施磷对陇中黄土高原春小麦耕层土壤磷组分及有效性的影响

Effects of phosphorus application on phosphorus composition and availability of spring wheat topsoil on the Loess Plateau of Longzhong

利用2017年设置在定西市李家堡镇麻子川村的长期定位施肥试验,设置4个施磷水平:P1(0 kg·hm^(-2))、P2(75 kg·hm^(-2))、P3(115 kg·hm^(-2))、P4(190 kg·hm^(-2)),测定收获后耕层土壤(0~20 cm)无机磷组分(Ca_(2)-P、Ca_(8)-P、Al-P、Fe-P、O-P、Ca_(10)-P)、有机磷组分(LOP、MLOP、MROP、HROP)。研究结果表明:土壤磷组分含量变化顺序为Ca_(10)-P>Ca_(8)-P>MLOP>O-P>HROP>Fe-P>Al-P>Ca_(2)-P>MROP>LOP。随着施磷量的增加,Ca_(2)-P、Ca_(8)-P、O-P、LOP、MLOP、MROP、HROP、有效磷、全磷含量增加,增幅为8.41%~56.95%;Al-P、Fe-P、Ca_(10)-P含量先增加后降低,最大值分别为43.45(P2)、37.64(P2)、341.63(P3)mg·kg^(-1),最小值分别为28.63、33.06、321.96 mg·kg^(-1)。随着施磷量的增加,Ca_(2)-P、Ca_(8)-P和MLOP占比增加,增幅分别为28.00%、24.46%、6.37%;Al-P、LOP先分别增加至6.00%(P2)、2.67%(P2)后减小至4.31%(P4)、2.11%(P4);Fe-P、Ca_(10)-P、MROP、HROP减小,减幅分别为5.75%、12.64%、21.37%、6.75%;O-P由9.17%(P1)先减小至8.08%(P3)之后增加至8.80%(P4);PAC(磷活化系数)增加,增幅最大为26.40%(P4);无机磷占全磷的相对含量和无机磷与有机磷之比先增大后减小,分别由增幅的80.41%、4.10%减小至76.32%、3.21%,有机磷占全磷的相对含量先减小至19.59%后增加至23.75%。土壤磷形态对有效磷的直接影响大小顺序为:Ca_(8)-P>Ca_(2)-P>MLOP>LOP>HROP>MROP>Fe-P>Al-P>O-P>Ca_(10)-P。相关分析和逐步回归结果表明,Ca_(2)-P是陇中黄土高原春小麦农田土壤有效磷的最主要磷源,长期施磷肥主要通过提高可供作物直接利用的Ca_(2)-P、LOP和具有缓效作用的Ca_(8)-P、Al-P、MLOP比例,降低土壤中难溶性Fe-P、O-P、Ca_(10)-P、MROP、HROP的比例从而增加有效磷的含量,进而提升了土壤潜在供磷能力。

This study was to examine the effect of phosphorus application on the distribution,transformation and availability of soil phosphorus components in order to provide a reference for the efficient use of phosphorus in farmland and soil nutrient balance in the dry farming area of the Loess Plateau in central Gansu.The study used the long-term location fertilization experiment in Mazichuan Village,Lijiabao Town,Dingxi City in 2017,and set four phosphorus application levels(P1=0 kg·hm^(-2),P2=75 kg·hm^(-2),P3=115 kg·hm^(-2),P4=190 kg·hm^(-2)).The Jiang Baifan-Gu Yichu method and Bowman-Cole method were used to analyze and determine the soil inorganic phosphorus(Ca_(2)-P,Ca_(8)-P,Al-P,Fe-P,O-P,Ca_(10)-P)and organic phosphorus components(LOP,MLOP,MROP,HROP)in the cultivated layer(0~20 cm)after harvest.The results showed that the change sequence of soil phosphorus content was Ca_(10)-P>Ca_(8)-P>MLOP>O-P>HROP>Fe-P>Al-P>Ca_(2)-P>MROP>LOP.With the increase of the amount of phosphorus applied,the content of Ca_(2)-P,Ca_(8)-P,O-P,LOP,MLOP,MROP,HROP,available phosphorus and total phosphorus increased,and the increase rates were ranged from 8.41%to 56.95%.The contents of Al-P,Fe-P,and Ca_(10)-P first increased and then decreased,with the maximum values being 43.45(P2),37.64(P2),341.63(P3)mg·kg^(-1)and the minimum values were 28.63,33.06,321.96 mg·kg^(-1),respectively.With the increase of phosphorus application rate,the proportions of Ca_(2)-P,Ca_(8)-P,and MLOP increased by 28.00%,24.46%,and 6.37%,respectively,Al-P and LOP first increased to 6.00%(P2)and 2.67%(P2),respectively,and then decreased to 4.31%(P4),2.11%(P4);Fe-P,Ca_(10)-P,MROP,and HROP decreased by 5.75%,12.64%,21.37%,6.75%,respectively.O-P decreased first from 9.17%(P1)to 8.08%(to P3)and then increased to 8.80%(P4).The maximum phosphorus activation coefficient increase was 26.40%(P4).The relative content of inorganic phosphorus in total phosphorus and the ratio of inorganic phosphorus to organic phosphorus were first increased to 80.41%and 4.10%,and then decreased to 76.32%and 3.21%.The relative content of organic phosphorus in total phosphorus first decreased to 19.59%and then increased to 23.75%.The order to the direct influence of soil phosphorus form on available phosphorus was:Ca_(8)-P>Ca_(2)-P>MLOP>LOP>HROP>MROP>Fe-P>Al-P>O-P>Ca_(10)-P.Correlation analysis and stepwise regression results showed that Ca_(2)-P was the main source of available phosphorus in spring wheat farmland soils in the Loess Plateau of Longzhong.In summary,Ca_(2)-P was the most effective source of phosphorus in the plough layer of dry-farming spring wheat on the Loess Plateau in central Gansu.Long-term application of phosphate fertilizer mainly reduced the insoluble Fe-P,O-P,Ca_(10)-P,MROP and HROP in the soil,and increased the ratio of Ca_(2)-P,LOP available for direct use,and Ca_(8)-P,Al-P,MLOP with slow effect,so as to improve the content of available phosphorus,which in turn increased the soil’s potential phosphorus supply capacity.