| Humic acid contains functional groups such as benzene ring,hydroxyl group,carboxyl group,methoxyl group,thiol group and so on.It is a kind of natural macromolecule organic substance,which has the effects of improving soil fertility,stimulating crop growth,and improving fertilizer utilization.In recent years,humic acid has received extensive attention as a fertilizer additive.In this paper,humic acid as the research material,through the cultivation test and pot experiment method,the effect of different additions of humic acid on urea was studied,and the effect of different additions of humic acid on soil nitrogen conversion and ammonia volatilization loss was discussed.To reveal the role of humic acid in regulating the fate of soil nitrogen,and to provide a theoretical basis for the development and promotion of value-added nitrogen fertilizers.The main results are follows:High addition of humic acid can inhibit ammonia volatilization loss,increase soil urease activity and soil ammonium nitrogen content,reduce soil apparent nitration rate.compared with control,humic acid could reduce ammonia volatilization significantly,each treatment decreased by an average of 12.08%,meanwhile,the more humic acid the greater inhibitory effect on ammonia volatilization.In the prophase of cultivation,the amount of 5%-50% of the humic acid could improve the soil urease activity and the average increase was 35.13% at the fifth day,but soil urease activity of 75% humic acid amount decreased by 13.23%,then humic acid enhanced it in the later period of incubation.Humic acid could increase soil ammonium nitrogen content,the increases were enhanced with the increase of humic acid adding proportions.The content of ammonium nitrate treated with humic acid increased averagely by 39.63% at the 112 ed day.During the whole culture period,the soil apparent nitration of humic acid treatment decreased averagely by 17.20% and the higher the amount of humic acid,the lower the soil apparent nitration rate.Humic acid can decrease ammonia volatilization losses,improve soil urease activity and nitrate nitrogen contents in the later period of incubation,inhibit urea hydrolysis and reduce nitrogen leaching losses.Compared with the CK2 treatment,the total ammonia volatilization of HA1,HA2,HA3 treatments were decreased respectively by 7.33%,8.39% and 9.13%,which got a best effect on HA3.Humic acid treatments enhanced soil urease activity after the 5th day,which were increased respectively by 15.87%,19.99% and 31.32% on the 14 th day.However,there were no significant effects on the prophase urease activity.Urea nitrogen amount of HA1,HA2,HA3 treatments increased respectively 15.94%,37.73% and 47.63% during the first 3 days of incubation,and the increases were enhanced with the increase of humic acid adding proportions.The humic acid decreased the leaching loss of urea nitrogen,ammonium nitrogen and nitrate nitrogen.In the pot experiment of rapeseed,adding humic acid can produce obvious synergistic effect,significantly increase the dry weight of small rapeseed,improve the quality of small rapeseed,increase the chlorophyll content of small rape,and increase root activity.Compared with CK2,the average increase rate was 19.48%;Soluble sugars and VC increased by 1.60%-6.92% respectively.The titratable acidity content decreased by 20.36%-29.94%;Chlorophyll content increased by 12.525-19.21%;Root activity increased by 0.88%-43.01%. |
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