The objective of the study was to assess spatial variability of soil nutrients in field, and their impact on grain yield and gross net returns in a uniformly managed 7 ha small-scale corn field. The study was conducted at Syferkuil agricultural experimental farm (23°50’ S; 29°40’ E) of the University of Limpopo, in the northern semi-arid region of South Africa. Prior to corn planting, a land suitability assessment for corn was carried out following FAO guidelines. Soil sample parameters, which included N, were collected and/or measured from geo-referenced locations on a 40 m grid. Spatial maps of nutrient distribution were produced with the support of GIS. There was significant variability (P≤0.05) of soil nutrients and pH across the corn field. Corn grain yield varied significantly with a range from 2.7 to 6.3 Mg ha-1. For an S1, highly productive Rhodic Ferralsol soil under linear irrigation in a semi-arid environment, these grain yields were considered low. The lower grain yields were associated with variability of soil nutrients, which negatively affected net returns. Spatial economic analysis revealed areas of loss that suggests that improvements in economic returns would be likely if small fields were managed site-specifically.
Key words: Precision agriculture, soil nutrient management, small-scale farming, spatial variability.
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