Effect Of Nitrogen Application Rates Under Different Organic Manure Conditions On Soil Hydrolase Activities

In recent years, agricultural rejectamentas are on the increase, dealing with them improperly can heavily pollute the environment. Agricultural rejectamentas contain rich organic matter and crop necessary nutrition element, they are important organic manures. Nitrogen fertilizer can increase crop yield, but using long-term single nitrogen fertilizer can cause soil hardened and influence crop yield. Soil enzyme can appraise soil fertility. To investigate the effects of nitrogen application rates under different organic manure conditions on soil hydrolase activity, crop yield and soil microbial community, a field experiment was conducted in Mei county, Shaanxi province. From June in 2008 to March in 2010, soil invertase, urease and alkaline phosphatase activities, summer maize and winter wheat yield, correlations among crop yield, soil hydrolase activity and soil physicochemical property were measured, functional diversity of soil microbial community was analyzed. The research results were as follows:1. During maize-wheat growth period, soil hydrolase activity had obvious changing characteristic. Hydrolase activities of different nitrogen trements under the same organic manure condition had conformable changing characteristic. The activities of soil invertase, urease and alkaline phosphatase had different changing trends.2. According to average invertase activity during maize-wheat growth period, under zero organic manure rate, the N1, N2 and N3 treatments were higher compared to the N0 treatment, and the N2 treatment was highest 25.37 mg glucose/(g.24h). Under low organic manure rate, N3>N0>N1, N2. Under middle organic manure rate, the N1 treatment was highest which was 11.51% higher than the N0 treatment. Under high organic manure rate, the N1, N2 and N3 treatments were 17.87%, 19.37% and 31.61% higher than the N0 treatments which was significant different with other treatments(P<0.05). In zero N fertilizer treatment, M2>M1>M0, M3. In other N fertilizer treatments,M2>M0>M1, M3。Comparing different organic manure and N fertilizer treatments, the M2N1 treatment was highest 31.11 mg glucose/(g.24h) which was 74.38% higher than the M0N0 treatment.3. Comparing average urease activity during maize-wheat growth period, under zero and low organic manure rates, N1>N0>N2, N3. Under middle organic manure rate, the N0 treatment was highest 1.15 mg NH3-N/(g.24h). Under high organic manure rate, N3>N0>N1, N2. In zero and low N fertilizer treatments, M2>M0>M1, M3。In middle N fertilizer treatment, the M2 rate was 29.31%, 37.04% and 23.33% higher than the M0, M1 and M3 rates, it was significant different with other rates(P<0.05). In high N fertilizer treatment, M2, M3>M0>M1。According to effect of different organic manure and N fertilizer on average urease activity, the M2N0 treatment was highest 1.15 mg NH3-N/(g.24h) which was 46.09% higher than the M0N0 treatment.4. According to average alkaline phosphatase activity during maize-wheat growth period, under zero and middle organic manure rates, the N1, N2 and N3 treatments were higher than the N0 treatment, and the N2 treatment was highest. Under low organic manure rate, the N1 treatment was highest 2.30 mg hydroxybenzene/(g.24h)。Under high organic manure rate, N1, N2>N0>N3. In zero and low N fertilizer treatments, M1>M0>M2, M3. In middle and high N fertilizer treatments, the M0 rate was highest, all rates were not significant different(P>0.05)。Comparing different organic manure and N fertilizer treatments, the M2N0 treatment was lowest 1.85 mg hydroxybenzene/(g.24h), other treatments were not significant different, the M1N0 and M1N1 treatments were higher than the others.5. According to effect of N applications under different organic manure rates on maize grain yield, under low organic manure rate, the N1, N2 and N3 treatments were higher than the N0 treatment, and the N2 treatment was highest. Under other organic manure rates, N1>N2, N3>N0. In zero N fertilizer treatment, the M1, M2 and M3 rates were higher than the M0 rate,and the M2 rate was highest. In low N fertilizer treatment, M2, M3>M0>M1. In middle N fertilizer treatment, M1, M3>M0>M2. In high N fertilizer treatment, the M0 rate was highest, all rates were not significant different(P>0.05). Comparing different organic manure and N fertilizer treatments, the M3N1 treatment was highest which was 1.41 times higher than the M0N0 treatment.According to effect of N applications under different organic manure rates on wheat grain yield, under high organic manure rate, the N1, N2 and N3 treatments were 14.4%~36.4% higher than the N0 treatment, and the N3 treatment was hihgest. Under other organic manure rates, N2>N1, N3>N0. In zero and middle N fertilizer treatment, the M2 rate was highest which was 40.2% and 14.0% higher than the M0 rate, they were significant different(P<0.05). In low N fertilizer treatment, the M2 rate was highest which was 8.0% than the M0 rate. In high N fertilizer treatment, M3>M2>M1>M0. Comparing different organic manure and N fertilizer treatments, the M2N2 treatment was highest which was 97.0% higher than the M0N0 treatment.6. According to correlation analysis, Significantly positive correlation was found between maize grain yield and soil available K. There was a significantly positive correlation between soil invertase activity and total K. Significantly positive correlation was found between soil urease activity and total N, among soil alkaline phosphatase activity, organic C and available P.7. Comparing effect of N application rates on functional diversity of soil microbial community, during maize growth period, AWCD, Shannon index(H) and Richness index(S) in the N1, N2 and N3 treatments were higher than the N0 treatment,and the N2 treatment was highest. Principal component analysis demonstrated that there were significant different among different N application rates depended on carbohydrates and amino acids.