Farmers' Ability to Interpret Soil Tests Increases both Profits and Water Quality

Agriculture and Natural Resources Extension
Iowa State University

Title of Success Story

Farmers’ Ability to Interpret Soil Tests Increases both Profits and Water Quality

Public Value (now or future)
(Impact:  Who benefits beyond participants and how?  What conditions changed?)

Phosphorus (P) and Potassium (K) fertilizer costs for crop production have doubled in the last 5 years and are 3-fold higher than what they were 10 years ago.  To maintain sustainable farm operations, plus their value-added contributions to the economy, it is more imperative than ever for farmers to understand soil fertility management.  In addition, a leading cause of surface water impairment is high Phosphorous (P) levels causing eutrophication.  The consequences of eutrophication include algal blooms, low levels of dissolved oxygen, fish kills, turbidity, and shifts in plant and animal populations in surface waters.  Avoiding over application of P fertilizer in crop production reduces P movement into surface waters, lessening any water impairments.

(Why is it important to address this issue with education?  What are the desired changes?)

Soil tests are an important guide for applying proper levels of fertilizer for crop production, however, most farmers do not understand how to read and interpret a soil test.  Most rely on the private soil testing lab recommendations, with many labs recommending higher fertilizer recommendations then what Iowa State University recommends; or agricultural provider recommendations which again are often higher than what Iowa State University recommends.  The main goal of this program is to sufficiently educate farmers to be able to read and interpret their own soil tests, or at a minimum at least be able to recognize when third party recommends are too high.

(Outputs: activities, numbers reached, publications, products)

In the winter of 2010, the ISU Extension Agronomist in northeast Iowa initiated a pilot project with farmers, conducting a few sessions on how to read and interpret soil test reports.  Each year since, a few more meetings are conducted.  The combination of increasing public concerns with water quality and the rapid increase in fertilizer costs has spurred farmer interest in obtaining a better understanding of nutrient management on their farms.  In 2011, 5 more sessions were conducted with a total of 57 farmers.  Farmer’s own soil tests were used to explain how to read them, what the labs recommended, what ISU recommends, and how the farmer can maximize their rate of return to fertilizer applied.

RESULTS (Outcomes:  specific changes that occurred in Learning, Actions, Conditions; how outcomes were measured)

Pre-meeting surveys found that only 7% of attendees thought they had an adequate understanding of how to read soil tests and make fertilizer recommendations. Post-meeting surveys brought that level up to 68%, with the remaining 32% being pleased with the information presented, but still wanted to follow their fertilizer suppliers’ programs.  The 55 attendees that filled out the survey represented approximately 27,000 acres of cropland.  With the knowledge gained they estimated that they would be able to reduce P fertilizer applications by an average of 32%, although K fertilizer applications would actually increase by about 18%.  Overall, this program reduced farmer costs by an average of $12 per acre, for a total benefit with this group of about $324,000.

Desired Changes

The program continues to succeed with a win-win situation for farm income and potential improvements in water quality, both benefiting local communities.  Intentions are to continue this program for many more years.  Nearly 200 farmers have participated in this program during the last 5 years with an average adoption rate by farmers of 74% and a total economic benefit of about $1 million.  Unfortunately, there is no way to streamline this program.  Its success is largely dependent on some hands-on one-on-one activity which greatly limits the number of participants per season.

Extension Lead(s)
(name, position, counties served, contact information)

Brian Lang, Extension Field Agronomist, Allamakee, Clayton, Fayette, Howard and Winneshiek, Winneshiek County Extension, 325 Washington St., Decorah, IA 52101, Office 563-382-2949, Cell 563-387-7058.

Your Position

­­­­­__x__Field                                        _____Campus                         _____Both

POW # and Team

 ­­­­­__x__100 Corn and Soybean Production and Protection
­­­­­_____ 110 Dairy
­­­­­_____ 120 Farm and Business Management
­­­­­_____ 130 Horticulture: Commercial and Consumer
­­­­­_____ 140 Iowa Beef Center
­­­­­_____ 150 Iowa Pork Industry Center
­­­­­__x__ 160 Natural Resources and Stewardship

ANR Priority (select all that apply)

­­­­­__x__Global Food Security and Hunger
­­­­­_____Regional Food Systems
­­­­­__x__Natural Resources & Environmental Stewardship
­­­­­_____Food Safety
­­­­­_____Sustainable Energy – Biofuels & Biobased Products
­­­­­_____Climate Change

Knowledge Areas: (USDA categories)


Continuing Story

_____No                __x__  Yes (If continuing, what story?)
Previous story title:  “Farmers’ Knowledge of Soil Tests Increases both Profits and Water Quality”

Major Partners or Collaborators


Where story took place
(Region, campus, multi-regional)

Allamakee, Fayette, Clayton, Delaware and Winneshiek counties in Northeast Iowa.

Fiscal Year


Multi-state or Integrated (Ext + Research)


Funding Source

Northeast ISU Extension Agronomist Program


Soil fertility, Phosphorus, Water quality


Page last updated: March 22, 2012
Page maintained by Julie Honeick,