Zambian Kalahari Sands and Zambezian - Miombo Loamy Sands Respond Differently to Agricultural Expansion

Previous research showed varying degrees and types of impacts of agricultural expansion (AE) into natural habitats on soil-biodiversity-water compartments due to climatic, vegetation, and soil factors. Limited research on sandy soil responses to anthropogenic stresses, particularly duration of cultivation, calls for more attention. The study investigated the effects of farmers’ resources and farm age on soil properties in high (Chitokoloki) and medium rainfall (Lukweta) zones of Zambia plagued by AE. Farms were categorized into: newly converted native vegetation and fallow (one-year each), three-, five-, and ten-year-old farms under three wealth categories (WCs) identified through a participatory approach, yielding 25 farms per wealth category with 75 farms in each agroecological zone (AEZ). Soils collected at 20 cm depth were processed for standard laboratory analyses. WCs did not influence soil properties. Chitokoloki Arenosols (CAs) had varying trends of decline with farm age, notably bulk density, pH, ∆pH, cations, soil organic carbon (SOC), and sulfur. Conversely, Lukweta Acrisols (LAs) had mixed response patterns. SOC of CAs declined (p < 0.018) on average by 1.2 g kg^-1 up to five years of cultivation, while SOC of LAs (p = 0.001) declined by 0.8 g kg^-1 up to ten years. These suggest pronounced declines in Arenosols, revealing vulnerabilities of the humid zones to disturbance. Soil properties respond differently to AE, depending on AEZ, and permutations of climate-parent material interactions. Future research calls for integration of technological and sociological factors to understand the dynamics of AE and soil properties.