Study On Nitrogen Transformation And Effects Of Nitrogen On Winter Wheat Seedlings Growth In Saline Soil In Yellow River Delta

There are large amount of salinized soil in the Yellow River Delta,and the soil is easy to board and low in fertility.Soil salinity seriously restricts the productivity of land.High salt in soil inhibits shoot and root growth in the vegetative stage and reduces the filling rate during the reproductive growth stage which eventually lead to a reduction in crop yields.The winter wheat seedling stage is the most senstive to the salt.It's important for the whole growth period to manage winter wheat seedling and the rational application of nitrogen fertilizer is beneficial to alleviate the inhibition of salt to winter wheat seedling.In the first part,the effects of soil salinity on soil nitrification and nitrification were observed.In the second part,it was found that saline soil could inhibit the available nitrogen,and the second part tried to simulate different saline soil to find proper nitrogen ratio to the winter wheat seedling.Salt stress and drought stress often exist at the same time in the Yellow River Delta,and the third part is based on the results of the first part of the study?differences in soil fertility due to different salt content?,the physiological response of winter wheat seedling under salt-drought stress was studied by simulating different fertility soils.In the first part,soil incubation experiments were conducted under different salt conditions.The soil salitiny level was set at 0.9,1.9 and 2.9 g/kg.The treatment of mineralization had no exogenous nitrogen,adding 0.2 g/kg?NH₄?₂SO₄ in the nitrification test,and the temperature of the medium was 28°C for 42 days.In the second part,Three degrees?S1:0.9g/kg,S2:1.9g/kg,S3:2.9g/kg?of coastal saline soils as objects were set in this experiment.Pot experiments were set to investigate the effects of different ratios of NO₃^--N to NH₄⁺-N on wheat seedling growth?Ratios of NO₃^--N:NH₄⁺-N were 100%:0?N100A0?,75%:25%?N75A25?,50%:50%?N50A50?,25%:75%?N25A75?,0:100%?N0A100??.In the third part,we set two salitiny treatments as S1?1.9 g/kg?and S2?2.9 g/kg?and two water treatments as W1?78%of field capacity?and W2?47%of field capacity?.Results showed that:the soil sanility of 0.9 and 1.9 g/kg had no significant effect on accumulated mineralization and mineralization rate,and soil sanility of 2.9 g/kg significantly limited soil mineralization.The same with soil nitrification.As the time was prolonged,the differences among the treatments were more significant.The effect of soil sanility below1.9 g/kg on soil nitrogen mineralization and nitrification was not significant,and medium salt significantly inhibited the effective process of Soil Nitrogen.In comparison with N100A0 and N0A100 treatments,N25A75,N50A50 and N25A75 treatmens were better for winter wheat seedlings growth.The shoot and root dry weight of and total nitrogen content of winter wheat at seedling stages were significantly increased at N50A50 treatment.The chlorophyll and soluble sugar content of winter wheat were increased at N75A25 or N50A50 treatment.It can be conclued that the optimal ratios of NO₃^--N to NH₄⁺-N were 50%:50%and 75%:25%which promoted uptake of nitrogen nutrients and accumulation of soluble sugar,chlorophyll and dry matter in the winter wheat seedling stages.The increase of salinity significantly limited the growth of wheat.The shoot and root dry weight,total nitrogen and of winter wheat decreased significantly and the soluble sugar content content increased.Effect of low salt with drought sitimulated wheat seedling growth.Shoot and root dry weight and nitrogen;chlorophyll and soluble sugar content were the most in all treatments.Interaction between medium salinity and drought aggravates the restriction on the growth of wheat seedlings.Above all,2.9 g/kg saline soil inhibited the effective process of soil nitrogen,decreased the effective nitrogen content,and made the soil fertility lower than that of non-salt soil.It was found that the ratio of nitrate to nitrogen was 50%:50%or 75%:25%could promote the growth of winter wheat seedlings and alleviate salt inhibition It is beneficial to the growth of winter wheat seedling by simulating the appropriate drought stress in low-salt soils in different fertility soils.