摘要:品种间作竞争具有优化作物个体形态特征和生物量分配的生态效应。综合干旱环境、密度和降雨年际变化影响下的品种间作生物量分配机制研究，可为旱区作物增产增效栽培提供理论依据。试验于2011年（降雨量645.0 mm，湿润年份）和2012年（降雨量497.1 mm，干旱年份）调查了两个玉米品种（‘郑单958’和‘沈单16号’）、两种密度（4.5万株·hm-2和7.5万株·hm-2）隔行间作处理下，地上部生物量和地下部根系形态特征，并分析了品种间作下生物量分配策略、根系竞争机制与产量、水分利用效率的关系。结果显示：1）干旱显著降低玉米根系表面积（SA），低密度间作下‘沈单16号’扬花期SA显著降低而‘郑单958’显著增加，高密度间作‘郑单958’的SA显著下降25.3%，间作下根系对于水资源的竞争随种植密度的增加而加剧；两个种植密度和两个不同降雨年份，间作系统0~20 cm土层根长密度（RLD）显著增加，增加种植密度和雨水亏缺，刺激根系向深层土壤生长，导致30~40 cm土层RLD的增加，且‘郑单958’的RLD增加幅度远高于‘沈单16号’。2）间作竞争下生物量积累具有品种差异，‘郑单958’集中在营养生长期，而‘沈单16号’集中在生殖生长期；且随种植密度的增加，间作栽培下单株生物量显著降低。3）群体收获指数（HI）在高密度间作下，两个不同降雨年份出现平均6.0%的增加幅，雨水充足促进群体HI的提升；根冠比因降雨和种植密度而变，雨水充足、低密度间作下根冠比较大，干旱和高密度下资源竞争造成‘郑单958’根冠比显著下降。4）干旱年份玉米品种间作增产优势显著，高、低密度间作增产率分别为10.3%和21.4%，水分利用效率（WUE）分别增加28.2%和42.0%；且‘郑单958’增产和增效能力分别较‘沈单16号’高17.6%和50.0%。综上所述，品种间作栽培下‘郑单958’具有更合理的地上部生物量分配和响应机制，其根系通过减少冗余生长，降低资源消耗来应对土壤干旱，高效的根系自我调节能力和生物量分配机制在间作系统产量形成和WUE提升中起到了关键作用。
关键词:夏玉米/
品种间作/
生物量分配/
资源竞争/
水分利用效率/
半干旱地区/
黄土塬区
Abstract:On the Loess Plateau, maize morphological structure and yield performance are restricted by low rainfall and limited soil nutrient. Resource competition in intercroped cultivation have a postive effect on individual establishment and biomass allocation of maize cultivars. It was necessary to research root morphology and biomass allocation of maize under the combined effect of rainfall, planting density and intercropping for exploring effects of intercropping models on grain yield and water use efficiency (WUE) of maize in the Loess Plateau. To this end, a field experiment was conducted at Changwu Agri-ecological Station in the Loess Plateau, Chinese Academy of Science which is located in the classic dry farmming region in the semi-arid region of the Loess Plateau in Northwest China. Two maize cultivars ('Z958' and 'S16a') were intercroped under two planting densities (45 000 plants·hm-2 and 75 000 plants·hm-2) with 1:1 lines ratio. The aboveground and belowground growth and biomass accumulation were investigated at different growth stages of maize in tow rainfall year types, 2011 with rainfall of 647 mm and 2012 with rainfall 497 mm. The study also measured and analyzed the correlation among biomass allocation, root distribution, grain yield and WUE. The results showed that:1) soil water deficiency had a negative effect on root surface area (SA) of 'S16a' at flowering stage under low intercropped planting density. Also while SA of 'Z958' decreased by 30.5% under high intercropping density, WUE increased with increasing intercropping density. After two years of experimentation, root length density (RLD) in the 0-20 cm soil layer significantly increased under 'Z958' and 'S16a' intercropping. Also with increasing planting denstiy, rainwater deficiency led to deeper root growth to enhance water uptake. This in turn enhanced root competition for water and eventually obviously increased RLD in the 30-40 cm soil layer. Root distribution of 'Z958' was higher than that of 'S16a' for the two planting densities. 2) Biomass accumulation under two cultivars intercropping was genotypically different, with enhanced 'Z958' growth during vegetative period and enhanced 'S16a' growth during reproductive period. The individual biomass of two maize cultivars decreased with increasing intercropping density. The increase in dry weight at reproductive growth period was higher for 'S16a' than for 'Z958' in 2011 under low intercropped planting density. With high density and drought condition, individual biomass accumulation decreased under maize cultivars intercropping after flowering. 3) There was on average 6.0% increase in harvest index (HI) under high intercropping density and HI increased with increasing rainfall. Root and shoot growth was normal due to light competition under sufficient precipitation and low planting density. Soil drought and high intercropping density resulted in significant decrease in root to shoot rate (RSR) of 'Z958' as root competition for water increased. 4) In drought year (2011), competitive advantage was fully apparent in the two cultivars intercropping system, with yield and WUE increases of respectively 10.3% and 21.4%, 28.2% and 42.0% under two intercropping densities. Furthermore, yield and WUE of intercropped 'Z958' were 17.6% and 50.0% higher than that of 'S16a' for the two-year experimental period. Finally, 'Z958' showed rational biomass distribution and response to soil drought when intercropped with 'S16a' via reducing redundant root growth and decreasing excessive resouces use. Effective root morphological adjustment and biomass distribution of 'Z958' were responsible for the yield and WUE increase.
Key words:Summer maize/
Cultivar intercropping/
Dry matter distribution/
Resource competition/
Water use efficiency/
Semi-arid region/
Loess highland
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