Is Carbon Management Index Suitable to Account Variability in Soil Carbon Sequestration?.

Soil carbon dynamics in response to management practices is important to enhance ecosystem services. To evelaute the effects of various combinations of multi-functional  cover crops mix under continuous no-till on soil C sequestration, a field study was conducted was conducted. Composite soil samples (n = 36) from each replicated plot at 0-10, 10-20 and 20-30 cm depth, respectively were collected from (1) contnuous no-till without any cover crops; (2) cover crops mix-1 with Pearl millet-4#, Sorgum sudan grass-4#, Soybean-10#, Cowpea-15#, Tillage radish-2#, Turnip-1#, Sunflower-1#, and Clover-5#; (3) cover crops mix-2 with Sun hemp-10#, Cowpea-15#, Soybeans-10#, Pearl millet-8#, Tillage radish-2#, Turnip-1#, Sunflower-1#, Ryegrass-5#, and Sweet clover-2#; (4) cover crops mix-3 with Tritcale-60#, Austrian winterpea-30#, Vetch-15#, Turnip-2#, Rape seed-5#, and Phacelia-5#; and (5) cover crops mix-4 with Sun hemp-10#, Cowpea-10#, Tillage radish-2#, Tritcale-30#, Pearl millet-8#, Ethiopian cabbage-2#, Soybeans-15#, and Buck wheat-5#. Soil samples were analyzed for microbial biomass C, total, active, soluble and particulate organic C and N and other properties. Using the measured C values, several C management indices (CMI) were calculated. Results showed that cover crops mix-2 followed by cover crops mix-1 and cover crops mix-3 had significantly higher total, active, soluble, microbial and particulate organic C compraed with the control. Cover crops mix-4 did not perform well. Likewise, carbon pool index (CPI), carbon lability (L), C lability index (LI), and CMI values were higher in cover crops mix treatments than the control. When using particulate organic, microbial biomass, soluble and active C as a measure of labile C pools to calculate CMI, the CMI based on soluble C did not vary significant among the treatments. The CMI was more sensitive to continuous no-till cover crop magement practices when active C was used as a measure of labile C followed by particulate organic C and microbial biomass C.