缓释氮肥与尿素掺混对玉米生理特性和氮素吸收的影响

【目的】 研究不同施氮量下尿素与缓释氮肥掺混对大田玉米生理特性、氮素吸收和土壤硝态氮残留的影响，以期探索减少土壤硝态氮淋失、提高氮肥利用效率的高效施氮管理模式。 【方法】 试验在西北农林科技大学节水灌溉试验站进行，供试土壤质地为壤土，玉米品种为郑单958。设置了3种氮肥类型为尿素 (U)、缓释氮肥 (S)、尿素和缓释氮肥以 3∶7比例掺混 (SU)； 4 个施氮 (N)水平为 90 kg/hm2 (N1)、120 kg/hm2 (N2)、180 kg/hm2 (N3)、240 kg/hm2 (N4)，以不施氮肥 (N0) 为对照，共13个处理。在生育期内对玉米的产量和生理指标进行观测，并测定玉米主要生育期植株养分和土壤硝态氮含量。 【结果】 尿素掺混缓释氮肥 (SU) 处理的玉米生长后期叶绿素总量最大值分别比尿素 (U) 处理和缓释氮肥 (S) 处理最大值提高7.7%和1.3%。各生育期尿素掺混缓释氮肥 (SU) N3处理的净光合速率和蒸腾速率最高，分别高于其他处理6.9%～88.6%和3.4%～90.3%。尿素掺混缓释氮肥 (SU) 处理能够更好地促进玉米对氮素的吸收利用，其中尿素掺混缓释氮肥 (SU) N3处理氮素吸收量和籽粒的氮素分配量达最大，分别为156.0 kg/hm2和79.7 kg/hm2，高于其他处理8.1%～67.3%和6.2%～54.1%。尿素 (U) N3处理与缓释氮肥 (S) N2处理的氮素吸收量和籽粒的氮素分配量无显著差异；尿素掺混缓释氮肥 (SU) 在N3施氮量下，产量达到最高为 6200.4 kg/hm2，比尿素 (U) N3处理和缓释氮肥 (S) N2处理的产量分别增加了20.7%和19.8%。与单施尿素 (U) 和缓释氮肥 (S) 处理相比，尿素掺混缓释氮肥 (SU) 处理能充分利用0—40 cm土层养分，减少土壤氮素向更深土层淋失，提高氮肥利用率，降低土壤环境污染的风险。 【结论】 尿素与缓释氮肥掺混条件下，施氮量180 kg/hm2是提高试验区玉米叶绿素含量和光合作用，促进氮素吸收，减少硝态氮向土壤深层淋失的最佳施肥管理模式。

Effects of blending of slow-release nitrogen fertilizer and urea on maize physiological characteristics and nitrogen uptake

【Objectives】 To understand the effects of mixed regular and slow-release nitrogen fertilizers on maize physiological characteristics, nitrogen uptake and the distribution for effective reduction of soil NO₃–-N leaching and improving of N use efficiency. 【Methods】 An experiment was conducted at the Experimental Station of Water Saving Engineering, Northwest A&F University, with the tested soil of loam and maize cultivar of ‘Zhengdan 958’. A randomized complete block design with three kinds of nitrogen fertilizers and 4 N supply levels was used. Three nitrogen fertilizers were conventional urea (U), slow-release nitrogen fertilizer (S) and a mixture of slow-release nitrogen fertilizer and conventional urea with N ratio 7∶3 (SU). Four N application rates were 90 kg/hm2 (N1), 120 kg/hm2 (N2), 180 kg/hm2 (N3) and 240 kg/hm2 (N4), plus a control without N application (CK). A total of 13 treatments were established. The maize yield and physiological property, plant N content and soil NO₃–-N concentrations were determined. 【Results】 Compared with urea (U) and slow-release nitrogen fertilizer (S), the maximum total chlorophyll content with SU treatment was increased by 7.7% and 1.3% under N3 levels, while the maximum photosynthetic rate and transpiration rate were increased by 6.9%–88.6% and 3.4%–90.3%, respectively. Fertilizer SU treatment increased uptake and utilization of nitrogen. Under N3 level, the maximum plant nitrogen assimilation and grain nitrogen assimilation with SU treatment were 156.0 kg/hm2 and 79.7 kg/hm2, which were respectively increased by 8.1%–67.3% and 6.2%–54.1%, compared with the fertilizer U and S treatment. There was no significant difference in plant and grain nitrogen assimilation between U (N3) and S (N2) treatment. The highest grain yield (6200.4 kg/hm2) was achieved with the treatment of SU (N3), which was 20.7% and 19.8% higher than the treatments of U (N3) and S (N2), respectively. Compared with the fertilizers U and S treatment, SU treatment reduced soil N leaching by more uptake of soil nutrient at the 0–40 cm soil depth and reducing leaching of NO₃–-N to deeper soil so as to improve N use efficiency and reduce the risk of soil environmental pollution. 【Conclusions】 Applying the mixture of conventional urea and slow-release fertilizer at the N application rate of 180 kg/hm2 is recommended for increasing chlorophyll content and photosynthesis of maize, promoting nitrogen uptake and reducing N leaching in the test area.