The Study Of Phosphorus Availability Of Black Soil And Its Influencing Factor

It is important to understand phosphorus availability and affecting factors to improve phosphorususe efficiency. Therefore, three-year field experiment, long-term experiment soil analysis and160-dayincubation experiment was carried out to study the effect of phosphorus amount （0,60,75kg P22O5/hm）,different fertilizer management （NK, NPK, NPK+Manure, NPK+Straw） and different temperature （5,15℃,25℃,35℃） on the phosphorus availability in black soil. Maize yield, Olsen-P, total phosphoruscontent, different forms of organic and inorganic phosphorus contents were measured to analyze therelationship between different phosphorus forms and Olsen-P. The main conclusions were as follows:（1） Three-year field experiment: Maize yield in the field was not different among P0, P60and P75treatments in the first two years. However, in the third year, maize yield under P0treatment wassignificantly lower than that of P60and P75treatments. While maize P uptake showed significantdifference （P0<P60<P75） from the second year. And in the third year, the difference was much moresignificant. In P0treatment, Olsen-P and Fe-P decreased year by year. In P60treatment, Olsen-P keptstable over three years, and Al-P increased linearly. In P75treatment, both Olsen-P and Al-P increasedlinearly. The correlation analysis of Olsen-P with different inorganic phosphorus forms indicated thatAl-P was the most efficient inorganic form, and Fe-P followed the next. Appropriate amount ofphosphate fertilizer （60kg P22O5/hm） could maintain maize yield and Olsen-P content in the soil.（2） Different fertilizer combinations on phosphorus availability in black soil: Olsen-P contentincreased13times under NPKM treatment, increased more than twice under NPK and NPKS treatments,whereas, decreased50%under NK treatment. Total phosphorus and inorganic phosphorus contents werein order of NPKM>NPKS>NPK>NK. NPKS treatment significantly increased organic phosphoruscontent from35%to44%. Different treatments had significant effects on the content of inorganicphosphorus. For Ca₂-P, Ca₈-P and Al-P and Ca₁₀-P, different fertilizer combinations had different effecton them, and the contents were in order of NPKM>NPKS>NPK>NK, but for Fe-P, the effect of NPKwas larger than that of NPKS. For organic phosphorus forms, labile organic P with NPK, NPKM andNPKS treatments increased4times,9times and4times, respectively. Highly stable organic P withNPKM treatment decreased27.98%. Correlation analysis between Olsen-P and the phosphorus formsshowed that, in addition to the highly stable organic P, other of phosphorus forms were significantlyrelated to Olsen-P. Multiple linear stepwise regression analysis between Olsen-P and the phosphorusforms showed that only Ca₂-P and moderately labile organic P were in significant regression, and theregression equations were Y=7.94+1.05X and Y=81.21+0.86X. NPKM treatment increased Ca₂-P, Ca₈-P,and Al-P, labile organic P, moderately labile organic P and moderately stable organic P, and reduced thehighly stable organic phosphorus, which would significantly increase Olsen-P content and improvephosphorus availability.（3） Effect of different temperatures on effectiveness of phosphorus availability in black soil. Theresults of cultivation incubation experiment under different temperatures indicated that: Olsen-P content increased with the increase of temperature under NK, NPK, NPKM and NPKS treatments. And Olsen-Pcontent, under15℃,25℃and35℃treatments were significantly higher than that of5treatment.Soil total phosphorus and organic phosphorus followed similar trends. For inorganic phosphorus forms,Fe-P content of different temperatures was stable under different temperatures. And low temperaturepromoted the formation of Ca₁₀-P. Ca₂-P content increased with the increase of temperature. Thechanges of Ca₈-P and Al-P content weren’t consistent under different fertilizer and temperaturetreatments. For organic phosphorus forms, labile organic P content under different fertilizer treatmentsreduced with the increase of temperature. The moderately and highly stable organic P contents under5and15were higher than those under25℃and35℃. Moderately labile organic P content wasaffected by temperature without regularity. Soil phosphorus availability and temperature was positivelycorrelated.In conclusion, the content of inorganic phosphorus and Olsen-P increased with the increase ofphosphate fertilizer input. From improving all phosphorus forms, NPKM treatment was better thanNPKS treatment. High temperature increased Olsen-P content. Therefore, appropriate amount ofphosphate, fertilizer combination and soil temperature were all suitable to increase the content ofOlsen-P in the soil.