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January 2011 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.

Are There Differences In Nitrogen Inhibitors?

Jan 31, 2011

Yes, there are differences in nitrogen inhibitors, and you want to make the correct choice based on your field conditions. If you don’t use the right inhibitor in the right application, it can lead to nitrogen loss that you weren’t expecting. There are different types of inhibitors, which are based on the type of nitrogen loss they help control: volatility, leaching and denitrification. One type of inhibitor helps with volatility, which is the loss of ammonia nitrogen from the loss of urea. This form of nitrogen comes as an application of granular urea applied to the surface and liquid urea including 28% and 32%, which are half urea.  When the urease enzyme breaks down the urea, ammonia can be created, and if it’s not incorporated into the soil by tillage or rain, in two to three days, 20% to 30% of the urea can be lost. So you need an urease inhibitor to stop volatility, which is designed to protect surface-applied nitrogen. The other type of inhibitor helps control loss of applied ammonium sources of nitrogen. When nitrogen is converted into nitrates from an ammonium source, it can be leached away or denitrified. In this process, nitrogen goes from ammonium to nitrite to nitrate.  We need to stop bacteria from driving that process, and these types of inhibitors stop nitrification. The top lesson to apply when using inhibitors is to know what process of nitrogen loss you’re trying to stop. Learn more in episode 11 of Corn College TV.


This blog is provided as an interactive way for you to have your questions answered by our Farm Journal Agronomists. E-mail your nitrogen, soil fertility, soil density, planter set-up, scouting, and other questions to:

How Much Sulfur Should I Apply To Corn-on-Corn?

Jan 25, 2011

Question: How much sulfur should I apply to corn-on-corn? What is the best way to broadcast it, can I put it in with my preplant 28%/harnass?

Answer: A 200 bu/A corn crop has a sulfur (S) uptake of about 30 lb/A S and an actual removal rate of around 15 lb/A S. In recent years there has been a greater yield response to applying sulfur for corn production. Soil fertility specialists believe the sulfur response is increasing because of the reduction of sulfur atmospheric deposition (cleaner air, less pollution). Also, fertilizer sources are cleaner (less incidental sulfur in them) and there are fewer manure applications. Broadcast applications of sulfur are common. There are several sources of dry fertilizer products that contain sulfur: ammonium sulfate (AMS 21-0-0-24S), K-Mag or sulpomag (0-0-22-11Mg-22S), elemental sulfur, some MicroEssentials products, and several others. Liquid sources of sulfur can also be used. Liquid AMS (8-0-0-9S) contains 9 lbs of S for every 10 gallons applied. Liquid ammonium thio-sulfate or ATS (12-0-0-26S) contains nearly 29 lbs S for every 10 gallons applied. Application rates are often between 15 lb and 30 lb S/ac. Select a product that best fits your other fertility program needs. For example, in corn-on-corn we are also trying to break down residue with a broadcast application of ammonium nitrogen (AMS, for example). If you apply 150 lbs of AMS per acre you would get 30 lbs of ammonium N per acre to help with residue breakdown and would be getting 36 lbs S per acre. Refer to your herbicide label for compatibility issues when adding a liquid sulfur product to your weed-control program.
This blog is provided as an interactive way for you to have your questions answered by our Farm Journal Agronomists. E-mail your nitrogen, soil fertility, soil density, planter set-up, scouting, and other questions to:

How Do I Access Available Phosphorus

Jan 21, 2011

Question: I have soil tests showing very low levels of phosphorus using the bray 1 method and very high levels with the bray 2 method. Will the phosphorus become available later? What do I need to do to free it up?                                   

Answer: P1 measures phosphorus that is readily available to plants. P2 measures readily available phosphorus plus a part of the active reserve phosphorus in the soil. A P1:P2 ratio less than 0.5 could indicate tie-up issues. It could also be due to a history of rock phosphate use, which is not very plant available. The high P2 will not become readily available for plant uptake. There are several things you can do to reduce the negative effect of a P1:P2 ratio of less than 0.5. Apply phosphorus in the spring just prior to crop use instead of making fall applications. Consider fertilizing every year instead of every two years. A banded application of phosphorus would also be preferred. In addition, there most likely would be a high response to starter fertilizer for corn. Also, the response to sulfur and zinc use should be good. 

Will My Upgraded Planter Improve Yield Results?

