Guan'gai paishui xuebao (Jun 2022)
The Combined Effect of Planting Density and Water Stress on Grain Traits of Maize
Abstract
【Objective】 Planting density and irrigation are two agronomic practices which can be manipulated to improve water use efficiency and crop yield in semi-arid regions. In this paper we studied their combined impact on formation of maize grain as well as mass translocation from leave to seeds in northwest China. 【Method】 The field experiments were conducted at the National Field Scientific Observation and Research Station on Efficient Water Use of Oasis Agriculture at Wuwei, Gansu province. There were two planting densities: 70 000 plants/hm2 and 90 000 plants/hm2, and three water stress treatments: sufficient irrigation, mild water stress, and moderate water stress. For each treatment, we measured the grain-filling traits, biomass accumulation, crop yield and yield components, as well as mass translocation. 【Result】 ①Increasing planting density reduced the 100-grain weight of the seeds, while imposing water stress reduced the 100-grain weight of seeds on the basal and middle parts of the cobs only. The difference in grain weight between treatments was mainly due to the difference of seeds on the basal part of the cobs. Increasing planting density combined with water stress shortened the active grain-filling period of the seeds. Increasing planting density alone reduced the average grain-filling rate of the seeds, while water stress reduced the average grain-filling rate of the seeds on the middle and basal part of the cobs. ②Water stress reduced biomass per plant, as opposed to increase in planting density which reduced the biomass per plant. The yield per plant, ear length and diameter, grains per ear and 100-grain weight all decreased as the water stress increased. Increasing planting density significantly increased yield, but reduced the 100-grain weight, grains per ear and yield per plant, with the reduction in yield per plant mainly caused by the decrease in reduced 100-grain weight and grains per ear. ③Change in 100-grain weight of seeds at different locations on the cobs was affected by different factors, with that on the tip, middle and basal parts of the cobs impacted by average grain-filling rate and active grain-filling period, average grain-filling rate, and active grain-filling period, respectively. The grain-filling parameters of seeds on the middle cob was best correlated with the yield per plant and yield components. The yield per plant was significantly affected by the average grain-filling rate. ④The yield depended on mass translocation from leaves to grain which varied with planting density. Dense planting density combined with mild water stress maximized conversion of vegetive biomass into economic yield. 【Conclusion】 Increasing planting density and water stress shortened the active grain-filling period, and reduced the average grain-filling rate of the seeds on the middle and basal part of the cobs. The average grain-filling rate affected the yield per plant and yield per unit area. Dense planting density combined with mild water stress was the optimal agronomic practice.
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