Introducing Extension Spotlight

Corn Belt

Potassium Use in Ohio Agriculture

Ohio State University Extension

Potassium (K) is a primary macronutrient essential for crop growth. In agriculture, K is supplied by soil-derived potassium, supplemented by nutrient applications from organic sources—primarily livestock manure—and by commercial fertilizers manufactured from mined deposits of potassium chloride (KCl) originating from ancient seabeds.

Potassium uptake by plants occurs primarily through diffusion, a process driven by nutrient concentration gradients near the root surface. Soil testing measures the soil’s ability to supply K. Fertilizer recommendations are based on correlations between soil test levels and the amount of added K required to achieve a yield response in a given crop. Tracking soil-test trends helps guide long-term nutrient management to support increasing crop yields.

This factsheet summarizes trends in the use of K sources applied for Ohio crop production, the mass balance of nutrient additions and removal at a state and regional scale, and state soil test K trends.

West

Effective Soil Sampling for Sustainable Crop Production

University of Arizona Cooperative Extension

Soil testing is essential for successful crop production. Using a soil test report, a producer can determine the best way to treat and manage their soils for sustainable crop production. Traditional soil testing includes the assessment of fundamental soil chemical parameters like pH (acidity or alkalinity), electrical conductivity (EC, also known as soluble salts), cation exchange capacity (CEC), and available or extractable essential soil nutrients; essential soil nutrients include both macronutrients (nitrogen, phosphorus, potassium) and micronutrients (iron, zinc, manganese). Often, soil physical and biological properties are measured for specific purposes; for example, soil health assessments include measurements of various soil physical, chemical, and biological properties. These soil properties, which are crucial for plant growth and optimal crop production, are measured with the goal of determining the amendments (fertilizers, gypsum, organic manure, lime, etc.) that should be applied to the soil to achieve increased crop productivity and overall food security. 

This publication provides practical guidance on collecting representative soil samples, selecting appropriate testing strategies, and interpreting results to support nutrient management decisions, improve soil health assessments, and maximize the value of soil testing investments.

Pacific Northwest

A Practical Guide to Soil Health Indicators for Monitoring Shifts in Soil Organic Matter

Washington State University Extension

Improving and maintaining soil health can have a wide range of economic benefits, including reduced input costs and improved crop growth, quality, and yield. Soil organic matter (SOM) is a commonly used metric for assessing soil health but can be slow to respond to management changes, taking years or even a decade for measurable changes to occur. Soil health indicators that can detect shifts in microbial activity, carbon (C) cycling, and nutrient cycling are more responsive than SOM and can help producers see if they are moving in the right direction.

This publication provides an overview of soil health indicators that are related to shifts in SOM but can respond more rapidly to management changes. This practical guide will help producers navigate the names of tests, their availability in the Pacific Northwest, and the relevance of each test to production systems.