小麦各生育期对土壤不同深度标记硝态氮的利用

 在人为控制灌水的条件下，采用将15N标记到不同土壤层次的土柱试验，研究小麦不同生育期对土壤不同深度硝态氮的利用。结果表明，拔节、孕穗、扬花、成熟4个生育时期，小麦对不同深度标记硝态氮的吸收量及利用率均随深度增加而降低，拔节期对10～20、40～50和70～80 cm深度标记硝态氮的利用率分别为15.7%、3.4%和1.2%，孕穗期对3个标记深度硝态氮的利用率分别为30.6%、10.7%和3.9%，扬花期分别为33.1%、13.1%和5.1%，成熟期分别为32.5%、12.4%和4.7%；小麦对10～20 cm深度标记15N的吸收利用在孕穗期基本接近最高值，40～50、70～80 cm中下层标记硝态氮吸收峰值出现较10～20 cm标记处理推迟，至扬花期达最高值；不同层次土壤标记硝态氮的利用率与相应土层的根长密度和根干重呈显著的正相关关系。

Recovery of Labeled Nitrate-N in Different Soil Layers by Wheat in Different Growth Stages

Recoveries of labeled nitrate-N in different soil layers by wheat at different growth stages were investigated with soil column experiment under the controlled irrigation condition. The results showed that recovery and uptake of labeled nitrate-N by wheat at any stage decreased with the increase of depth of labeled-N in the soil profile. The recovery of labeled nitrate-N in 10-20 cm, 40-50 cm, 70-80 cm soil layer were 15.7%, 3.4% and 1.2% at shooting stage, respectively, and the corresponding recovery were 30.6%, 10.7% and 3.9% at earring stage, 33.1%, 13.1% and 5.1% at flowering stage; and 32.5%, 12.4% and 4.7% at maturing stage. Uptake of labeled nitrate-N in 10-20 cm soil layer by wheat almost maximized at earring stage, but the maximum uptake of 40-50 cm and 70-80 cm layers occurred at flowering stage. Recoveries of labeled nitrate-N in different soil layers by wheat were significantly correlated with the root density and its dry weight in corresponding layers.