Shock, Clinton C.;Shock, Candace B.

Oregon State Univ, Malheur Expt Stn, Ontario, OR 97914 USA;Sci Ecol Serv, Ontario, OR 97914 USA

DCPA;drip irrigation;groundwater nitrate;irrigation management;irrigation scheduling;nutrient management;voluntary cooperation

Agriculture in southeastern Oregon and southwestern Idaho known collectively as the Treasure Valley has depended on furrow irrigation using heavy inputs of water and nitrogen (N) fertilizer. Crop rotations include onion, corn, wheat, sugar beet, potato, bean, and other crops. By 1986 groundwater had become contaminated with nitrate and residues of the herbicide chlorthal-dimethyl (DCPA); an official groundwater management area was established by the Oregon Department of Environmental Quality along with an action plan and well monitoring network. The action plan allowed for a trial period to see whether voluntary changes would improve trends. Researchers, producers, and agencies cooperated to develop production options that had the possibility of being both environmentally protective and cost effective. Options were tested to improve irrigation practices, increase N fertilizer use efficiency on several rotation crops, and find a cost effective replacement for DCPA. Research demonstrated the opportunity for increased productivity through both irrigation scheduling and the adoption of drip and sprinkler systems. Fertilizer research demonstrated that smaller, more frequent N applications were more efficient than a single large application. Effective, lower cost herbicides replaced DCPA. Research results were effectively delivered through many means and voluntarily adopted. Both groundwater nitrate and DCPA residues are declining. Productivity has increased.