2.3 Sampling and Chemical Analysis
Soil samples were collected from the center of each pot at 0-10 cm depth prior to and one month after cover crop growth. Soil samples were air dried and ground to pass through a < 1 mm mesh sieve for chemical analysis. The
experiment was terminated at the time when any one of these cover crops was flowering, which was about 90 days for both winter and summer cover crops under the experimental conditions. The aboveground plant biomass was harvested, and fresh and dry weights (at 75 oC for 7 d) of biomass were recorded. A subsample of the aboveground biomass was ground to pass through a < 0.5 mm mesh sieve for chemical analysis. Total Carbon and nitrogen (N) contents in the soil and cover crops were analyzed using CNS Auto-analyzer (Vario Max Elementar, Hanau, Germany). Soil inorganic Carbon was
determined via pressure calcimeter method and the organic Carbon was calculated by subtracting the inorganic Carbon from the total C [27].