To explore the impacts of global climate change on the suitable sowing date for winter wheat in north winter wheat area of China, we carried out a wheat sowing date experiment during growing seasons of 2019-2021 at the Beijing Experimental Base of the Institute of Crop Sciences, CAAS. Two winter wheat cultivars with different tillering powers were selected as experimental materials. Four different sowing dates were set: September 25th (J), October 5th (S0), October 15th (S1) and October 25th (S2), to examine the responses of population quality, individual characters, and stem and tiller physiology to the accumulated temperature difference before overwintering. The results showed that with the delay of sowing date, the accumulated temperature before winter and their difference between the adjacent sowing dates decreased gradually. The accumulative temperature at the sowing J and S0 both exceeded 550 ℃, which met the basic condition for the formation of strong wheat seedlings before winter. The average accumulated temperature at sowing S1 and S2 was 148.0 and 282.4 ℃ lower than that of S0, which was not conducive to the establishment of strong wheat seedlings before winter. The average accumulated temperature decreased by 204.0, 148.0 and 134.4 ℃, when the sowing date was delayed by 10 days under the four different sowing dates, respectively. The days from sowing to emergence were affected by the average daily temperature. The days from sowing to emergence gradually increased with the delay of sowing date when the daily average temperature was lower than 15 ℃, while the days from sowing to emergence were constant when the daily average temperature was higher than 15 ℃. The total stem number, leaf area index, dry matter weight, nitrogen accumulation and tiller number per plant of wheat also decreased with the decreases of pre-winter accumulated temperature. The soluble sugar content and nitrate reductase activity at the seedling increased first and then decreased with the decreases of accumulated temperature before winter, while the soluble protein content and glutamine synthetase activity to accumulated temperature performed differently among varieties. According to the population quality and individual traits of wheat before winter, among the four different sowing dates, the total stem number and tiller number per plant of wheat before sowing on October 5 were the closest to the standard of strong seedlings before winter in north winter wheat area. The accumulated temperature before winter is conducive to the formation of strong seedlings. When the daily average temperature is 15-17 ℃, it is the best sowing time for winter wheat in Beijing.

为解决我国北部冬麦区因播期推迟造成越冬前小麦苗情较弱的实际问题,于2019—2021年在中国农业科学院北京试验基地进行晚播试验,设3个播期:10月5日适期播种(S0)、10月15日适当晚播(S1)、10月25日过晚播(S2),以S0为对照,对晚播S1、S2采取覆膜和补施氮肥的调控措施,研究覆膜和补施氮肥对晚播小麦冬前群体质量、个体性状以及茎蘖生长的影响.结果表明:晚播不利于小麦冬前群体和个体质量的形成,以及茎蘖的生长.晚播覆膜增温可提高冬前群体总茎数,与不覆膜处理相比,适当晚播和过晚播覆膜处理提高了小麦冬前群体生长率和相对生长率,群体总茎数平均分别提高42.9％、148.4％;植株冬前叶龄增加,个体分蘖数平均分别增加1.6个和2.0个;覆膜增温延长主茎上第1分蘖至第3分蘖营养生长进程,提高苗期茎叶、分蘖节、根部可溶性糖含量以及叶片中生长素与玉米素核苷的比值(IAA/ZR),增加冬前群体总茎数.对各处理进行晚播苗情评价可得出,适期播种条件下均有利于2个不同分蘖力品种冬前群体综合质量的提高,其中,多穗型品种中麦8号在晚播覆膜条件下其晚播苗情较好,大穗型品种航麦501则在适当晚播无调控措施、适当晚播+补施氮肥、适当晚播+覆膜和过晚播+覆膜条件下其晚播苗情较好,同时2个不同分蘖力品种在晚播条件下对覆膜增温的响应存在差异.中麦8号在适期播种或晚播覆膜条件下更有利其冬前群体综合质量的提升,而航麦501在适期播种、适当晚播和过晚播覆膜条件下均有利于其晚播苗期质量的提高.补施氮肥则对晚播小麦冬前群体质量、个体性状和茎蘖生长无明显调控效应.综上所述,在晚播条件下,覆膜可有效改善小麦冬前群体和个体的综合质量,进一步促进茎蘖的生长.

针对冬小麦因播期推迟造成产量损失的问题,以2个不同分蘖能力的冬小麦品种中麦8号和航麦501为供试材料,研究苗期覆膜和补施氮肥对晚播小麦产量及氮素利用的影响.试验设置3个播期:10月5日适期播种(S0,对照)、10月15日适当晚播(S1)和10月25日过晚播(S2).结果表明:随着播期推迟,小麦产量逐渐降低.晚播条件下,苗期覆膜和补施氮肥可调控冬小麦产量构成因素、农艺性状、茎蘖生长、成穗率以及氮素的吸收利用.综合而言,晚播条件下,覆膜和补施氮肥有利于提高小麦穗长、总小穗数及冬前群体数量;同时,覆膜可显著提高2个品种晚播条件下的分蘖成穗率和过晚播条件下的植株氮素积累量(PNA)及氮肥偏生产力(PFP),增幅分别为46.4％～89.1％、12.7％～26.5％和19.5％～20.1％;补施氮肥在过晚播条件下有利于成穗率的提高,增幅为18.5％～34.7％.2种调控措施均有利于增加晚播小麦产量,增幅达1.4％～19.5％.但不同分蘖力的小麦对2种调控措施的响应存在差异.综合考虑产量及氮素利用等各方面因素,在晚播条件下,相比于补施氮肥,苗期覆膜更有利于提高晚播小麦产量,弥补晚播造成的产量损失,但在实际操作和节约生产成本方面,前者优于后者.

为了探索不同施氮量对冬小麦光合生理指标及产量的影响,在中国农业科学院作物科学研究所北京试验基地,以3个强筋冬小麦品种藁优2018(C1)、师栾02-1 (C2)、石优20 (C3)和1个中筋冬小麦品种济麦22 (C4)为试验材料,设置0、180、210、240、270kg/hm2 5个氮肥处理,分别用N0、N180、N210、N240、N270表示.结果 表明:N240处理下不同冬小麦品种的旗叶净光合速率、SPAD值、旗叶长度、旗叶宽度,叶面积指数、归一化差值植被指数、籽粒产量及其构成因素等指标均达到最高值,且显著高于不施氮肥的处理,但与N270处理间无显著差异.综合考虑光合生理、植株性状、产量构成因素等指标,施氮量240kg/hm2是充分发挥不同冬小麦品种植株光合性能及产量潜力的适宜施氮水平.