Evaluation of sustainability of mixed food crop fields by monitoring particulate organic matter (POM) status and nutrient concentrations

Abstract

Particulate organic matter (POM) status is a useful indicator to assess labile soil organic matter (SOM) and to evaluate soil fertility under different agricultural systems, mainly in low-input agriculture as practiced in most of the sub-Saharan region of Africa. Total POM (53–4000 µm), different sized POM fraction characteristics (mass, C and N contents), and nutrient concentrations of soils were evaluated under 2 mixed food crop field types: a preceding forest fallow (forest) and a preceding fallow dominated by Chromolaena odorata (King & Robinson) (Chromolaena spp.) in the 0–0.10 m horizon of Rhodic Kandiudult, Typic Kandiudult, and Typic Kandiudox soils. The mass and C and N contents of total POM were higher in the Typic Kandiudox than in the Typic Kandiudult, while the Rhodic Kandiudult was intermediate. The pH was lower in the Typic Kandiudox (4.67). Forest had higher pH, Ca2+ and Mg2+ concentrations, and effective cation exchange capacity, while Chromolaena had higher C content in medium (2000–250 µm) and fine (250–53 µm) POM fractions and higher N content in coarse POM (4000–2000 µm). Considering nutrient concentrations, forest appears to be more suitable for a mixed-crop field-crop system than Chromolaena; however, the opposite was found when considering POM status.