Effect of Continuous Vegetable Cultivation on Phosphorus Levels of Fluvo-Aquic Soils

摘要

Soil P status, inorganic P fractions, and P sorption properties were studied using sandy fluvo-aquic horticultural soils, which are high in organic matter content for vegetable production in comparison with a soil used for grain crop production in Zhengzhou, Henan Province, China P fractions, Olsen-P, and OM were determined at different depths in the soil profile and sorption isotherm experiments were performed Most P in excess of plant requirements accumulated in the topsoil and decreased with soildepth. Total P, inorganic P, and OM concentrations increased with continued horticultural use Olsen-P concentrations in the 0-20 cm depth of horticultural soils were 9 to 25 times higher than those of the grain crop soil. A linear transformation of the Langmuir equation showed that the P adsorption maximum (491.3 mg P kg~(-1)) and the maximum phosphate buffering capacity (162.1 L kg~(-1)) for 80--100 cm were greater in the grain crop soil than the horticultural soils. Thus, the most immediate concern with excess P were in areas where heavy P fertilizer was used for vegetable crops and where soil P sorption capacities were low due to sandy soils and high organic matter content.