Impacts of Conservation Tillage, Cover Crops and Watertable Management On Water Partitioning and Nutrient Losses From Agricultural Soils.

In humid climates, soil and crop management practices including conservation tillage, cover  crops and water table management systems are recommended as beneficial management practices to improve soil and water quality without compromising crop productivity.  In many situations, they have achieved their intended objective.  For example, conservation tillage systems increase the amount of surface residue and thereby provide a physical barrier which slows water movement and reduces surface runoff and soil erosion. However, there can be unintended consequences of conservation tillage such as an increase in the amount of water and nutrients available for leaching through soil. The increased water flow through soils under conservation tillage is partially intercepted by the network of tile drains under most clay and clay loam soils in humid regions of N. America which could increase nutrient entry into ditches, streams or lakes.  Cover crops are a common management option for capturing surplus fertilizer nitrogen remaining in the soil after harvest as well as transpiring excess soil water during the fall and spring when the cover crops are actively growing. However, cover crops also reduce surface runoff and thereby enhance water infiltration into the soil which may reduce their effectiveness from a water quality perspective.  This presentation will focus on the benefits and risks associated with several soil and crop management practices and discuss how a holistic approach is required to maintain crop productivity while reducing environmental impacts.