Influence of Cultivars and Nitrogen Fertilizer Rates and Application Mode on Yields and Quality Parameters of Ratoon Sugarcane in Western Kenya

Productivity of sugarcane in Kenya has declined despite use of recommended production practices including introduction of elite high yielding and early maturing sugarcane varieties. Farmers continue to use recommended agronomic inputs for the old low yielding and late maturing varieties on these elite varieties. Nitrogen fertilizer rates in single or split doses for old varieties are still in use yet their appropriateness on new varieties remains untested culminating to decline in sugarcane productivity in Kenya. Currently, cane payment is based on delivered milling cane weight. The industry plans to change payment to a combination of quality and yields. Influence of agronomic inputs and timing of harvesting period on proposed mode of payment is unknown. Harvesting age in western Kenya remains 18-20 months after ratooning (MAR). However, optimal age that combines quality and yields is not documented. Influence of these agronomic practices on quality, yields and optimal harvesting age of ratoon crop of new (D8484) and old (CO421) varieties were evaluated in a 2x4x3 split-split-plot design replicated three times. Four rates of nitrogen as urea, all applied at 3 MAR, split once (50-50%) and applied at 3 and 6 MAR or split three times (40-30-30%) and applied at 3, 6 and 9 MAR were evaluated. Yields and quality parameters were monitored from 10th-24th MAR. Variety D8484 out-yielded (p≤0.05) CO421 throughout demonstrating its superiority. Yields reached maximum at 20 and 19 MAR for CO421 and D8484, respectively. Maximum pol and brix were attained at 18 and 15 MAR for CO421 and D8484, respectively, while commercial cane sugar (CCS) was maximum at 18 and 17 MAR for CO421 and D8484, respectively. Results demonstrated that for high returns, D8484 should be harvested between 15-18 MAR while CO421 between 17-19 MAR. The 60 kg N/ha, that produced higher (p≤0.05) output in both varieties, from 16th MAR is recommended for both varieties. Split fertilizer application did not affect productivity.