Effects Of Water And Nitrogen Supply On Nitrogen Transformation Bacteria And Related Enzyme Activities Of Pepper Cultural Substrate In Greenhouse

In order to explore the suitable irrigation and nitrogen amount of pepper growth,using substrate cultivation(cultural substrate formula for corn straw: cow dung: mushroom residue: slag =2.5 V:2.0 V:2.0 V:3.5 V)to study the effects of different water and nitrogen treatment on pepper cultivation substrate microorganism which related to nitrogen transformation,enzyme activity and physicochemical properties of the substrate.The experiment designed two factors of irrigation amount and nitrogen application,the irrigation amount there were three gradients.They were W1,W2 and W3 respectively.80%,60% and 40% of field capacity respectively,and the amount of fertilizer application had four gradients of F0,F1,F2,F3.F0:0 kg N·hm-2,F1:139.51 kg N·hm-2,F2:93.00 kg N·hm-2,F3:46.50 kg N·hm-2.The main results are as follows:1 The effect of different water and nitrogen treatment on physicochemical properties and its correlation with microorganisms: on the 30 days to 60 days,total nitrogen content and avaliable nitrogen content was the highest in the W2F2 treatment,The decrease of ammonium nitrogen and nitrate nitrogen in the treatment of 90 day W2F2 was greater,but the decrease of ammonium nitrogen content was less than that of nitrate nitrogen;the increase of nitrogen application rate could decrease the p H value of the substrate,and the excessive application of nitrogen could increase the conductivity of the substrate;The ratio of carbon to nitrogen in the whole growth and development process of pepper,the range of W2F1 was 18.28-24.08,the change range of W2F2 was 18.60-23.81,which was in line with the optimum carbon and nitrogen ratio.The results showed that there was a significant positive correlation between the anaerobic azotobacter and ammonium nitrogen,p H,and significantly negative correlation with total nitrogen,nitrate nitrogen and organic matter;there was a significant positive correlation between aerobic azotobacters and ammonium nitrogen and nitrate nitrogen,which was significantly positively correlated with organic matter and EC,and negatively correlated with p H;there was a significant positive correlation between nitrifying bacteria,nitrite bacteria and nitrite nitrogen and ammonium nitrogen;there was a significant negative correlation between denitrifying bacteria and NH4+-N,EC,and significantly negative correlation with organic matter and p H;there was a significant negative correlation between ammonifiers and p H.2 Effects of different water and nitrogen treatments on the activity of substrate enzymes and their correlation with physical and chemical properties: moderate water and nitrogen supply was beneficial to improve urease and cellulase activity,while the increase of water and fertilizer supply was helpful to improve the activity of sucrase.The decrease of irrigation amount was beneficial to improve the activity of catalase and urease with low nitrogen application rate.There was a significant positive correlation between substrate urease and total nitrogen,organic matter and EC,and was positively correlated with nitrate nitrogen;sucrase was significantly positively correlated with total nitrogen and nitrate nitrogen,and positively correlated with ammonium nitrogen and organic matter;Cellulase was significantly positively correlated with total N and NH4+-N,and positively correlated with nitrate nitrogen;Urease,sucrase and cellulase were significantly negatively correlated with p H,but catalase was significantly positively correlated with p H.3 Effects of different water and nitrogen treatments on substrate microorganisms and their correlation with enzymes: the number of aerobic azotobacters and anaerobic azotobacter were the highest in W2F2;Ammonifiers,nitrifying bacteria,nitrite bacteria are all W2F2 the highest number in the treatment of 90 day and 210 day,to facilitate the nitrogen transformation in substrate and fix nitrogen,and the number of denitrifying bacteria W2F1 in 210 day is the highest,the minimum number is W3F0.There was a significant positive correlation between aerobic azotobacters and urease,invertase and cellulase under the condition of water and nitrogen supply;there was a significant negative correlation between anaerobic azotobacters and urease,sucrase and cellulose;ammonifiers,nitrifying bacteria and nitrite bacteria were significantly positively correlated with urease,sucrase and cellulase,while there was a significant negative correlation between ammonifiers and catalase;Denitrifying bacteria was significant positive correlated with cellulase,and was significantly negatively correlated with catalase.