UACES Facebook Don't Guess, Soil Test - February 2011

Don't Guess, Soil Test - February 2011

You Tube - Link to watch video on You Tube.Link to transcript

 

Audio/Video  Script:

[Title Slide - Don't Guess, Soil Test. Your Arkansas Soybean Podcast, University of Arkansas Division of Agriculture, Arkansas Soybean Promotion Board.]

[Dr. Leo Espinoza - Extension Soil Scientist] With the high price of fertilizers, especially potassium, it is important that we test the soil for this and other nutrients. Everything starts with taking a good soil sample.

[Picture showing a soil sample tool - soil sample to 4 inches deep in soybean.] University of Arkansas recommendations call for a soil sample four inches deep for soybeans. A shallow soil sample may give an abnormally high potassium reading, as the nutrients tend to accumulate in the top few inches, especially under reduced tillage systems. [Bar chart showing stratification of K in a field under reduced tillage.]

[Picture of Dr. Espinoza in a soybean field. Slide - 1. Sample sent to lab; 2. Report shows - potassium, yield potential]  The sample is sent to the lab, the soil test report will show not only the concentration of potassium but also a classification based on yield potential. In the example provided, the concentration of potassium is ninety-two P-P-M or parts per million. Such level is classified as medium, phosphorus on the same report is classified as low.

Soil Test Report
Nutrient Availability Index

Nutrient Concentration Soil Test Level
(Mehlich 3)
ppm lb/acre
P 17 34 Low
K 92 184 Medium
Ca 876 1752 --
Mg 91 182 --
SO4*S 12 24 --
Zn 1.4 2.8 Very Low
Fe 243 486 --
Mn 85 170 --
Cu 0.7 1.4 --
B 0.1 0.2 --
NO3*N     --

But what do we mean by medium or low? The table shows the interpretation of soil test levels for potassium.

Interpretation of Soil Test Levels for Potassium

K Level Classification Yield Potential
ppm    
<61 Very Low <65%
61-90 Low 65-85%
91-130 Medium 85-100%
131-175 Optimum 100%
>175 Above Optimum 100%

A potassium level of medium means that eighty-five to a hundred percent of the yield potential will be obtained if no fertilizer is applied. A very low level means that less than sixty five percent of yield potential will be obtained if no potassium fertilizer is applied.

Next, fertilizer recommendations. The table shows the potassium recommendations according to soil test level for full-season soybeans.

University of Arkansas' Potassium Recommendations
for Full Season Soybeans

K Level Classification Yield Potential
ppm   Lb K2O/acre
<61 Very Low 160
61-90 Low 120
91-130 Medium 60
131-175 Optimum 50
>175 Above Optimum 0

As much as a hundred and sixty pounds per acre are recommended if the level is classified as very low. A split application is recommended for this rate as it may aggravate soil problems in affected areas in the state.

[Dr. Leo Espinoza] So don’t guess, soil test.

[Narrator] Your Arkansas Soybean Podcast is a production of the University of Arkansas Division of Agriculture and was funded in part by the Arkansas Soybean Promotion Board. For more information about soybean farming in Arkansas, contact your local county Extension office.

[Title slide - For more information contact your local county Extension office. Your Arkansas Soybean Podcast, University of Arkansas Division of Agriculture, Arkansas Soybean Promotion Board]

 

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