稻茬过晚播扬麦25产量形成与氮素积累利用特征

为明确过晚播种（较适播期晚30 d左右）对小麦产量及氮素积累与利用的影响,2018―2020年以长江中下游地区主栽品种扬麦25为供试材料,在11月1日（适期播）和12月1日（过晚播）条件下设置 225×10株·hm^-2和375×10株·hm^-2两种种植密度，分析过晚播和适期播小麦产量、氮素积累与分配和氮素利用效率的差异。结果表明,与适期播相比，过晚播小麦的播种至出苗阶段延长9 d，出苗至成熟阶段缩短36 d，总生育期缩短27 d，单穗重降低。适期播条件下低密度的小麦产量较高；过晚播小麦在低密度下与适期播相比两年平均减产20.37%，过晚播高密度小麦较适期播低密度处理平均减产12.41%。过晚播条件下增加密度有利于小麦产量提升，平均产量达8 129.80 kg·hm^-2。过晚播小麦各生育时期氮素积累量较适播小麦下降，密度增加至375×10株·hm^-2能显著提高各生育时期氮素积累量和分蘖至拔节、开花至成熟期的阶段氮素吸收量，与适播低密度处理相比各时期氮素吸收量虽降低，但花后氮素吸收速率与百分比均显著提高，因此过晚播小麦氮肥吸收利用能力显著提升。在本研究条件下，11月1日适期播种时，扬麦25采用密度225×10株·hm^-2，产量可达9 000 kg·hm^-2以上，氮肥表观利用率在45%左右；12月1日过晚播种时，采用密度375×10株·hm^-2，可以协调产量构成三因素，产量达8 000 kg·hm^-2以上，氮肥表观利用率在40%左右。

Characteristics of Yield Components and Nitrogen Accumulation and Utilization of Extremely-Late Sowing Wheat Yangmai 25 Following Rice

In order to clarify the effect of extremely-late sowing(about 30 days later than the suitable-sowing date) on wheat yield and nitrogen accumulation and utilization,Yangmai 25,a wheat cultivar in the middle and lower reaches of the Yangtze River,was used as the test material from 2018 to 2020.Two planting densities of 225×10 plants·hm^-2 and 375×10 plants·hm^-2were set up on November 1(suitable sowing date) and December 1(extremely-late sowing date) to analyze the differences of wheat yield,nitrogen accumulation and distribution,and nitrogen use efficiency. The results showed that compared with the suitable sowing date,the sowing to emergence stage of late sowing wheat was prolonged by 9 days; the emergence to maturity stage was shortened by 36 days; the total growth period was shortened by 27 days,and the single spike weight was reduced. The wheat grain yield was the highest under suitable-sowing and low-density(SSLD) conditions. Compared with SSLD treatment,the yield under extremely-late sowing and low-density(ESLD) conditions was reduced by an average of 20.37% in two years,and the average yield under extremely-late sowing and high-density(ESHD) conditions was reduced by 12.41%. Increasing the density under the condition of extremely-late sowing was beneficial to the increase of yield,with an average yield of 8 129.80 kg·hm^-2. Nitrogen accumulation in each growth period of extremely-late sowing wheat was lower than that of suitable-sowing wheat. Increasing the density to 375×10 plants·hm^-2significantly increased the nitrogen accumulation in each growth period and the growth and development stages from tillering to jointing stage as well as from flowering to maturity stage. Compared with wheat under SSLD,although nitrogen uptake amount of wheat under ESHD was reduced at each stage,the nitrogen uptake rate and percentage after anthesis were significantly increased.Therefore,the nitrogen fertilizer absorption and utilization capacity of wheat under ESHD were significantly improved. Under the conditions of this study,the yield of Yangmai 25 can reach more than 9 000 kg·hm^-2 and the apparent nitrogen use efficiency is about 45% when sowing at the right time on November 1 and planting at the density of 225×10 plants·hm^-2; the yield can reach more than 8 000 kg·hm^-2 and the apparent nitrogen use efficiency is about 40% when sowing too late on December 1 with the planting density of 375×10 plants·hm^-2.