Evaluation of Selected Soil Fertility Parameters for Improvement of Fertilizer Recommendations in Zambia

The fertilizer practice among smallholder farmers in Zambia is to apply the same amount of fertilizers to crops regardless of soil type and climatic conditions. The blanket fertilizer application across soil types and agroecological regions (AERs) is not efficient. In this study we evaluate the influence of soil type and climate on selected soil fertility parameters that are used to determine fertilizer recommendations. Samples of three different soil types were obtained from AER I and IIa and analyzed for selected soil fertility parameters using standard laboratory methods. Individual parameters were subjected to a two-way ANOVA to determine any differences among soil types and across AERs using the general linear model procedure. The soil variables showed that significant differences in soil fertility status exist among soil types and across AERs at various p values. The differences associated with soil types are more pronounced in soil chemical fertility parameters (p < 0.01 and p < 0.05), while differences associated with AERs are evident in the soil physical parameters (p < 0.01 and p < 0.001). The measured values of soil fertility parameters are categorized into different classes in terms of optimality, levels of adequacy and deficiency. Results of the study suggests that the current blanket fertilizer recommendation is inadequate because it does not take into account variations in the soil fertility status across soil types and AERs. Understanding how the soil fertility characteristics and their interaction with AERs influence soil fertility status is an important guide to more efficient fertilizer recommendations.