5%, respectively relative to sowing in mid-June. However, parameters such as number of pods per plant, pod yield and seed yield were not influenced significantly by fertilizer rate. Variety SAMNUT-23 produced significantly more pods per plant and higher pod, seed and haulm yields than SAMNUT-22. Significant interactions were observed between the treatment factors for most yield attributes. In most cases variety was a function in the response of the parameters to treatments. It was found that when SAMNUT-23 was sown in mid-June it significantly out-performed SAMNUT-22. We conclude that early sowing enhanced positive response of pod yield to NPK fertilizer application while the optimum sowing date for good yield performance in both varieties is mid-June.