Application of piggery waste to soils in pots: effect on dry matter yield and uptake of nitrogen, potassium, calcium and magnesium by ryegrass and white clover

Abstract

The effect of piggery waste application on the yield and uptake of nitrogen, potassium, calcium and magnesium by ryegrass (Lolium perenne) and white clover (Trifolium repens) growing in three soils was studied in pot culture. Waste was applied six times during a 108-d growth period. The total waste applied to different treatments was equivalent to 0,5.3,9.4, 12 2 and 18.0 t dry matter (DM)/ha. Application of waste resulted in significant increases in the yield of ryegrass on all soils, and white clover on one soil. There was no significant decrease in yield at the highest application rate, indicating the absence of an excess soluble salt effect. Application of waste at 9.4 t DM/ha corrected a dietary deficiency of potassium in ryegrass and clover growing on a potassium-deficient podzolic soil. However, application of waste at 5.3 t DM/ha caused the K: (Ca + Mg) ratio of ryegrass growing on an alluvial soil and a red brown earth to exceed 2.0, considered to be an index above which grass tetany may develop in ruminants. Application of waste to ryegrass at 18 t DM/ha or clover at greater than or equal to 9.4 t DM/ha caused the plant tissue nitrate concentration to exceed 0.2% N, which is pitentially toxic to farm animals.