Effects Of Different Nitrogen Application Rates On Spatial And Temporal Distribution Of Nitrogen And Growth Of Tobacco Plants Under Drip Fertigation

In order to explore the feasibility of reducing fertilizer nitrogen application,the change of soil nitrogen supply capacity and the growth of tobacco plant under the condition of integrated application of water and fertilizer with carbon base fertilizer,experiments were set up in Da Jindian town and Yingyang town,Dengfeng,Henan Province in May to October of 2016 and May to October of 2017,respectively.Five treatments were set up:T0: no nitrogen fertilizer;T1: normal nitrogen application(45kg /hm~2);T2: 15% reduction in nitrogen;T3: 30% reduction in nitrogen;T4: 45% reduction in nitrogen,the carbon fertilizer consistent.The main results are as follows:(1)The reduction of nitrogen fertigation has no significant influence on the total nitrogen and C/N in the 0-60 cm soil layer,but it can significantly affect the nitrate nitrogen,ammonium nitrogen content of the 0-20 cm soil layer in 40 d and 50 d and the content of nitrate nitrogen in the 40-60 cm soil layer in 50 d,with the decrease of nitrogen application,the content of inorganic nitrogen gradually declines,after 60 d there is no significant relationship between them.Nitrogen application in drip irrigation can significantly increase the content of alkali hydrolysable nitrogen in the 0-20 cm soil layer in 40 d,and the content of alkali hydrolysable nitrogen in the 20-40 cm soil layer significantly increased in 40-60 d.There is no relationship between the content of alkali hydrolysable nitrogen in the 40-60 cm soil layer and the amount of nitrogen applied.Under this experimental condition,soil microbial biomass nitrogen content and urease activity in the plough layer were less affected by chemical fertilizer application.(2)The reduction of nitrogen fertilizer has no obvious influence on the agronomic characters and photosynthetic characteristics of tobacco plants during the growth period,the accumulation of dry matter and the nitrogen of tobacco plants are greatly influenced by nitrogen application,and there are differences in the influence degree of nitrogen application in different areas.In the 2016 experiment,the dry matter and nitrogen accumulation were greatly influenced by the amount of nitrogen application at 40 d and 50 d,there was no obvious relationship later.In 2017,the experimental results showed that after the topping(60d),the amount of dry matter and nitrogen accumulation decreased gradually with decreasing of nitrogen application,and there still has significant differences between treatments in 90 d.(3)After transplanting 45d-90 d,the NDVI value of the canopy of the tobacco plants was greatly influenced by the application of nitrogen fertilizer fertigation,T4 and T0 was significantly lower than the other treatments.The content of chlorophyll and the SPAD of the flue-cured tobacco were obviously influenced by the application of nitrogen fertilizer.With the increase of nitrogen,the content of chlorophyll a and the total chlorophyll in 40-60 d increased,and the SPAD value in 30-75 d increased gradually as well,and each treatment's SPAD value reached significant difference.Later,there was no clear relationship between chlorophyll content and SPAD value in leaves with nitrogen application rate.(4)The total nitrogen,nicotine,reducing sugar and sugar and alkali ratio of the middle leaves were greatly influenced by nitrogen application.The content of nitrogen and nicotine decreased gradually with the decrease of nitrogen application,and the reducing sugar and sugar alkali ratio increased with the decrease of nitrogen application.Neoplytadiene and the products degraded by carotene and cembrane in cured-leaf is greatly influenced by the amount of nitrogen applied,T1,T2 and T3 was obviously higher than other treatments.(5)The sensitivity of soil nitrogen supply capacity and nitrogen nutrition status to nitrogen fertilizer application in two areas is different.Therefore,the difference between regions should be considered in fertigation.In the Da Jindian region,15%-30% nitrogen off is recommended in fertigation,while in the Yingyang region,normal nitrogen application or 15% nitrogen off is recommended.The effect of reduced nitrogen application on soil nitrogen supply capacity and growth status of tobacco plants needs to be further studied.