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Nitrogen Distribution at Grass-Soil System and Growing Dynamic on Russian Wildryegrass Pasture as Influenced by Grazing

Bai Keyu; Wang Pei ;Han Jianguo(Institute of Grassland Science, China Agricultural University, Beijing 100094)Sun Ruichen(Chengde Yuershan Farm, Yuershan 068359)  
The N distribution at grass-soil system and growing dynamic under light grazing(LG 0. 134 hm2/sheep), medium grazing (MG0. 08 hm:/sheep), high grazing (HG 0. 067 hm2/sheep ), and no grazing (CK)was carried out on a pasture established using Russian Wildryegrass (PSathyrstachys juncea (Fishch)NeVki)during growing season (from June to September)in 1997. The total N concentration of the pasture was 663. 5~938. 4g/m2,the most of which (99% )was present in the soil,less then 1% was present in the plant. The soil layer of O-2ocm contained 60~70% of the total N. There were no significant changes in soil -N over the growing season (June-September). Medium grazing is good to grass N utilized rate. The nitrogen reserve in soil showed a "T"-pattern in distribution and decreased exponentially with soil depth and had a tendency to accumulate at soil surface with increasing of grazing intensity,while there was no such tendency at ungrazed site. SOil N percentage at high grazing site was highest,and the others is ranked as CKLGMG,the plant N at grazed site was higher than that at ungrazed site,and grazing result in more N allocation in roots,the allocation of nitrogen in aboveground was lower than that at ungrazed site.
【Fund】: 国家科技攻关!96-016-01-04
【CateGory Index】: S812
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