Effects Of Different Water And Fertilizer Treatments On Nitrogen Absorption And Utilization Characteristics Of Open-air Vegetable Fields

The field experiment was conducted to study the effects of regular amounts of fertilizers and irrigation(CK),reducing chemical fertilizer application rates by 20%(80F),reducing irrigation amount by 20%(80W)and reducing irrigation and fertilizer rates by 20% plus Straw(80WF+Straw)on the characteristics of migration and utilization of nitrogen and nitrogen uptake in cabbage,focusing on vegetable black soil in open-air in lalin county,Heilongjiang Province.The main results showed follows:1.The variation characteristics of soil available nitrogen in different layers in the soil profiles under different water and fertilizer management were obvious,with the contents of ammonium and nitrate increasing with the increase of soil depth in all treatments.Within the depth of 0-50 cm,the contents of ammonium nitrogen and nitrate nitrogen in 80 F were significantly higher than that of CK,80 F,and 80 WF + straw(p<0.05),followed by CK,80 F,and 80 WF + straw.There was no significant difference between treatments below 50 cm.The variation patterns of soil ammonium content and nitrate content under different water fertilizer management were inconsistent during the growth period of Chinese cabbage.The soil ammonium contents during the growth period of Chinese cabbage was: seedling stage > core stage > bulb stage;however,the content of nitrate nitrogen in soil was: seedling stage > globule stage in rosette stage.During the same growth period,soil ammonium content and nitrate content under different water fertilizer management were80 W >80F >80WF+straw,and the ammonium content and nitrate content were respectively 6.29%,22.39%,14.61% and 28.75% higher than the other two treatments.The total nitrogen content in soil between the four treatments did not reach the significant level(p<0.05).2.The nitrate content in the leachate was significantly higher than the ammonium content in the leachate at different growth periods in the field under different water and fertilizer treatments.In the same treatment,the content of ammonium in different growth stages was: seedling stage > rosette stage >core stage> heading stage;however the contents of nitrate showed a reverse trend when compared with ammonia.During the same growth period,the change characteristics of nitrate and ammonium content in the leachate were consistent,both of which were 80WF+straw < 80 W <80F< CK.Compared with other two treatments,the ammonium and nitrate contents decreased by 44.8%,39.1%,and 16.58%,8.02%,respectively.The total nitrogen content of leachate under different water and fertilizer treatments was CK >80F >80W >80WF+ straw,but the difference was not significant(p>,0.05).3.The effects of different water fertilizer treatments on the nitrogen absorption of leaves and roots of field cabbage were as follows: CK>80F>80W>80WF+straw,and water reduction treatment was 4.39%,10.16% and 1.18%,2.14% higher than the other two treatments,respectively.The effects of different water fertilizer treatments on the quality and yield of dried matter in Chinese cabbage were the same as that on nitrogen absorption,both of which were CK >80W >80F>80% WF+ straw.