Leguminous fallows improve soil quality in south-central Cameroon as evidenced by the particulate organic matter status

Abstract

Three experiments were conducted on three soil types in south-central Cameroon to evaluate the effects of leguminous fallows on soil quality as compared with nonleguminous fallows. Soil quality was assessed by analysing the status of particulate organic matter (POM) fractions (4000–53 μm): (i) at the end of fallow and after cropping of 3-year-old Chromolaena odorata, fallow with C. odorata removed by hand, and Pueraria phaseoloides fallow; (ii) in soil from 1-year-old C. odorata and P. phaseoloides fallow, before and after 6 weeks of growing maize in a pot experiment, which had two treatments: T1= +P −N and T2= +N −P; and (iii) at the end of a 2-year-old Calliandra calothyrsus and a 2- and 4-year-old C. odorata fallow. Both, the herbaceous ( P. phaseoloides) and tree ( C. calothyrsus) leguminous fallows improved soil quality of a nonacidic Typic Kandiudult and a Rhodic kandiudult. The N content of either the coarse (4000–2000 μm) or the medium (2000–250 μm) POM fraction was increased as compared to the nonleguminous C. odorata fallow. This trend was also found after cropping all fallows. C. odorata fallow is better adapted to improve soil quality in the acidic Typic Kandiudox, than both leguminous fallows. N addition to soil from C. odorata fallow increased maize growth in the pot experiment as well as the weight of coarse POM (cPOM). P addition to soil from P. phaseoloides fallow had the same effect in the Rhodic Kandiudult, while a more pronounced response to P addition was found in soil from C. odorata fallow in the Typic Kandiudult. A negative effect on cPOM weight after P and N addition was mainly found in soil from P. phaseoloides fallow in the Typic Kandiudox.