Jan 18, 2011

Question: I am looking to upgrade my planter. My average corn yield is 175 bu/A. How much yield gain can I expect from better seed placement?

Answer: Corn yields are based on the number of ears per acre and the size of the ears (number of rows around, kernels long and kernel depth).  A 1,000 ears per acre is equal to 5 to 7 bu/A.  The best way to determine what you can expect for a yield increase is to determine your current ear count and the reasons for ear count losses.  For example, if you currently have 30,000 plants per acre but your ear count is only 27,000 ears per acre you have the potential to increase yields 15 to 21 bu/A by increasing your ear count to 30,000 ears per acre (on the 30,000 plants per acre in the field).  Not all ear count loss is due to plant spacing.  With a picket fence stand (uniform spacing), you could still be losing ear count due to uneven emergence.  However, a picket fence stand will help increase ear count.  Keep in mind that a new planter will also need to be set up properly in order to achieve a picket fence stand and increased ear count. If you can, consider attending one of the Farm Journal Planter Clinics this winter where we’ll be covering this particular topic.
Check here for more information on upcoming clinics.


Is There Any Benefit To Applying Fungicide To V5 Corn?

Jan 08, 2011

Question: Several of my neighbors applied fungicide to their corn after tassel last year. They didn't find that it raised yield, but it did raise moisture levels. Is this a common outcome of using fungicides? Is there any response benefit to spraying fungicide on corn at V5? 

Answer: A common effect from corn fungicide is a healthier, greener plant. This stay green and plant-health effect result in high moisture levels early in the harvest season, and this is a common outcome. The yield response will vary depending on several things: genetics/hybrid, crop rotation and environment. For example, some corn hybrids have more natural defensive characteristics and don’t respond as much to corn fungicides. We have plot data that shows anywhere from a zero response to greater than a 50 bu/a response. Again, the genetics and environment play a big role. Corn-on-corn rotations typically have greater disease issues than rotated corn following soybeans. Remember that the environment each year will be different, whether it’s hot and dry or cool and humid, etc. 2010 was the first year we evaluated the V5 fungicide application on irrigated plots in southern Michigan. The response to applying fungicide on irrigated V5 corn ranged from a low of 1.0 bu/a to a high of 11.8 b/ac increase, again depending on hybrid and crop rotation. The same irrigated plots also evaluated R1 or post-tassel applications, which increased yields from 5.0 to 12.4 bu/a. If feasible, consider setting up some trials on your own farm to evaluate fungicide applications on several of your hybrids. 
Check out this information to evaluate fungicide use in corn.
This blog is provided as an interactive way for you to have your questions answered by our Farm Journal Agronomists. E-mail your nitrogen, soil fertility, soil density, planter set-up, scouting, and other questions to:

Do Soybeans Need Potash As Much As Corn?

Jan 03, 2011

Question: I have been reading several Agweb blogs on fertilizer recommendations for corn versus soybeans. I was wondering if the potash we put out in 2010 on soybeans was really doing any good, or if it was just as well to put out a little more to the corn land the previous year since we have a corn-soybean-corn rotation? If the beans don't really benefit from applied potassium (K), then what are my benefits to applying K before I plant soybeans if the soil levels are adequate? Would K be available if I applied it to the bean land in the fall of the previous year after we cut the corn?

 Answer: Soybeans are big users of potash. A 60 bu/A soybean crop removes 87 lbs K20 which is equal to 145 lbs potash (0-0-60) per acre. A 200 bu/A corn crop removes 58 lbs K20 which is equal to 97 lbs of potash. So yes, soybeans need potash as well as does corn. Depending on soil type and soil test levels, some growers choose to apply potash one time for both crops. In this yield example, you would need to apply 242 lbs of potash just for crop removal on soybeans and corn. A soil test will tell you what levels you have in the soil. If your soil-test levels are medium or below, you may want to consider fertilizing for each crop each year (removal rates + soil test build levels). If you have high soil test levels you may be able to fertilizer two crops in one year. Sandy and sandy loam soils may not be able to hold large amounts of potash, so consider every year spreads on these soil types as well.   Also, consider the economic aspects as well. Potash price and grain prices have fluctuated greatly over the last several years. Fall applications of potash can work well. More information on this topic is provided at the following link.
This blog is provided as an interactive way for you to have your questions answered by our Farm Journal Agronomists. E-mail your nitrogen, soil fertility, soil density, planter set-up, scouting, and other questions to:
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