氮肥运筹对稻茬小麦土壤硝态氮含量时空分布和氮素利用的影响

研究了不同氮肥运筹对土壤硝态氮时空分布及小麦氮肥利用效率的影响。结果表明,小麦氮素利用效率随施氮量的增加而显著降低,增加追肥比例提高了产量和氮肥利用效率,品种间趋势一致。0～60 cm土层土壤硝态氮含量冬前最高,随着生育进程而逐渐降低。随施氮量增加土壤硝态氮含量升高,特别是下层土壤硝态氮含量在施氮处理下更为明显。从播种至成熟,不施氮处理土壤氮素出现了表观亏缺,施氮处理均表现氮素盈余,且随施氮量的增加而增加。因此,在小麦生产中应避免在播种时一次性大量施用氮肥,而分期施肥有利于小麦吸收利用,并且可以减少深层土壤硝态氮的累积。

Effects of nitrogen fertilization on spatial-temporal distributions of soil nitrate and nitrogen utilization in wheat season of rice-wheat systems

Nitrogen is the key nutrient for crop growth, and proper N applications not only improve soil productivity but also reduce N losses. Knowledge of soil N supply is the basis for making optimum N fertilization recommendation. Field experiments were conducted to explore effects of different N strategies, including N application rates and topdressing, on nitrogen use efficiency (NUE) and spatial-temporal distribution of NO₃^--N. Results show that NUE obviously decreased with increasing N rate. Soil NO₃^--N content was highest at the beginning of winter, and then decreased, but it increased with nitrogen application rate and more significant in the deep soil layer (40~60 cm) than in the middle soil layer (20~40 cm). After crops were harvested, N deficit was found in zero N treatment appeared N deficit, while N surplus was in all fertilization treatments, and increased with N application rate. This study recommends that it is not advisable to apply a large quantity of N fertilizer all at once as basal dressing. Splitting N application favors N absorption by wheat and reduces soil nitrate accumulation in the deep soil layer.