Effect Of Modified Urea On Ammonia Volatilization And Soil Carbon, Nitrogen Mineralization During Corn Seedling

In this paper, the indoor cultivation of soil and corn seedling pot experiment method were used to study effects of different nitrogen fertilization treatments on the amount of ammonia volatilization, soil pH, soil urease, invertase, catalase and polyphenol oxidase activities and soil carbon and nitrogen mineralization. At the same time, the corn seedling dry matter, nitrogen, phosphorus and potassium accumulation and nitrogen use efficiency under modified urea were also measured. There were10experimental treatments, urea, modified urea and urea and modified urea were added different doses of nitrification inhibitors and urease inhibitors. Control treatment was also set. The results showed that:1. Modified urea could significantly inhibit ammonia volatilization, and which was reduced by about30%compared to that of the common urea, reaching a significant level. And within a certain range, the more soil water content was the lower amount of ammonia volatilization, thus reduced nitrogen volatilization loss. However, nitrification inhibitor dicyandiamide (DCD) and urease inhibitor thiourea (TU) had no significant effect on ammonia volatilization.2. In preliminary cultivation, modified urea could reduce soil pH, and with incremental incubation time the soil pH gradually increased; however, modified urea treatments of the DCD, pH did not reduce and was closed to neutral, indicating that DCD could effectively inhibit nitrification process, and then affect the soil pH.3. Early in the cultivation was a strong inhibitory effect time. DCD could significantly enhance the soil urease activity and catalase activity. Within a certain range, the higher DCD content was the stronger the soil urease and catalase activities. Late in the cultivation was a period of weak inhibitory effect. DCD could significantly enhance the soil invertase and polyphenol oxidase activities. TU had no significant effect on soil urease, which illustrated that within a certain range, TU was a weak urease inhibitor. Adding a relatively small amount of TU would not achieve any inhibition. In the pre-incubation, DCD could significantly enhance soil catalase activity; late in incubation, it could significantly improve soil invertase and polyphenol oxidase activities. Modified urea had no significant effect on soil urease and catalase activities. However, early in the incubation, modified urea could significantly increase soil invertase and polyphenol oxidase activities.4. Modified urea could increase the carbon and nitrogen contents of soil microbes. In early cultivation, high levels of DCD inhibited the activity of soil microorganisms; microbial carbon and nitrogen contents of microorganisms were low. In the late cultivation, due to the weakening effect of suppression, soil microbial decomposition ability was enhanced, and the carbon and nitrogen content of microorganisms were subsequently raised. In the late cultivation, the TU could increase microbial biomass carbon content, but had little effect on soil microbial biomass nitrogen content. According to the content of soil ammonium, nitrate and inorganic nitrogen and nitrification inhibition rate and apparent nitrification rate, it could explain that:DCD as a nitrification inhibitor in early cultivation had very significant inhibitory effect, effectively preventing the transformation of ammonium to nitrate. Within a certain range, the greater amount of DCD was added, the better the inhibition effect, but the TU had no nitrification inhibition. Added the same content of the DCD, compared to common urea, modified urea could significantly improve soil inorganic nitrogen and ammonium nitrogen contents and nitrification inhibition rate, and significantly lowered the apparent nitrification rate. Therefore, adding DCD to modified urea could reduce nitrogen losses.5. Modified urea with DCD could significantly increase accumulation of dry matter, nitrogen, phosphorus and potassium of the corn plants, and so did nitrogen use efficiency. TU could significantly improve dry matter accumulation and potassium and nitrogen use efficiency of corn plants in the late cultivation, but had no significant effect on nitrogen and phosphorus accumulation of the corn plants. Compared with common urea, modified urea could significantly improve seedling corn nitrogen use efficiency, increased by about45%, thereby reducing the loss of nitrogen.