新疆早熟棉花不同水分下临界氮稀释曲线的构建与验证OA北大核心CSTPCD

[Objectives]Based on the critical nitrogen concentration(Nc),we constructed nitrogen nutrition index(NNI),nitrogen uptake(Nupt),and cumulative nitrogen deficit(Nand)models of early-maturing cotton under different water conditions,to provide a quick and accurate method for diagnosing nitrogen nutritional status of cotton and improving water and fertilizer use efficiency.[Methods]Field experiments were conducted in 2021 and 2022 in Shihezi City,Xinjiang,and Xinshi K-18,an early maturity cotton cultivar,was used as test material.A complete block design was used for the experiment,with four watering criterions(W):moderate deficit(W1,3000 m3/hm2),mild deficit(W2,3750 m3/hm2),moderate(W3,4500 m3/hm2),and sufficient(W4,5250 m3/hm2).Five nitrogen levels(N):0,225,262.5,300,and 337.5 kg/hm2(denoted as N0,N1,N2,N3,and N4,respectively),totalling 20 treatments.At 60,75,90,105,and 120 days after emergence,cotton samples were collected and divided into stems,leaves,and bolls,and the cotton bolls after blowing were further divided into boll shell,seed,and lint,for the determination of dry weight and N content.Also the number of cotton plants,boll number per plant,boll weight per plant,lint yield and clothing percentage at 120 days were investigated.The critical nitrogen dilution curve(Nc)was constructed based on plant dry weight and N content under different water conditions.The reliability of Nc dilution curve was verified by root mean square error(RMSE)and standardized root mean square error(n-RMSE).Based on Nc,the N nutrition index,N uptake,and cumulative N deficit models of cotton plants were established to recommend the optimal amount of N in cotton under different water conditions.[Results]Shoot dry matter,cotton yield,and N content increased with the increases of water and N application rates at all growth stages,and both the highest seed cotton yield(5892 kg/hm2)and lint cotton yield(2747 kg/hm2)were recorded in W3N3 treatment.Under water criterions from W1 to W4,the R2 values of the critical nitrogen concentration dilution curve were 0.999,0.912,0.952,and 0.974,respectively,and the RMSEs were 0.284,0.280,0.243,and 0.269,respectively,indicating that the model had satisfactory accuracy.The nitrogen nutrition index,nitrogen uptake,and cumulative nitrogen deficit models based on Nc all showed that N3(300 kg/hm2)was the optimal N application level for cotton nitrogen nutrition under all the four watering criterions.Considering yield and nitrogen level,the optimal N application rate was 262.5 kg/hm2 under moderate water deficit(W1),and 300 kg/hm2 under mild deficit,moderate and sufficient water conditions(W2,W3 and W4),respectively.[Conclusions]The constructed critical nitrogen dilution curve of cotton and the derived nitrogen nutrition index,nitrogen uptake,and cumulative nitrogen deficit models could accurately predict nitrogen nutritional status of cotton under different water conditions,so can be used for nitrogen nutrition diagnosis and as the reference of efficient water and nitrogen management of cotton.