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模拟试验和田间试验结果表明,灌淤土麦田施磷量与土壤速效磷增量之间呈直线关系,其斜率称为“土壤需磷系数(C)”,供试土壤的C值为0.32kg P_2O_5/μgg~(-1).灌淤土对水溶性磷肥的固定率很高,一周后达60%,以后趋于稳定.土壤速效磷增量随施磷后的时间按指数函数衰减,其减半期(t1/2)约为30天.用临界点法和土测值回归方程法共同得出灌淤土麦田相对产量99%时的土壤速效磷(P)为15.6μgg~(-1).相关分析表明,土壤需磷系数与土壤肥力指标效应函数法所确定的两种施磷量间呈极显著正相关(r=0.995~(**)).供试灌淤土麦田可按公式Q=0.32×(15.6-P_0)×2.29估算土壤需磷量.
The results of simulation and field experiments showed that there was a linear relationship between the amount of phosphorus application and the increment of available P in irrigated soil. The slope was called “Phosphorus requirement of soil (C)”, and the C value of tested soil was 0.32kg P_2O_5 / μgg ~ (-1) .The irrigated silt soil had a high fixation rate of water-soluble phosphate fertilizer, up to 60% after a week and stabilized thereafter.The increment of soil available phosphorus decay exponentially with the time after phosphorus application The half-period (t1 / 2) was about 30 days. Using the critical point method and the regression equation of soil measured values, the available phosphorus (P) in the soil was 99.6% ) Correlation analysis showed that there was a significant positive correlation (r = 0.995 ~ (**)) between soil phosphorus demand and soil fertility index, The formula Q = 0.32 × (15.6-P_0) × 2.29 to estimate soil phosphorus demand.