This spring has brought us cool weather, wet/dry spells, and now potassium deficiencies. We have mainly been hearing about corn and soybean potassium deficiencies on the Macon Ridge. However, this does not mean that they are not showing up throughout our alluvial soils.
Potassium is very important for water use efficiency in crops. This means that irrigation on the fields showing deficiency symptoms will need to be managed diligently. There are a few reasons that symptoms could be showing up: 1) Dry soils, 2) Compaction, 3) Low soil test K, and 4) Reduced early-season root growth. Potassium cannot be taken up efficiently in the soil without the presence of water, which can cause a deficiency to appear even if adequate potassium was applied to the soil. Compaction can also cause a potassium deficiency to appear because the roots are not able to find enough potassium in the un-compacted soil. If a soil sample is collected and the results show that the soil is low in potassium, then the recommended amount of potassium should be applied after the current cropping season. Lastly, due to some of the weather that was experienced this spring, there could have been reduced root growth in spots affected by standing water or cold weather. This reduced root growth creates a smaller zone of potassium available to the plants.
Deficiency symptoms in corn and soybeans are denoted by edge of leaf necrosis.
Currently, the LSU AgCenter soil fertility research group does not currently have data on the yield benefits of foliar-applied potassium. Furthermore, research throughout the region has shown little to no yield benefits for foliar potassium applications. Additionally, if yield benefits are seen, there is a chance that the cost of application will often outweigh any yield benefit. Therefore, caution should be used prior to any in-season foliar potassium application. If a foliar K is going to be added, follow the label carefully due to the chance of leaf burn.
If you have any questions, please contact:
Beatrix Haggard, Northeast Region Soil Specialist: (318) 498-2967
Josh Lofton, Agronomist: (318) 498-1934
Dan Fromme, Corn and Cotton Specialist: (318)880-8079
We have reached a point in society where most of the population is talking about information overload. For some relief, this fact sheet provides information and background on the SoilWeb phone application. The phone used for this was an iPhone® 5s; the author did not have an AndroidTM to test.
- Great app for general knowledge of what soil series are found in your fields or property.
- Beneficial for understanding any major soil features that could be problematic in your fields – clay pans, natric horizons (salt), fragipans, etc.
- Should NOT be used for determining soil pH and organic matter percentage.
- If a field has been precision-leveled, caution should be taken for soil textures.
SoilWeb is a great starting point for determining soil series located on your farm. But as with any Web application, there are limitations. First, let us look at how we use the app.
- There is an information button in the top right-hand corner of the application. When you click here, the accuracy threshold, which is in the lower left-hand corner can be adjusted. This is letting you know how accurate your GPS is on your phone. This will depend on if you are under any structures or dense vegetation and your cell phone coverage. The smaller the number, the better. At best you will typically be around 10-20 m.
- Once the accuracy has been set, then you can select the Get My Location button at the top of the application screen. The application will then display a picture representation of the soil series, which accounts for color and horizon depths.
- You can then click on the soil series name that is blue, and it will take you to a screen displaying data concerning the soil series taxonomic description and lab data from the original data collected for the series. This is the point when we start to look at the limitations of this application for production agriculture.
- Basic understanding of texture changes throughout a field.
- Knowledge of some limiting horizons that could be present in a soil. (If you look at the last screen shot and notice how the percent clay increases 10%, this increase is the reason why Gigger soils have issues forming a plow pan due to the clay pan already present from soil formation.)
- The application is also showing what percentage of other soils might be found. There is an 85% that can be seen after the soil series name. This is basically saying that in normal situations that of a 10-acre field, 8.5 acres would be Gigger and 1.5 acres would be another geographically associated soil (i.e. a soil typically found nearby).
- Soil series descriptions provide information collected when the soil was originally described or whenever the series was updated. In the case of the Gigger, the chemical data is from 1992, which is more recent than when the soil was originally mapped in 1979.
- Management practices can change properties in the soil.
- pH has likely been altered by lime applications. Therefore, depending on the value found on the phone app, would not be recommended.
- Texture would be affected if a field was land-leveled. This is especially true for any soils that are Alfisols (Gigger, Calhoun, Crowley, etc).
- Organic matter is heavily influenced by management practices and will typically be different than what is shown on this phone app.
The disadvantages are listed not to discourage the use of the application but to know its limitations. The application is a great tool when you start trying to figure out what might be happening at deeper depths in the field that could cause problems or be beneficial.
If you have any questions concerning the use of this phone app or any of the data it provides, please contact:
Beatrix Haggard – (318) 498-2967 – firstname.lastname@example.org
- Developed by Dylan E. Beaudette and Anthony T. O’Geen of the Soil Resource Laboratory at the University of California-Davis
- Data sourced from USDA-NRCS Soil Survey data (SSURGO)