THE EFFECT OF PIG SLURRY ON EXCHANGEABLE POTASSIUM IN CALCAREOUS SOILS

Pig slurry in quantities of 200, 400, 500, 600, 800, and 1000 m3 ha-1 year-1) was added to two calcareous soils, which differed in concentration and type of clay minerals. The soils were cultivated with two successive crops of pepper and tomatoes grown in containers. A control was given no slurry. The soils were analysed after harvesting for exchangeable K+. Differences in exchangeable K+ were studied in relation to the concentration and type of clay minerals. The soil with the higher clay content and of the illite type retained K in the exchangeable form to a much greater extent than the soil with the low clay content. In the soil with the lower clay content, of the interstratified illitic- montmorillonite type, very little K was incorporated into the exchange complex. The exchange capacity being low, the amount of K added had little effect on the level of exchangeable K+.