Spatial variability of soil secondary and micronutrients under smallholder maize production system in sub-humid condition of Zimbabwe

Achieving household and national food security is the core focus for policy makers in sub-Saharan Africa (SSA). However, land degradation and dearth of effective soil nutrient management strategies for spatially variable soils is significantly contributing to food insecurity in SSA. The aim of this study was to establish the spatial variability of soil secondary and micronutrients (SMN) under smallholder maize production system in sub-humid condition of Zimbabwe. Geo-referenced samples collected in all maize fields in seven of the eleven villages in ward 10 of Hurungwe district using purposive sampling were analyzed for Ca, Mg, Fe, Mn, Cu and Zn using standard methods. Pearson's correlation analysis was conducted to reveal the relationships among the nutrient status. The linear mixed model (LMM) was used to analyse spatial variation of the data with evidence for spatial dependence in the random component of the model assessed by calculating Akaike's information criterion (AIC). The results indicate that only Ca was significantly (p < 0.05) influenced by field type with larger concentrations in home fields compared to outfields. Soil texture had a significant (p < 0.05) effect on Ca, Mg and Zn with the largest values for Ca and Mg found in the sandy clay loams (with the largest clay content) compared to sand, loamy sand and sandy loam. Loamy sand had the largest Zn concentration with sandy clay loams having the least. There was evidence for spatial dependence in Ca and Mg with field type, latitude and longitude as fixed effects; hence these nutrients were mapped in the GIS environment. It can be concluded that SMN tend to be deficient in some areas and vary spatially as influenced by soil intrinsic conditions and management, even at ward level.