Effect Of Nitrogen Synergist And Biochar On Nitrogen Transformation And Utilization Efficiency Of Paddy Soil

Nitrogen fertilizer is easy to lose in paddy field,and it's utilization rate is low.Urease inhibitors can delay the hydrolysis of urea into ammonium nitrogen by inhibiting urease activity while nitrification inhibitors can inhibit the oxidation of ammonia.Therefore,the application of urease and nitrification inhibitors is a valid management measure of nitrogen fertilizer and an effective way to improve its utilization rate in rice fields.In this study,two typical paddy soils(acid paddy soil and neutral paddy soil)in south China were selected as the research objects.Through pot experiment in the whole growth period of rice,the most suitable amount of 3,4-dimethylpyrazolphosphate(DMPP)and n-butyl thiophosphoryl triamide(NBPT)were selected based on soil nitrogen transformation nitrogen absorption and utilization,and ammonia-oxidizing microorganism,Furthermore,the effects of DMPP/NBPT combined with biochar prepared at different temperatures on nitrogen transformation in paddy soil were investigated,and the microbial mechanism of nitrogen fertilizer synergist combined with biochar was discussed as well.The results provide theoretical support for rational application of DMPP and NBPT,and scientific basis for optimizing nitrogen nutrient management and reducing nitrogen loss in rice field ecosystem.The main results are as follows:1.From the perspective of improving nitrogen absorption and utilization of rice,single application of DMPP/NBPT or combined application of biochar can improve the nitrogen fertilizer utilization rate in paddy soil,and the performance effect is different on different paddy soils.When DMPP/NBPT is applied alone,DMPP is suitable for acid paddy soil,while NBPT is suitable for neutral application.In the acid paddy soil,compared with CK,2% DMPP and 0.5% NBPT have the highest nitrogen fertilizer utilization rate,which can be increased by 15.3% and 14.1%,respectively.NBPT has the highest nitrogen fertilizer utilization rate,which is 11.8% and 18.2% higher than CK,respectively.Combined application of biochar can enhance the effect of DMPP/NBPT on the utilization rate of nitrogen fertilizer,and it has different effects on different paddy soils.After NBPT combined with biochar,the effect of nitrogen fertilizer utilization on two paddy soils is significantly improved,the performance on acid paddy soil is higher than that on neutral paddy soil.The effect of combined application of biochar on DMPP is significantly improved on neutral paddy soil,but the effect on acid paddy soil is not significant.Overall,in acid paddy soil,NBPT+300BC treatment has the best effect of improving nitrogen fertilizer utilization rate,while in neutral paddy soil,DMPP+300BC treatment has the best effect.2.The inhibition effect of DMPP/NBPT or biochar on soil nitrification and denitrification was shown as acid paddy soil > neutral paddy soil.When DMPP/NBPT was applied alone,the nitrification inhibition rate of 2% DMPP and 0.5% NBPT was the highest in acid paddy soil,while that of 0.5% DMPP and 0.1% NBPT was the highest in neutral paddy soil;In terms of the inhibitory effect of denitrification activity,NBPT is better than DMPP.Compared with CK,the application of 0.5% NBPT in acid paddy soil reduced the denitrification activity of soil by 62%(P <0.05),which was significantly higher than that of CK.The application of 2% DMPP(a decrease of 11%);the denitrification activity of 0.1% NBPT decreased by 26.2% within 7 days of neutral paddy soil treatment,while the application of 0.5% DMPP decreased 16.7%.The combined application of biochar prolonged the nitrification inhibition time of DMPP/NBPT,but had different effects on the nitrification inhibition of them.The combined application of biochar significantly improved the nitrification inhibition effect of NBPT,and the effect in acid paddy soil was higher than that in neutral paddy soil,but the effect on the nitrification inhibition effect of DMPP was not significant.The effect is also different for different biochars.In acid paddy soil,biochar prepared at different temperatures can increase the nitrification inhibition rate of NBPT(0.53-3.70 times),while in neutral paddy soil,only 300 BC can improve the nitrification inhibition rate of NBPT(0.51-1.04 times).For denitrification activity,the application of biochar can enhance the inhibitory effect of DMPP/NBPT on denitrification,and significantly extend the duration of action in acid paddy soil;There are difference in denitrification activity inhibited effect of different biochar on different soil,In the acid paddy soil,the inhibition effect of DMPP and NBPT on denitrification activity combined with 500 BC is better,which is increased by 2.73 times and 2.11 times,respectively;In the neutral paddy soil,the inhibition effect of DMPP and NBPT on denitrification activity combined with 300 BC is better,which is increased by 80% and 46%,respectively.The effect of biochar prepared at different temperatures is also different.In acid paddy soil,after applying 300 BC and 500 BC,the effect of DMPP increased by 5.9% and 1.6%,the effect of NBPT increased by 10.2% and 8.2%,and There was no significant difference between biochars at different temperatures;in neutral paddy soil,the effect of combined application of 300 BC on DMPP was better,a significant increase of 12.0%,and the effect of combined application of 500 BC on NBPT was better,which could significantly increase by 5.7%.3.The effect of single application of DMPP/NBPT or combined application of biochar on soil ammonia-oxidizing microorganisms is DMPP > NBPT,and the effect on ammonia-oxidizing bacteria(AOB)is greater than that of ammonia-oxidizing archaea(AOA).Single application of DMPP significantly inhibited the abundance of AOB and anaerobic ammonia-oxidizing bacteria(AAOB)in paddy soil without affecting AOA,while single application of NBPT had no significant effect on soil ammonia-oxidizing microorganisms,but 0.1% NBPT was applied to neutral paddy soil can significantly inhibit anaerobic ammonia oxidation microbial abundance.Compared with single application of DMPP,the effect of combined application of biochar on AOB abundance was different in different paddy soils.AOB abundance on acid paddy soil was improved,while that in neutral paddy soil was suppressed,and both the effect of 500 BC biochar is more significant;Compared with single application of NBPT,combined application of biochar can significantly inhibit(4.4-22.4%)the abundance of AOB in acid paddy soil during the middle growth stage of rice,while the AOB abundance in neutral paddy soil has no significant effect.Pearson correlation analysis found that the correlation between the abundance of ammonia-oxidizing microorganisms in the paddy soil and the concentration of ammonium nitrogen in the soil was significant,and the application of biochar significantly adjusted the relationship between the ammonia-oxidizing microorganisms in neutral paddy soil and ammonium effect.