施氮量及底追比例对小麦产量、土壤硝态氮含量和氮平衡的影响

Effects of nitrogen fertilizer rate and ratio of base and topdressing on yield of wheat,content of soil nitrate and nitrogen balance

研究了高产麦田中施氮量和底追比例对冬小麦籽粒产量、土壤硝态氮含量和氮素平衡的影响。田间试验在山东省龙15市中村进行，试验区小麦各生育阶段的降雨量和零度以上的积温分别为：82．9mm，649．8℃（播种-冬前）、33．3mm，578．7℃（冬前-拔节）、28mm，359℃（拔节-开花）、84．3mm，837．6℃（开花-成熟）。试验设3个施氮量：0kg·hm^-2（CK）、168kg·hm^-2（A）、240kg·hm^-2（B）；在施氮量168kg·hm^-2和240kg·hm^-2条件下分别设3个底追比例：1／2：1／2（A1和B1）、1／3：2／3（A2和B2）、0：1（A3和B3）。结果表明：不同施氮处理之间植株氮积累量无显著差异；与不施氮处理相比，施氮可显著提高籽粒产量和蛋白质含量，施氮量为168kg·hm^-2、底追比例为1／3：2／3的处理A2与处理B2、B3差异不显著，但处理A2显著提高了氮肥利用率，降低了土壤残留量和氮素表观损失量；施氮量相同，适当增加追施氮肥的比例可显著提高籽粒产量、蛋白质含量和氮肥利用率。试验还表明，在拔节期，底施氮量为84kg·hm^-2和120kg·hm^-2的处理A1、B1，在80-100cm和100—160cm土层分别出现硝态氮的累积；而底施氮量为56kg·hm^-2的处理A2，在0—200cm土层硝态氮含量和累积量与不施氮处理无显著差异。在成熟期，追施氮量大于160kg·hm^-2的处理B3、A3和B2，硝态氮在120—180cm土层出现累积高峰，已下移到小麦根系可吸收范围之外，易于造成淋溶损失；而追氮量为112kg·hm^-2的处理A2，在100—200cm土层硝态氮累积量与对照无显著差异。试验中，施氮量为168kg·hm^-2底追比例为1／3：2／3的处理A2的籽粒产量、蛋白质含量、地上部植株氮肥吸收利用率、氮肥农学利用率和籽粒氮肥吸收利用率均较高，100—200cm土层未出现硝态氮的明显累积，氮素表观损失量最少，为最佳氮肥运筹方式。

Application of nitrogen （N） fertilizer is one of the most important measures that increase grain yield and improve grain quality in winter wheat （ Triticum aestivum L. ） production, so there is a huge number of investigation experiments in this field on the different nitrogen fertilizer applying regimes. However, currently, still there exists a serious problem of low nitrogen use efficiency, especially under winter wheat high yield condition ： unsuitable nitrogen fertilizer often leads to lower income benefit and the larger accumulation of nitrate in soil, bringing potential risk to environment. A lot of previous studies are mostly involved in the effects of nitrogen fertilizer rate and ratio of base and topdressing on wheat grain yield. Now in wheat production, a shortage still is the effects of nitrogen fertilizer applying regimes on wheat grain yield, N utilization, N balance and residual soil NO3^- -N under high yield field. In order to explore the optional regime of nitrogen fertilizer application suitable for environment and economy, a field experiment on the different rate and ratio of base and topdressing of nitrogen fertilizer at the different growth period of winter wheat was conducted. The field experiment was conducted from the fall of 2003 to the summer of 2004 in Zhongcun village, Longkou city,Shandong province, China. The brown soil nutrient components were： organic matter at 13. 1g·kg^-1, and available nitrogen （N）, phosphorus （P） and potassium （K） at 87.5 mg·kg^-1, 10.49 mg·kg^-1 and 84 mg·kg^-1, respectively. Winter wheat Variety： Jimai 20, typical strong gluten cultivar currently used locally was selected for this experiment. The field experiment of three replicates for each treatment was randomly arranged in a split-plot design. The major plot was nitrogen fertilizer rate as urea at the three level of 0 kg N per hm^2 （CK）, 168 kg N per hm^2（A）, and 240 kg N per hm^2（B） ; sub- plot was ratio of base and topdressing nitrogen fertilizer at the different development period of wheat, which are 1/2：1/2 （A1 and B I ）, 1/3：2/3 （A2 and B2） and 0：1 （A3 and B3）. Treatment B1 is a regime applied now in local region. Basal N fertilizer, total P20s （135 kg＇hm-2） and K20 （105 kg＂ hm-2） was applied before sowing; topdressing N fertilizer was at jointing stage. Each plot size was 3 by 8 m. At the three-leaf stage of seeding, plants each plot were thinned to a density of 150 plants per m^2 . The date of sowing wheat seeds was October 4, 2003 and harvested date was June 15, 2004. Totally, 3 times irrigation （before winter stage, jointing stage and 28d after flowering were taken through wheat life. Two soil sites were sampled randomly each plot in 20cm increments to a depth of 200cm at five growth stages [ sowing, before winter, jointing （before fertilization）, flowering and maturity ] with a soil auger and the sample was obtained after mixing and frozen immediately. The procedure for treating sample was： （1） sifting after mixing the defrosted sample with a 2mm-sieve; （2） 5g each sample was weighted and was extracted in 0.05L of0.01mol/L CaCl2 on a horizontal shaker for 0.5 hour; （3） Nmin were determined using an auto analyzer （AA3） after filtering. Soil water content each sample was measured as well. Plant samples taken at jointing and maturity stage were oven dried at 70 degree up to a constant weight. The nitrogen content in plant tissue and grain were determined by the standard macro-Kjeldahl digestion method. It was showed that the amount of N accumulation in plant have no significant difference between treatments with applying nitrogen fertilizer. Grain yield and grain protein content were all elevated remarkably by applying nitrogen fertilizer compared with those of treatment CK; there was no significant difference of grain yield and grain protein content between treatment A2 and treatment B2 and B3. However, compared with those of treatment B2 and BS, treatment A2 increased nitrogen using efficiency and reduced residual soil NO3^- -N and N losses. On the condition of the same rate of nitrogen fertilizer, increasing topdressing nitrogen rate clearly elevate grain yield, grain protein content and nitrogen using efficiency markedly. The results indicated that residual soil NO3^- -N amount in treatment A1 and B1 accumulated higher than those in treatment CK at 80 - 100cm and 100 - 160cm soil layers at jointing stage, but that of treatment A2 have no significant difference compared with that of treatment CK at 0 - 200cm soil layers. At maturity stage, in treatments B2, B3 and A3 more residual soil NO3^- -N were detected than those in treatment CK in 120 - 180cm soil layers, which could not be absorbed by roots of wheat, and lead to be eluviated easily. But soil NO3^--N accumulation amount in treatment A2 have no significant difference compared with that of treatment CK at 100 - 200cm soil layers. In conclusion, treatment A2, whose nitrogen fertilizer rate is 168 kg·hm^-2 and the ratio of base and topdressing is 1/3：2/3, had higher grain yield and grain protein content, and heightened N using efficiency and minimized the risk of NO3^- -N leaching, which will be one of the most appropriate nitrogen fertilizer applying regimes in wheat production in local region, China.