| In view of the problem of alpine grassland degradation in Qinghai-Tibet Plateau and the negative impact of fertilization on grassland ecosystem and atmospheric environment,we are required to take the appropriate development path.Although nitrogen is the guarantee of grassland productivity,it is also faced with some environmental problems caused by poor nitrogen use and irrational fertilization and management.Therefore,this paper studied the seasonal variation of soil nitrogen and the interannual dynamics of artificial grassland in Qinghai Tongde pasture.The application of urease/nitrification inhibitor in the process of fertilization of alpine grassland was studied by 15 N marker fertilizer.Grassland yield,with a view to providing a theory for the health and sustainable development of alpine grassland ecosystems.The conclusion is as follows:(1)The soil nitrogen characteristics of the alpine artificial grassland in the past four years were as follows: 0-10 cm soil layer,soil ammonium nitrogen content after the first drop on the trend,and the trend of growth is significant,four age artificial grass grow by about 17.85% compared with a age;Soil NO3--N content have significant decline,down about 67.70%;Soil soluble organic nitrogen and the total soluble nitrogen were downward trend after rising first,in the second peak age period were 101.86 mg · kg 1 and 161.90 mg·kg-1.10-20 cm soil layer,soil ammonium nitrogen in addition to the two ages a high content of artificial grass,other allmaintained at a lower level of 6.53 mg·kg-1-17.02 mg·kg-1;Soil NO3--N content are highest in the first two years,and then the content of two years,about 69.77% lower.(2)Using field plot test,the cumulative ammonia volatilization of nitrogen fertilizer at the alpine grassland showed that CO(15NH2)2(727.77 g N·hm-2)>CO(15NH2)2 + DMPP(439.30 g N·hm-2)> CO(15NH2)2 + NBPT(94.85 g N·hm-2)>CO(15NH2)2 + DMPP+NBPT(80.01 g N·hm-2).Statistical results showed that there were significantly different among treatments except between CO(15NH2)2+NBPT and CO(15NH2)2 +DMPP+NBPT treatment.The primary productivity of alpine grasslands in different treatments were as follows: That in CK treatment was 565.57 g m-2 y-1,that in CO(15NH2)2 application treatment was 652.36 g m-2 y-1.The primary productivity in CO(15NH2)2+DMPP,CO(15NH2)2+NBPT and CO(15NH2)2+DMPP+NBPT treatment were 678.33-704.41 g m-2 y-1 respectively.(3)15N fertilizer recovery rate from plant stem leaf,root and soil in different treatments were as follows: 15 N fertilizer recovery rate in only CO(15NH2)2 application treatment was 57.67%,that in CO(15NH2)2+DMPP treatment was 58.08%.15 N fertilizer recovery rate in CO(15NH2)2+NBPT and CO(15NH2)2 +DMPP+NBPT treatment were 68.74% and 79.82%.Statistical results showed CO(15NH2)2+NBPT and CO(15NH2)2 +DMPP+NBPT treatment can significantly increase N fertilizer recovery rate of alpine grassland.In addition,15 N fertilizer recovery rate from plant stem leaf was 28.45-51.81% in four fertilizer treatments and that from plant root was1.20-2.59%.15 N recovery rate from soil layer from 0-40 cm was 25.90-43.93% in four fertilizer treatments.(4)By indoor culture experiments,for with dark chestnut soil,fertilization of urea ammonia volatilization loss of 18.61 kg N·hm-2,accounting for 33.7% of the total amount of nitrogen;Urea + DMPP ammonia volatilization loss of 15.29 kg N·hm-2,accounting for 27.71% of the nitrogen is always;Urea+NBPT and urea+NBPT + DMPP ammonia volatilization loss of 10.02 kg N·hm-2 and 8.77 kgN·hm-2,accounted for 18.15% and 15.88% of N application rate.And for sea north station of alpine meadow soil,fertilization of urea ammonia volatilization loss of14.12 kg N·hm-2,accounting for 25.58% of the total amount of nitrogen;Urea +DMPP ammonia volatilization loss of 13.32 kg N hm-2,accounting for 24.12% of the nitrogen is always;Urea + NBPT and urea + NBPT + DMPP ammonia volatilization loss of 3.85 kg N·hm-2 and 3.98 kg N hm-2,accounted for 6.98% and 7.20% of N application rate.(5)The addition of urease / nitrification inhibitor to nitrogen fertilizer increased the content of ammonium nitrogen in the alpine meadows with 9.42%-71.69,3.75%-28.47%(alpine meadow soil).The content of NO3--N in soil treated with urea +DMPP was lower than that of urea,but the content of NO3--N in alpine meadow soil was higher than that in urea treatment Of the content.For urea + NBPT + DMPP treatment,the conversion time of urea amide nitrogen to ammonium nitrogen can be retarded in dark chestnut soil,but it is not obvious for the inhibition of nitrate nitrogen content.For alpine meadow soil,In the first 16 days,the inhibitory effect of ammonium and nitrate was more obvious than that of urea alone. |
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