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May 2013 Archive for Ask an Agronomist

RSS By: Farm Journal Agronomists, Farm Journal

Have your agronomic questions answered by a Farm Journal agronomist. E-mail us directly at, and we’ll respond on this blog to provide an interactive dialogue.

Does Dry Soil Affect Soil pH Readings?

May 31, 2013

 Does Dry Soil Affect Soil pH Readings?

 Question: I recently read in a magazine article that the extreme dryness of the soil could affect the soil pH readings.  If this is true, are there any guidelines as to how much?  When I took the soil samples, the soil was absolutely dry with no significant rain in the last half of the growing season.

 Answer: Unfortunately there are no solid guidelines.  What we do here is because we have farmers on a two-year, soil-testing regiment I can look back over the past four or five soil testing application scenarios and have a good idea of where the soil pH should be for a particular field.  When I see a field that’s moved sharply acidic, then I look at where I would expect it to be and align it as such. If I had a brand-new field that I didn’t have any history on and I tested it during the drought or last fall and it was extremely acid, I’d apply only half of the limestone the test calls for and then I would make the field verify that it is that acid.  I’d do that by retesting the field in two years. I wouldn’t wait five or six years to verify it.  I’d also set up my budget now so I’m prepared to put the remaining half of the limestone application on the field – if the field does indeed verify it needs the remaining amount in two years.

What Causes Corn Leaves To Turn Purple? Soil pH is key to phosphorus availability because if soil pH is too high or too low, the nutrient will not be available to the plant.

Residual N Lowers pH Areas of Ohio and Indiana have enjoyed recent precipitation events that have gone a long way to pull those areas of the cornbelt out of drought.

Evaluate Soil pH and Buffer pH To Determine Lime Needs Water pH and buffer pH levels can indicate whether you have residual acidity that needs to be neutralized.

How can I use potash effectively in soybeans?

May 22, 2013

Question: I have two questions for you.  To get 100-bushel soybeans, Soybean College suggested approximately using 187 lbs/acre potash. I am interested in placing 200 lbs of 0-0-62 per acre and then 3 gallons of 0-0-21-13 liquid fertilizer at planting in 2x2 on 30-inch rows because I also have white mold issues. Do I need to be concerned about root injury? Also, in winter soybean meetings, the use of boron blended at 3.5lbs/acre in 0-0-62 potash was recommended by the Michigan soybean board if soil tests were below .8ppm (which mine are). Do you advise the same?


Answer: The first answer is you don’t need to be concerned, as burn injury shouldn’t be an issue. The second answer is tougher to give you as I don’t know which extraction method your Michigan resource used, and the soil test extraction for micronutrients can vary quite a bit. 

You’ll need to line up that .8 ppm recommendation with the extraction method used by your source, such as the Mehlich 3 extraction method, a DPTH extraction method or an ammonium acetate extraction method. I ran samples under three different extraction methods here to see what I came up with, using the DTPA, HCL and Mehlich 3 extraction methods to check for zinc. Under the DTPA I got a reading of .8; under the Mehlich 3 method I got 2.44; and under HCL I got a 1.8. With most laboratories when you get results back, they’ll say high, medium or low, and the results will be calibrated to the extraction.  So, if Michigan is using the HCL extraction method, then the 1.8 would be in a medium to high range; with a DTPA extraction you have a medium to low range; with Mehlich 3 it would be drastically low. I can’t tell you without knowing which extraction was used. Boron is one of those nutrients, that when I do a soil test, and the results are medium to low, the soil tests and tissue tests don’t always line up.  In a dry year, I almost always see a deficit in the tissue test. If I saw .8 here in my area, then I would make a boron application.  But remember if you over-apply boron, it can be toxic.  When we talk about a 3.5 pound-per-acre application of boron, that’s a pretty good-sized application. We talk a lot more about 1 pound to 1.5 pound application of boron here. Personally I wouldn’t do this large boron application without some tissue testing to follow it up.  There’s good data from Michigan, so check into that.  Now, we have done starter plots with potassium and phosphorus on our beans down here and looking at different starter rates, but we haven’t been very successful yet. I can’t tell you that putting 3 gallon of 0-0-21-13 liquid fertilizer down will be successful. I can tell you good potassium levels help the soybean plants hold blooms better and improve yields. You might do some plots to see if you can move the needle.  You also might be better off elevating your potash levels if potash availability is a concern. I want to emphasize that you need to analyze test results in a way that lines up with the laboratory results and how that information is provided


Red Potash vs. White Potash - What Is The Difference?

Both red and white MOP lend valuable potassium and chloride to the soil.


Micronutrient Deficiency Detection

Step-by-step guide to identifying micronutrients that your soils might lack.


How do I get rid of algae in my nurse tank?

May 16, 2013

How Do I Eliminate Algae in My Nurse Tank?

Question:  My nurse tank has turned green.  How do I get rid of the algae? 

Answer: There are several things you can consider.  The best option is to use copper sulfate. Mix 2 ounces of copper sulfate with 16 ounces of water, then apply 4 ounces of this mixture for every 1,000 gallons of water in the tank. That should take care of your algae problem pretty well. Another option is to use 1 cup of bleach for every 1,000 gallons of water in the tank. However, you need to be really careful with this option as the bleach can spike your pH and cause some antagonism with some pesticides.  Make sure you rinse the tank well if you decide to use bleach.  I’ve also heard that swimming pool tablets are effective to get rid of algae, but I don’t have any experience with this.  Your best bet is probably the copper sulfate.

Water Quality in the Spray Tank

Have you checked the water quality in your spray tank lately?


Water Quality in the Spray Tank

Have you checked the water quality in your spray tank lately? This is something farmers frequently neglect



Will My Planter Set-Up Close The Seed Trench?

May 03, 2013

Question: I am interested in putting a 1/4" x 15" spiked wheel opposite a rubber closing wheel in no-till.  I live in northwest Missouri and farm primarily hill ground with varying soil types.  I have a Kinze planter with double-heavy, duty-down pressure springs and uplift bags.  My question is will this combination work well together to properly close the trench and limit compaction?
Answer: It will do a pretty good job for you. I’d add a drag chain to help make sure that trench closes and cleans up the micro-environment. For instance, a drag chain can help clean up any divots in the soil.
Field agronomist Missy Bauer recommends last-minute tips to make sure your planter is ready for spring. Bauer suggests checking through almost every aspect of your planter. Some key areas to check out are the planter's row units, drive chains, row cleaners, wheels and frame.  
A poorly calibrated yield monitor can still match scale tickets, but it doesn’t mean it always will. Check out what Ken Ferrie, Farm Journal field agronomist, says about calibrating your yield monitor.

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