尿素浓度对喷灌夏玉米生长和产量的影响

喷灌施肥灌溉时叶片对尿素的直接吸收作用是提高氮肥利用率的潜在因素之一。以地面灌溉、尿素撒施处理为对照(CK),通过设置不同的尿素喷施浓度,研究夏玉米生理生态指标和产量的响应特征。结果表明,追施尿素后叶片相对叶绿素含量(SPAD)增加,但不同尿素喷施浓度处理的夏玉米株高、SPAD无显著差异(P>0.05)。尿素喷施浓度对叶面积指数(leaf area index,LAI)和产量的影响具有较大的年际变化,2017年不同尿素喷施浓度处理的产量差异达到了显著水平,尿素喷施浓度为0.146%处理的产量(12.5 t/hm^2)显著高于尿素喷施浓度≥0.178%处理的产量(11.3 t/hm^2),2018年尿素喷施浓度为0.188%处理的LAI在喷灌施肥后的一段时间内出现了显著降低。喷灌施肥后,叶片吸收尿素对光系统活性和光化学效率的影响与SPAD有关,2017年SPAD较高时,喷施尿素后光系统活性和光化学效率呈先减小后增大规律,且尿素喷施浓度≤0.146%处理的抑制作用仅发生在施肥后1 d,尿素喷施浓度≥0.178%处理的抑制作用持续至施肥后3~5 d;2018年SPAD较低时,与CK处理相同,喷施尿素后所有处理的光系统活性和光化学效率均呈先增大后稳定规律。与CK处理相比,施氮量小于等于CK的喷灌处理的产量和水分利用效率与CK处理无显著差异,但氮肥偏生产力显著高于CK处理,证明了喷灌施肥灌溉的可行性及其节肥、增产潜力。

Effects of urea concentration on summer maize growth and yield with sprinkler fertigation

Abstract: The direct absorption of leaf to urea is one of the main potential factors improving the nitrogen use efficiency with sprinkler fertigation. To verify the feasibility of sprinkler fertigation for summer maize, the crop growth parameters, including plant height, leaf area index (LAI), leave relative chlorophyll content (SPAD), chlorophyll fluorescence characteristics, and yield were compared among sprinkler fertigation treatments with different urea concentrations and the comparison treatment of surface irrigation with broadcast fertilization (CK). This experiment was conducted at the experimental station of China Institute of Water Resources and Hydropower Research in Daxing District, Beijing City (39.65°N and 116.25°E) in 2017 and 2018. Five solution concentrations of 0.048%, 0.105%, 0.146%, 0.178%, and 0.312% in 2017 and 0.090%, 0.146%, 0.188%, 0.219%, and 0.292% in 2018 (referred to as N1, N2, N3, N4, and N5) were used in the sprinkler fertigation of summer maize. The corresponding total N application amount in these 5 treatments was 170, 215, 248, 273, and 380 kg/hm2 in 2017 and 170, 215, 215, 248, and 273 kg/hm2 in 2018, respectively. There were 6 treatments in total, and all the treatments had 3 replicates and the same irrigation schedules. The irrigation was triggered when the difference between cumulative crop water requirement and effective rainfall was not less than 20 mm. In 2017 season, the effective rainfall was 175 mm and the irrigation amount was 70 mm. Because the precipitation (200 mm) mainly happened after the elongation stage of summer maize, the irrigation amount 150 mm was applied in 2018 season. The fertilization was applied in the flare opening stage of summer maize. The results showed that the SPAD increased in all the treatments after the fertilization, while there were no significant differences in plant height and SPAD among sprinkler fertigation treatments. There were great inter-annual variations in urea concentration effects on leaf area index (LAI) and yield. The yield of N2 treatment (12.5 t·hm-2) was significantly greater than treatments with higher urea concentrations in 2017. In these two seasons, the greatest yield of summer maize was obtained in treatment with 215 kg/hm2, which was consistent with the N application amount recommended by soil testing and fertilization recommendation technology. After the sprinkler fertigation, the influences of leave absorption to urea on PSII photosystem activity and photochemical efficiency of plant had relationship with SPAD content. In 2017 season with high SPAD value, photosystem activity and photochemical efficiency decreased firstly and then increased. When the urea concentration was less than and equal to 0.146%, the decreasing of photosystem activity and photochemical efficiency happened on the 1st day after the fertigation. While it lasted until 3 to 5 days for treatments with urea concentration greater than and equal to 0.178%. In 2018 season with low SPAD value, photosystem activity and photochemical efficiency increased firstly and then kept constant in all the treatments like in CK treatment in these two seasons. Compared with CK treatment, the sprinkler fertigation treatments with less N application than CK had similar yield and water use efficiency, and significant greater partial factor productivity from applied N. These results demonstrated that the sprinkler fertigation was feasible and had the potential to save N fertilizer and sustain yield of summer maize. To develop the sprinkler fertigation schedule, the nitrogen amount could be calculated according to soil testing and fertilization recommendation technology.