氮肥运筹对稻茬小麦土壤硝态氮含量、根系生长及氮素利用的影响

以宁麦9号为材料,研究施氮量及氮肥基追比例对稻茬小麦土壤硝态氮含量、根系生长、植株氮素积累量、产量和氮素利用效率的影响。结果表明,拔节前0-60cm土层硝态氮含量随基施氮量的增加而显著增加,随生育进程的推进各处理硝态氮显著向下层土壤淋洗;拔节期追施氮肥显著提高了孕穗期0-40cm土层硝态氮含量,且随追施氮量的增加而显著增加,N300和N3/7处理硝态氮显著向40-60cm土层淋洗。根系主要生长于0-20cm土层,拔节前各土层根长密度均随基施氮量的增加而增加,拔节后则随施氮量增加和适当的追肥比例而增加。各施氮处理均以拔节至开花期为小麦氮素积累高峰期。适宜增加施氮量并适当提高追肥比例,有利于提高产量、植株氮素积累量和氮素利用效率。因此,在小麦生产中,适当降低施氮量并提高拔节期追肥比例有利于促进小麦根系生长和植株氮素积累,进而提高小麦产量并减少硝态氮淋洗损失。

Effect of Nitrogen Application on Soil Nitrate Nitrogen Content, Root Growth and Nitrogen Utilization of Winter Wheat in Rice-Wheat Rotation

Field experiments with Ninmai 9(Triticum aestivum L.) were conducted in Nanjing to investigate the effects of nitrogen(N) application rates and basal-topdressing ratios on soil nitrate nitrogen content,root growth,N accumulation,grain yield and N utilization efficiency in 2008-2010.The results showed that high basal N rate enhanced NO-3-N content in the soil layer of 0-60 cm before jointing,and NO-3-N leached to deeper soil layer with plant development stages.The NO-3-N content in 0-40 cm soil layer at booting increased with the increase of topdressing N rate at jointing,NO-3-N leached to 40-60 cm soil layer in the treatment N300 and N3/7.The roots mostly grew in 0-20 cm soil layer at different growth stage;root length density increased as the basal N rate increased before jointing and also increased with an increase of the topdressing N dose after jointing.For each N treatment,the uptake of N was the highest in the duration from jointing to anthesis stage.Grain yield,N accumulation amount and N utilization efficiency increased at the appropriate N rate and topdressing N ratio.Data from two growth seasons showed that properly reducing nitrogen rate and increasing topdressing N ratio gave better root growth,increased grain yield,plant N uptake and N utilization efficiency,and reduced leaching loss of NO-3-N.