Fig 1. Change in soil organic carbon (SOC, a) and total nitrogen (N) (b) in bulk soil from the control (CK) or soil that has received 32 years of chemical fertilizer application (N, P: phosphorus, K: potassium) and either 0 (M₀), 30 (M₃₀) or 60 (M₆₀) t manure ha^-1 yr^-1.

Note: Different letters above the bars indicate significant differences at 5% probability level. Capped bars are standard error of the mean (n = 3).