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Soil & Water Resources Publications

Agricultural Lime & Liming

Part 1. Introduction: This section contributes to the discussion on the increasing incidence and severity of acid soils in the IPNW and emphasizes: i) soil sampling and monitoring concepts to consider when managing acid soil conditions; ii) the role of soil testing; and iii) characterization of liming materials used to elevate pH of acid soil.

Part 2. Laboratory Testing to Determine Lime Requirements: This section delves more deeply into variations among soil types and why laboratory testing is used to characterize soil pH. We define the terms “lime requirement” and how it relates to soil buffering capacity. We also provide information on lime requirement test methods commonly performed by soil testing laboratories. A companion lime requirement calculator based on common buffer tests and base saturation is provided for reference. Lime Requirement Calculator (Excel file).

Part 3. Agricultural Liming Material Selection and Comparison User Guide: This document is a user’s guide for the interactive online utility “Agricultural liming material selection and comparison.” The publication describes the attributes used to perform calculations to characterize liming material, while the interactive utility provides a platform to compare up to three liming materials for their relative effectiveness, costs and economic efficiency.

Conservation Tillage

Best Management Practices for Summer Fallow in the World’s Driest Rainfed Wheat Region (TB26)
Abstract: Wind erosion from excessively tilled soils is a severe problem, especially in south-central Washington. Tillage of fallow land in the world’s driest rainfed wheat production region is considered necessary, but it is also a major safety, environmental, and soil quality concern. This publication outlines the results of a 5-year study to determine the effects of three fallow management systems—traditional tillage, undercutter tillage, and no tillage—and suggests best management practices for farmers in this region.

Economic Comparison of Undercutter & Traditional Tillage Systems for Winter Wheat-Summer Fallow
Abstract: Wind erosion and blowing dust are major problems for traditional winter wheat-summer fallow tillage in eastern Washington due to reduced soil productivity and air quality. Although conservation tillage summer fallow can reduce wind erosion markedly, relatively few farmers in the low-precipitation (less than 12 inch/year) region of the Inland Pacific Northwest use it because of investment requirements for conservation tillage machinery and reluctance to change “tried and proven” traditional tillage methods. This bulletin addresses these barriers by comparing economic results from using a conservation V-sweep undercutter and traditional fallow tillage systems on a case-study farm near Ritzville, Washington. The undercutter produced a similar wheat yield to the 46 bu/ac eight-year average with traditional fallow. Furthermore, the conservation method was more profitable than the traditional system on the case-study farm due to slightly lower production costs. Eligibility for conservation payments further strengthened the profitability advantage of the undercutter system.

Wheat Farmers Adopt the Undercutter Fallow Method to Reduce Wind Erosion and Sustain Profits (TB24)
Abstract: 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.

Nutrient Management

Canola Growth, Development, and Fertility (FS045E)
Abstract: The purpose of this guide is to summarize current information on canola growth and fertilizer requirements. Canola is a relatively new crop to the Pacific Northwest and little fertility research has been conducted in this region. The information contained in this guide is intended to serve as a reference until the results of ongoing, local research are available. Canola is distinct from wheat in terms of growth habit, nutrient uptake, and nutrient removal in the seed. According to published research and fertilizer recommendations, canola requires more nitrogen and sulfur than wheat to achieve the same yields. Soil test-based requirements for phosphorus and potassium are similar to wheat, but boron requirements are higher. Because canola plant residue is higher in nitrogen and phosphorus than wheat straw, cycling of nutrients from residue to the subsequent crop may be an important rotational benefit of canola.

Dryland Winter Wheat Fertilizer Guide (EB1987E)
Abstract: Nutrient management is essential to the economical production of high-yielding, high-quality crops, and to preserving soil, air, and water quality.

Hard Red Spring Wheat Nitrogen and Protein Management Guide
Abstract: This guide reviews the basic principles governing hard red spring wheat yield and protein responses to nitrogen and presents an abbreviated method for calculating nitrogen fertilizer to meet yield and protein goals.

Hard Red Winter Wheat Nitrogen and Protein Management Guide
Abstract: This guide presents an abbreviated method for calculating nitrogen fertilizer rates to meet hard red winter wheat yield and protein goals, and reviews the basic principles governing hard red winter wheat yield and protein responses to nitrogen.

