Management effects on forms of phosphorus in soil and leaching losses

We should know the effects of soil use and management on the contents and f orms of soil phosphorus (P) and the resulting potential for leaching losses of P to prevent eutrophication of surface water. We determined P test valu es, amounts of sequentially extracted forms of P, P sorption capacities and degrees of P saturation in 20 differently treated soils and compared these data with leaching losses in lysimeters. One-way analyses of variance indi cated that most fractions of P were significantly influenced by soil textur e, land use (grassland, arable or fallow or reafforestation), mineral ferti lization and intensity of soil management. Generally, sandy soils under gra ss and given large amounts of P fertilizer contained the most labile P and showed the largest P test values. Fallow and reafforestation led to smalles t labile P fractions and relative increases of P extractable by H2SO4 and r esidual P. Arable soils with organic and mineral P fertilization given to c rop rotations had the largest amounts of total P, labile P fractions and P test values. The mean annual concentrations of P in the lysimeter leachates varied from 0 to 0.81 mg l(-1) (mean 0.16 mg l(-1)) and the corresponding leaching losses of P from < 0.01 to 3.2 kg ha(-1) year(-1) (mean 0.3 kg P h a(-1) year(-1)). These two sets of data were correlated and a significant e xponential function (R-2 = 0.676) described this relation. Different soil t extures, land uses and management practices resulted in similar values for P leaching losses as those for the amounts of labile P fractions. Surprisin gly, larger rates of mineral P fertilizer did not necessarily result in gre ater leaching losses. The contents of P extracted by NaHCO3 and acid oxalat e and the degrees of P saturation were positively correlated with the conce ntrations of P in leachates and leaching losses. As the P sorption capacity and degree of P saturation predicted leaching losses of P better than did routinely determined soil P tests, they possibly can be developed as novel P tests that meet the requirements of plant nutrition and of water protecti on.