施氮量和底施追施比例对土壤硝态氮和铵态氮含量时空变化的影响

研究了高产栽培条件下，不同施氮量和底施追施比例对土壤硝态氮和铵态氮含量时空变化的影响，同时计算了不同生育阶段土壤氮素的表观盈亏量.结果表明，与氮肥分期施用处理比较，氮肥全部用于拔节期追施处理降低了拔节期之前的土壤硝态氮含量，减少了拔节期之前土壤氮素的表观盈余量，降低了氮素向深层的淋洗；而挑旗期土壤硝态氮含量与氮肥分期施用处理无显著差异，但提高了土壤铵态氮含量；增加了成熟期0～60 cm土壤各土层土壤硝态氮含量和0～20 cm土壤铵态氮含量.氮肥全部用于拔节期追施的两处理间比较，在240 kg·hm^-2的基础上降低施氮量至168 kg·hm^-2，降低了挑旗期土壤硝态氮和铵态氮的含量，减少了挑旗期到成熟期土壤氮素的亏缺量，也使成熟期土壤硝态氮的含量降低.不同处理间籽粒产量和蛋白质产量无显著差异，施氮量为168 kg·hm^-2且全部用于拔节期追施的处理籽粒蛋白质含量最高.

Effects of nitrogen application rate and its basal-/top-dressing ratio on spatio-temporal variations of soil NO3--N and NH4+-N contents

Under high-yielding cultivation condition, this paper studied the spatiotemporal variations of soil NO3 -N and NH4+ -N contents as affected by different nitrogen application rate and its basal-/top-dressing ratio, and calculated the apparent budget of soil nitrogen at different growth stages of wheat. The results indicated that compared with split application, applying all fertilizer nitrogen at jointing stage decreased the soil NO3- -N content and apparent surplus of soil nitrogen before jointing stage, and decreased the nitrogen leaching to deeper soil layers. Applying fertilizer nitrogen at flagging stage had no significant difference with split application in soil NO3- -N content, but increased soil NH4+ -N content. Applying fertilizer nitrogen at maturing stage increased the soil NO3- -N content in 0-60 cm and 0-20 cm layers. In comparing with applying 240 kg x hm(-2) of fertilizer nitrogen at jointing stage, applying 168 kg x hm(-2) of fertilizer nitrogen at the same stage decreased the soil NO3- -N and NH4+ -N contents at flagging stage, soil nitrogen deficit from flagging to maturing stage, and soil NO3- -N content at maturing stage. The grain yield and its protein content had no significant difference among different treatments, but applying all 168 kg x hm(-2) fertilizer nitrogen at jointing stage induced the highest grain protein content.