Sheep grazing stimulated plant available soil nitrate accumulation in a temperate grassland

We investigated the effects of increasing grazing i ntensities on n availability (inorganic n,in-n,for plant and microbial growth,e.g.,no3 --n,nh4 +–n) and variability in soils of 0–10 cm depth during 2009–2010,within a framework of a long-term grazing study. the results showed that the relationship for grazing intensity with respect to soil no3 ––n (r2 = 0.988,p = 0.006) was well depicted by curvilinear equations. moreover,soil no3 ––n,nh4 +–n and inorganic n varied significantly with sample date,year,and soil water content (swc,%). there were also significant correlation between date and grazing intensities on soil no3 ––n,nh4 +–n and in-n. swc and temperature had more impact on soil available n than grazing,especially with respect to the seasonal dynamics of the soil n pool. grazing intensity,in combination with swc (precipitation) and temperature,controlled soil n availability and,therefore,affect the n cycles and plant growth within semiarid grasslands. © 2015,pakistan botanical society. all rights reserved.