Effects of application dosage of nitrogen on photosynthetic characteristics and yield of direct-seeding cotton after harvesting rapeseed oil
The early-maturing cotton cultivar Huamian 3097 was used to study the rational application dosage of nitrogen for the direct seeding cotton after harvesting rapeseed oil in the cotton area of the Yang-tze River Basin based on the concept of"increasing yield without increasing input".Field experiments were conducted in 2022 and 2023 to investigate the effects of six application dosages of nitrogen including N180(180 kg/hm2),N210(210 kg/hm2),N240(240 kg/hm2),N270(270 kg/hm2),N300(300 kg/hm2),and N330(330 kg/hm2)on the growth and development,photosynthetic characteristics,and yield of cotton.The results showed that the yield of cotton under N270 and N300 was comparable,but higher than that under N180 and N330.The two-year average yield of cotton seed and the number of bolls per unit area under N270 in-creased by 7.0%and 5.4%,24.9%and 21.6%compared to that under N180 and N330,respectively.There was no difference in plant height,number of fruit branches,height of the first fruit branch,number of green leaves,and number of nodes between treatments.The light transmittance of cotton canopy decreased with the process of growth and the increase of application dosage of nitrogen.The light transmittance of cot-ton canopy within the canopy height of 30-50 cm and the cotton row of 20 cm under N270 was 23.9%higher than that under N330,10.0%lower than that under N180,and comparable to that under N300.The net photo-synthetic rate,transpiration rate,and stomatal conductance under N270(N300)was higher than that under N180 and N330.The concentration of intercellular CO2 under N270 was lower than that under N180 and N330.It is indicated that applying 270 kg/hm2 nitrogen fertilizer to direct-seeding cotton after harvesting rapeseed oil is conducive to the growth and development of cotton,can increase the number of bolls per unit area and im-prove light transmission of canopy to enhance photosynthetic performance,and thus can achieve a higher yield.
direct-seeding cottonthe application dosage of nitrogenlight transmittance of canopyphotosynthetic characteristicsyield"increasing yield without increasing input"
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