施氮量对玉米/大豆套作系统土壤微生物数量及土壤酶活性的影响

为揭示玉米/大豆套作体系下土壤氮素转换的调控机理和根际微生态效应,以种植模式为主因素[设玉米单作(MM)、大豆单作(SS)和玉米/大豆套作(IMS)3种处理],以玉米、大豆施氮总量(玉米、大豆施氮比例为3∶1)为副因素[设不施氮(NN,0 kg?hm~(-2))、减量施氮(RN,180 kg?hm~(-2))和常量施氮(CN,240 kg?hm~(-2))3个处理],研究了玉米/大豆套作系统下不同施氮量对作物根际土壤微生物数量及土壤酶活性的影响。结果表明:与相应单作相比,套作下玉米根际土壤真菌、放线菌数量分别提高25.37%和8.79%;套作大豆根际土壤真菌、放线菌、固氮菌数量高于单作大豆;套作玉米根际土壤蛋白酶、脲酶活性和套作大豆根际土壤蛋白酶活性均显著升高。各施氮水平间,减量施氮下玉米、大豆根际土壤真菌数量较常量施氮和不施氮均有所提高;施氮提高了玉米、大豆根际土壤放线菌数量;大豆根际土壤固氮菌数量以减量施氮最高,比不施氮和常量施氮高17.78%和5.67%;玉米根际土壤蛋白酶活性、脲酶活性和大豆根际土壤脲酶活性均以减量施氮为最高。适宜的施氮量不仅能增加玉米/大豆套作土壤中真菌、放线菌、固氮菌的数量,还能提高土壤蛋白酶、脲酶活性,调节土壤氮素的转化,促进玉米/大豆对土壤中氮素的吸收,实现节能增效。

Effects of nitrogen application rate on soil microbial quantity and soil enzymes activities in maize/soybean intercropping systems

To study the effects of nitrogen rate on soil microbial quantity and enzyme activity in maize/soybean intercropping system, a 2-factor design was developed. The main factor in the design was planting pattern, which included monoculture maize (MM), sole soybean (SS) and maize/soybean relay strip intercropping system (IMS). Then the sub-factor of nitrogen application rate N for maize and soybean were no nitrogen application[0 kg(N)·hm^-2, NN], reduced nitrogen application[180 kg(N)·hm^-2, RN], and conventional nitrogen application[240 kg(N)·hm^-2, CN]. The results showed that the quantities of fungi and actinomycetes in rhizosphere soil of intercropped maize were 25.37% and 8.79% higher than those of monoculture maize, respectively. Also the quantities of soil fungi, actinomycetes and nitrogen-fixing bacteria in the rhizosphere soil of intercropped soybean were higher than those of sole soybean. Soil protease and urease activities in the rhizosphere soil of intercropped maize and protease activity in rhizosphere soil of intercropped soybean significantly increased compared with the corresponding monoculture. Under different nitrogen application rates, the quantities of soil fungi, actinomycetes and nitrogen-fixing bacteria in the rhizosphere of maize and soybean were higher under RN than under NN and CN, respectively. In addition, nitrogen application increased the quantity of actinomycetes in the rhizosphere soil of maize and soybean. The quantities of nitrogen-fixing bacteria in the rhizosphere soil of maize were 17.78% and 5.67% higher under RN compared with those under NN and CN, respectively. Moreover, the activities of soil protease and urease in the rhizosphere of maize and activity of soil urease in the rhizosphere of soybean were highest under RN compared with those under NN and CN. Reduced nitrogen fertilization increased the degree of soil microbial and enzyme activities in the rhizosphere of maize/soybean relay strip intercropping system, promoted nitrogen uptake of maize and soybean, and thereby saved fertilizer use.