Hard White Spring Wheat Nitrogen and Protein Management Guide
Abstract: This guide presents an abbreviated method for calculating nitrogen fertilizer rates to meet hard white wheat yield and protein goals, and reviews the basic principles governing hard white wheat yield and protein responses to nitrogen.

Management of Urea Fertilizer to Minimize Volatilization (EB173)
Abstract: Urea (46-0-0), first introduced in 1935, is now the primary source of dry nitrogen (N) fertilizer in the U.S. due to its relatively high N content, ease of handling, and price. Although ammonium nitrate (34-0-0) may be superior in some situations to urea, due to liability concerns it is no longer available in many regions of the U.S.

Nitrogen Management for Hard Wheat Protein Enhancement (PNW578)
Abstract: Managing nitrogen to produce both high yields and acceptable protein of hard winter or spring wheat, especially in high rainfall and irrigated systems, has been frustrating for Pacific Northwest growers and those who serve them in an advisory capacity.

Nutrient Management Guide for Dryland and Irrigated Alfalfa in the Inland Northwest (PNW0611)
Abstract: Nutrient management is necessary to produce high-yielding, high-quality alfalfa economically, while at the same time preserving soil, air, and water quality.

Phosphorus Fertilization of Late-Planted Winter Wheat in No-Till Fallow (PNW 631)
Abstract: Wheat growers interested in experimenting with or transitioning to no-till fallow are concerned about reduced yields caused by late planting. Late planting is necessary in no-till fallow because seed-zone moisture during optimum planting dates (late August to mid-September) is almost always inadequate for germination and emergence.

Physiology Matters: Adjusting Wheat-Based Management Strategies for Oilseed Production (FS244E)
Abstract: For more than a century, growers have honed their management practices to meet the needs of the wheat-dominated Inland Pacific Northwest. As a result, even though we have a broad range of soil types and environments, the region lacks crop diversity. Oilseeds, however, are recognized as potential rotational crops due to their ability to extract deep soil moisture in arid environments. For growers interested in adjusting wheat-based management strategies for oilseed production, this publication describes the physiological differences between crops and recommends modifications based on those differences.

Precision Agriculture

Unmanned Aerial Systems in Agriculture: Part 1 (Systems)
Abstract: A vehicle is classified as an unmanned aerial system (UAS) when there is no person on board to guide controls, or decide direction or speed of the vehicle. UAS is equipped with onboard flight and navigation controls to be piloted remotely or through Global Positioning System (GPS) waypoints in autopilot mode. In general, the shape and size of the system governs classification of UAS into four different types (explained below). Proposed regulations from the Federal Aviation Administration (FAA) classify a UAS with a gross weight of less than 55 lbs (25 kg) as a small UAS (sUAS). Most of the newer sUAS are controlled from ground stations using remote control, multi channel bi-directional communication systems, which generally use a frequency of 2.4 GHz in the United States. Most systems also have autopilot and auto land capability. From an application standpoint, sUAS, which is the focus of this fact sheet, are integrated with sensing modules on board that appear to have a wide range of applications in agricultural production management when combined with soil, weather, and relevant crop growth information.

Unmanned Aerial Systems in Agriculture: Part 2 (Sensors) New
Abstract: Sensors play a critical role in meaningful use of small unmanned aerial systems (UAS) in agriculture. Sensor types and pertinent specifications govern quality of data available for either the overall crop scouting or for more specific biotic and abiotic crop stressors detection. This publication describes the types and suitable uses of specific sensors in agricultural applications. Discussed are also issues with form factor, payload capabilities, and data analytics that may influence the sensor selection being integrated with small UAS.

Variable Rate Nitrogen Application: Eric Odberg
Abstract: Eric Odberg’s, a grower in Genesee, ID, shares his experience of 12 years Precision Agriculture practices. This is his story.

Soil pH & Liming

Acid Soils: How Do They Interact with Root Diseases? (FS195E)
Abstract: As soil acidification continues to be a concern for growers in the Pacific Northwest, WSU researchers are working to provide information and recommendations for how to mitigate adverse effects. Root diseases are one of many factors influenced by acid soils, depending on the soilborne pathogen. This publication explains how soil pH affects root diseases and also offers examples of common ones in the PNW.

