追施氮肥对苏丹草碳氮代谢及种子产量的影响

以新苏2号苏丹草(Sorghum sudanense ‘Xinsu No.2')为材料,采用单因素完全随机区组设计,在拔节、孕穗和灌浆期以固定比例追施尿素(0, 150, 300, 450, 600, 750 kg·hm^-2),揭示不同氮(N)处理苏丹草碳氮代谢及种子产量性状变化规律.结果表明:追施氮肥有效提高了碳氮代谢水平,随氮肥追施量增加,苏丹草叶片与茎秆中碳氮含量显著增高,施氮量大于600 kg·hm^-2后,总糖和全氮含量均不同程度下降.整个生长期随施氮量增加,苏丹草茎叶碳氮比(C/N)呈逐渐减小趋势,且不追肥、施氮肥150 kg·hm^-2与其它处理间存在显著差异(P < 0.05).氮肥可有效增加种子千粒重、穗粒数,从而使苏丹草种子产量明显增加.然而,随施氮量增加产量增加幅度明显减小,施氮150与300 kg·hm^-2产量增幅分别达23.7%和32.2%,而施氮750 kg·hm^-2产量增幅仅为3.9%,追施氮肥600 kg·hm^-2可获最大种子产量3815 kg·hm^-2.综合碳氮积累、C/N及种子产量表现,试验条件下以追施氮肥600 kg·hm^-2为最佳.

Effects of Carbon and Nitrogen Metabolism and the Seed Yield of Sudangrass under Different Topdressing Nitrogen Fertilizers

The effects of carbon and nitrogen metabolism on the seed yield of Sudangrass under different nitrogen application rates(0, 150, 300, 450, 600 and 750 kg·hm^-2) were studied using Sorghum sudanense ‘Xinsu No.2'.The results showed that the total sugar and total nitrogen contents of Sudangrass leaf and stem increased significantly with the increase of nitrogen topdressing. Nitrogen fertilizer could improve the metabolism levels of carbon and nitrogen. However, the metabolism levels of carbon and nitrogen decreased as nitrogen levels were beyond 600 kg·hm^-2. The carbon to nitrogen (C/N) ratios of Sudangrass stem and leaf showed the trend of decreases with the increases of nitrogen application amounts in the whole period. There were significant differences between control (no fertilizer), low nitrogen(150 kg·hm^-2) and other nitrogen treatments. Nitrogen fertilizer could effectively improve 1000-grain weight, grains per spike, and also increase Sudangrass seed yield significantly. However, the growth rate of seed yield decreased significantly with the amount of fertilizer increasing. The best strategy of application was 600 kg·hm^-2 nitrogen fertilizer, and Sudangrass had the maximum (3815 kg·hm^-2) yield at this level.