关键词: 磷肥品种, 塿土, 玉米, 无机磷组分, 土壤有效磷

Abstract:

【Objective】Synthetic phosphorus fertilizers may vary in their behavior when applied to soil because of their inherent differences in nature. In order that the phosphate fertilizers could well match the crops’ P requirement, the selection of appropriate types of P sources are of paramount importance in practice. To achieve this, it is necessary to make a thorough investigation on phosphorus distribution among different soil P fractions and their bioavailability when P applied to soil in various varieties of synthetic phosphate fertilizers. 【Method】We conducted a pot experiment on a calcareous tier soil with a lower Olsen P level, which was collected from a plot without P addition for 20 years. Eight treatments were established: (1) no phosphate fertilizer (Control); (2) superphosphate (SSP); (3) calcium magnesium phosphate (CaMg P); (4) mono-ammonium phosphate (MAP); (5) di-ammonium phosphate (DAP); (6) ammonium poly-phosphate (Poly P); (7) Urea phosphate (Urea P); (8) superphosphate plus ammonium sulfate (SSP+ASA). A maize variety ‘Zhengdan 958’ was used as a test crop. We analyzed the correlations between P uptake in above-ground biomass of maize, soil Olsen P and the content of soil P fractions, which were determined with a P fractionation method modified by Jiang & Gu. 【Result】Results showed that the contents of soil available P (Olsen P) and its dynamics varying with treatments. The average Olsen P contents followed an order of DAP＞Urea P≥Poly P＞MAP＞SSP+ASA＞SSP＞CaMg P＞Control based on their statistical significance during the experimental period of two months. Compared with the control treatment, all treatments receiving P significantly increased the above-ground biomass, phosphorus uptake and phosphorus use efficiency of maize by 64.8%-221.3%, 114.1%-593.0% and 2.1%-11.0%, respectively. The largest increase was observed in treatments receiving DAP and poly P. Both the phosphorus uptake and above-ground biomass of maize were positively and significantly correlated with soil Olsen P. Phosphorus fractions of Ca₂-P, Ca₈-P, Al-P and Fe-P were enhanced by 36.9%-610.0%, 21.7%-85.5%, 57.2%-83.0%, 28.5%-77.8% in all phosphorus application treatments except O-P and Ca₁₀-P, which remained unchanged except in CaMg P treatment. Of which, the greatest increases in Ca₂-P and Ca₈-P were observed in treatments given MAP, DAP, poly P and Urea P; the largest increases in Al-P and Fe-P were found in SSP+ASA and SSP treatments; significant increases in O-P and Ca₁₀-P were only obtained in CaMg P treatment. The Poly P treatment had the significantly greater Ca₂-P than MAP and Urea P treatments, only lower that DAP treatment, but it contained a significantly lower Ca₈-P relative to DAP, MAP and Urea P treatments. Compared with SSP, SSP+ASA significantly increased the contents of Ca₂-P and Al-P by 24.9% and 11.9%, respectively, and the available phosphorus content increased by 11.4%. The inorganic P fractions of Ca₂-P, Ca₈-P and Al-P showed a significant and positive correlations with soil available phosphorus and phosphorus uptake by plants. 【Conclusion】Under the tested soil conditions, DAP had a lower phosphorus fixation and thus a greater available phosphorus pool. Poly P inhibited the transformation of Ca₂-P to Ca₈-P and therefore reduced the precipitation of phosphorus. The results suggested that Poly P is equivalent to DAP in bioavailability, and these two varieties of phosphate fertilizers could be used where there is an urgent need to improve and maintain soil Olsen P. The application of physiological acidic fertilizer ammonium sulfate combined with SSP in calcareous soil not only increased the content of available phosphorus, but also reduced the fixation of phosphorus.

Key words: variety of synthetic phosphate fertilizer, tier soil, maize, inorganic phosphorus fractions, soil available phosphorus