Determination of N, P, and K Fertilizer Optimum Rates for Bambara Groundnut (Vigna subterranea [L.] Verdcourt).

Abstract

Bambara groundnut is the one of nuts that have a high potential to be developed. Bambara groundnut has the best drought resistance among other nuts, but it also has another advantage that is tolerant of unfertile soils. The average yield of dry pod weight from agricultural fields in Indonesia were under 4 ton ha-1, that value is still low. Therefore, must be an efforts to improve Bambara groundnut production. Fertilization is the key efforts for increased the productivity of Bambara groundnut. The objective of the research was to determine optimum rate of N, P, and K fertilizer for Bambara groundnut (Vigna subterranea [L.] Verdcourt) production. Three experiments were conducted at Cikarawang Farm, Dramaga, Bogor from March to July 2013. Each experiment tested different rates of N or P or K fertilizer with randomized compeletely block design and three replications. The fertilizer rates were 0, 50, 100, 150, and 200% of reference rate (100% N = 45 kg N ha-1, 100% P = 54 kg P2O5 ha-1, 100% K = 45 kg K2O ha-1). On all experiments, 100% P, 100% K, and 30% N were applied at planting, while 70% N was applied at 5 week after planting. Plot size was 6 m x 3 m, with plant spacing of 60 cm x 30 cm. Harvesting were conducted at 16 week after planting. The result showed that leaf P content increased linearly with N fertilizer application. Leaf N content decreased linearly with P fertilizer application. Root fresh weight, seed N content, and shoot dry weight quadratically increased with K fertilizer application. Because of very limited numbers of variable that were significantly affected by the treatment, optimum rate of N, P, K fertilization can not be determined through multi nutrient response technique in these experiments. Only the optimum rate of K fertilizer that can be determined with the range of 51.48-69.78 kg K2O ha-1. Based on production, the highest productivity estimation were 30.91 kg N ha-1, 54.81 kg P2O5 ha-1, and 46.85 kg K2O ha-1 although not significant.