不同年限紫云英配施减量化肥对土壤磷吸附解吸特征的影响

Effects of Chinese milk vetch combined with reduced chemical fertilizer on soil phosphorus adsorption and desorption characteristics in different years

为明确不同年限紫云英配施减量化肥对土壤磷吸附解吸特征的动态影响。本研究依托于河南省信阳市长期定位试验,设不施肥(CK)、单施化肥(CF)、22500 kg·hm^(-2)紫云英+80%化肥(G+80%CF)、22500 kg·hm^(-2)紫云英+60%化肥(G+60%CF)、22500 kg·hm^(-2)紫云英+40%化肥(G+40%CF)共5个处理,分析2011、2016、2020年土壤磷吸附解吸特征变化趋势及其与土壤理化性质之间的关系。结果表明:Langmuir等温吸附方程能较好地拟合土壤磷的吸附特征(R2为0.9804~0.9949,P<0.01)。随种植年限的增加,不同处理各参数变化并不相同。G+80%CF、G+60%CF、G+40%CF处理土壤磷最大吸附量(Q_(max))随种植年限的增加呈降低趋势,磷吸附常数(K)和磷最大缓冲容量(MBC)随种植年限的增加呈增加趋势,其中2020年较2011年,Q_(max)分别降低了11.30%、12.95%、15.47%,K分别增加了20.73%、22.50%、27.27%,MBC分别增加了8.63%、6.43%、6.28%;CF处理与之相反,土壤磷的Q_(max)随年限的增加呈增加趋势,K和MBC随年限的增加呈降低趋势,与2011年相比,2020年土壤磷的Q_(max)增加了8.80%,K降低了12.20%,MBC降低了2.97%;各处理土壤磷吸附饱和度(DPS)随种植年限的增加无规律性变化。CK和CF处理土壤磷的平均解吸率随年限的增加呈降低趋势,G+80%CF和G+40%CF呈先降低后增加趋势,G+60%CF处理呈降低趋势。相同年份,紫云英配施减量化肥较CK降低了土壤磷的Q_(max)、增加了土壤磷的K、MBC、DPS及平均解吸率。相关性分析表明,Q_(max)与土壤阳离子交换量(CEC)呈极显著正相关,MBC与CEC呈极显著负相关,DPS与碱解氮(AN)、有效磷(AP)呈极显著正相关,解吸率(DR)与速效钾(AK)呈极显著负相关,与p H呈显著负相关。冗余分析结果表明,CEC、AP、AK是影响土壤磷吸附解吸特征的主要因素,贡献率分别为26.7%、18.5%、16.2%(P<0.05)。综上,土壤对磷的吸附解吸主要受土壤阳离子交换量、有效磷、速效钾的影响。长期紫云英配施减量化肥可降低土壤对磷的吸附,增加土壤对磷的解吸,长期单施化肥效果则相反。综合考虑土壤磷吸附解吸特性及土壤理化性质,以减量20%~40%化肥配施22500 kg·hm^(-2)紫云英效果较好。本研究为豫南稻区合理施肥提供了理论依据。

The aim of this study was to clarify the dynamic effects of Chinese milk vetch coupled with reduced chemical fertilizer on soil phosphorus adsorption and desorption characteristics in different years.This long-term field study was conducted in Xinyang,Henan province.The experimental design consisted of a control(no fertilizer,CK)and four treatments:fertilizer only(CF),22500 kg·ha^(-1) Chinese milk vetch+80% fertilizer(G+80%CF),22500 kg·ha^(-1) Chinese milk vetch+60% fertilizer(G+60%CF),and 22500 kg·ha^(-1) Chinese milk vetch+40% fertilizer(G+40%CF).We determined the change trends of soil phosphorus adsorption and desorption characteristics,as well as their relationships with soil physicochemical properties in 2011,2016,and 2020.The results showed that the Langmuir isothermal adsorption equation provided a good fit for the adsorption characteristics of soil phosphorus(R2=0.9804-0.9949,P<0.01).The maximum phosphorus adsorption capacity(Q_(max))of soil samples from the G+80%CF,G+60%CF,and G+40%CF treatments decreased from 2011 to 2020,whereas the phosphorus adsorption constant(K)and maximum phosphorus buffer capacity(MBC)increased over the same time period.Compared with their respective values in 2011,the Q_(max) of the G+80%CF,G+60%CF,and G+40%CF treatments had decreased by 11.30%,12.95%,and 15.47%;K had increased by 20.73%,22.50%,and 27.27%;and the MBC had increased by 8.63%,6.43%,and 6.28% in 2020.In contrast,in the CF treatment,the Q_(max) of soil phosphorus increased with increasing age,whereas K and MBC decreased with increasing age.Compared with their respective values in 2011,the Q_(max) of soil phosphorus had increased by 8.80%,K had decreased by 12.20%,and MBC had decreased by 2.97%in 2020.In all treatments,the soil phosphorus adsorption saturation(DPS)did not show any consistent changes over the experimental period.The average desorption rate of soil phosphorus decreased during the experimental period in the CK and CF treatments,initially decreased and then increased in the G+80%CF and G+40%CF treatments,and showed a decreasing trend in the G+60%CF treatment.Compared with CK,the application of reduced chemical fertilizer coupled with Chinese milk vetch decreased the Q_(max) of soil phosphorus and increased the K,MBC,DPS,and average desorption rate of soil phosphorus in the same year.The results of correlation analysis showed that Q_(max) was significantly positively correlated with soil cation exchange capacity(CEC),MBC was significantly negatively correlated with CEC,DPS was significantly positively correlated with alkali-hydrolyzed nitrogen(AN)and available phosphorus(AP),and the desorption rate(DR)was significantly negatively correlated with available potassium(AK)and pH.The results of a redundancy analysis revealed that CEC,AP,and AK were the primary factors affecting soil phosphorus adsorption and desorption characteristics,with contribution rates of 26.7%,18.5%,and 16.2%,respectively(P<0.05).In summary,our results indicate that the adsorption and desorption of soil phosphorus are mainly affected by the soil CEC,AP,and AK.Long-term application of Chinese milk vetch coupled with reduced chemical fertilizer decreased P adsorption and increased P desorption in soil,while the long-term application of fertilizer alone had the opposite effect.Considering the adsorption and desorption characteristics of soil P and soil physical and chemical properties,the best effects were obtained by reducing chemical fertilizer usage by 20%-40% combined with 22500 kg·ha^(-1) Chinese milk vetch.Our findings provide scientific guidance for reasonable fertilization in the rice-growing area of south Henan province.