密植条件下种植方式对夏玉米群体根冠特性及产量的影响

选用平展大穗型品种鲁单981(Ludan981,LD981)和紧凑中穗型品种鲁单818(Ludan818,LD818),在两种种植密度(60000和90000株/hm2)和两种种植方式(单株和双株)下,研究了密植及种植方式对夏玉米冠层和根系结构与功能以及子粒产量等的影响.研究发现,随种植密度增加,冠层垂直分布呈现干重比例权重上移的趋势,根系则呈现下移的趋势.密植条件下,LD981冠层对生长空间更为敏感,其根系对生长空间的竞争强于冠层,其群体产量限制因素是子粒库容；LD818根系对生长空间更为敏感,冠层对生长空间的竞争强于根系,其群体产量限制因素是单位面积穗数.60000株/hm2下,LD981的群体结构质量和功能较优,双株种植可缓解其冠层竞争,根、冠协调,表现增产；在90000株/hm2下,LD818的群体结构质量和功能较优,双株种植可缓解其根系竞争,部分改善冠层群体结构质量和功能,根、冠协调,表现增产.

Effect of different planting methods on root-shoot characteristics and grain yield of summer maize under high densities

In order to investigate high densities and planting methods of summer maize in north China, in 2010-2011, two varieties (Ludan 981, LD981, and Ludan 818, LD818) were selected and planted in two densities (6 0000 and 90000 plants/hm²) at two planting methods (single and double plants at one place). In this experiment, eight treatments were designed to study the effect of planting methods on root-shoot development and grain yield of summer maize under high densities. The results showed that vertical distribution of canopy resulted in a trend that dry matter weight increased with planting density increased; however, root vertical distribution resulted in a opposite trend. Under high density conditions,there were different competitive ability of root and shoot between different maize varieties. The canopy of LD981 was more sensitive to space, and its space competition of root was stronger than that of the canopy, hence, the yield limiting factor of LD981 was the kernel storage capacity; however, the root of LD818 was more sensitive to space, and its space competition of canopy was stronger than that of the root, hence, the yield limiting factor of LD818 was the spike number per unit. Under the condition of 60000 plants/hm², the quality of canopy structure and function of LD981 was better, double plants at one place reduced competitive stress in the canopy, as a result, achieved root and shoot equilibrium. Hence, the population yield enhanced; under the condition of 90000 plants/hm², the quality of canopy structure and function of LD818 was better, double plants at one place alleviated root competition, the quality of canopy structure and function improved partly, therefore, the root and shoot coordinated, which let to the yield increased.