Application of 15N isotope tracing technique: The economical fertilizing amount of different grazing intensity pastures in temperate desert steppe

摘要

Aim: To determine the economical fertilizing amount of different grazing intensity pastures in temperate desert steppe, provide theoretical basis and data support for the restoration and rational utilization of degraded desert grasslands in China.Methods: The economical fertilizing amount was studied using 15N isotope tracing technique and determined by the value of the loss amount of labeled nitrogen/the recovery amount of nitrogen in plants.Results: With the increasing of nitrogen application amount, the ratios of loss to recovery in moderate grazing pasture gradually increased, while it increased at first and then decreased in heavy grazing pasture.The ratios were all greater than 1 except when nitrogen application amount was 12.25 g N.m-2 in heavy grazing pasture.Conclusions: There exists high risk for adding nitrogen to temperate desert steppe.Related works should be carefully planned, low amount of nitrogen should be chosen to avoid wasting nitrogen fertilizer.12.25gN·m-2 is the minimum loss/recovery value of moderate and heavy grazing grasslands and the economical fertilizing amount of the temperate desert steppe.This date can be used as a reference in restoration and update of such degraded grasslands.