Long term effects of slurry on grassland

Abstract

The herbage yield of a ryegrass (Lolium perenne) sward receiving fertilizer, pig slurry or cow slurry applications for 16 years showed a typical response curve to the amount of soluble nitrogen (N) applied. Pig slurry supplied more phosphorus (P) than did cow slurry while the reverse was found for potassium (K). Herbage P and K contents were correlated with the amounts applied. Herbage sodium (Na) content declined under the largest pig slurry dressing and all dressings of cow slurry, probably due to antagonism between K and Na and also to changes in sward botanical composition. Large slurry dressings reduced the proportion of L. perenne in the sward. Pig slurry had an acidifying effect on the soil but only the largest dressing lowered soil pH more than did the fertilizer treatment. The largest dressing of cow slurry maintained soil pH at the original value of 6.3. Substantial accumulations of soil P from pig slurry and K from cow slurry occurred in the top 15 cm of soil, especially at the highest slurry application rate (200 m3ha-1yr-1).