Effect of 32 years of manuring and fertilization on carbon budgeting and carbon pools under sorghum-wheat cropping sequence in Vertisol of Central India

Long-term fertilizer experiments in various agroecological regions of India investigate different aspects of carbon budgeting and carbon pools in relation to crop productivity.

The LTFE has been in operation in Akola since 1988–89, with a sorghum-wheat cropping sequence on a Vertisol of Central India to study changes in soil quality and crop productivity. This study examined C inputs from sorghum and wheat in relation to SOC pools and indices. Seven treatments, 50% NPK, 75% NPK, 100% NPK, 150% NPK) and farmyard manure (FYM) at a rate of 5 and 10 t ha⁻¹, and control were replicated three times in randomized complete block design.

The yield and sustainable yield index (SYI) of sorghum and wheat was increased significantly with the application of 100% NPK + FYM. SOC pools were increased significantly with the application of FYM alone and 100% NPK + FYM. The magnitude of contribution follows the sequential order of non labile > labile > very labile > less labile. The application of 100% NPK + FYM resulted in increased SOC stock, carbon buildup, buildup rate, stabilisation rate, and carbon sequestration. The SOC pool indices were higher with 100% NPK + FYM. The higher carbon input with critical carbon input values of 1.72, 0.46, and 2.18 Mg C ha⁻¹ year⁻¹ was estimated for sorghum, wheat and sorghum + wheat, respectively.

Thus, the use of FYM alone and 100% NPK + FYM had a positive effect on carbon stability, carbon pools, and carbon pools indices, resulting in increased crop productivity.