Determinants of Soil Nutrient Dynamics Under Cashew Cultivation in the Sudan Savanna Zone of Nigeria.

Abstract

Due to the poor management practices, and prolonged cultivation of farmlands by local farmers who were unable to identify the key soil nutrients needed to counter the declining cashew yield, this study assessed the main determinants of soil nutrient dynamics under cashew (Anacardium occidentale) in part of the Sudan Savanna, Nigeria. Soil samples were collected from eight 20 x 20 m quadrats at a depth of 0-30 cm in cashew cultivated field. Standard laboratory techniques were used for the determination of particle size distribution, OM, TN, soil pH, EA, Ca²⁺, Mg²⁺, NA⁺, K⁺, AP, CEC, and BS. Principal Component Analysis (PCA) identified the main determinants of soil properties influencing nutrient dynamics under the cashew  crops. The results showed only the first two components accounting for 74.6% were retained to explain the variables. The first component named nutrient supply, featured six fertility-related variables with the highest loadings: EA (0.953), BS (0.944), K⁺ (0.943), pH (0.923), CEC (0.923), and OM (-0.890), and AP (0.750). These variables highlight nutrient availability dynamics and their implications for soil management. The second component, named soil texture component, comprised of variables defining texture with the highest: clay (-0.943), sand (0.919) and silt (0.889). This component illustrates soil texture's role in nutrient retention. Coefficient of variation and means complemented the result of the PCA results. Except for EA (18.83%) and Mg²⁺ (16.57%), which showed a moderate variability, all other variables exhibited relative homogeneity across the field. The results suggest that increases in EA, soil pH, K+, AP, and CEC positively influence soil fertility, while declines in OM and BS may lead to nutrient depletion. This underscores the need to manage soil acidity and nutrient levels to enhance cashew productivity while sustaining soil health. Additionally, the negative loading of clay implies that the prevalent sandy texture in the study area promotes nutrient leaching, necessitating soil amendments to improve nutrient absorption and moisture retention. These insights are vital for smallholder farmers seeking to optimize crop yields amid increasing agricultural intensification.