A. C. Mahony
In trials done by the Malheur Experiment Station, furrow irrigation has consistently proven less efficient than drip or sprinkler in terms of onion yield per amount of water used. That being said, it is the least expensive and the most often used form of irrigation in the Pacific Northwest because it is what growers already have. Furrow irrigation is the least expensive only because large investments in land leveling were made in the past. Although it is the least efficient, the efficiency of furrow irrigation can be improved by surge irrigation techniques, which can conserve irrigation water and topsoil.
In surge irrigation, a butterfly valve is placed in the center of the top of the field. Gated pipe leads out of the valve and goes in both directions along the top of the field. The valve oscillates water from one side to the other at predetermined intervals. (In conventional surface irrigation systems, the water flows continuously during the irrigation set.) The alternating flow of water on each side of the valve causes an intermittent wetting and soaking cycle in the irrigated furrows. The alternating wetting and soaking cycle causes soil particles to settle to the bottom of the furrow. As these soil particles partially seal the soil surface, the water intake rate is reduced. As a result, less water is lost to deep percolation at the beginning of the row and the water can advance down the furrow faster. Precise timing shuts off the water flow before much of it flows off the field at the end of the rows. By reducing deep percolation at the beginning of the row and tailwater runoff at the end, the result is more uniform water application, less total water applied, and much lower water runoff (Shock et al., 2011).