施氮量和密度对机直播双季稻产量与氮素利用率的影响研究

为探究施氮量和播种密度相互作用对机直播双季稻(Oryza sativa L.)产量与氮素利用率的影响,2018—2019以优质稻柒两优2012与美香占2号为材料进行试验,设4个施氮量(早稻分别为0、120、150、180 kg·hm^-2,晚稻分别为0、120、165、210 kg·hm^-2,早、晚稻均以N₀、N₁、N₂、N₃表示)与3个机直播密度(早稻分别为86、143、200 粒·m^-2,晚稻分别为57、114、172粒·m^-2,早、晚稻均以S₁、S₂、S₃ 表示)分析双季稻群体生长发育、产量、产量构成及氮素吸收利用的特征。结果表明,施氮与增密促进双季稻增产,早、晚稻分别在N₃和N₂时产量最高,较N₁增产11.41%~12.32%和8.58%~9.21%;早稻S₂与S₃分别较S₁增产8.71%~10.38%和8.33%~10.89%,晚稻增产6.33%~8.11%和6.78%~8.56%;早稻N₂S₂与N₃S₂间产量无显著差异。施氮与增密的增产因素是机直播双季稻较高的抽穗后干物质量、叶面积指数及氮素积累量,在分蘖期具备碳、氮物质积累优势。机直播双季稻中,N₂S₂的抽穗后叶面积指数、干物质量及氮素积累量较高,同时具备较高的氮素农学利用率、氮素生理利用率及氮素吸收利用率。因此,机直播早、晚稻的施氮量与直播密度组合分别为150 kg·hm^-2与143粒·m^-2处理、165 kg·hm^-2与114粒·m^-2处理时,可以达到增产与氮高效协同。本研究为机直播双季稻密植与优化氮素管理提供了理论依据。

Effects of Nitrogen Application Rate and Density on Yield and Nitrogen Use Efficiency of Double Cropping Rice Under Mechanized Direct-Seeding

In order to investigate the effects of nitrogen application rate and planting density on grain yield and nitrogen use efficiency of double cropping rice production system (Oryza sativa L.) under mechanized direct-seeding, two high quality rice varieties such as Qiliangyou 2012 and Meixiangzhan 2 were used in field trials in 2018 and 2019. Four nitrogen application rates such as 0 (N₀), 120 (N₁), 150 (N₂) and 180 (N₃) kg·hm^-2were for early season rice and 0 (N₀), 120 (N₁), 165 (N₂) and 210 (N₃) kg·hm^-2were for late season rice. In addition, three mechanized direct-seeding densities i.e. 86 (S₁), 143 (S₂), 200 (S₃) seeds·m^-2were for early season rice, and 57 (S₁), 114 (S₂), 172 (S₃) seeds·m^-2were for late season rice. The growth and development, grain yield, yield components, characteristics of nitrogen uptake and utilization of double cropping rice population were investigated. The results showed that the increase of nitrogen application and sowing density were beneficial to the increase of double cropping rice yield. The highest yields of early and late rice were obtained under N₃ and N₂treatments, and increased by 11.41%~12.32% and 8.58%~9.21% compared with N₁treatment, respectively. Compared with S₁treatment, S₂ and S₃ treatments increased yield by 8.71%~10.38% and 8.33%~10.89% for early rice, respectively; and yield increased by 6.33%~8.11% and 6.78%~8.56% for late rice, respectively. There was no significant difference in yield between N₂S₂ and N₃S₂ treatments for early rice. The possible reasons for the increased yield of mechanized direct-seed double cropping rice may attribute to the higher dry matter accumulation and leaf area index, the higher amount of nitrogen uptake after heading and the advantage of carbon and nitrogen accumulation at tillering stage. The N₂S₂ treatment showed a higher leaf area index, dry matter mass and nitrogen accumulation, and which also had higher nitrogen agronomic utilization, nitrogen physiological utilization and nitrogen absorption utilization for mechanized direct-seed double cropping rice. Therefore, yield improvement and higher efficiency of mechanized direct-seed double cropping rice be integrated in the combination of 150 kg·hm^-2with 143 seeds·m^-2for early rice and 165 kg·hm^-2with 114 seeds·m^-2for late rice. The study provides a theoretical basis for rational dense planting and optimal nitrogen management for mechanized direct-seeding double cropping rice production.