不同施氮措施对冬小麦农田土壤酶活性和氮转化的影响

Effect of Different Nitrogen Application Measures on Soil Enzyme Activities and Nitrogen Turnover in Winter Wheat Cropland

为研究农田生态系统土壤酶活性和氮转化对不同施氮措施的响应机理,以河南省平顶山市冬小麦农田为研究对象,设置了5种施氮措施[尿素+硝化抑制剂(U+DCD)、尿素+脲酶抑制剂(U+HQ)、尿素+脲酶抑制剂+硝化抑制剂(U+HQ+DCD)和包膜尿素(PCU),并以普通尿素(U)作对照],研究了冬小麦栽培关键期土壤脲酶和蔗糖酶活性、铵态氮(NH4+-N)和硝态氮(NO3−-N)含量的变化趋势。结果表明:与U相比,其他4种施氮措施对土壤蔗糖酶活性的影响均不显著(P>0.05),而U+DCD、U+HQ+DCD和PCU均显著提高了土壤脲酶活性(P<0.05),增幅分别为9.45%、11.91%、32.10%;与U相比,其他4种施氮措施均提高了土壤NH4+-N含量,其中U+HQ、PCU和U+HQ+DCD影响较显著,增幅分别为33.77%、33.65%、24.26%,但均在一定程度上降低了土壤NO3−-N含量,仅U+HQ+DCD和PCU影响显著,降幅分别为30.37%、30.02%。随着小麦的生长,土壤脲酶活性呈现先下降再升高的趋势,在拔节期达到最低(P<0.01);而土壤蔗糖酶活性、NH4+-N和NO3−-N含量均呈先升高再降低的趋势,并在开花期达到峰值(P<0.01)。相关性分析表明,5种施氮措施下土壤蔗糖酶活性均与土壤含水率、NH4+-N或NO3−-N含量呈显著正相关关系(P<0.05),且NH4+-N和NO3−-N之间亦呈极显著正相关关系(P<0.01);除PCU,其他4种施氮措施下土壤NH4+-N和NO3−-N含量大部分与土壤速效磷及速效钾含量呈显著负相关关系(P<0.05)。线性回归表明,土壤酶活性和矿质氮均主要受土壤速效磷含量和土壤含水率的影响(P<0.01)。综合分析表明,与农民习惯施氮措施相比,包膜尿素和普通尿素配施脲酶抑制剂与硝化抑制剂可以有效提高氮肥利用效率。

In order to find out the response mechanism of soil enzyme activity and nitrogen turnover to different nitrogen application measures in agricultural ecosystem,five kinds of nitrogen(N)application measures,urea+urease inhibitor(U+HQ),urea+nitrification inhibitor(U+DCD),urea+urease inhibitor+nitrification inhibitor(U+HQ+DCD),polymer coated urea(PCU)and urea(U)as the control,were set up in winter wheat cropland in Pingdingshan city,Henan province.Soil urease and invertase activities,ammonium nitrogen(NH4+-N)and nitrate nitrogen(NO3−-N)contents were analyzed in the main cultivation stages of winter wheat.The results showed that compared with U,the other 4 N application measures had no significant effect on soil invertase activity(P>0.05).Moreover,U+DCD,U+HQ+DCD and PCU all significantly increased soil urease activity(P<0.05),the growth rates were 9.45%,11.91%and 32.10%,respectively.Compared with U,the other 4 N application measures all increased soil NH4+-N contents,among which U+HQ,PCU and U+HQ+DCD had significantly increased by 33.77%,33.65%and 24.26%.However,they all reduced soil NO3−-N contents to a certain extent,and only U+HQ+DCD and PCU had significant effects,with a decrease of 30.37%and 30.02%,respectively.With the growth of wheat,soil urease activity tended to decrease first and then increase,and reached the lowest level in the jointing stage(P<0.01).While soil invertase activity,NH4+-N and NO3−-N contents all showed a trend of first increasing and then decreasing,and reached the peak value in the flowering period(P<0.01).Correlation analysis revealed that soil invertase activity under the 5 nitrogen application measures was significantly positively correlated with soil water content,NH4+-N and NO3−-N contents(P<0.05),and there was also an extremely significant positive correlation between NH4+-N and NO3−-N contents(P<0.01).Except for PCU,Soil NH4+-N,NO3−-N contents under the other 4 nitrogen application measures were significantly negative correlated with soil available phosphorus and potassium contents(P<0.05).Stepwise regression analysis showed that soil enzyme activity and soil inorganic nitrogen contents were mainly affected by soil available phosphorus content and soil water content(P<0.01).In general,compared with the conventional N application measures,PCU and U+HQ+DCD treatments can effectively improve the utilization efficiency of N fertilizer.