Regulating plant density is an important practice to improve winter wheat productivity under limited irrigation in North China Plain. Field experiments were carried out over two seasons (2014–15 and 2015–16) under three plant densities (D h : 480–570, D m : 360–390, D l : 240–270 10 4 plants hm −2 ) and three irrigation levels (W0: no irrigation; W1: irrigated 80.0 mm only at the jointing stage, which also means limited irrigation; W2: irrigated 60.0 mm each at the jointing and the flowering stages). Results showed that higher numbers of spikes and higher yield were obtained at high density than that at low density under limited irrigation. Under the same irrigation, wheat culms at ripening stage and the proportion of main stem spikes increased with plant density increasing, along with the increasing of transportation amount, transportation rate, and contribution rate of pre-anthesis storage material to grain. But accumulation amount and contribution rate of post-anthesis dry matter, which was influenced by irrigation level, showed a declining trend with increasing plant density under W2 and W1. Therefore, (1) under limited water condition, yield loss could be compensated by increasing contribution rate of pre-anthesis storage material to grain with increasing plant density. (2) Meantime, under the same limited water condition, higher plant densities could promote nitrogen accumulation in grain and plant of wheat, which was significantly correlation to wheat yield. (3) Considering water and nitrogen use efficiency, medium plant density (D m ) is recommended in wet years, high plant density (D h ) may be considered to increase wheat yield in dry years.

中文翻译：

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华北平原限制灌溉条件下优化种植密度保持高产

调节植株密度是提高华北平原有限灌溉条件下冬小麦生产力的重要措施。在三个植物密度（D h ：480-570，D m ：360-390，D l ：240-270 10 4 植物 hm -2 ）下进行了两个季节（2014-15 和 2015-16）的田间试验三个灌溉水平（W0：不灌溉；W1：仅在拔节期灌溉 80.0 mm，这也意味着限制灌溉；W2：在拔节期和开花期各灌溉 60.0 mm）。结果表明，在有限灌溉条件下，高密度比低密度获得更多的穗数和更高的产量。在相同灌溉条件下，随着植株密度的增加，成熟期小麦秆和主茎穗的比例增加，随着运载量、运载率、花前贮藏物对粮食的贡献率。但花后干物质的积累量和贡献率受灌溉水平的影响，在W2和W1下随着植株密度的增加呈下降趋势。因此，（1）在有限水分条件下，随着植株密度的增加，可以通过提高花前贮藏物质对籽粒的贡献率来弥补产量损失。(2)同时，在相同的有限水分条件下，较高的植株密度可促进小麦籽粒和植株氮素积累，与小麦产量显着相关。(3) 考虑到水和氮的利用效率，丰水年建议采用中等种植密度（D m ），旱年可考虑采用高种植密度（D h ）来提高小麦产量。