Water quality consequences of conservation tillage: New technology is needed to improve the water quality advantages of conservation tillage

Excerpt

CONSERVATION tillage, which leaves some or all of the residue from the previous crop on the soil surface, effectively protects the soil against erosion. Use of conservation tillage has other environmental implications as well, particularly for water quality.

The reduced soil erosion possible with conservation tillage compared with moldboard plow or clean tillage systems is an obvious advantage because of the reduction in sediment and sediment-associated chemical losses. In some cases, runoff is also less with conservation tillage, which can reduce losses of soluble, nonadsorbed chemicals. However, maintenance of crop residue on the soil surface currently limits fertilizer and pesticide use options in conservation tillage, thus affecting chemical concentrations and losses in surface runoff water and sediment.

Water quality concerns

Drainage water and sediment from agricultural land carrying dissolved and adsorbed nutrients and pesticides are major sources of nonpoint pollution. The primary nutrient forms carried are ammonium-nitrogen (NH₄-N), nitrate-nitrogen (NO₃-N), and phosphate-phosphorus (PO₄-P).

These are discussed in an Environmental Protection Agency document, “Quality Criteria for Water” (22). The volume recommends criteria for different water quality goals. However, knowledge of the kind and extent of effects of dissolved chemicals on water quality is incomplete …