Soil organic carbon (SOC) pool is the largest among terrestrial pools. The restoration of SOC pool in arable lands represents a potential sink for atmospheric CO2. Restorative management of SOC includes using organic manures, adopting legume-based crop rotations, and converting plow till to a conservation till system. A field study was conducted to analyze soil properties on two farms located in Geauga and Stark Counties in northeastern Ohio, USA. Soil bulk density decreased with increase in SOC pool for a wide range of management systems. In comparison with wooded control, agricultural fields had a lower SOC pool in the 0–30 cm depth. In Geauga County, the SOC pool decreased by 34% in alfalfa (Medicago sativa L.) grown in a complex rotation with manuring and 51% in unmanured continuous corn (Zea mays L.). In Stark County, the SOC pool decreased by 32% in a field systematically amended with poultry manure and 40% in the field receiving only chemical fertilizers. In comparison with continuous corn, the rate of SOC sequestration in Geauga County was 379 kg C ha−1 year−1 in no-till corn (2 years) previously in hay (12 years), 760 kg C ha−1 year−1 in a complex crop rotation receiving manure and chemical fertilizers, and 355 kg C ha−1 year−1 without manuring. The rate of SOC sequestration was 392 kg C ha−1 year−1 on manured field in Stark County.
Restoration of soil organic carbon (SOC) in arable lands represents a potential sink for atmospheric CO2 (Lal and Kimble, 1997). Strategies for SOC restoration by adoption of recommended management practices (RMPs) include conversion from conventional tillage to no-till, increasing cropping intensity by eliminating summer fallows, using highly diverse rotation, introducing forage legumes and grass mixtures in the rotation cycle, increasing crop production, and increasing carbon (C) input into the soil (Lal et al., 1998, Lal, 1999, Desjardins et al., 2001 and Hao et al., 2002). In the US, cropland under no-till increased from 14.7% in 1995 to 19.6% in 2002 (Fawcett and Towery, 2003). There is a strong interaction among RMPs with regards to their effect on SOC concentration and soil quality (Jarecki and Lal, 2003). Adopting no-till in combination with other management practices can enhance SOC sequestration. In combination with minimum or no-till management, crop rotations can reduce soil erosion, enhance SOC concentration and sequester soil C (Lal, 2001). West and Post (2002) observed that changing plow till to no-till increased SOC pool at the rate of 57 g C m−2 year−1 (or 570 kg ha−1 year−1). Relatively lower rates (14 g C m2 year−1) of increase in SOC pool were associated with adoption of complex crop rotations. The efficiency of a no-till system for SOC sequestration is enhanced when used in combination with high intensity crop rotations and elimination of summer fallow (Potter et al., 1997 and Campbell et al., 1998). Converting a monoculture to a crop rotation also leads to SOC sequestration, which increases residue inputs to the soil (Robinson et al., 1996, Drury et al., 1998 and Halvorson et al., 2002). Increase in SOC may not occur in crop rotations, which include high frequency of low residue producing crops, such as soybean (Glycine max L.) ( Omay et al., 1997, Dick et al., 1998 and Studdert and Echeverria, 2000). Buried residues and roots decay faster than above ground or surface applied residues as is the case in a no-till system ( Ghidey and Alberts, 1993). A strong interaction between C, water and N cycles impacts the SOC pool and soil erosion risks ( Reicosky, 1994).
The data on SOC sequestration rate under on-farm conditions are scanty, but needed for assessing the C credits and evaluating the impact of management system on soil quality. Therefore, the objectives of this study were to compare SOC and N pools, and other soil properties under different crop management systems under on-farm conditions on selected farms in northeastern Ohio, USA.
The on farm data reported herein support the following conclusions:
(1)
Increase in C input to the soils through manuring, judicious use of fertilizers and adoption of complex crop rotations is beneficial in enhancing agronomic productivity, which in turn enhances soil organic carbon pool.
(2)
Manuring enhanced the soil organic carbon pool compared to chemical fertilizers because of additional input of carbon, improvement in soil quality, and increase in aggregation and structure.
(3)
Adoption of no-till on-farm conditions in Ohio leads to similar rates of soil carbon sequestration as that
