| [Objective] In this study,the long-term evolution of P application level,P use efficiency and P fertilizer type in Xinjiang was investigated to provide the theoretical basis for reasonable P fertilizer application strategy and improve P use efficiency.[Method] Through collecting data from the relevant statistical sources and published literatures closely involved in P study in Xinjiang,the changes of crop productivities of wheat,maize and cotton and the variation of both chemical(N + P2O5 + K2O)and P fertilizer(P2O5)input level over years were analyzed,also,crop P using efficiency was evaluated via Meta-analysis.[Result](1)It was found that crop productivities of wheat,maize and cotton increased gradually over years during the past six decades,and the yield increasing tendency of the three main crops could be distinctly divided into the following three stages including steady rising stage(1949-1980),rapid rising stage(1981-1997)and slow rising stage(1998-2012).The application rates of chemical fertilizer and P fertilizer increased from 35.4 kg/hm2 and 8.3 kg/hm2 in 1979 to 376.1 kg/hm2 and 95.5 kg/hm2 in 2012,respectively.Thus,the average chemical fertilizer and P fertilizer annual increment level were 10.6 kg/(hm2·a)and 2.8 kg/(hm2·a),and the annual increment rates of 7.4% and 7.7% were archived,correspondingly.It was showed that either chemical or P fertilizer partial productivity of wheat,maize and cotton increased with year prolonging.For instance,the chemical fertilizer partial productivities were 44.2 kg/kg for wheat,61.2 kg/kg for maize and 9.3 kg/kg for cotton in 1979,respectively,and those dropped to 14.2 kg/kg,18.4 kg/kg and 5.5 kg/kg,thus,the average annual decrement rates of 3.4%,3.6% and 1.6% were obtained,accordingly,in 2012.Similarly,the P fertilizer partial productivities were 189.1 kg/kg for wheat,262.0 kg/kg for maize and 39.8 kg/kg for cotton in 1979,respectively,those reduced to 72.5 kg/kg,55.9 kg/kg and 21.5 kg/kg,respectively,and the average annual decrement rates of 3.6%,3.8% and 1.8% were presented in 2012.In addition,a slight increment of P fertilizer using efficiency was found by meta analysis method,e.g.,the average P fertilizer using efficiency of 18.2%(median=17.9%,n=334)was gained,and the average annual P fertilizer using efficiency increment rate of 1.7% was obtained over years from 1981 to 2012.(2)We studied the changes of phosphorus fractions(Olsen-P,total P,Resin-P,Na HCO3-P,Na OH-P,HCl-P,Residue-P)and soil phosphorus fertility in response to long-term from 1981 to 2013 supplementing of P fertilizers on calcareous soil of cropland vers uncultivated land and within five vertical soil layers as 0 to10,10 to 20,20 to 30,30 to 60,and 60 to 80 cm.The experiment samples were distributed in Shihezi Recalmation of Xinjiang province in China.The soil samples were analyzed in 0-10,10-20,20-30,30-60 and 60-80 cm soil profiles.The results showed that:(1) Phosphate application has more influence on Olsen-P than total P fraction.The soil Olsen-P fraction were straight linear with fertilizer P rate and planting years(P<0.001),the ratio of Olsen-P:Total-P was positively correlated with planting years(P<0.001).(2)Long-term phosphate application were notably increased the 0-20 cm profiles Olsen-P contents,both the Olsen-P and Total P fractions were decreased with downward to soil profiles.(3)The labile(Resin-P and Na HCO3-P)and moderately labile Pi fractions(Na OH-P)both in cropland and uncultivated land were gradually decreased,conversely,the non-labile Pi fractions(HCL-P and Residue-P)were increased.The contents and ratio of Pi fractions both in cropland and uncultivated land profiles were: HCl-P > Residue-P > Na HCO3-P > Na OH-P > Resin-P.(4)The ratio of Olsen-P: total P both in 0-10 cm,10-20 cm,and 20-30 cm cropland and uncultivated land profiles were larger than 1.0%,and applied-P obviously affected the topsoil available P fractions,instead the less-available or recalcitrant fractions.[Conclusion] Overall,it can be concluded that P supply rate increased significantly with years prolonging in Xinjiang.However,the yield increasing effect of per unit applied P significantly decreased.A relative low P fertilizer using efficiency was observed,and that showed a slight rising trend along with year increasing.Moreover,it was found that the ratio of the P fertilizer accounted for the total NPK fertilizer increased with the year increasing.Furthermore,the P fertilizer type was changed from low concentration to high concentration,meanwhile,P fertilizer application methods gradually shifted from basal to basal plus dressing application in Xinjiang.Long term fertilization significantly affected the topsoil available phosphorus content;0-30 cm soil total phosphorus and available phosphorus content were with years of fertilization increased and increased;0-30 cm labile inorganic P content increased,accounting for inorganic phosphorus group scores declined slightly. |
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