PHOSPHATE FERTILIZATION PRIMES PRODUCTION OF RANGELAND ON BROWN RENDZINA SOILS IN THE GALILEE, ISRAEL

Primary production on terra rossa and brown rendzina soils on the hill s of the Galilee in Israel is severely restricted by nutrient, mainly phosphorus, deficiency. The purpose of this study was to investigate t he residual effects of a single application of P fertilizer and the lo ng-term role of P in the production and botanical composition of herba ceous vegetation. A fertilizer trial on brown rendzina soil (Lithic Ha ploxeroll) with P and N treatments was established and monitored for 6 years. Phosphate fertilization consisted of a single surface applicat ion of 45 or 90 kg P ha(-1) as enriched superphosphate (25% P2O5). In the first year, yield of herbaceous vegetation in P fertilized plots i ncreased fourfold compared with the control, and about two-fold during the following 5 years. In the sixth year, production in the fertilize d plots diminished, but was still significantly higher than in the con trol plots. In addition, there was a large increase in the legume cove r that improved the nutritional quality of the range vegetation. Conce ntration of P and N in the plants as well as total P and N uptake, inc reased significantly. Available P concentration in the soil increased two- to five-fold in the year after fertilizer application and a stron g residual effect persisted for up to 5 years. A single application of P (45-90 kg ha(-1)) on brown rendzina soil in the Galilee raised the total 5-year primary production from 780 g m(-2) dry matter in the con trol plots to 1840-2100 g m(-2) dry matter in the fertilized plots. Fo rage quality was also improved for an extended period of over 5 years. Phosphate nutrition was shown to be the key to raising productivity o f these soils. The long duration of the effect increases the chance th at infrequent P fertilization on these rangelands will be economically feasible in certain conditions.