Soil pH and lime requirement for high potential communal areas of Zimbabwe

Abstract

A steady increase in the use of acidifying nitrogenous fertilisers by Zimbabwe’s communal area farmers since 1980 has not been matched by liming the soils to correct soil pH. A study was conducted in 1995 to assess the pH status of soils based on soil samples submitted to the Chemistry and Soil Research Institute of the Department of Research and Specialist Services by the communal area farmers in 1982-84 and 1992-94 so as to assess the lime requirement of the soils. Results showed that there was a gradual acidification of the soils. During the 10- year period the proportion of soils with pH of 5,0 or less increased from 42% to 77%. The soil pH results implied potential problems of crop production which included low fertiliser effectiveness in 77% of the soils with pH of 5,0 or less, Al toxicity and P deficiency in 43% of the soils with pH of 4,5 or less, and micronutrient deficiency (e.g. Mo).