Figure 2.

Accumulation of soil organic carbon (SOC), t/ha, resulting from an annual application of farmyard manure (FYM), 35 t/ha in the Broadbalk Wheat Experiment, Rothamsted. The amount of SOC has been corrected for the change in soil bulk density at the end of each sampling period. Each of the three series of data started in different years: Series 1. FYM from 1843 to 1914 (×), and again from 1967 to 2000, (○). Series 2. FYM from 1885 to 1914 (+), and again from 1967 to 2000, (∆). Series 3. FYM from 1967 to 2000 (□). To create a common timeframe, the calendar years for Series 2 and 3 data were shifted back to coincide with Series 1 before fitting the exponential model