Study On Effects Of Sowing Date And Variety Combination On The Whole Year’s High-yield Of Double Cropping Maize In Southern Paddy

A field experiment was conducted in Baitutan town, Liling city of Hunan province in2012, in order to excavate paddy grain production potential and make the best use of high-yield and high-efficiency advantages of C4crop.The experiment was designed two factors,including sowing date (Spring sowing date:Sl:5th, Mar;S2:22th,Mar;S3:28th,Mar)and varieties(V1:Zhengdan958;V2:Denghai9;V3:Xianyu335). The characteristics of yield formation, distribution and utilization of light and heat resources and their physiological attributes were studied under different sowing dates and variety combinations of double cropping maize. The results were as follows:(1) With the scope of sowing date from March15in the spring to July28in autumn sowing, double cropping maize could normally mature. The whole stage leaf area duration (LAD) of spring maize showed that spring-sowing S2was highest, in which variety-V3was also highest(258m2·dm-2), that of autumn maize performed that spring-sowing S1in summer-planting was highest; With the sowing date delaying,mean crop growth rate (MCGR) of each of varieties of double cropping maize showed a trend of decreasing, varying somewhat between varieties; Annual dry matter accumulation in spring-sowing S2is significantly higher than other sowing dates, and in which variety combination V3+V3was highest(dry matter accumulation of spring,autumn and the annual, respectively, up to24001kg/hm2,15141kg/hm2, and39142kg/hm2).(2) Annual yield showed significant differences between sowing dates and variety combinations. Annual yield of spring-sowing S2(18058.2kg/hm2) was highest, which was increased by2.5%and8.1%than S1and S3, respectively, otherwise Variety combination V3+V3and V3+V1were highest, up to18352.8kg/hm2and18352.8kg/hm2, respectively. Annual yield with S2-(V3+V3) treatment was highest (19103.6kg/hm2). Yield of double cropping maize was closely related to yield performance parameters, which reached extremely significant correlation with grain NO. per ear and grain weight, and mean leaf area index (MLAI) and harvest index (HI) showed higher values. (3) Yield performance of double cropping maize was in accordance with light, temperature resources possession and productivity efficiency throughout the year. the highest Light and temperature resources possession was S2-V3+V1(2494MJ·m-2and3079℃), and annual Light and temperature production efficiency with S2-V3+V1and S2-V3+V3was highest, annual yield with S2-V3+V1and S2-V3+V3was highest, which light energy distribution was close to1:1, heat resource allocation was partial to early season (1.2:1),in regard as better form of light and temperature resource allocation. Annual land utilization ratio was about65%in double seasons, and which of S2-V3+V3and V3+V2were highest (66.7%).Under this test condition, it was apt for spring-sowing to choose around March22with late-maturity breed, and for summer-planting autumn maize to choose late-maturity and mid and early-maturity varieties, to give consideration to double seasons crop contradictions, coordinate light and temperature resource allocation of double cropping, make sure that light and temperature resource and land use efficiency were highest, which was conducive to perform of high-yield and high-efficiency potential of double cropping maize in paddy.