Effects of Fertilizers on Exchangeable Cation Ratios and Crop Nutrition in Northern Nigeria

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Abstract
SUMMARY Annual applications of calcium, potassium and nitrogen (as urea) over three years caused significant differences in soil exchangeable cation ratios and in the yields of subsequent groundnut and maize crops. High rates of potassium and nitrogen, combined with low rates of calcium, lowered groundnut yields, and high rates of potassium, enhanced by ploughing in crop-residue ash, seriously reduced the exchangeable Mg: K cation ratio and maize magnesium status. Maize yields were significantly negatively correlated with soil potassium status. The balance between exchangeable cations in these soils is very easily upset by injudicious combinations of fertilizers and management practices.