Quantified soil evolution under shifting agriculture in southern Cameroon

Open Access JournalIn 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 modeling 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 modeled 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

Effects of soil properties on maize growth under increasing phosphorus fertilization in three contrasting acid soils in southern Cameroon

Plant growth response to phosphorus (P) fertilizer in acid soils is affected by several soil properties. We conducted pot experiments with P using three contrasting acid soils from southern Cameroon (i) to study the main soil factors causing differences in growth responses of maize (Zea mays L.) to applied P, and (ii) to statistically model variation in soil qualities across soil types and their relationships to dry matter production. The soils studied were classified as Typic Kandiudox (TKO), Rhodic Kandiudult (RKU) and Typic Kandiudult (TKU). Shoot dry yield (DMY) was significantly affected by soil type (P = 0.000) and P rate (P = 0.000) but the interaction term was not significant. Predicted maximum attainable DMY was lowest in TKO (26.2 g pot–1) compared to 35.6 and 36.7 g pot–1 for RKU and TKU, respectively. Properties that enhanced DMY were the inorganic NaHCO3-P pool, individual basic cations (Ca, Mg and K) and pH, whereas exchangeable Al and C/N ratio significantly depressed DMY. Principal component analysis yielded similar results, identifying 4 orthogonal components which accounted for 84.68% of the total system variance (TSV). Principal component 1 identifying soil nutrient deficiency explained 35.9% of TSV. This soil quality varied significantly among the studied soils, emerging as the only soil quality which significantly (