| Purple soil is an important cultivated soil in subtropical area of China,which is widely distributed in Sichuan basin.Land use patterns does not only influence the development process of purple soil,but also affect the physical and chemical properties of soil.Although various about N2O studies has been reported as for investigation of N20 emissions and its influencing factors via farmland soil,studies on the characteristics of N2O emissions from purple soil are still scarce.In this study,properties of purple soils in various sites of Sichuan province have been studied,according to the result generated from incubation experiments,studies have been carried out based on different conditions:the different land uses patterns condition(namly,orchard,woodland and cultivated land),interaction effects of moisture and temperature(under conditions of 60%WHC,25℃;30%WHC,25℃;60%WHC,15℃ and 30%WHC,15℃respectively.Note:WHC stands for water hoilding capacity)and nitrification inhibitor(Dicyandiamide(DCD)and 3,4-dimethylpyrazole phosphate(DMPP))applications,then discuss these three factors’ effect on net conversion rate of nitrogen and N20 emissions in purple soil,there by revealing mineralization and nitrification of nitrogen and N2O emissions characteristics of purple soil,and providing theoretical basis to reduce the loss of purple soil N03--N and N2O emissions from purple soils and alleviate environment stress caused by irrational application of nitrogen fertilizers.The main conclusions are as follows:(1)The application of NH4C1 solution promoted the nitrification process and N20 emissions of both acid purple soil and calcareous purple soil.pH is an important factor affecting nitrogen conversion rate.The average nitrogen nitrification rate(0.83～1.64mg kg-1d-1)of acid purple soil was lower than that of calcareous purple soil(2.52～2.94 mg kg-1d-1).Moreover,the N2O emission rate of calcareous purple soil was significantly higher than that of acid purple soil(P<0.05).The rate of nitrification in purple soil nitrogen under different land use patterns varied significantly.As for Acidic Purple Soil,cultivated land soil nitrogen net nitrification rate(5.17mg kg-1d-1)was higher than that of tea plantation soil(4.92mg kg-1d-1)and woodland soil(1.96 mg kg-1d-1).In calcareous purple soil,the nitrification rate in cultivated land soil(7.44mg kg-1d-1)was higher than that in woodland soil(7.03mg kg-1d-1).And the net nitrification rate and N2O emissions rate of cultivated soil were higher than other land use patterns.Duing to different land use patterens through which having changed the environment factors of the putple soil and increased nitrification and N20 emission.(2)The result of moisture and temperature interaction experiment show that despite the differences between soil types N2O emission rate corresponds stably with both moisture and temperature,in which under the condition of 60%,250C,the N2O emission rate reaches the highest.At the same temperature and moisture,the average net nitrification rate in calcareous purple soil(7.85～3.75 mg kg-1d-1)was higher than in acid purple soil(1.04～6.70 mg kg-1d-1),and this may be attibuted to the high pH calcareous purple soil.With the increasing of temperature and moisture ratio promoted the emission of N2O from purple soil.In the moisture content of 60%,there was no significant difference in N2O emissions of acid purple soil at different temperatures(P>0.05).However,there was no significant differences between the two treatments(P>0.05)in calcareous purple soil under 15℃.The sensitivity of N2O emission rate to temperature and moisture was different in these two kinds of purple soil.(3)The employment of different concentrations of nitrification inhibitor DMPP and DCD could decrease the amount of mineral nitrogen into ammonium nitrogen,delay nitrogen nitrification process,net nitrification rate thus inhibiting the N2O emission rate effectively for purple soil.The inhibitory effect of DCD and DMPP decreased with time,but there were still some inhibitory effects after 28 days’ cultivation.The inhibiting effect of nitrification inhibitor on nitrogen nitrification rate in acid purple soil(inhibition rate 31.7%～78.9%)was significantly higher than that of calcareous purple soil(inhibition rate 31.6%～66.8%).With the presence of high concentration of nitrification,the inhibiton rate to net nitrification was higher than that of the low concentrations(acid purple soil DCD 15%concentration inhibition rate:40%;5%concentration DCD inhibition rate:31.7%;1.5%concentration the inhibition rate of DMPP inhibition rate:78.9%;0.5%concentration the inhibition rate of DMPP inhibition rate:31.7%.Calcareous purple soil concentration of 15%DCD inhibition rate:39.5%;concentration of 5%DCD inhibition rate:31.6%;1.5%concentration the inhibition rate of DMPP inhibition rate:66.7%;0.5%concentration the inhibition rate of DMPP;57.1%),the inhibitory effect of low concentration of DMPP was higher than that of DCD. |
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