减氮及增施腐殖酸对玉米产量和氮肥利用率的影响

Effects of nitrogen reduction and humic acid application on yield and nitrogen use efficiency of maize

保障作物产量,同时控制氮素投入、提高养分利用效率,是中国农业绿色发展的重要途径。本研究采用常规施氮(普通尿素,施氮250 kg·hm^(-2))为对照,设置两个减氮水平(20%和40%)以及减氮+腐殖酸处理的田间小区试验,分析土壤氮供应、植株氮吸收动态、光合特征、氮同化关键酶活性及产量构成,评价玉米种植中添加腐殖酸的减氮增效潜力和机制。结果表明:与常规施氮相比,减氮20%及20%减氮+腐殖酸处理均未降低玉米产量,氮利用率提高了35.8%~48.3%,而减氮40%后玉米减产20.6%~24.4%,氮肥利用率提高了20.4%~31.5%;同时,减氮20%提高了根系吸氮量和光合氮利用效率,增加了收获指数;相比于常规氮肥,减氮20%+腐殖酸增加了土壤硝态氮、铵态氮含量和地下部氮吸收量,增强了叶片光合作用,提高氮吸收总量1.2倍和谷氨酰胺合成酶活性19.9%,降低秃尖长42.9%;减氮40%后无论是否添加腐殖酸,均导致土壤硝态氮含量下降,玉米氮吸收总量、净光合速率和光合氮利用效率大幅降低;减氮20%和减氮20%+腐殖酸均可实现玉米减氮不减产并提高氮肥利用率,且相同减氮水平时,尿素+腐殖酸比单施尿素在提高氮素吸收及利用上具有优势。

It is important to maintain crop yield,control nitrogen input,and improve nutrient use efficiency for agricultural green development in China.In this study,we carried out a field experiment with two nitrogen(N) reduction levels(20% and 40%) and N reduction(20% and 40%) + humic acid,with the conventional N application(urea,250 kg·hm^(-2)) as control.We measured soil N supply,plant N uptake,photosynthetic characteristics,N assimilation-related enzyme activity and yield components of maize to evaluate the potential and mechanism of nitrogen reduction and efficiency enhancement by humic acid addition in maize cultivation.The results showed that compared with conventional N application,maize yield was not reduced and 20% N use efficiency was improved by 35.8%-48.3% in the treatment with 20% N reduction and humic acid addition,while maize yield was reduced by 20.6%-24.4% and N use efficiency was improved by 20.4%-31.5% under the treatment of 40% N reduction.The 20% N reduction treatment improved root N uptake and photosynthetic N use efficiency and increased the harvest index.Compared with conventional N fertilization,20% N reduction with humic acid application increased soil nitrate and ammonium content and root N uptake,enhanced leaf photosynthesis,increased total N uptake by 1.2 times and glutamine synthase activity by 19.9%,and reduced barren tip length by 42.9%.Regardless of humic acid application,the 40% N reduction reduced soil nitrate content,total N uptake,net photosynthetic rate,and photosynthetic N use efficiency of maize.The 20% N reduction and combination of 20% N reduction with humic acid application can achieve no reduction in maize yield and improve N fertilizer use efficiency.Compared with urea application alone,urea application with humic acid addition has advantages in improving N uptake and use efficiency.