Effects of nitrogen on cotton growth,macronutrients distribution and nitrogen use efficiency
[Objective]This study aims to screen the suitable nitrogen(N)concentration and investigate its effects on the growth,macronutrients uptake and N use efficiency of cotton at seedling stage.[Methods]HM3097 was used and cultured with nutrient solution for 21 d of six N concentrations with 0,0.04,0.4,1,4,8 mmol·L-1 Ca(NO3)2,named N0,N0.04,N0.4,N1,N4,N8,respectively.The root and shoot morphology,biomass,absorption and distribution of macronutrients,photosynthetic capacity,N uptake efficiency(NUpE)and N utilization efficiency(NUtE)of cotton seedlings were determined.[Results]With the increase of N concentration,the growth(include root and shoot),biomass,macronutrients accumulation and photosynthetic capacity of cotton seedlings increased first and then decreased,and 4 mmol·L-1 Ca(NO3)2 was the most appropriate N concentration for cotton at seedling stage,at which the cotton growth was the most vigorous.The maximum accumulations of N,P,K,and Ca of cotton seedlings were 34.4 mg,6.3 mg,41.6 mg,and 16.5 mg per plant,respectively,with the ratio of 1∶0.2∶1.2∶0.5.NUpE and NUtE were positively correlated with root-shoot ratio,and the change trend were also consistent with the root biomass distribution proportion,root average diameter,and the root macronutrients distribution proportion,which decreased with the increase of N concentration.In the range of 0-4 mmol·L-1 Ca(NO3)2,the contents of N,K,and Ca,leaf biomass and the shoot macronutrients distribution proportion all increased with the increase of N concentration.[Conclusion]4 mmol·L-1 Ca(NO3)2 was the most appropriate N concentration for cotton at seedling stage,which could significantly promote the absorption of N,P,K,and Ca of cotton seedlings.1 mmol·L-1 Ca(NO3)2 could increase the root macronutrients distribution proportion,promote root elongation and proliferation,and improve NUpE and NUtE.
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