Effects of N and K fertilization of sugarcane (Saccharum oficinarum) on acrisols in western Kenya

Abstract

Sugarcane fertilization in Kenyan plantations is largely concentrated on Nitrogen and Phosphorus. Use of Potassium, secondary nutrients and micronutrients is altogether missing. Recent soil analysis results indicate that soils in the Mumias Sugar zone of western Kenya that accounts for 50-60 % of national production are K- deficient. In examining the quality factor in sugarcane payment systems as envisaged in recent legislation, adoption of balanced nutrition by inclusion of K would help improve sugar cane productivity and enhance sugar recovery. This paper reports the effect of K, N and their interaction on sugarcane yield and juice quality on acrisols. Four experiments were established in several locations from 2009- 2011. The treatments included a factorial combination of four rates of K at 0, 60, 120 and 180 kg/ha K2O and four rates of N at 0, 46, 92 and 138 kg/ha N. Recommended basal phosphate was included in every plot at 92 kg/ha P2O5. Each experiment was harvested after 18 months of growth. Results showed significant responses to K and N. Agronomic efficiency was higher in plots supplied with K along with N. Nitrogen and K2O application rates that produced optimum cane yields were: N = 46kg/ha and K2O = 60 kg/ha; however, economically profitable rates were N = 46-92 kg/ha and K2O at 60 kg/ha. Productivity gains did not offset costs when rates were higher than 120 kg/ha of K2O and 138 kg/ha of N. The results imply that the inclusion of K in the sugar cane fertilization regime at Mumias will be beneficial. An initial rate of 60kg/ha K2O (2 bags of 50 kg muriate of potash is recommended on soils with K-deficiency. There were strong indications that with K fertilization the current N recommendation of 120 – 150 kg N/ha could be reduced to only 78-92 kg/ha due to better N utilization from the interaction with K.