长期紫云英配施减量化肥对土壤铵态氮吸附解吸特征的影响

Effects of long-term Chinese milk vetch application coupled with reduced chemical fertilizer usage on soil ammonium nitrogen adsorption and desorption characteristics

为明确长期紫云英配施减量化肥对土壤铵态氮吸附解吸特征的影响,以13年长期定位试验为平台,设不施肥(CK)、单施化肥(CF)、22500 kg/hm^(2)紫云英+80%化肥(G+0.8CF)、22500 kg/hm^(2)紫云英+60%化肥(G+0.6CF)、22500 kg/hm^(2)紫云英+40%化肥(G+0.4CF)共5个处理,研究了不同施肥处理对土壤铵态氮吸附解吸特征的影响,并分析了土壤吸附解吸特征参数与土壤理化性质的关系。结果显示,Langmuir等温吸附方程能较好地拟合土壤铵态氮的吸附特征(R^(2)为0.9969~0.9979,P<0.01)。与CK相比,紫云英配施减量化肥处理土壤铵态氮的最大吸附量、最大缓冲容量分别降低了4.85%~13.46%、4.55%~7.36%;土壤铵态氮的平均解吸量和解吸率为G+0.8CF>G+0.6CF>G+0.4CF>CF>CK。与CK相比,紫云英配施减量化肥处理土壤全氮和速效氮含量分别增加了19.42%~46.60%、15.24%~25.88%。相关性分析结果显示,解吸率与土壤全氮、土壤速效氮呈显著正相关,与土壤pH呈显著负相关;冗余分析结果显示,pH和速效氮是造成土壤铵态氮吸附解吸特征参数差异的主要因素,分别解释了全部变异的56.7%和39.1%(P<0.05)。综上所述,长期紫云英配施减量化肥降低土壤对铵态氮的吸附,增加土壤对铵态氮的解吸,减少了土壤对氮的固持,提高氮的有效性。综合考虑土壤铵态氮的吸附解吸特性及土壤养分含量,以减量20%~40%化肥配施22500kg/hm^(2)紫云英处理效果较好。

This study aimed to clarify the effects of the long-term application of reduced chemical fertilizers combined with Chinese milk vetch on the adsorption and desorption characteristics of ammonium nitrogen in soil.A 13-year long-term positioning test was conducted using five treatments:no fertilizer(CK),fertilizer only(CF),22500 kg/hm^(2) Chinese milk vetch+80%fertilizer(G+0.8CF),22500 kg/hm^(2) Chinese milk vetch+60%fertilizer(G+0.6CF),and 22500 kg/hm^(2) Chinese milk vetch+40%fertilizer(G+0.4CF).The ammonium nitrogen adsorption and desorption characteristics of soil subjected to different fertilization treatments were examined,and the relationship between soil ammonium nitrogen adsorption and desorption characteristic parameters and soil physicochemical properties was analyzed.The results showed that Langmuir’s isotherm adsorption equation demonstrated a good fit with the adsorption characteristics of soil ammonium nitrogen(R^(2)=0.9969–0.9979,P<0.01).Compared with those in CK soil,the maximum adsorption amount and maximum buffering capacities of ammonium nitrogen in soil subjected to Chinese milk vetch+reduced fertilizer treatment decreased by 4.85%–13.46%and 4.55%–7.36%,respectively.The average desorption amount and desorption rate of soil ammonium nitrogen were in the following order:G+0.8CF>G+0.6CF>G+0.4CF>CF>CK.Compared with those of CK soil,the total nitrogen and available nitrogen concentrations of soil treated with Chinese milk vetch combined with reduced fertilizer increased by 19.42%–46.60%and 15.24%–25.88%,respectively.Correlation analyses revealed that the desorption rate had significantly positive correlations with soil total nitrogen and available nitrogen and a significantly negative correlation with soil pH.Redundancy analysis demonstrated that pH and available nitrogen were the main factors causing the differences in adsorption and desorption characteristic parameters of soil ammonium nitrogen,accounting for 56.7%and 39.1%of all variations,respectively(P<0.05).In summary,long-term Chinese milk vetch application coupled with reduced chemical fertilizer usage reduced soil adsorption of ammonium nitrogen,increased soil desorption of ammonium nitrogen,reduced soil nitrogen fixation,and improved nitrogen availability.Considering the adsorption and desorption characteristics of soil ammonium nitrogen and soil nutrient content,treatments involving a chemical fertilizer reduction of 20%–40%combined with 22500 kg/hm^(2) of Chinese milk vetch were potentially suitable for the southern Henan rice area.