Irrigation and Mechanization for Seed Production of Sulfur Buckwheat, a Native Forb

Sulfur buckwheat (Eriogonum umbellatum) is one of many forbs native to the intermountain west of the United States. Sulfur buckwheat has been selected for use in rangeland revegetation. Like many native plants, seed production technology is virtually unknown for wild Eriogonium species. Commercial seed production is necessary to provide the quantity of seed needed for rangeland restoration efforts. The seed production response of sulfur buckwheat to irrigation was tested in 2006, 2007, and 2008 at the Malheur Experiment Station in the Treasure Valley of eastern Oregon and southwestern Idaho. Sulfur buckwheat was established in 2005 by direct drilling of the seed in rows 30 inches apart. Irrigation treatments were applied to plots four rows wide and 30 feet long arranged in a randomized complete block design with four replicates. Irrigation was applied using drip tape installed at 12 inch depth between two rows of plants spaced 30 inches apart. The drip tapes were installed on alternating inter-row spaces (5 feet apart). Sulfur buckwheat was submitted to three irrigation rates: 0, 1, and 2 inches of water applied starting at the beginning of flowering four times for a total of 0, 4, and 8 inches. Weeds were controlled by mechanical cultivation, hand weeding, and broadcast applications of herbicide. Insect and disease pests were not noted. Seed was harvested using a Wintersteiger Nurserymaster small plot combine with a dry bean concave. Seed was cleaned mechanically. In 2006, seed yield increased with increasing water applied up to the highest amount tested of 8 inches. In 2007 and 2008, seed yield showed a quadratic response to irrigation rate. Seed yields were maximized by 8.1 inches and 7.2 inches of water applied in 2007 and 2008, respectively.