Effect of nitrogen application on growth,nutrient uptake and yield of cotton under deficit irrigation practices
The effects of water-saving irrigation regime combined with nitrogen fertilizer management on dry matter accumulation,physiological response,nutrient uptake and yield of cotton were studied to provide a theoretical basis for agronomic practice of increasing cotton yield and efficient use of water and fertilizer in arid regions.The effects of different nitrogen application rates(N1:210 kg·hm-2;N2:300 kg·hm-2;N3:390 kg·hm-2)on dry matter accumulation,photosynthetic physiological characteristics,nutrient uptake,antioxidant defense,osmotic adjustment,and yield of cotton were investigated using cotton"Xinluzao 72"as the test material under two irrigation regimes(W1:normal irrigation;W2:deficit irrigation).The results showed that deficit irrigation reduced seed cotton yield by decreasing dry matter accumulation,net photosynthetic rate,antioxidant enzyme activity and nutrient uptake,compared to conventional irrigation.However,compared with the moderate nitrogen application treatment under deficit irrigation(W2N2),increasing nitrogen application treatment(W2N3)increased net photosynthetic rate and leaf area index by 12.5%and 10.9%,antioxidant enzyme activity and osmoregulatory substances by 13.6%and 42.6%,respectively,which mitigated the damage caused by deficit irrigation to cotton growth,promoted nutrient uptake and dry matter accumulation,increased seed cotton yield 5.6%.In addition,increased nitrogen application after deficit irrigation(W2N3)did not reduce seed cotton yield,instead,it prolonged the duration of dry matter accumulation by improving canopy photosynthetic capacity,antioxidant defense,and osmoregulation,allowing plants to end the reproductive process 3-4 days earlier,compared to the normal irrigation and fertilizer management treatment(W1N2).In summary,when carrying out water-saving irrigation measures for cotton in arid region,it is recommended to increase the amount of nitrogen applied by 30%on top of the conventional amount of nitrogen,which can save more irrigation water while ensuring that cotton yields will not be reduced,and this measure is of great significance for energy conservation,efficiency and sustainable production in drip-irrigated cotton production in arid region.
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