This study compared three corn-soybean cropping systems: (1) conventional 2-yr rotation with chemical inputs, and residues returned to soil; (2) a longer (than 2 years), organic rotation with grass/legume hayed and returned to soil in manure; and (3) a longer (than 2 years) organic rotation with grass/legume turned back into the soil directly. Even though the conventional system returned more total residue to the soil, carbon sequestration was significantly lower for the conventional system than for the two organic, legume-based systems. Authors suggest that this is due to greater temporal plant diversity from the longer rotations, and higher quality residue (greater N:C) in the two legume-based organic systems. Furthermore, CO2 emissions were lower in the legume-based organic systems due to 50% lower energy use.
Even though the conventional system returned more total residue to the soil, carbon sequestration was significantly lower for the conventional system than for the two organic, legume-based systems. Authors suggest that this is due to greater temporal plant diversity from the longer rotations, and higher quality residue (greater N:C) in the two legume-based organic systems. [Drinkwater] |
Drinkwater, L.E., et al, 1998, Legume-based cropping systems have reduced carbon and nitrogen losses, Nature 396, https://www.nature.com/articles/24376.