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7057. Van Doren, G.S.. 1983. The form and distribution of soil phosphorus as affected by management and soil variability.. M.S. Thesis, Dept. of Agronomy and Soils, WSU, Pullman, WA.
Studies were initiated in the Pacific Northwest to determine long-term effects of cropping systems and tillage management practices on the form and distribution of soil phosphorus. Studies indicated that, in comparison with the native Palouse prairie, organic phosphorus in Palouse soils has declined more than 50% with cultivation and cropping. Stratification of phosphorus, with increasing concentration towards the soil surface, was found in no-till soil. A cropped soil which has been managed without utilizing chemical fertilizer showed total and organic phosphorus accumulations in the upper 30 cm of the soil profile with depletions lower in the profile. This was not evident in the adjacent, conventionally farmed soil. However, soil varibility often masked the effects of soil and crop management on phosphorus forms and distribution in soil. For example, soil series induced wider variation (significant at the 0.01 level) in phosphorus values than did management in a study which included detailed soil mapping. This study demonstrated that many experiments are not designed to quantify variations in soils; in fact, some are designed to mask soil differences by statictical analysis. Sequential testing is suggested as an appropriate experimental design to quantify soil variability.