Wheat Farmers Adopt the Undercutter Fallow Method to Reduce Wind Erosion and Sustain Profits

Wheat Farmers Adopt the Undercutter Fallow Method to Reduce Wind Erosion and Sustain Profits

Douglas Young, School of Economic Sciences, Washington State University, William Schillinger, Department Crop and Soil Sciences, Washington State University
Excessive tillage—especially in the low-precipitation wheat production region of the Inland Pacific Northwest—causes blowing dust, which results in soil loss as well as air quality degradation. Yet more than 90% of rainfed cropland in the Inland PNW is on a two-year, tillage-based winter wheat-summer fallow rotation. The undercutter system was developed to mitigate wind erosion and achieve profitable yields. This publication outlines the results of a multi-year, on-farm study conducted with 47 farmers who adopted the undercutter method.
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Abstract

Blowing dust from excessively tilled fallow fields is a major soil loss and air quality concern in the low precipitation (<12 inches annually) wheat production region of the Inland Pacific Northwest (PNW). A 2-year, tillage-based winter wheat-summer fallow (WW­SF) rotation is practiced on more than 90% of rainfed cropland in the region. Earlier research proved that the undercutter method for non-soil inversion primary spring tillage is not only environmentally superior but also agronomically and economically equivalent to high-soil disturbance conventional tillage. In this study, we conducted comprehensive surveys of 47 wheat farmers who purchased undercutters through the USDA­Natural Resources Conservation Service (NRCS). Farmers received 50% cost shares on the condition that they use the undercutter as prescribed by university scientists on at least 160 acres of land for three consecutive years. Participating farmers were interviewed each year from 2008 to 2010 regarding the agronomic and economic performance of the undercutter versus conventional fallow on their farms. The survey revealed equivalent average winter wheat grain yields and profitability for the two systems from 104 paired comparisons. Survey results also showed that 90% of farmer participants were satisfied with the undercutter system. We conclude that the undercutter system offers a costless air quality gain to society and soil conservation benefit for farmers.

Introduction

This study focuses on the low-precipitation (<12 inches annually) zone of east­central Washington and north­central Oregon that encompasses 3.7 million acres of non­irrigated cropland. Essentially, all this cropland is in a tillage­based WW­SF rotation. Excessive tillage during summer fallow causes recurrent wind erosion, which seriously degrades soil, and blowing dust, which poses a hazard for human health. Urban locations within this region frequently fail to meet federal clean air standards for PM10 emissions during windstorms (Sharratt and Lauer 2006). The sandy silt loam soils found throughout the WW­SF region have a greater potential to emit PM10 even though these soils are composed of a smaller percentage of PM10 compared to the finer­textured silt loam soils found in the intermediate- and high­precipitation zones of the PNW (Feng et al. 2011).

Long­term cropping systems studies in the low-precipitation zone have examined the feasibility of direct seeding spring­sown wheat, barley, and numerous other crops as well as the practice of no­till summer fallow where herbicides are used as a substitute for all tillage operations. Studies have shown that no alternative crop or cropping system tested so far can compete with WW­SF for average and stable profitability (Schillinger and Young 2004; Schillinger et al. 2007). The absence of significant summer rainfall in the PNW penalizes yields and returns of spring crops and increases their riskiness. Other studies have shown that no­till summer fallow, although ideal for wind erosion control (Sharratt et al. 2010), loses seed-zone water at a faster evaporative rate than tilled summer fallow during the hot, dry summer (Hammel et al. 1981; Wuest 2010). This loss often makes it difficult or impossible for farmers to plant winter wheat into carryover soil moisture in late summer with no-till summer fallow. However, with tilled summer fallow, adequate seed-zone moisture for planting in late summer can generally be achieved. The physics of water loss in tilled versus no­till summer fallow and the grain yield penalties associated with delayed planting of winter wheat are described by Wuest and Schillinger (2011) and Higginbotham et al. (2011).

Research conducted in the past two decades indicates that the most realistic method for farmers to mitigate wind erosion and achieve stable and profitable yields in the low­precipitation zone is to practice conservation tillage in a WW­SF rotation. The undercutter system of WW­SF farming was developed for this purpose. The undercutter is a primary tillage implement used in the spring to sever capillary pores and channels to halt liquid flow of water to the soil surface as required to retain seed­zone water in summer fallow. Undercutter implements are equipped with 32­inch­wide blades with 28­inch spacing between blades on two tiers. Blades have a narrow pitch to allow slicing below the soil surface with minimum soil lifting or disturbance of surface residue (Figures 1 and 2). With this system, a tank cart is pulled in front of the undercutter (Figure 1) to deliver nitrogen, and often sulfur fertilizer, through a manifold and tubing plumbed beneath both wings of individual undercutter blades. The optimal operating depth for the blades is about five inches to provide a relatively thick, dry surface soil mulch to retard evaporation during the summer (Wuest 2010).

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Copyright 2016 Washington State University

Published July, 2016

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