基施氮肥对冬小麦产量、氮肥利用率及氮平衡的影响

Effect of N Application as Basal Fertilizer on Grain Yield of Winter Wheat,Fertilizer N Recovery and N Balance

通过田间小区试验研究了氮肥一次基施对高肥力土壤上冬小麦产量、吸氮量及氮肥利用率的影响 ,旨在了解高肥力土壤上减少基肥氮的可行性。结果表明 ,高肥力土壤上冬小麦产量对氮肥的反应不明显 ,而施用氮肥显著增加了冬小麦吸氮量。根据差值法计算结果 ,当施氮量为 75、1 1 2 .5和 1 5 0 kg/ hm2 时冬小麦的氮肥利用率分别为 1 6 .0 %、1 4 .5 %和1 3.5 % ,表明多达 84 %～ 86 .5 %以上的基肥氮未被作物吸收利用。氮平衡计算的结果进一步表明 ,未被当季小麦利用的肥料氮主要以无机氮的形式残留于 0～ 1 m土体中 ,当施氮量分别为 75、1 1 2 .5和 1 5 0 kg/ hm2时氮肥的土壤残留率依次为83.3%、4 6 .0 %和 5 8.8% ,而相应的表观损失率为 0 .5 %、38.9%和 1 9.0 %。由此可见 ,在高肥力土壤上应严格控制基肥氮的用量或不施基肥 ,否则将造成氮素资源的大量浪费。

Application of N fertilizer is one of the most important measures that increase crop yield in agriculture. According to statistical data from FAO (1995), the contribution of N fertilizer application to the newly increased yield reaches 50% since 1960's in the whole world. However, misuse of N fertilizer (particularly overuse) will also cause the decline of economic effects and related environmental problems like N gas emission to atmosphere and NO_3-N leaching to groundwater. Thus it is of course significant to optimize N fertilizer application in crop production. The amount, date and methods of N fertilizer application are three key factors that control the effect of N fertilizer on crop yield. The application of basal N fertilizer in autumn is forbidden in most of western European countries because of large amount of rainfall during the whole winter, which may lead to NO_3-N leaching. On the contrary, the basal N fertilizer has been considered as a critical method to ensure high grain yield and to maintain soil fertility in Chinese traditional agriculture. Winter wheat, as the most important crop in Northern China, consumes the majority of N fertilizer. It is of typical significance to identify the role of basal N fertilizer on winter wheat in Northern China Plain. \; A field experiment was carried out at a field station of China Agricultural University (16.5km northwest of Beijing, China) with the objective of assessing the effect of nitrogen application as basal fertilizer on grain yield, N recovery and N balance in winter wheat. The experiment was conducted on a calcareous meadow cinnamon soil with pH 8.25, organic matter 26.7 g/kg, total N 1.43 g/kg, Olsen-P 41.9 mg/kg, NH_4OAc-K 99.5 mg/kg. According to Beijing Classification Standard for Soil fertility, the tested soil belongs to high fertile soil. The supplied variety of winter wheat is Nongda 101. Four N treatments (0, 75, 112.5 and 150 N kg/hm 2) were randomly placed in 12 plots as 3 blocks. All of N fertilizer was incorporated into 0~10cm surface soil before sowing. Meanwhile, concentrated superphosphate (90 P_2O_5 kg/hm 2) as P fertilizer was applied to soil as broadcast before sowing. Dynamics of shoot dry matter, shoot N content and soil Nmin (mineral N) were monitored during wheat growing period. After harvest, the grain yield and straw yield were calculated according to the weighed results from sampling mini-plot (10 m 2). Apparent N recovery was calculated by method of difference. N balance between N input and N output was calculated according to both different growth stages and whole growth stage of winter wheat. \; The results showed that wheat grain yield (dry matter), which ranged from 4217 to 4450 kg/hm 2, did not respond to N fertilizer in the high fertile soil. But N removal by harvest significantly increased with N application as basal fertilizer, showing luxury N uptake by winter wheat under condition of higher N supply. The apparent N recovery was only 16.0%, 14.5% and 13.5% when N rates were 75, 112.5 and 150 N kg/hm 2 (N_ 75 , N_ 112.5 and N_ 150 ) respectively, showing a declining trend with the increasing N rate. On the contrary, soil N dependent rate (percentage of soil contribution to shoot N uptake) was 90.6%, 87.6% and 85.1% at the corresponding N treatments of N_ 75 , N_ 112.5 and N_ 150 . During the whole growing period of wheat, both shoot dry matter and N uptake did not show obvious differences among different N treatments, which were consistent with the results at harvest. Soil N_ min increased with the application of N fertilizer. From sowing to winter, soil N_ min significantly increased with the application of basal N fertilizer. After that, N_ min dramatically declined in all N treatments until shooting stage because of large N uptake from regreening to shooting stage. Then soil N_ min partly recovered from shooting to harvest. But the N_ min content in N_ 112.5 and N_ 150 was much higher than that in N_0 (control) and N_ 75 after harvest. The research on N balance showed that N surplus (apparent N losses) m