Negative effects of animal manure on grassland due to surface spreading and injection

The effects of animal manure generally are a combination of positive and negative effects. Negative effects are apparent when they are larger than the positive effects or when the positive effects are masked. The paper deals with a selection of negative effects, mainly of cattle manure: 1) Variability in nutrient content, with an example of surface spreading from storage tanks containing unmixed and well-mixed slurry; 2) Uneven distribution of nutrients from surface spreading and injection. With surface spreading the unevenness may result in reduction in herbage yield and quality. With injection it has been observed that the concentrations of nitrogen, nitrate and phosphorus in the herbage decreased with increasing distance from the injection slit. 3) Sward damage caused by surface spreading. This concerns smothering, scorching and possibly other, as yet unknown effects, often resulting in a decrease in herbage yield. This negative effect is most apparent in the first cut after spreading and strongest at the highest rate of manure application. There were no essential differences in yield decrease between cattle slurry and farmyard manure. Dilution of slurry and addition of water immediately after surface spreading reduced or even prevented the negative effects. 4) Sward damage caused by injection. The injection equipment damages the sward, resulting in a yield decrease in the first cut(s). After passage under dry conditions a strip of grass along the injection slit may die and there may be an ingress of unwanted species. The paper gives possible ways to reduce the negative effects. The paper gives possible ways to reduce the negative effects.