Livestock production on Mediterranean grassland in relation to residual phosphate

Abstract

Available pasture, liveweight gain, milk yield and supplementary feeding of Awassi sheep were monitored for four seasons (1991/92 to 1994/95) on pasture fertilized with superphosphate between 1984 and 1990. The experimental plots received three rates of phosphate (0, 25 and 60 kg P₂O₅/ha) annually, but no application after September 1990. The experiment was grazed at low (1·1 sheep/ha per year) and high (2·3 sheep/ha per year) stocking rates. The experimental site was typical of communally owned grasslands within the cereal zone of west Asia, where cropping is not possible because of shallow, stony soil and steep slopes. Plots with residual phosphate contained significantly more herbage and supported heavier animal liveweights, especially in the first two seasons. Milk yield and lamb production were greater and the need for supplementary feeding was reduced due to increased herbage. The results suggest that benefits of residual phosphate on pasture and livestock production can be considerable and should be included when assessing the value of applying fertilizer to degraded marginal lands in west Asia. Provided that the stocking rates remain within the range tested in the study, the pasture would suffer no harm. However, the higher stocking rates now practiced in the spring under communal grazing might severely limit flowering and seed-set. The property right to own or use the grazing land is seen as a key factor, deserving attention from governments in west Asia in order to apply new technologies to improve degraded marginal lands.