[Effects of extremely-late sowing on the grain yield, nitrogen uptake and utilization, and grain protein content in winter wheat].

In order to explore the cultivation techniques for high yield, quality and nitrogen use efficiency of wheat and guide the production practice of late sowing, a two-year experiment of different sowing times and plant densities in fixed plots was conducted from October 2012 to June 2014. Weak-spring cultivar of Yanzhan4110 (YZ4110) and semi-winter cultivar of Aikang58 (AK58) were sowed with two cropping patterns: Normal sowing (sowing in the middle of October, 2.4×106 plants·hm-2 ) and extremely-late sowing (sowing in the middle of November, 6.0×106 plants·hm-2 ). The nitrate-N content in 0-40 cm soil, the nitrogen (N) uptake and utilization, grain yield, grain protein content and N uptake efficiency in winter wheat were investigated. Compared with normal sowing, extremely-late sowing significantly increased the nitrate-N content in 0-40 cm soil at jointing and anthesis stages, which in turn promoted the N uptake and accumulation of plants after jointing stage and increased the N distribution ratio of spikes at maturity. As a result, the grains with extremely-late sowing had higher protein contentin both YZ4110 and AK58, and higher protein yield and N uptake efficiency in YZ4110 than that with normal sowing. However, the effects of extremely-late sowing on grain yield were different in the two cultivars. Compared with normal sowing, extremely-late sowing clearly raised the grain yield of YZ4110, but significantly decreased that of AK58. These results indicated that extremely-late sowing is an alternative cropping technique to increase grain yield and protein content for winter wheat in irrigation zones through maintaining the soil N supply after jointing stage and increasing N uptake efficiency.