Quantified Soil Evolution Under Shifting Agriculture in Southern Cameroon

Martin Yemefack,David G. Rossiter,Rosaline Njomgang

doi:10.3389/fenvs.2019.00016

Abstract

In the tropical rain forest zone of Southern Cameroon, shifting cultivation and perennial plantations of cocoa are the main farming systems practiced by small-scale farmers to ensure subsistence food crop production and a small income. This research used scientific modelling tools to produce quantitative information on the evolution of soils under this shifting agricultural system. An analysis of farming system led to the development of a conceptual model of the spatio-temporal dynamics of shifting agriculture, including transition matrices of rotational cycles that guided the sampling strategy for the study of soil evolution under the system. The study of soil variability showed that 30-35% of the total variance of some topsoil (0-20 cm) properties was due to the influence of land use practices. Five soil properties (pH, calcium, available phosphorus, bulk density and organic carbon) that are the most sensitive to these agricultural practices were empirically modelled and linear/quadratic fractional rational functions were successfully fitted to time series soil variables to derive quantitative measures on temporal changes in soil with land use. Data and methods produced are useful for soil quality assessment and spatio-temporal dynamic simulation in order to guide decision-making for sustainable land-use planning and soil resources management.

Highlights

The imbalance between the luxurious forest stands and the low agricultural production of soils of the tropical rain forest region raises several questions about their capability to sustain intensive agriculture
The conceptual model of land use dynamics and their transitions showed that the short rotational fallow cycle (RSFS) is increasingly being used due to the farmers’ desire to replace cash income from cocoa with cash food crops
This may require intensification; with tighter integration into the market economy and some purchased inputs in order to enjoy the benefits of the shorter fallow cycles in minimizing both deforestation and labor demand

Summary

Introduction

The imbalance between the luxurious forest stands and the low agricultural production of soils of the tropical rain forest region raises several questions about their capability to sustain intensive agriculture. PH, pH water; OC, organic Carbon; P. av, Available P; Ca, exchangeable Calsium; Bd, Bulk density. The first phase responds to the effects of heat and liming ashes from burning and corresponds to an increase of pH water, Calcium, Available P, and bulk density.

Results

Conclusion