The responses of soil nitrogen to the conversion of cropland from perennial M.sativa grassland in the semi-arid loess area was investigated in two years of field experiments.Compared with M.sativa grassland,soil total nitrogen decreased rapidly and soil mineral nitrogen increased in the two years after the conversion.The crop phase in the rotation had a significant effect on the soil nitrogen changes.In the second year after the conversion,planting Zea mays or Solanum tuberosum increased the soil NO_3~--N a...
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