Tillage and Weed Management Affects Winter Wheat Yield in an Integrated Pest Management System

Abstract Adoption of conservation practices by U.S. Pacific Northwest growers to meet farm bill legislation for erosion control is limited by the inability to control weeds and other pests in cereal and pulse crops. A 6‐yr, 16‐ha integrated pest management field study was conducted in the subhumid wheat area of the Pacific Northwest from 1985 through 1991 to develop a crop production system that controls weeds effectively and reduces soil erosion. Farm‐size machinery were used to till, plant, and harvest crops grown in either a continuous wheat ( Triticum aestivum L.) sequence or a 3‐yr rotation of winter wheat‐spring barley ( Hordeum vulgare L.)‒spring pea ( Pisum sativum L.) in conservation and conventional tillage systems. Minimum, moderate, and maximum weed management levels were superimposed over each cropping by tillage system. Position of winter wheat within a cropping system influenced yield so that wheat produced more grain following spring pea > spring wheat >> winter wheat. Insects and root diseases were not yield‐limiting factors in either conventionally tilled monoculture wheat or no‐till wheat in the 3‐yr cropping system. Yield of winter wheat in the conventionally tilled, continuous wheat system was similar for all three weed management levels. Yield of winter wheat in conservation tillage systems increased at both the moderate and maximum level of weed management compared with the minimum level. No‐till winter wheat planted after either pea or spring wheat at the moderate and maximum weed management levels yielded a minimum of 605 kg ha −1 more than conventionally tilled wheat at the same management levels.