How Soil pH Affects the Activity and Persistence of Herbicides (FS189E)
Abstract: Decreasing soil pH, also called soil acidification, is a growing concern in eastern Washington and northern Idaho. Researchers and farmers have measured soil pH values below 5.0 throughout the Palouse region, in particular. Decreasing soil pH has serious implications for the cropping systems of the Palouse.

Recommended Crop Species and Wheat Varieties for Acidic Soil (FS169E)
Introduction: As discussed in the Implications for Management – An Introduction, not all crop species—nor all varieties within species—respond the same to acidic soil (Figure 1). Of the crops commonly grown in eastern Washington and northern Idaho, legumes are the most sensitive to soil acidity, while wheat and barley are less sensitive, followed by triticale and grass hay/seed crops, which can tolerate more acidic soil (Table 1). Canola and buckwheat also fare better on acidic soils than legumes and some wheat varieties, although canola is relatively sensitive to manganese (Mn) toxicity, which can be a problem on some acidic soils.

Soil Acidity and Aluminum Toxicity in the Palouse  Region of the PNW (FS050E)
Abstract: In the early 1980s, Dr. Robert Mahler of the University of Idaho published several research articles and Extension bulletins on soil acidification on the Palouse. At that time, Mahler and other researchers cited recent and archival data that indicated pH in the surface foot of soil had declined from near neutral (7.0), before farming began, to values below 6.0 in up to 65% of the fields surveyed.

Soil Acidity Impacts Beneficial Soil Microorganisms (FS247E)
Abstract: Beneficial soil microorganisms are also absolutely critical to soil fertility and plant nutrition, but soil acidification in the Pacific Northwest threatens their effectiveness. This publication outlines the response of beneficial soil microbial populations to acidification and how understanding this response may provide valuable in enacting sustainable approaches to soil acidification problems.

Soil pH and Implications for Management: An Introduction (FS170E)
Abstract: Decreasing soil pH, also called soil acidification, is a growing concern in eastern Washington and northern Idaho. Researchers and farmers have measured soil pH values below 5.0 throughout the Palouse region. Decreasing soil pH has serious implications for the cropping systems of the Palouse. This introduction is the first in a series of fact sheets on soil acidification and introduces the fundamentals of soil pH and acidification. Other fact sheets in the series will cover more specific information on topics such as the influence of pH on pathogens and microbes, herbicide activity, crop nutrition, liming, and variety selection.

Using a pH Meter for In-Field Soil pH Sampling (FS205E)
Abstract: Soil pH continues to decline across much of the Palouse and the Pacific Northwest, primarily as a result of the application of nitrogen for the production of wheat and other crops. A handheld sampling meter can be utilized for infield checking of the soil pH with good results. Within a few minutes of arriving at a field location it is possible to collect a soil sample, test the soil, and record the pH values.

STEEP Reports (Solutions to Environmental & Economic Problems)

STEEP Impact Assessment (EB2035A)
Abstract: The 30-year-old STEEP (Solutions to Environmental and Economic Problems) research and education program has gained national reputation as a landmark in conservation development for the Pacific Northwest. The basic strategy for STEEP was a systems approach that addressed all of the characteristics of conservation farming from planting to harvesting.

STEEP Impact Executive Summary (EB2035Eb)
Abstract: Both traditional and electronic, have been a critical component of the steep effort, resulting in farmers’ rapid adoption of new practices based on research results.

Water Management & Irrigation

Practical Use of Soil Moisture Sensors & Their Data for Irrigation Scheduling (FS083E)
Abstract: Good management of irrigation water will increase crop yields, improve crop quality, conserve water, save energy, decrease fertilizer requirements, and reduce nonpoint source pollution. All of these are positive benefits and help contribute to profitable crop production.

Predicting Wheat Grain Yields Based on Available Water (EM049E)
Abstract: Wheat is the principal crop grown in many Mediterranean-like climate zones around the world, including the 8.3 million acre dryland cropping region of the U. S. Inland Pacific Northwest. Farmers in the low and intermediate precipitation areas of this region know that planting spring wheat will help them control winter-annual grass weeds and that spring wheat production can be profitable with adequate available water. However, farmers are often reluctant to plant spring wheat because grain yields are highly variable compared to winter wheat after summer fallow.

Washington State University