减量施磷对土壤磷库组成及解磷微生物的影响

Effects of Phosphorus Reduction on Soil Phosphorus Pool Composition and Phosphorus Solubilizing Microorganisms

【目的】研究连续减施磷肥对土壤磷组分以及解磷微生物的影响,探究土壤磷素转化规律,为合理施用磷肥,高效利用土壤磷提供理论依据。【方法】于2014年在四川省绵阳市龙门镇开展减磷定位试验,试验设置4个处理,即P0(不施磷肥)、P1(减施磷肥1/2,45 kg·hm^(-2))、P2(减施磷肥1/3,60 kg·hm^(-2))、P3(正常施磷肥,90 kg·hm^(-2)),采集0—20 cm土层土样,测定并分析土壤全磷、有效磷、磷活化系数、磷组分以及解磷微生物变化特征。【结果】减施磷肥显著降低了土壤全磷(TP)含量,较2014年相比,连续处理3年后P0、P1处理分别下降了7.2%、0.9%,P2、P3处理分别增加了2.6%、7.3%。连续处理6年后处理间差异进一步扩大,与6年前相比P0、P1处理分别下降了15.2%、5.7%,P2、P3处理分别增加了7.8%、21.6%。有效磷(AP)含量变化趋势与全磷相似,连续处理3年后P0处理有效磷含量下降了18.1%,P1、P2、P3处理分别增加了21.2%、72.2%、132.1%。与6年前相比,连续处理6年后各处理有效磷含量的变幅扩大至-24.6%—201.6%。磷活化系数(PAC)由有效磷及全磷含量决定,其变化趋势总体上与有效磷一致。减施磷肥主要造成了H2O-P、NaHCO_(3)-Pi、NaOH-Pi含量显著减少,对Residual-P没有显著影响,其中NaOH-Pi是导致土壤全磷含量变化的主要磷形态,NaHCO_(3)-Pi是土壤磷素活化过程中最关键的磷组分。不同磷肥处理解磷微生物丰度存在差异。冗余分析结果表明,类诺卡氏菌属(Nocardioides)、分支杆菌属(Mycobacterium)、芽孢杆菌属(Bacillus)、生丝微菌属(Hyphomicrobium)以及根瘤菌属(Rhizobium)与各形态磷均呈正相关,其中生丝微菌属与NaHCO_(3)-Pi及NaOH-Pi相关性均较高。【结论】减施磷肥显著改变了土壤磷库组成,土壤有效磷及全磷含量变化主要受NaHCO_(3)-Pi以及NaOH-Pi含量变化的影响。连续减施磷肥6年后各处理土壤解磷微生物丰度存在显著差异,其中生丝微菌属是参与本试验区域磷素转化的关键微生物。连续6年减施1/3磷肥(施磷肥60 kg·hm^(-2))能有效减少本试验区域土壤缓效态磷积累的同时维持较高的有效磷水平。

【Objective】The effects of continuous reduction of phosphorus fertilizer application on soil phosphorus components and phosphorus-solubilizing microorganisms were studied,and the transformation law of soil phosphorus was explored to provide a theoretical basis for rational application of phosphorus fertilizer and efficient utilization of phosphorus in soil.【Method】In 2014,the phosphorus reduction positioning test was carried out in Longmen Town,Mianyang,Sichuan province.The test set 4 treatments,namely P0(no phosphorus fertilizer),P1(1/2 reduction,45 kg·hm^(-2)),P2(1/3 reduction,60 kg·hm^(-2)),and P3(normal fertilization,90kg·hm^(-2)),and 0-20 cm soil samples were collected to measure and analyze soil total phosphorus(TP),available phosphorus(AP),and phosphorus activation coefficient(PAC),phosphorus fractions and the change characteristics of phosphorus-dissolving microorganisms.【Result】Reducing the application of phosphorus fertilizer significantly reduced the TP content of the soil;compared with 2014,after 3 years of continuous treatment,the TP content under P0 and P1 treatments decreased by 7.2%and 0.9%,respectively,however,which under P2 and P3 treatments increased by 2.6%and 7.3%,respectively;after 6 years of continuous treatment,the TP difference between treatments was further expanded:compared with 6 years ago,the TP under P0 and P1treatments decreased by 15.2%and 5.7%,respectively,which under the P2 and P3 treatments increased by 7.8%and 21.6%,respectively.The variation trend of AP content was similar to that of TP.After continuous treatment for 3 years,the content of AP under P0 treatment decreased by 18.1%,while that under P1,P2,and P3 treatments increased by 21.2%,72.2%,and 132.1%,respectively;compared with 6 years ago,the AP variation of each treatment expanded to-24.6%-201.6%after continuous treatment for 6 years.The PAC was determined by the content of AP and TP,and its variation trend was generally consistent with that of AP.Reducing the application of phosphorus fertilizer mainly caused a significant decrease in the content of H2O-P,Na HCO3-Pi and NaOH-Pi,but had no significant effect on Residual-P.Among them,NaOH-Pi was the main phosphorus form that caused the change of soil TP content,and NaHCO3-Pi was the most critical phosphorus fraction in the process of soil phosphorus activation.There were differences in the abundance of phosphorus-solubilizing microorganisms in different phosphorus fertilizer treatments.Redundancy analysis results showed that Nocardioides,Mycobacterium,Bacillus,Hyphomicrobium and Rhizobium were positively correlated with each form of phosphorus,among which,the genus Hyphthora was highly correlated with NaHCO_(3)-Pi and Na OH-Pi.【Conclusion】The reduction of phosphorus fertilizer significantly changed the composition of soil phosphorus pool,and the changes of soil AP and TP were mainly affected by the changes of NaHCO_(3)-Pi and NaOH-Pi.There were significant differences in the abundance of soil phosphorus-dissolving microorganisms after 6 years of continuous reduction of phosphorus fertilizer,and the genus Hyphomicrobium was the key microorganism involved in the transformation of phosphorus in the experimental area.Reducing the application of 1/3 phosphorus fertilizer for 6 consecutive years could effectively reduce the accumulation of slow-release phosphorus in the soil in this experimental area while maintaining a high level of available phosphorus.