种植方式对夏玉米光合生产特征和光温资源利用的影响

为研究套种与直播两种种植方式对夏玉米光合生产特征和光温资源利用的影响，选取郑单958和登海661为研究对象，设置3个播期，密度为67500株·hm^-2，以地上干物质积累量和作物生长速率、叶面积指数、穗位叶的单叶光合速率来评价夏玉米的光合生产特征；以Richards模型拟合籽粒灌浆过程；结合气象数据计算夏玉米光能利用率.结果表明：直播处理比套种处理籽粒产量增加1.17%～3.33%（P<0.05），但千粒重显著降低；生育期随播期提前而延长；直播条件下叶面积指数和单叶光合速率在灌浆前期显著高于套种，但灌浆后期下降较快；与套种相比，直播开花前和开花后具有较高的干物质积累量和较快的作物生长速率.Richards模型解析表明，直播处理达到最大灌浆速率的时间明显早于套种，起始势较套种高，但灌浆期、活跃灌浆期和灌浆速率最大时的生长量均低于套种；与套种相比，直播处理生育期间总积温和总辐射量分别减少150～350 ℃·d和200～400 MJ·m^-2，但籽粒光能利用率较套种提高10.5%～24.7%.因此，直播较套种有优势，在夏玉米大田生产条件下，重视叶片的光合生产特征，延缓叶片衰老，有利于提高夏玉米的光能利用率，进一步挖掘增产潜力.

Effects of cropping patterns on photosynthesis characteristics of summer maize and its utilization of solar and heat resources

In order to investigate the effects of interplanting and direct seeding on the photosynthesis characteristics of summer maize and its utilization of solar and heat resources, two summer maize cultivars (Zhengdan 958 and Denghai 661) were planted in the farmlands of Denghai Seed Co. Ltd in Laizhou City of Shandong Province, with 67500 plants·hm^-2 and three sowing dates. The above-ground biomass, plant growth rate, leaf area index, and net photosynthetic rate per ear leaf were measured to reveal the photosynthesis characteristics of test cultivars. In the meantime, the characters of grain-filling were simulated by Richards’ model, and the solar resource utilization efficiency of the cultivars was calculated, in combining with meteorological data. Comparing with interplanting, direct seeding increased the grain yield by 1.17%-3.33%, but decreased the thousand-grain weight significantly. Growth stages were extended under earlier sowing. The leaf area index and net photosynthetic rate from flowering to 30 d after anthesis were significantly higher under direct seeding than under interplanting, but after then, they decreased faster. Direct seeding induced a higher accumulation of dry matter and a faster plant growth rate before and after flowering. Under direct seeding, the maximum grain-filling rate reached earlier, the starting potential was higher, but the grain-filling period, active grain-filling period, and W_maxwere lower, compared with those under interplanting. Also under direct seeding, the total accumulative temperature and solar radiation during growth period decreased by 150-350 ℃·d and 200-400 MJ·m^-2, respectively, but the solar resource utilization efficiency of grain increased by 10.5%-24.7%. All the results suggested that direct seeding was superior to interplanting for the summer maize production under field condition. In order to enhance solar and heat utilization efficiency and excavate yield potential, it would be essential to improve the leaf photosynthesis efficiency and postpone leaf aging.