As a result some studies have shown that conservation tillage practices may increase the concentrations of nutrients in surface runoff. Under certain circumstances, this increase may even be enough to offset the benefits of the reduced volume of runoff, so that waterway loadings of contaminants may be increased. Higher levels of organic matter also result in cooler, wetter soil conditions that could delay seeding on soils with high clay content. As well, weed populations can increase under reduced tillage and no-till, especially on summerfallow in the Prairies. In this case, weed control may require the use of more herbicide or a different herbicide, and possibly different management practices.
More research is needed to give a complete picture of the pros and cons of conservation tillage.
Cover crops Cover crops are used to minimize the effects of the main crop. They provide a protective cover that reduces the risk of runoff and erosion between two growing seasons. There are two main types of cover crop. Intercrops are grown along with the major crop. For example, a forage crop can be seeded between corn rows or spring wheat underseeded with red clover.