Therefore, a wide variety of primary and secondary tillage implements are used on the remaining cropland. Table 1 summarizes the effects of tillage operations on residue cover. Note that there are two categories for crop residue, non-fragile and fragile. The numbers in Table 1 are provided for planning purposes, but whenever possible, producers should estimate residue cover after each pass with an implement to ensure that the desired level of residue cover is maintained. In general, the number of passes can be as important as the type of tillage operation selected.
Residue cover is also sensitive to depth and speed of equipment operation and to row spacing.
Ultimately, no-till systems will provide the highest level of residue cover. With higher levels of crop residue present, surface-applied nitrogen may result in high volatilization rates. Therefore, nitrogen should be placed beneath the crop residue by either knifing or injection methods. The type and positioning of coulters and row cleaning and fertilizer attachments will affect residue levels, however, and the least aggressive units available for a given operation should be used. In addition, cover crops can suppress weed growth, decrease additional nitrogen requirements, and aid in field moisture management.