No-till farming started in the 1960’s and gained steam in the 1970’s (fuel crisis) and the 1980’s (agricultural financial crisis). Glyphosate (Roundup ®) and genetically modified organisms (GMO) innovations also increased no-till farming. But true long-term no-till farming on every acre every year occurs on less than 4-5% of Ohio farms, with most farmers doing some tillage. Farmers are decreasing their tillage intensity and are now considering ways to capture soil carbon for payment which may require they move to towards regenerative practices like no-till and cover crops.
Tillage breaks up soil aggregates and loses carbon dioxide to the atmosphere within 5-10 minutes; while long-term no-till with cover crops starts the slow process of recovering lost carbon. Adding soil carbon is all about roots exudates (active carbon) and root turnover (building humus from microbes). Crop rotation, moisture, climate, and soil characteristics all influence how quickly soil carbon stabilizes. Farm management decisions like tillage, crop rotation, and vegetation intensity (cover crop type, frequency) can be detrimental or beneficial to carbon sequestration.
The biggest reasons farmers till the soil are to create a drier, warmer seed bed for new plants; break up soil compaction; and to kill weeds. Unfortunately, the benefits are generally short-term. Tilled soils generally lose 0.5-1.0 inch of cold spring moisture which helps warm the soil. The excess oxygen from tillage also releases many soil nutrients from the soil organic matter (SOM) but then reduce the soil’s ability to store those nutrients long-term. Till soils lose SOM as carbon dioxide and start to compact, forming hard pans or soil crusting, resulting in poor drainage. Tillage may kill existing or emerging weeds, but weed seeds thrive and germinate even faster in tilled soils, so a vicious downward cycle begins.
The greater the tillage intensity (aggressive tillage like plowing, deeper tillage, higher frequency) the more carbon is lost. Fortunately, aggressive tillage methods like plowing have decreased 35% but no-till farms have only increased about 1% (US Census). Almost 90% of Ohio farmers use some form of tillage like minimum tillage or vertical tillage, tilling soils 2-4 inches deep, especially in front of corn.
Cover crops with no-till mimics natural cycles to restore soil health. Cover crop acreage has increased 50% from 2012-2017 (US Census). Cover crops add roots, improve soil structure, and build carbon. Keeping the soil undisturbed allows keeps carbon to stabilize in soil aggregates and improves water storage and drainage. Live roots create macropores and micropores for clean water and improved drainage. Beneficial soil organisms like mycorrhizae fungi, beetles, and springtails and many pollinators start to flourish due to stabile soils and a steady food source from actively growing plants. While soils may be improving by capturing carbon, improving soil aggregation, reducing weeds, and improving drainage; crop yields are usually the last metric to improve.
The problem is that the transition to healthy soils may take 3-7 years, which can be difficult financially for most farmers. Adding high carbon grass cover crops that aggressively break up soil compaction may decrease this transition time. Cover crops also compete with weeds which grow on disturbed or bare soils. Adding manure or grazing livestock, if feasible, stabilizes carbon and speeds up the transition. Multi-species cover crops with good crop rotations increases carbon at various soil depths, building soil carbon reserves. Farmers need to keep the soil covered with live crops year-round to build soil carbon.
Following NRCS soil health principles is the best way to build soil carbon. First, reduce or eliminate soil disturbance to preserve SOM and soil carbon. Farmers can reduce their tillage intensity or till only part of field where ruts or weeds occur. Second maintain surface soil residue to provide habitat for soil organisms and to reduce soil erosion. Third, increase live roots year-round by planting cover crops to increase carbon sequestration. Fourth, increase plant diversity with crop rotations and cover crops. Finally, add livestock if possible, to improve carbon sequestration and stabilization. These regenerative practices are natural ways to improve soil carbon and soil health simultaneously.
Regenerative practices like soil health are becoming more mainstream. General Mills has converted one million acres to regenerative farming practices with Cargill pledging 10 million acres. Walmart, Kellogg, Hormel, Patagonia, Danone and many other companies are doing similar things. Other benefits to increasing carbon include less nutrient runoff leading to improved water quality and less pests (weeds, diseases, insects). Heathy plants have greater photosynthetic ability to produce nutrient dense healthy foods and higher yields, in time. Healthy soils create healthy plants, healthy animals, and healthy people while improving the environment.