Transitional no-till represents the years from the beginning of no-till until the soil is truly transformed to have no-till characteristics. The number of years required to complete the transition can be shortened by practices such as cover cropping, adding manure or compost, utilizing diverse crop rotations, and maintaining crop residue on the soil surface. In research, the results during the transition are important and critical to understand the soil dynamics; however, the results should not be referred to as “no-till” until the soil has reached the biological, physical, and chemical status of true no-till.
It is important to understand the processes soils will go through during the transition phase. Soils abused by tillage and erosion do not have a diverse soil biological community and have limited water infiltration or gas exchange rates. The loss of soil organic matter, resulting from decades of tillage, increases the bulk density of soil because the soil aggregates are unstable. Bulk density is a primary measure of soil aeration and soil compaction, and from its definition, shows why a high bulk density has little pore space.
As soil organic matter increases under long term no-till, soil bulk density decreases, and plant roots can utilize organic sources of nutrients deeper in the soil profile and bring them to the surface. Plant-available water from deeper in the soil profile becomes a pathway for organic nutrients.
Short-term three-year research studies that convert a conventionally tilled field, start no-tilling, and call this a no-till system often have lower yields and bad comparison data. If the soil was previously compacted by heavy equipment, the soil has not yet made the transition to “true” no-till. It often takes seven to nine years to correct the “tillage effect” and give the soil time to heal the natural biological communities. Therefore, it is our opinion that all past or future short-term research trials (three years or less) should use the term transitional no-till to describe the soil’s health condition when comparing other tillage systems to no-till. These soils in transition are not yet providing the same ecosystem services observed under long-term no-till.
Source: Crops & Soils magazine, November-December 2018. Grigar, Hatfield, & Reeder authors.