MU test revisions aim to meet crop needs

Good news for patient crop farmers: Soil test reports and fertilizer recommendations from the University of Missouri soil lab will be updated by 2012.

John Lory, MU Extension nutrient management specialist, told of planned changes to those attending the annual MU Crop Management Conference in early December.

“We are just starting the change, but we want your ideas,” Lory told an audience of crop advisers, MU Extension specialists and farmers.

“You are the ones we must convince to use the new recommendations. A healthy dialogue will help. The soil-test update is needed as crops change, yields go up and we learn more from the research. It is time for a change.”

Basically, soil-test recommendations do two things: First, bring the soil up to recommended levels. Second, they give information on replacing fertility removed by the crop. The first requires chemical analysis of the submitted soil sample. The second is calculated based on crop information supplied by the farmer.

Key Points

MU soil lab plans to update soil test reports by 2012.

An update is needed as crops change and agronomists learn more.

Precision agriculture is affecting soil test recommendations.


One needed change will come in calculating removal rates for different crops. For this, the latest reports from the National Research Council will be used to estimate the chemical makeup of crops being harvested. These are based on thousands of feed tests.

“This new information gives a more scientific basis for our recommendations,” Lory said. “In addition, the scientific literature on soil testing is being studied during the update.”

As part of the update, the analysis process will be simplified for easier use. The soil tests for forages will be simplified by grouping the forages. For example, the warm-season prairie grasses will be grouped together.

Another simplification planned is to condense the categories of soil nutrient levels. The “excessively high” category will be removed. A narrow “optimum” zone will replace the current “medium” zone. The “very low” category will be retained.

Dozens of variables affect actual fertility replacement values, Lory said. Clay soil, for example, will require more phosphorus, as there is much more surface area available than a sandy soil.

The overall aim is to improve soil fertility recommendations. “We are trying to hit the center of a very large dartboard,” he said.

More guidelines

On the grower’s side, that requires careful collection of soil samples. An accurate soil-test recommendation requires a realistic estimate of the yield goal entered on the soil test form. Trend corn yields have gone up 16 bushels in the last 10 years. Goals should match realistic yield potentials.

With modern precision agriculture, soil test recommendations will be changing. “The use of variable-rate fertilizer application, now possible with GPS guided equipment, allows tailoring fertilizer applications to those needed for a specific grid in a field,” Lory noted. “As we use more variable applications, fertility variability in fields will be reduced.”

For highest precision on replacement values, the nutrient content of the harvested crop can be measured. That can be matched to the soil test for a particular field.

“You may have some clients who will be doing this,” Lory told crop advisers. “Some of you already have large data sets of local conditions to work with.”

The revision process will first determine needed changes. Then computer software must be written “to spit out the fertilizer recommendations for the various soils,” Lory added.

“We’re still a couple of years away from implementing a new program,” Lory said. “The goal is to simplify and improve accuracy. We just wanted to give a heads-up on the changes coming.”

Soil test samples can be submitted to the state lab through local university Extension centers in each county. Regional Extension agronomists can assist with interpretations of results.

Source: MU Cooperative Media Group

This article published in the January, 2011 edition of MISSOURI RURALIST.

All rights reserved. Copyright Farm Progress Cos. 2011.