Partnerships, Pesticides, and Potatoes

To address widespread concerns about pesticide contamination in Idaho's Fort Hall Indian Reservation wells, NRCS, the Shoshone-Bannock Tribal Business Council, the Three Rivers RC&D, the Shoshone-Bannock Land Use Commission, area agronomists, and the non-profit Northwest Coalition for Alternatives to Pesticides have joined together to develop an outreach and demonstration project on the reservation to identify and showcase alternatives to fumigants to the local potato growers who lease land from the tribe. And thanks in part to a Sustainable Agriculture and Research Education (SARE) grant that funded the 160-acre demonstration trial, eastern Idaho farmers substituting mustard greens in place of fumigants are now better able to manage plant parasitic nematodes and verticillium wilt in their wheat-potato rotations.

The Shoshone-Bannock tribes lease approximately 115,000 acres to area potato growers – about one third of the state acreage for potatoes, and one of the largest potato growing areas in the U.S. “Any way we can utilize sustainable agriculture and decrease man-made chemicals to raise crops goes a long way to preventing further contamination of ground water,” said Kurt Cates, NRCS district conservationist for the Shoshone-Bannock Tribal Natural Resources Conservation District. During the trial, Cates helped collect potato yield data and sampled cover crop residue following incorporation to ensure that the system met erosion requirements.

University researchers in the Northwest had already documented the effectiveness of brassicas to control plant-parasitic nematodes. The project team selected mustard and radish for the trial; both plants grow well during the cooler temperatures and shorter autumn days in southeastern Idaho, and fit well into the existing two-year wheat-potato sequence.

Upon decomposition, mustard releases a compound similar to the widely used fumigant metam sodium.  Results from the first year of the trial revealed that the area planted to mustard returned more US no. 1. potatoes than all other treatments. The mustard plots also returned $280 more per acre than the metam sodium treatment. Potato yields were poor in the plots planted to radishes, so the team only planted mustard the second year of the trial, which again performed competitively with the chemical treatments.

The method is not without its drawbacks, cautioned Cates. The mustard uses 9-10 extra inches of water and requires an extra application of fertilizer. However, university researchers are trying to develop mustard varieties that require less irrigation, and a portion of that extra nitrogen should carry over to the following potato crop. Cates also believes that the added biomass from the cover crop helps reduce erosion since the crop is only lightly disked into the soil.

“The best part of the project is that we now have growers and tribal leaders coming up with solutions to these problems together,” said Jennifer Miller, Sustainable Agriculture Program Coordinator for the Northwest Coalition for Alternatives to Pesticides. Leaseholders tripled the amount of acreage they planted with cover crops, after attending presentations and field days showcasing the results of the trial.

Word of mouth has generated a lot of interest off the reservation, said Cates. By some estimates, added Miller, 15-20,000 acres of cover crops across eastern Idaho are now being used in potato rotations.