夏直播棉花产量与冠层微环境的关系OA北大核心CSTPCD

The yield of cotton under summer direct seeding can be comparable to that of conventional cotton in a short growing period.However,the mechanisms behind high yield formation and its relationship with the canopy microenvironment remain unclear.Therefore,this experiment employed a completely randomized block design,with six different planting densities(7.50,8.25,9.00,9.75,10.50,and 11.25 plants m-2).The field experiment was conducted in Wuhan from 2022 to 2023.Temperature and humidity within the canopy were recorded using an automated meter,while light radiation intensity at various heights of the can-opy during boll setting stage was measured using a canopy analyzer.Cotton was manually harvested to calculate the yield.The results indicated that cotton yield initially increased and then decreased with increasing planting density.Among them,the highest yield(3246.5 kg hm-2 of seed cotton and 1203.2 kg hm-2 of lint)was observed at a density of 9.75 plants per square meter,which was significantly higher than the yield at 7.50 plants m-2(15.0%and 17.8%higher)over the two years.As planting density in creased,the average daily temperature,maximum temperature,and minimum temperature within the canopy decreased,while relative humidity,maximum humidity,and minimum humidity increased.Canopy light transmittance exhibited a"V"shape hori-zontally,with the maximum at the middle of the cotton row.Vertically,light transmittance in the middle and lower part(10-50 cm above the ground)decreased with increasing planting density,while the upper part(50-70 cm above the ground)showed an in-crease.Population leaf area index initially increased and then decreased with planting density,with the highest value observed at 9.75 plants m-2,averaging 2.6 over the two years.Correlation analysis showed that cotton yield decreased with the increase of average daily temperature and maximum temperature,while it increased with the increase of relative humidity and maximum humidity.Cotton yield decreased with increased light transmittance in the middle and lower part of the canopy,but increased with increased light transmittance in the upper part of the canopy.In conclusion,under summer cotton direct seeding,appropriately increasing the planting density(9.75-11.25 plants m-2)is beneficial for increasing boll number per unit area and improving the canopy microenvironment,ultimately increasing cotton yield.The optimal canopy microenvironment conditions are as follows:canopy transmittance of above 85%at 70 cm,37%-40%at 50 cm,14%-16%at 30 cm,and below 9%at 10 cm;canopy tempera-ture of 26.5-27.0℃;and canopy humidity of 74%-77%.