不同水分条件下常规尿素和控释尿素对玉米根冠生长及产量的影响

为了进一步探讨控释尿素在玉米上的应用效果, 于2006—2007年在防雨棚中, 应用郑单958进行了池栽试验。在不同水分条件下, 比较了施用常规尿素和控释尿素后, 玉米各生育阶段的根系活力、植株生长及籽粒产量。与常规尿素(全部基施和基施+小喇叭口期追施)相比, 地上部干重、叶面积指数开花前较低, 开花后较高；成熟期籽粒产量显著高于不施氮对照和两个常规尿素处理, 生物产量显著高于不施氮对照和常规尿素全部基施处理。从籽粒产量看, 维持土壤田间最大持水量的50%时, 控释尿素处理分别比常规尿素全部基施处理和分次施处理高27.3%和12.1%；维持土壤田间最大持水量的75%时, 分别比常规尿素全部基施处理和分次施处理高17.4%和8.1%。相同氮肥处理, 土壤田间最大持水量维持75%处理比维持50%处理籽粒产量和生物产量平均分别高20.6%和17.0%, 差异均达极显著水平。与常规尿素处理相比, 控释尿素处理花前根系数量、活性和根冠比均较低, 但花后三者能维持较高水平。可见, 控释尿素对玉米生长具有明显的“前控后保”效果；控释尿素与水分对玉米产量的耦合效应高于常规尿素, 其原因是生育后期能维持较高的根系数量及活性, 促进地上部干物质积累和转移。

Effects of Normal Urea and Release-Controlled Urea on Root and Shoot Growth and Yield of Maize in Different Water Conditions

As a prosperous fertilizer in crop production, release-controlled urea (CU) promotes the yield of maize (Zea mays L.) and nitrogen use efficiency with less environmental pollution than normal fertilizers. However, the interaction effects of CU and soil water content on the growth and development of maize have been rarely reported. In this study, the maize cultivar Zhengdan 958 was used to compare the differences of root activity, root and shoot growth, and yield between treatments with normal urea and CU under two water soil moisture conditions. The experiments were carried out in pools (10 m in length, 60 cm in width, and 1.2 m in depth) under a mobile water-proof shelter in 2006–2007. The normal urea was applied with basal (100% applied before sowing, NU) and split (40% applied before sowing and 60% applied at pretasselling stage, NS) dressing methods, whereas, the CU was totally applied before sowing. No urea applied was taken as the control. The results showed that the shoot dry weight and leaf area index of CU treatments were higher after anthesis and lower before anthesis than those of NU and NS treatments. As a result, the grain yield of CU treatment was significantly higher than those of NU and NS treatments, and the biomass of CU treatment was significantly higher (P < 0.05) than those of NU treatment and control. Under the condition of soil moisture at 50% of field capacity (W1), the grain yield of CU treatment was higher than those of NU and NS treatments by 27.3% and 12.1%, respectively. Under the condition of soil moisture at 75% of field capacity (W2), the grain yield of CU treatment was higher than those of NU and NS treatments by 17.4% and 8.1%, respectively. In the same urea treatment, the average values of grain yield and biomass were higher by 20.6% and 17.0% under W2 than those under W1, respectively. Root weight, root activity, and root/shoot ratio were lower before anthesis in CU treatment than in NU and NS treatments, but higher after anthesis in CU treatment than in NU treatment. The results suggest that the CU could have a remarkable early-decrease-and-late-increase effect on maize growth, and its coupling effect with soil moisture was higher than that of normal urea. The positive coupling effect of CU might be caused by the higher root activity and root/shoot ratio after anthesis, which could increase the accumulation and transportation of dry matters in the aboveground organs.