Abstract In order to investigate the high efficient utilization model of N in leaf vegetables substrate
cultivation at northern China in winter,this paper took pakchoi as material and total NO3--N as the contrast;
conducted pot experiment and designed 25%,40%,60% of 3 N increasing level treatments;observed the
growth and activity of root system and N metabolism key enzyme activity during the growth process of pakchoi;and
measured its nutrient absorption,yield and quality.The results showed that the treatment of increasing 25%-40%
NH4+-N could increase the root length,root surface area and root volume,promote root system development;
enhance its absorbtion of N and P.Compared with total NO3--N treatment(CK)this treatment of increasing
NH4+-N ratio could significantly decrease the nitrate content,increase the content of soluble sugar,and yet had
no significant effect on the single plant mass.The nitrogen partial factor productivity of increasing 40% NH4+-N
treatment was respectively 3.7% and 3.8% higher than that of increasing 25%,60% NH4+-N treatments,and
the above-ground dry matter of the pakchoi was significantly increased either.To sum up,in northern China
for protected vegetable cultivation of pakchoi in winter,the suitable N application(17.33 mmol·L-1),plus
increasing 40% NH4+-N can achieve the best effect.
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