WSU CAHNRS

CAHNRS and WSU Extension

Wheat and Small Grains

Soil Acidification in the Inland Pacific Northwest

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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. The WSU Extension team is developing an interrelated series of fact sheets that introduce the fundamentals of soil pH and acidification. These fact sheets will be published as soon as they’re available.

Soil pH Video Series

Published Fact Sheets

Soil Acidity Impacts Beneficial Soil Microorganisms (FS247E) New

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.

Acid Soils: How Do They Interact with Root Diseases? (FS195E) New

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.

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.

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.

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.

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.

Agricultural Lime and 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.

In Progress Fact Sheets

  • Regional Map and Susceptibility Risk
  • Soil pH and Nutrition
  • Introduction to Soil pH and Microbes
  • Introduction to Soil pH and Pathogens

Additional Resources

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