Effects Of Different Tillage And Rotation Systems On Soil Phosphorus Fractions

A multi-year(5yrs) experiment was conducted to compare the effects of conservation tillage with conventional plow tillage on phosphorus fractions and content in the 0-5cm,5-10cm,10-30cm depth in loess soil in Longzhong loess plateau.Basically, the experiment was designed with rotation. The rotation sequence was spring wheat (w) followed by field pea (p). Therefore, there are two phrases, spring wheat and field pea. The results were the following.Against the background of conventional tillage, the treatments of no-till with straw cover (NTS) , no-till with no straw cover (NT)and conventional tillage with straw incorporated (TS) could increase the content of L-OP, ML-OP, MR-OP, HR-OP and Ca₂-P. When different tillage types were applied to the tested soil at the same layer, the content of organic phosphorus fractions and Ca₂-P among treatments varied in the order of NTS>NT>TS>T. In addition, the content of total organic phosphorus with NTS was more than the content of other treatments, and the treatment of T is the lowest.Other inorganic phosphorus fractions fluctuated with different tillage types either. Against T, the treatments of NTS,NT and TS could decrease the content of Ca₈-P and O-P . The content of Ca₈-P varied in the order of NTS>NT>TS> T. In the 0-5cm depth, the content of Ca₁₀-P with the treatments of NTS,NT and TS was less than the treatment of T, however, didn't show clear changes in the 5-10cm and 10-30cm depth. The treatment of NTS can increase the content of Al-P,Fe-P, but the content of Fe-P had no significance(p<0.05) among the four treatments.Inorganic P(Pi) occupied the most part of soil P and accounted for 79.4% on average, then organic P(Po) accounted for 20.6%.Of the total Pi, Ca phosphates(Ca-P) were the dominant Pi fractions and accounted for 78.4% on average. Pi fractions varied in the order of Ca₁₀-P >Ca₈-P >O-P>AI-P >Fe-P>Ca₂-P. Of the total Po, ML-OP was the dominant fraction and accounted for 70.0% more, followed by HR-OP, then MR-OP, and L-OP was the lowest.The P fractions, and particularly the Po fractions and Ca₂-P,Ca₈-P,Al-P,Fe-P tended to decline with the soil depth among the four treatments. Of the Pi, Ca₁₀-P accumulated in the 5-10cm depth of the tested soil.O-P didn't show clear changes in the soil depth despite some fluctuation.The Po fractions and Pi fractions didn't show clear changes with time (1year) under the...