Soil erosion and water runoff from treated fields are the main sources of pesticides in surface water. Ground water can become contaminated from pesticides leaching through the soil profile. Keeping pesticides out of surface and ground water reduces potential human health risks. Impact of conservation tillage on surface water quality Conservation tillage's greatest effect on surface water quality is reduced runoff. Residues protect the soil surface from the impact of raindrops and act like a dam to slow water movement.
Rainfall stays in the crop field allowing the soil to absorb it.
With conservation tillage less soil and water leave a field. Table 1 shows the effects of residue cover on surface runoff and soil loss. An increase in residue cover significantly decreases runoff and sediment from a field. Effects of surface residue cover on runoff and soil loss. Ammonium nitrogen loosely attaches to soil particles and nitrate nitrogen dissolves in surface runoff.