Growth, quality and yield responses of some new sugarcane Varieties to rates of nitrogen and potassium fertilizers in Kibos -western Kenya

Abstract

About 60% of the world's sucrose comes from sugarcane (Saccharum ojjicinarum L.). In Kenya, sugar is produced exclusively from sugarcane grown in the Nyanza, part of the Rift Valley the Western Kenya sugar belts and Kwale County at the Coast. "Production in Kenya has declined despite increased area under cane and introduction of high yielding varieties. The yields continue to decline possibly due to use of agronomic inputs recommended for old varieties which may be inappropriate for these elite varieties. Optimal nutrients, especially nitrogen and potassium fertilization have not been established for the new varieties. The Kenya Sugar Industry is changing the policy to pay farmers on sucrose content of cane. However influence of nitrogen and potassium fertilization on sucrose content of the new varieties is unknown. This research was conducted to establish the variations of growth parameters, yield and cane quality due to varieties, nitrogen and potassium fertilizer. The experimental design was split- split plot with four replications of three varieties CO 421 (control), KEN 83-737 and KEN 82-472 as main plots, four nitrogen rates (0, SO, 100,lS0 Kg Nlha) as sub plots and two potassium rates (0, 100 Kg K201 ha) as sub-sub plots. There was significant (pSO.OS)difference due to varieties in tillers from 4 months after planting (MAP) and girth from 14 MAP and height from12 MAP. CO 421 yielded significant higher (pSO.OS) than the other varieties followed by KEN 83-737. All varieties yielded higher than the yields recorded in commercial scale suggesting, improper application of other inputs may be responsible for the observed low commercial yields. Stalk height from 12 MAP and girth from14 MAP were significantly correlated with yield, (R-squared =0.S9 and 0.66 respectively) suggesting that these parameters can be used as yield predictors. Nitrogen continued to increase growth parameters, yield and quality beyond lS0Kg N Iha suggesting the need to establish whether the recommended fertilizer rates are optimal and include potassium for improved productivity in new varieties. There was significance response in yields to potash of the KEN varieties but not CO 421, confirming that these new varieties would benefit from its application. There was varietal difference in leaf nutrient content with age of the plant suggesting that for advisory purposes sampling time must clearly be defined. Commercial Cane Sugar (CCS %) of varieties was different, CO 421 had significantly (pSO.OS) higher CCS% than the new varieties, showing that it may still be a potential variety for payment on Sucrose. pol% levels reached maximum at 16 MAP for, KEN 8KEN 83-737 and KEN 82-472 demonstrating that new varieties should be harvested at 16 MAP for realization of high sugar output. These outcomes will establish nutrients diagnostic guide, Nand K rates and optimal harvesting time that will guarantee better quality and yield for new sugarcane varieties.