May 13, 2024

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Fast Facts

• Surveys indicated no kudzu bugs in Arkansas in 2012
• “It’s only a matter of time before the bug finds its way to Arkansas.” – Gus Lorenz
• Can cause significant yield loss in soybeans

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By Brittaney Mann
U of A System Division of Agriculture

Fast facts

• Models developed to predict more information from routine soil testing
• Prediction models can be optimized with new soil samples for recalibration
• Tool could help farmers make crop management and fertilizer decisions faster

(945 words)

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FAYETTEVILLE, Ark. — Farmers in a time crunch have a new, speedier option for analyzing
the texture and organic matter content of the soil on their fields.

Gerson Drescher, assistant professor of soil fertility for the Arkansas Agricultural
Experiment Station, led a study to create prediction models for these key soil health
indicators based on standard tests already being used to analyze soil samples.

“We want to provide people with the maximal amount of information that they can get
from samples they are already submitting without the additional cost and time of analysis,”
Drescher said.

The newly developed prediction model can help add information about the soil’s properties,
which can guide fertilization, irrigation, and herbicide decisions, Drescher added.
Standard soil testing evaluates plant-available nutrient content and soil pH. However,
these properties are also affected by soil texture and organic matter in the soil,
which require additional expensive and time-consuming tests.

“The traditional methods used for both soil texture analysis and organic matter determination
are relatively time-consuming and, generally, producers are interested in a quick
turnaround when they submit a sample so they can make their nutrient management decisions
and make plans for the amount of fertilizer they need to apply,” Drescher said.

The research article titled “Soil texture and organic matter prediction using Mehlich-3 extractable nutrients” was published in the Agrosystems, Geosciences and Environment journal earlier this
year. Co-authors include Trent Roberts, professor and interim department head of crop,
soil, and environmental sciences; Nathan Slaton, associate vice president for agriculture
and assistant director of the Arkansas Agricultural Experiment Station; and Alden
D. Smartt, program associate in the crop, soil, and environmental sciences department.

The models are accurate for predicting the most common soils used in crop production
in Arkansas. However, the models are less accurate for sandy soils and soils with
very high organic matter, he said. The state’s common agricultural soils are fine
and medium categories, which include silt loams and silty clays.

The experiment station is the research arm of the University of Arkansas System Division
of Agriculture.

What’s in the soil?

The time a soil test takes depends on the information requested, Drescher said. Each
additional test on top of the routine soil analyses can add days or weeks to the total
testing time. Drescher’s prediction model for organic matter and soil texture cuts
those additional tests and can reduce turnaround time by at least half.

Soil samples sent to a lab for analysis are dried, ground and sieved for uniformity
to ensure the precision and accuracy of the analysis. In Arkansas, the experiment
station’s Marianna Soil Test Laboratory provides routine soil testing services, which
are free for Arkansas residents.

Routine soil testing calls for measurement of soil pH and the Mehlich-3 soil analysis,
which extracts and identifies the available nutrients in soil samples.

The two properties predicted by Drescher’s model — soil organic matter and soil texture
— require more extensive tests, Drescher said. Testing for soil organic matter is
determined by a method known as “loss on ignition,” which requires weighing samples,
subjecting them to high temperatures to combust the organic matter, and reweighing
the sample to measure weight loss.

Soil texture is measured using a device called a hydrometer, which determines soil
particle sizes, Drescher said. Understanding soil texture is an important aspect of
crop production because it dictates the ability of the soil to hold nutrients, the
rates of herbicide or fertilizer application, irrigation scheduling and soil sampling
protocols.

These tests help producers understand the health of their soil and guide fertilizer
applications and crop management decisions, Drescher said.

Better than a map

Maps, such as the Web Soil Survey offered by the U.S. Department of Agriculture’s Natural Resources Conservation Service,
can be used to provide information on soil type in different areas, but the resolution
of the map might not indicate changes in soil texture in a small amount of space within
a field, Drescher said. The new prediction model is more precise than a map because
it uses field-specific information.

The Marianna Soil Test Lab already provided soil texture predictions, but this new
research fine-tuned the model to make the estimation more accurate, Drescher said.

The Marianna Soil Test Lab analyzes about 200,000 soil samples every year. Routine
soil tests for nutrients and pH are free for Arkansas residents through the support
of Fertilizer Tonnage Fees. Non-routine tests of soil texture or organic matter analysis,
however, have a fee and take additional time for analysis.

The prediction models

Drescher used Mehlich-3 nutrient and soil pH data from soil samples submitted to the
Marianna Soil Test Lab to calibrate and validate the prediction models.

For the clay and sand prediction models, he used data from 409 soil samples, representing
different production systems and soils throughout Arkansas. About half were from row
crop fields and the other half from forage systems.

When developing the model for soil organic matter, he used data from 604 samples from
row crop fields and 415 samples from forage production areas.

After the calibration, Drescher validated the models by using 103 different soil samples
from row crop, forage, vegetable, fruit, turfgrass and ornamental production areas.

Over time, the models can be evaluated for accuracy and optimized with new soil samples
to improve soil texture and organic matter prediction. Drescher said the models could
be used in areas outside of Arkansas if they have similar soils.

Drescher said he appreciated the work performed by the Marianna Soil Test Laboratory personnel who assisted with soil analysis and provided the data for the models’ calibration.

The research was supported through Fertilizer Tonnage Fees administered by the Arkansas
Soil Test Review Board and experiment station funding related to Hatch Projects 2570
and 2800.

To learn more about Division of Agriculture research, visit the Arkansas Agricultural
Experiment Station website: https://aaes.uada.edu/. Follow us on Twitter at @ArkAgResearch. To learn more about the Division of Agriculture, visit https://uada.edu/. Follow us on Twitter at @AgInArk.

About the Division of Agriculture

The University of Arkansas System Division of Agriculture’s mission is to strengthen
agriculture, communities, and families by connecting trusted research to the adoption
of best practices.

 Through the Agricultural Experiment Station and the Cooperative Extension Service,
the Division of Agriculture conducts research and extension work within the nation’s
historic land grant education system.

The Division of Agriculture is one of 20 entities within the University of Arkansas
System. It has offices in all 75 counties in Arkansas and faculty on five system campuses.

The University of Arkansas System Division of Agriculture offers all its Extension
and Research programs and services without regard to race, color, sex, gender identity,
sexual orientation, national origin, religion, age, disability, marital or veteran
status, genetic information, or any other legally protected status, and is an Affirmative
Action/Equal Opportunity Employer.

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Media Contact: Nick Kordsmeier
U of A System Division of Agriculture
Arkansas Agricultural Experiment Station
[email protected]         
479-575-6368

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By Mary Hightower
The Cooperative Extension Service
U of A System Division of Agriculture

Media Contact: Mary Hightower
Dir. of Communication Services
U of A Division of Agriculture
Cooperative Extension Service
(501) 671-2126
[email protected]

Related Links

• Arkansas Farm and Ranch
• Arkansas Crops

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