IMPROVEMENT OF NITROGEN IN FERTILITY DEPLETED SUGARCANE SOILS THROUGH SHORT- TERM PREPLANTING OF LEGUMINOUS PLANTS

Abstract

Sugarcane is the main cash crop in the sugar belt of western Kenya and provides income for farmers, particularly poverty stricken smallholders, in the region. However, due to declining soil fertility particularly, soil nitrogen, sugarcane yields have been declining. The increased human population growth resulting in reduced farm sizes and continuous cropping of land has contributed to decline in soil fertility leading to land degradation and serious food insecurity. Leguminous plants are widely used for food, fodder, shade, fuel and constitute part of the cropping systems in rural areas. Other benefits include: attracting beneficial organisms to the cropping system by providing habitat for soil organisms and animals thus improving soil biological and physical structure. The main objective of this study was to screen selected leguminous plants to identify the most effective ones for improving nitrogen fertility depleted sugarcane soils. The study consisted of two field experiments: (i) Pre-plant six legume plants crops to improve the fertility of nitrogen depleted sugarcane soils (Bambara, Crotalaria, Sesbania, Cowpea, Soybean and Yellow gram) (ii) Sugarcane planted following the harvest of legume plants; in a 3 by 6 factorial experiment laid out with 3 types of starter fertilizer (Control, potassium as KCl and phosphorus as SSP). The study was conducted in Kibos area, Miwani division, Kisumu County (33020’ E and 35020’ E and latitudes 0020’S and 0050’S). The trial was for two seasons and the data generated was analyzed using GenStat12th Edition computer package. The results indicated that soils (0-15 cm depth) were acidic to neutral (pH 5.5-7.0); low in organic C, N and P; moderate in Ca. The soil texture was clay loam; soil class, Eutric Vertisol and Dystric Cambisol. There was a significant increment in soil nitrate-N content after harvesting of the legumes compared to initial soil nitrate- N content. The change in soil fertility status particularly increase in soil nitrate-N by legumes had a positive effect on the growth and development of sugarcane in terms of, height, tillering and harvestable fresh biomass (P≤0.05). There was no significant difference in sugarcane performance with or without application of starter (phosphatic or potassic) fertilizer in soils previously under legume establishment. Cow pea and Sesbania sesban improved soil nitrogen content most compared (P≤0.05). to other leguminous plants by fixing more N hence ideal and best suited for use in improvement of soil nitrogen fertility sugarcane growing soils.