Soil sampling key to fertilizer efficiency

by Doug Toburen

March 18, 2008 09:52 am

— Whether trying to grow the best forage possible or record-yielding corn or beans, every producer needs the same thing—soil fertility.
And, the only way to know what your soil needs is to do what Extension specialists have been telling producers to do every meeting they ever speak at.
“Everyone needs to soil sample,” Jay Chism, University of Missouri Extension agronomy specialist, says.
According to Chism, soil sampling is one of the easiest, most important things producers can do.
“Soil sampling, whether in pastures or crop systems is the only way you can determine the nutrient status of fields,” he explains.
Information obtained from soil samples can then be used to aid in building the nutrients back up if they need to be.
“Soil samples can tell you a number of different things but mainly we want to find out the soil pH value as well as levels of phosphorus, potassium, calcium, magnesium, zinc and manganese,” he explains.
After the nutrient levels are determined the sample will offer recommendations for the plants that are going to be grown.
“With fertilizer prices as high as they are now a $15 soil sample is pretty cheap,” he says.
Some of the equipment needed for soil testing includes:
•A soil sampler or probe
The probe or coring devices can be borrowed from your area Extension office, according to Chism.
•A clean plastic bucket
•A small box or bag
“It is really important that whatever you use to collect your sample in is clean,” Chism explains. “If it would have any type of residue in it it will really throw off your results.”
Chism recommends taking soil samples in cropping situations in the fall.
“It is important to do the testing when the cropland is idle. Then you are prepared for fertilizer in the spring,” he says.
For pastures, Chism recommends soil sampling in the spring.
“But, it is never too late to soil sample,”Chism says.
According to him, getting the information is the key.
“You may not be able to do anything to change the fertility in time for a crop or for forage yield but you will know where you stand,” he says.
In order to get an accurate soil sample Chism recommends breaking fields into areas not exceeding 20 acres.
“You need take at least 15 to 20 samples or cores in that 20 acre area,” he explains. “The cores represent the ground so take your time and do a good job.”
In a pasture situation, Chism recommends not sampling around feeding areas or under trees.
“The nutrient levels will be a lot different where the animals typically stand around and eat and drink,” he explains.
According to Chism, manure piles and urine spots will have elevated nutrient levels.
“After pulling the cores they all need to be thoroughly mixed,” he says.
The recommendation is to put about 1.5 cups of the mixture into a soil sample box and that is what will be sent off.
When getting the results back, Chism says they can be a little intimidating.
“When looking at the results, at the top of the page is what you have in your soil and at the bottom of the page is what you need in your soil,” he explains.
Chism says if the results are intimidating take them to your local Extension office and let them help you go over what they say.
“If you bring them in and we see the results we can then determine exactly what to do as far as fertilizing is concerned,” he says.
This, according to Chism, makes just as much sense as taking the soil sample in the first place.
“There is no reason to apply fertilizer that you don’t need,” he says. “Figuring out exactly what you need to apply is just another way of saving money.”
Chism says in a lot of cases, when pastures are concerned, fertilizer is applied that isn’t going to be used adequately.
“If you limit your nitrogen application in the spring then you don’t have to worry about wasting grass or nitrogen,” he explains.
Chism repeated a quote he once heard that he thinks sums up fertilization pretty clearly.
“A row crop operator would not apply nitrogen to his corn crop and then not harvest it, so why would we do it on grass?”
Soil sampling is something producers definitely need to do in order to keep their soil nutrient levels where they need to be.
However they don’t have to be done every year.
“Soil sample every three to four years, but do a good job when you do it,” Chism explains.
According to him, the results of the sample, are designed to help build the soil up over an allotted time, usually eight years.
“Soil sampling is an inexpensive way to find out ways of saving yourself more money in the end,” Chism concludes.

Copyright © 1999-2008 cnhi, inc.