tions typically occur in the spring. Secondary tillage can involve multiple passes but quite often a series of implements are pulled in tandem, making it a one-pass operation. If growers are practicing conservation tillage, more than 30 percent of residue is present on the soil surface after planting.
Weed management – may or may not include a half rate or full rate of soil-applied herbicides with residual activity before or after planting (preemergence or early postemergence to the crop). Modern sprayers are typically 90 feet in width or more, and this step requires very little time and fuel use. Some growers, however, have tanks mounted on their planters and spray the residual herbicides at planting, thus saving an operation. Herbicide-resistant crops are typically treated with glyphosate postemergence to the crop and weeds and may include other herbicides with different mechanisms of action. A second (and possibly a third) application of glyphosate is typically applied, especially in cotton and soybean. If one or more weeds have become resistant to glyphosate or the farmer’s herbicide of choice, then the grower may apply a substitute herbicide or use a tillage operation to control the weed.
Organic growers substitute tillage (cultivation) operations, typically three or more, for herbicides for weed control. The first operation is usually performed just after corn or soybean has emerged, using a rotary hoe. This step is usually followed by two cultivations, the first occurring when corn or soybean is quite small.
Pretillage – some growers may shred cornstalks.
Weed management – some growers will use a nonselective ”burn-down” herbicide, such as glyphosate, to kill existing weeds if they are present before planting. Farmers may also wait until after planting for the initial herbicide application. This treatment may include a combination of herbicides that provide residual control of weeds that emerge later in the season. Postemergence applications of herbicides may be used later in the season depending on the weed infestation.
Planting – involves more sophisticated versions of the planters used for conventional tillage. Typically, the planters have heavy coulters and other attachments to clear the residue from the previous crop in the planting row. Not all soils are suitable for no-till, especially wet and heavy soils in northern latitudes, and no-till may lead to increased pest occurrence because conventional tillage may reduce insect, pathogen, and weed occurrence. On the other hand, no-till is well adapted to well-drained soils in warm regions because no-till improves soil-water infiltration and reduces soil evaporation, thereby providing more soil water to the crop.