Continuous organic no-till is still considered unachievable. However, options for reducing tillage in the mid-Atlantic region have been identified and tried, including: (1) rotating annual grain crops with perennial forages; (2) decreasing depth and degree of soil inversion (e.g. chisel plowing and disking in place of moldboard plow); or (3) no-till planting cash crops into cover crops that are mechanically killed.
Cover crop-based, organic rotational no-till grain systems have focused on corn and soybean production in the mid-Atlantic region. Soybean is typically no-till planted into a fall-planted cereal rye cover crop, whereas corn is more commonly planted into a fall-planted hairy vetch cover crop.
Rodale Institute utilizes the roller crimper as the primary weed control tool in organic rotational no-till corn and soybean production. This method involves simultaneously rolling a dense cover and planting a cash crop into the mulch layer using a modified no-till planter. The chevron shape of the crimper blades ensures that the stems of the cover crop are broken in so many places that they cannot recover and will create an evenly distributed mulch layer.
In normal years, the thick mulch suppresses weeds season long. However, unexpected weather conditions such as high precipitation at the time of rolling crimping, late planting of the cover crop in the fall, or rolling the cover crop before the effective termination growth stage, which is normally at flowering or anthesis, can result in substantial weed infestation.
An innovative tractor-mounted implement called a high residue cultivator is utilized as a “rescue” response to manage weeds in a rotational no-till system. The high residue cultivator has coulters (residue slicers) that cut through the cover crop residue mulch to create a path for the sweeps to ride under the mulch, just below the soil surface to cut weed tops from their roots or uproot them. Two press wheels on either side of the coulter press down firmly on mulch residues thereby facilitating clean slicing of the residues ensuring that sweeps riding under the mulch leaves the mulch intact and relatively undisturbed. This is important in ensuring that weed suppression from the mulch is not impaired.
Dr. Emmanuel Omondi is the director of the Farming Systems Trial.