Effects Of NO₃^--N/NH₄⁺-N Ratio In The Nutrient Solution On Growth Of Sereval Kinds Of Greenstuff In Substrate Culture

In this research,typical greenstuff in north greenhouse culture including tomato,pumpkin and oilseed rape were selected from three categories of greenstuff: solanaceous vegetable,melon & fruit and leafy vegetable.Under the situation that the supply of N is uniform,according to different requirements of different greenstuff,five proportions of NO₃--N and NH₄⁺-N ratios were set,so as to study their effects on growth,plant physiological changes,quality,yield and N use efficiency of the greenstuff at different periods.On this basis,a TOPSIS model based on analytic hierarchy process and entropy weight method is adopted to comprehensively analyze the greenstuff' quality and efficient indexes,so as to confirm appropriate NO₃--N and NH₄⁺-N ratio for different greenstuff.?1?In the experiment of tomato,summer squash and rape,under the same N concentration,the growth of plant was effectively promoted by the increase of NH₄⁺-N proportion.In treatment of 20%³0% NH₄⁺-N percentage,there were more strong plant of tomato and summer squash,and rapid growth of rape plants was promoted by total NO₃--N treatment,but when NH₄⁺-N proportion was in the range of 25% 40%,the growth of rape roots was the best.And with the increase of NH₄⁺-N proportion,the NR activity of the leaves decreased and the GS activity gradually increased.?2?The chlorophyll content and photosynthesis in leaves were improved by the increase of NH₄⁺-N proportion.Under the ratio of 30%⁴0% NH₄⁺-N treatments,the net photosynthesis rate was significantly higher than other treatments in tomato seedling stage and flowering stage.In tomato formation stage and raping stage,the net photosynthesis rate was increased significantly by the 20% NH₄⁺-N proportion treatment.With increasing of NH₄⁺-N proportion in the nutrient solution,the net photosynthesis rate was enhanced of summer squash,and with in the range of 20% 40% of NH₄⁺-N proportion,the net photosynthesis rate was significantly higher than other treatments.?3?The quality indexes of different greenstuff were different when grown at different NO₃--N and NH₄⁺-N ratios under the same N supplementation.With the increase of NH₄⁺-N proportion,NO₃--N content decreased for all of the three kinds of greenstuff;and soluble sugar content in summer squash and rape increased;for tomato,however,soluble sugar level incresed first and then decreased,20% NH₄⁺-N proportionhad the maximum value finally.Vc and soluble protein content for the three kinds of greenstuff incresed first and then decreased with increasing of NH₄⁺-N proportion with increasing of NH₄⁺-N proportion.Organic acid content in tomato increased,and in rape 10%NH₄⁺-N proportiontreatmenthad the maximum value,but in summer squash was not affected significantly;Soluble solids content decreased with the increase of NH₄⁺-N nutrition;lycopene content in early spring tomato decreased,and in overwintering tomato was not affected significantly.?4?The yeild and efficiency of vegetable products was increased by proper increasing of NH₄⁺-N proportion,and excessive NH₄⁺-N proportion would constrain the greenstuff growth.There was the highest value in overwintering tomato yield per plant and NPFP under 30% NH₄⁺-N proportion treatment,and yield per plant increased by 10.01%.In early spring tomato NHI and N uptake had the highest value under the 10% NH₄⁺-N proportion.Under 40% NH₄⁺-N proportion,yield per plant of tomato was lower significantly than others.The yield per plant of summer squash was significantly higher than other treatment.Compared with the CK treatment,yield of summer squash increased by 29.56%,and there also was the highest value of NPFP and NHI under the30% NH₄⁺-N proportion treatment.There was no significant difference in fresh weight per plant,but the yield was the highest at 10% NH₄⁺-N proportion,which was 11.2% higher than that of total NO₃--N treatment.?5?TOPSIS model based on AHP and entropy method evaluated in terms of comprehensively yield,fruit quality and fertilizer use efficiency of three kinds of greenstuff.The optimal solution of overwintering and early spring toamto were the treatments of 30%NH₄⁺-N proportionand 10% NH₄⁺-N proportion respectively.The optimum ratio of NH₄⁺-N in summer squash and rape was 40%.