Soil carbon sequestration and aggregation by cover cropping

Agriculture is the foundation of human civilization. Transition from hunter-gatherer to settled agriculture, as evidenced by the use of crude implements for tilling and harvesting, may have occurred in modern day Iraq and elsewhere around 11,000 years ago (Troeh et al. 2004). The beneficial role of growing cover crops in improving soil productivity had been recognized for at least three millennia and probably longer. Use of cover crops as green manure had been advocated in most ancient cultures (e.g., Indus Valley and Middle East) to improve soil fertility. In China, for example, use of cover cropping dates back to the Zhou dynasty 3,000 years ago (Lipman 1912; Pieters 1927; Meisinger et al. 1991). Cato, a Roman philosopher during the 3rd century BC, advocated the use of green manure and compost to improve soil productivity (Winiwater 2006; Brevik and Hartemink 2010). By the 4th century AD, grain yields of wheat (Triticum aestivum) in Rome declined drastically due to the lack of cover cropping and were hardly 270 to 400 kg ha−1 (4 to 6 bu ac−1), and that of barley (Hordeum vulgare) were only 220 to 320 kg ha−1 (195.8 to 285.1 lb ac−1; Paine and Harrison 1993). Therefore, during 395…