玉米冠层结构和群体光合特性对增密的响应

2018~2019年以陕科9号和大丰30为材料,设置4个密度4.5万、6.0万、7.5万和9.0万株/hm^2进行田间试验,分析玉米冠层结构、光合性能以及产量构成指标,研究种植密度对玉米群体特征及产量的影响,确定陕北灌区玉米适宜种植密度。结果表明,两个品种子粒产量随密度增大呈先增加后降低的趋势,均在密度7.5万株/hm^2时产量最高,两年平均产量分别为14.1 t/hm^2和13.2 t/hm^2。随种植密度增大单位面积穗数显著增加,穗粒数和百粒重减少。随着密度的增加,两个品种能够调节穗上中部叶倾角、株型变紧凑,穗位层接收到更多的光能,增加了群体光合速率,积累更多光合同化物,高密度条件下陕科9号协调形态结构和生理功能方面优于大丰30。适当增加密度配合耐密品种是陕北灌区春玉米增产的重要途径,密度7.5万株/hm^2是该区玉米适宜种植密度。

Responses of Canopy Structure and Population Photosynthetic Traits on Increased Planting Density of Different Maize Cultivars

This study aimed to explore the canopy characteristics for high yield under increased plant density and determine the suitable planting densities in the irrigated region of northern Shaanxi. Four plant densities of 45000, 60000, 75000, and 90000 plants/ha were designed during 2018 and 2019 growing seasons. Two maize cultivars SK 9 and DF 30 were used to explore the effects of planting density on leaf area index, leaf direction value, light energy interception rate, photosynthetic characteristics, and yield traits of maize. The results showed that the grain yield of the two cultivars increased then decreased with the increase of density, and the highest yield was obtained at the density of 75000 plants/ha. The average yield of the two years was 14.1 t/ha and 13.2 t/ha, respectively. The number of productive ear was remarkably increased with the increasing of planting density, but the seed numbers per ear and 100-kernel weight decreased with the increase of planting density. With the increase of planting density, the two cultivars can adjust the leaf angle of upper ear, plant type becomes compact, the leaf layer of ear position receives more light energy, improving the photosynthetic performance of population, and resulting in making more accumulation of photosynthetic production; but the coordination morphological structure and physiological function of SK 9 are better than DF 30 under the higher plant density, indicated that the grain yield potential of SK 9 is higher than DF 30. Therefore, properly increased plant density couple with density tolerant cultivars is a potential way to improve the maize yield in the irrigation area of Northern Shaanxi. The optimal planting density of maize is 75000 plants/ha, which is suitable for the large-scale promotion in this area.