Multi-variate Analysis of the Soil Chemical Properties in the Mwea Irrigation Scheme, Kenya and its Implications on Agronomic Management

Abstract

Abstract Sub-Saharan Africa is a net importer of rice with self-sufficiency rates of as low as 14% in countries such as Kenya. More 80% of the rice produced in the country is cultivated in the Mwea irrigation scheme. Productivity in the irrigation scheme declined from 5.6 ─ 6.0 t ha− 1 to 1.3 ─ 4.6 t ha− 1 between 1977 and 2018 that could be attributed to site specific nutritional deficiencies and /or toxicities rendering the generalized agronomic recommendations inapplicable in some areas. This study aimed to evaluate variability in soil chemical properties within the irrigation scheme, cluster areas with similar nutritional status and provide area-specific agronomic recommendations. Four hundred samples were collected from the five sections of the Mwea irrigation scheme and analyzed for total organic carbon, soil pH, macro nutrients, micro nutrients and exchangeable cations. Principal components (PC) 1 ─ 4 accounted for 72.2% of the total variability within the irrigation scheme. Four clusters were generated in a scatter plot between PC1 and 2 and there were significant differences among the clusters for all the elements evaluated except for Na. Soil pH, potassium and zinc levels were found to be below optimum while available phosphorus and iron were above the critical levels leading to deficiencies and /or toxicities. Based on the findings of cluster analysis and variability of each nutrient among the clusters, specific management strategies were suggested to guide in developing of a package of good agronomic practices to improve rice productivity in the irrigation scheme.