Effect of grassland management on the amounts of soil organic N and C

Abstract

Annual fertilizer rates of N varied from 250-700 kg ha-1 under grazing and from 0-700 kg ha-1 under mowing. On grazed plots no significant accumulation of soil organic N occurred in a sandy soil; in a loamy soil an average N accumulation of 245 kg ha-1 yr-1 was found. Results confirm the suggestion that the surplus of fertilizer N is largely lost to the environment. About four years after the start of the experiment the amounts of soil N and C were considerably higher under grazing than under mowing. In spite of the higher amount of soil N under grazing compared to mowing, 71% and 57% of the extra amount of N returned to the soil by grazing is lost to the environment on the sandy and the loamy soil, respectively. The C/N ratio of the soil organic matter was lower in plots with fertilizer N application than in plots without fertilizer N, a difference probably caused by a difference in C/N ratio of dead grass and roots that were returned to the soil. -from Authors