低磷红壤无机磷组分特征及间作调控作用

Characteristics of inorganic phosphorus forms in low phosphorus red soils and the role of intercropping in its regulation

为明确间作和施用磷肥对低磷红壤无机磷组分的影响,促进酸性土壤磷肥高效利用,通过田间小区定位试验,采用玉米单作(MM)、玉米//大豆间作(MI)2种种植模式,在4个施磷水平(P2O50、60、90、120 kg·hm^(-2),分别记作P0、P60、P90、P120)下,研究玉米//大豆间作根际土壤无机磷组分变化特征,探讨间作对红壤玉米产量及其可持续性、磷吸收和磷素收支平衡、土壤无机磷组分的调控作用。结果表明,玉米籽粒产量及其可持续性指数(SYI)、磷吸收量随着施磷水平的增加而增加,在P90水平达到最大值。低磷红壤无机磷组分以O-P和Fe-P为主,二者占无机磷库的71.44%~80.18%,施用磷肥显著提高了红壤Fe-P和Al-P的含量与占比。玉米//大豆间作显著提高玉米产量,促进磷的吸收利用,减少土壤磷素盈余量,显著降低红壤O-P、Fe-P、Al-P含量。与单作相比,在P60、P90、P120水平下,间作玉米产量分别显著提高66.70%、52.44%、74.14%,SYI分别显著提高55.31%、42.18%、78.00%,磷吸收量分别显著提高61.97%、48.67%、74.33%,土壤磷盈余量分别显著降低33.39%、27.27%、17.06%。相较于单作,间作红壤中有效磷含量无显著差异,而O-P和Al-P含量在P0、P60、P90、P120水平下分别显著降低20.62%、16.79%、16.62%、18.48%和21.98%、21.08%、20.19%、20.18%,Fe-P含量在P60、P90、P120水平下分别显著降低19.37%、15.78%、17.72%。低磷供应(P0和P60)间作与单作红壤Ca-P含量无显著差异,在P90和P120水平下,间作红壤Ca-P含量降低23.50%和26.70%。随机森林模型分析表明,间作体系下,红壤Fe-P和Al-P是磷吸收的关键无机磷组分,间作总方差解释度较单作提高了7.95%。综上,在低磷红壤上,合理间作通过促进红壤中难溶性无机磷组分的活化增加玉米的磷吸收,具有减少土壤磷素固定、提高玉米产量及其可持续性的潜力。

To clarify the effects of intercropping and phosphorus fertilizer application on the inorganic phosphorus forms of low phosphorus red soil and to promote the efficient use of phosphorus fertilizer in acidic soil,two cropping patterns,maize monocropping(MM)and maize//soybean intercropping(MI),were used to investigate the effects of intercropping on the inorganic phosphorus forms of red soil at four levels of phosphorus application(P2O50,60,90,120 kg·hm^(-2),marked as P0,P60,P90,P120,respectively).The characteristics of inorganic phosphorus forms in the rhizosphere soil of maize//soybean intercropping was studied and the effects of intercropping on maize yield and sustainability,phosphorus uptake and phosphorus balance,and soil inorganic phosphorus forms were explored in red soil.The results showed that maize grain yield and its sustainability index(SYI),phosphorus uptake increased with the increase of phosphorus application level and reached the maximum at P90 level.The inorganic phosphorus forms of the low phosphorus red soil were dominated by O-P and Fe-P,which accounted for 71.44%-80.18%of the inorganic phosphorus pool.The content and proportion of Fe-P and Al-P in red soil were significantly increased by applying phosphorus fertilizer.Maize//soybean intercropping significantly increased maize yield,promoted phosphorus absorption and utilization,reduced soil phosphorus surplus,and significantly reduced the contents of O-P,Fe-P and Al-P in red soil.Compared with monocropping,under the P60,P90 and P120 levels,intercropping grain yield was significantly increased by 66.70%,52.44%and 74.14%,SYI was significantly increased by 55.31%,42.18%and 78.00%,and phosphorus uptake was significantly increased by 61.97%,48.67%and 74.33%,respectively,and soil phosphorus surplus was significantly decreased by 33.39%,27.27%and 17.06%,respectively.Compared with monocropping,available phosphorus content in intercropping red soil was not significantly different,while O-P and Al-P contents at P0,P60,P90,P120 levels were significantly decreased by 20.62%,16.79%,16.62%,18.48%and 21.98%,21.08%,20.19%,20.18%,respectively.The Fe-P content was significantly decreased by 19.37%,15.78%and 17.72%in P60,P90 and P120 levels,respectively.There was no significant difference in Ca-P content between intercropping and monocropping red soils with low phosphorus supply(P0 and P60).At P90 and P120 levels,Ca-P content in intercropping red soils were decreased by 23.50%and 26.70%,respectively.Random forest model analysis showed that Fe-P and Al-P were the key inorganic phosphorus forms in intercropping red soil.The total variance interpretation of intercropping increased by 7.95%compared with monocropping.In conclusion,rational intercropping in low phosphorus red soil can increase the phosphorus uptake of maize by promoting the mobilization of insoluble inorganic phosphorus forms in red soil,which has the potential to reduce soil phosphorus fixation and improve maize yield and sustainability.