为探讨共生期和密度对棉田套播油菜生长和产量的影响,设置3个共生期：棉油共生10 d (T10)、20 d (T20)和30 d (T30)及4个种植密度30(D1)、45(D2)、60(D3)和75万株 hm–2(D4)裂区试验。结果表明：(1)同一密度下,延长共生期,越冬期、蕾薹期和花期绿叶数、叶面积指数均增加,促进了根系及地上部干物质累积,根冠比、株高、根颈粗增加,茎秆酸不溶木质素和总木质素含量下降,可溶性糖、半纤维素和纤维素含量升高。油菜根倒角度虽增加,但茎倒角度、总倒伏角度减小,油菜单株和群体产量均增加,以 T30D2群体产量最高。(2)密度对油菜生长和产量的影响因共生期不同存在差异。相同共生期处理下,随密度增加,单株绿叶数减少,根系干物质、地上部干物质累积量降低,单株产量降低。T30条件下,叶面积指数(LAI)随密度增加呈先增后减的趋势,在D3密度时, LAI最大；在T20、T10条件下, LAI则随密度增加而增加。群体产量与LAI变化趋势一致。在T30、T20处理下,茎倒角度随密度增加呈先降后增趋势,在 T10处理下,则逐渐增加,与茎秆纤维素含量变化趋势相反,两试点均为 T30D3田间总倒伏角度最小。(3)武穴及天门试点棉田套播油菜产量所要求的共生期及密度最优配置分别为29.8 d、48.8万株 hm–2,29.7 d、57.6万株 hm–2；在此配置下,两试点油菜产量理论值分别为3243.0 kg hm–2和3082.8 kg hm–2,与当地棉田套播油菜常用栽培模式(共生期15 d,密度15.0~22.5万株 hm–2,产量约2625.0 kg hm–2)相比,可实现增产23.5%、17.4%。
Effect of Symbiotic Periods and Plant Densities on Growth and Yield of Rape-seed Intercropping Cotton
To explore the effect of symbiotic periods and densities on the growth and yield of rapeseed intercropping cotton, a split-plot experiment with three symbiotic periods [10 d (T10), 20 d (T20), and 30 d (T30)] and four levels of densities [30×104 (D1), 45×104 (D2), 60×104 (D3), and 75×104 plants ha–1 (D4)] was designed. The results showed as follows:(1) Prolonging sym-biotic periods was favorable for rapeseed growth in terms of the number of green leaves, LAI, root biomass, aboveground biomass, root-shoot ratio, plant height, crown diameter all increased, whereas angle of stem lodging decreased. These led to increase in yield both single plant and unit hectare. (2) The effects of plant density on rapeseed growth and yield depended on the symbiotic period. The number of green leaves, root biomass, aboveground biomass decreased with plant densities, which resulted in de-creased yield per plant. At T30, the maximum LAI was observed under D3, while it was increased with plant density at T20 and T10. The population yield had the same trend with LAI. The yield reached the maximum when the symbiosis period was 30 days and the plant density at 45×104 plants ha–1, whereas the angle of stem lodging reached the minimum at T30D3. (3) Based on the regressions, for Wuxue sites, the optimum symbiotic period was 29.8 days and the optimum plant density was 48.8×104 plants ha–1 while these for Tianmen were 29.7 days and 57.6 plants ha–1. Under these arrangements, Wuxue and Tianmen could achieve the yield about 3243.0, 3082.8 kg ha–1, which were increased by 23.5%, 17.4%, respectively, when compared to the traditional arrangement (the symbiotic period was 15 d, the plant density was 15.0 to 22.5×104 plants ha–1 and the average yield was about 2625.0 kg ha–1).
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