Effect of Continuous Intensive Cultivation on the Chemical and Microbiological Properties of Oxic Dystrandept Soils in the Western Highlands of Cameroon

Abstract

Soil fertility indices are well documented as they are directly related to land use and productivity. However, the effect of continuous intensive cultivation on the evolution of soil fertility is still poorly documented. The aim of this study was thus to assess the effect of continuous intensive cultivation on the chemical and microbiological properties of Oxic Dystrandept soils in the Western Highlands of Cameroon. Composite soil samples were taken between 0-15 cm depths on farmlands that have been subjected to continuous intensive cultivation for one, five and ten years meanwhile samples from plots that have never been cultivated served as control. The main results revealed that the ammonium contents dropped abruptly (86%-wt) from the first year of cultivation. The organic carbon (OC) content decreased from 1.81 ± 0.14 %-dm (in control) to 1.69 ± 0.09 % after one year, 1.66 ± 0.10 % after 5 years and 1.58 ± 0.07 % after 10 years. Compared to the control, available phosphorus (P) showed a 13 %-wt drop after one year, 46 % after 5 years and 85 % after 10 years. Dehydrogenase activity showed a 42 % decrease after one year, 50 % after five years and 73 % after 10 years. The other parameters were not significantly different (P<0.05) amongst treatments. Decline of soil productivity was undoubtedly related to the decrease of OC, P, microbial activity and ammonium with continuous intensive cultivation. Thus, management strategies for improved crop production should include selection suitable cropping systems and chemical methods. Keywords: Continuous intensive cultivation, enzymatic activities, soil chemical properties, Oxic Dystrandept, Cameroon western highland