黑龙港流域夏玉米产量提升限制因素

从产量构成因素及物质生产着手分析了黑龙港流域夏玉米产量进一步提高的限制因子.分析结果显示:穗数、穗粒数和千粒重均与产量显著相关,说明该地区夏玉米仍有继续增产的潜力；但在再高产过程中,单纯依靠穗数增加,产量增产幅度较小,应稳定在一定适宜的密度下,注重单位面积穗粒数和粒重的提高,但在穗数确定的情况下,穗粒数相对稳定,增加粒重成为再高产重要因素.因此,采取措施增强灌浆速率和延长灌浆时间是关键,即增强或稳定叶片在花后的有效光合能力.结果表明,增加叶片数量对产量贡献很小,而改善叶片质量、提高叶片功能,进而增加花后同化物合成至关重要.因此,茎秆和叶片的质量是再高产实现的关键技术突破点.同时,提高茎秆的花前物质转运比例也有助于提高于粒重,促进产量提升.在生产实践中,进一步挖掘产量必须搞清楚地上和地下两方面的关系,但目前对“根系-土壤”复合体的结构和功能研究相对较少.不合理耕作方式造成了土壤耕层太浅,严重影响了玉米根系生长发育,使生育后期吸收功能减弱,不利于产量形成.加之,吐丝前后阴雨寡照,造成穗粒数形成决定期的“源”不足,同时也限制了灌浆速率,提前播期,躲避灾害天气或推迟收获时期,延长灌浆时间等逆境栽培措施就显得尤为重要.

Analysis on the limiting factors to further improve yield of summer maize in Heilonggang River Valley

We conducted 10 years of experiments from 2001 to 2010 in the Heilonggang River Valley and analyzed factors limiting summer maize yield, with the aim of further improving yield. The results revealed a significant correlation between grain yield and yield components, such as the number of spikes per culm, the number of grains per spike, and the weight of 1,000 kernels, demonstrating the strong possibility of further improving crop yield. However, the increase in the number of spikes contributed little to increasing yield, while the high thousand kernel weight combined with a stable number of grains produced per unit area was more important. When density stabilized at a certain appropriate range and the number of grains per head was also relatively stable, increasing grain weight became an important factor in further improving yield. So, the key method of further increasing yield should be to increase the thousand kernel weight by enhancing grain filling. Taking measures to enhance the grain filling rate and to extend the filling time was very important in improving yield, which meant stabilizing and/or increasing leaf photosynthesis after anthesis. Our results show the maximum yield increased to 11,775 kg/hm² when the leaf area index (LAI) was 10.3; the harvest index was quite low, which led to a serious waste of resources. Also, the yield was only improved by 1500 kg/hm² when the LAI increased from 6 to 10, which shows that an increase in leaf number contributed little to further increasing grain yield, and leaf quality and leaf photosynthetic capacity, as measured by leaf thickness, specific leaf weight, leaf chlorophyll content, and so on, became critical factors; these factors improved post-anthesis leaf photosynthesis and dry matter production. Therefore, discovering the importance of the quality of the stem and leaves was a key technological breakthrough. Also, an increase of post-anthesis transportation of stem biomass could help to increase the 1,000-grain weight and improve yield. To get higher yield, we should analyze the relationships between both above- and below-ground plant characteristics. However, the structure and function of complex root-soil systems has been the subject of less research than aboveground systems perhaps because of the difficulty of both sampling and research methods. As we know, maize root is critical for plant growth and development. Unreasonable cultivation measures in a shallow plow pan, which seriously affected corn root growth, and then weakened root absorption in the later stages of growth, which was detrimental to crop yield. Also, the maize faced stress from cloudy and drizzly conditions during the silking stage, which resulted in a lack of resources at the time when the number of grains per spike was formed, and also limited the grain filling speed. The cultivation methods designed to resist stress such as advancing the sowing dates to avoid stress from adverse weather conditions or prolonging the harvest period to extend the filling time were very important. In the future, we should consider four potential problem areas. First, the contradiction between the early sowing time of summer maize and the late harvesting time of winter wheat will be taken into consideration. Second, the relationship between prolonging harvest time and filling rate during the late stages of growth should be studied more thoroughly. Third, we should strengthen research into the composition of root-soil relationships to study the causes of poor soil ventilation and extended soil saturation after a heavy rain, which prevents the root system from absorbing soil nutrients to a large extend.