Subjects: Biology >> Ecology submitted time 2017-11-29 Cooperative journals: 《中国生态农业学报》
Abstract： On the Loess Plateau, maize morphological structure and yield performance were restricted by rainfall capacity and soil nutrient status. Resource competition in intercroped cultivation can provide a postive effect on the individual establishment and biomass allocation of maize cultivars. The research on root morphology and biomass allocation of maize under integrated influence of annual rainfall level, planting densities and intercropped cultivation aimed for clear and definite the necessity and importance of intercropped models on the grain yield and water use efficiency (WUE) increase. Field experiment was conducted at a classic dry farmming region in a semi-arid region of Loess Plateau in Northwest China. Two maize cultivars (Zhengdan 958, Z958 and Shendan 16, S16) with two planting densities as 45000 plants. hm-2 and 75000 plants .hm-2, intercroped planting in two rows interlaced, above- and belowground competitive growth and biomass accumulation were measured and analyzed for assessing the correlation among biomass allocation, root distribution, grain yield and WUE. The results showed as: (1) Soil water deficiency showed an effective force to root surface area (SA) decrease of S16 at flowering stage under low intercroped density, and SA of Z958 decreased by 30.5% under high intercroped density, water competition was intensified with the intercropped density increase. Over two experimental years, Z958 and S16 intercropping increased root length density (RLD) in 0-20 cm soil layer significantly, denstiy increase and rainwater deficiency both stimulated root growing deeper for water uptaking which then enhanced root competition for water, finally, caused the RLD obvious increase in 30-40 cm soil layer and Z958 appeared deeper root distribution capacity than S16 in two planting densities. (2) Biomass accumulated advantage under intercroped planting had a gentype difference, Z958 appeared growing promotion during vegetative period and that of S16 was during reproductive period. Individual biomass of two maize cultivars decreased with the intercroped density increase, and there had a increase in S16 dry weight during during reproductive growing period compared with that of Z958 in 2011under low intercroped planting density; with high density and more drought condition, maize cultivars intercrops decreased individual biomass accumulation after flowering. (3) the high intercroped density system obtained a increase of harvest index (HI) by 6.0% averagely over two different rainfall years, and ample rain promoted the HI of intercroped group. Root and shoot could grow normally due to inefficient light competition under the sufficient precipitation and low planting density; Soil drought and high intercroped density resulted in the significant decrease of root to shoot rate (RSR) in Z958 because the root competition for water was enhanced. (4) In the drought year (2011), competitive advantage was fully appeared in the two intercroped systems, showed as final yield and WUE increased by 10.3 and 21.4% , 28.2 and 42.0% respectively in the two intercroped densities, furthermore, yield and WUE of Z958 under mixed system were 17.6 and 50.0% higher than S16 over two years. Finally, Z958 showed reasonal biomass distribution and response mechnisim to soil drought under intercropping with S16, through decreased root redundant growth and useless resouces consume. Effective root morphological adjustment and biomass distribution of Z958 were responsible for yield and WUE increase.
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