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January 2012 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.

What do you recommend about split nitrogen applications in winter wheat?

Jan 30, 2012

Question: What do you recommend about split nitrogen applications in winter wheat? 

Answer: Split-applied nitrogen is used by most of my clients who target yields of 100 bu. per acre and higher. Split applications minimize risk and push yields higher by allowing the grower to more accurately determine the total nitrogen requirement later in the season. When split applying spring nitrogen, the first application should be timed at or slightly prior to the green-up stage. Base your application rates on tiller densities and plant health. Apply higher rates to later planted, thinner fields and lower rates to early emerging, over-tillered fields. Then, apply the balance of spring nitrogen at about jointing. In some situations, wheat producers will apply between 20 lb. and 30 lb. per acre of late-season nitrogen just prior to flag leaf emergence if yield potential seems higher than initially fertilized for. While it means another pass, you will have added another 5 bu. to 10 bu. per acre. With current prices, that’s worth the trip.
It’s the small incremental changes you make in your management practices that really add up to greater yields at harvest.

Is glyphosate a good weed control option prior to planting wheat?

Jan 23, 2012

Question: I am planning on spraying a pre-emerge herbicide before planting hard red spring wheat. If I use glyphosate, how long should I wait before planting? Do I need to wait at all? I do not have any glyphosate-resistant weeds here (northern Minnesota). Is glyphosate the best choice for me? Grass control is my number one problem with broadleaf control a close second.

Answer: If you’re confident you don’t have any glyphosate-resistant weeds, a single, full-rate application of glyphosate prior to planting is still a sound, cheap weed control option. If you’re no-tilling, using a single disc seeder (which doesn’t disturb much of the soil surface), you could spray after seeding with a pre-emerge herbicide application. If you’re going to use a hoe-drill (that does disturb soil), then an application prior to seeding will be required, as some weeds may be partially covered with soil, reducing weed control. If you plan to use a hoe-drill, I would suggest you make the glyphosate application at least 24 hours prior to seeding to allow the product to be taken up by any weeds present and actively growing, before they are potentially moved within the soil.

Is There Any Benefit to Tissue Tests in Wheat?

Jan 18, 2012

Question: Is there any benefit to wheat tissue testing since I soil test pretty regularly?

 Answer: While soil testing is an important tool to determine soil nutrient levels and nutritional requirements, I use tissue tests to refine the soil tests further and make more accurate post-applied nutrient recommendations. Tissue tests are ideally taken when the plants are 4” to 6” tall in the spring, usually around two or three weeks after green-up. At this point, the plants are taking up nutrients but there is still adequate time to apply the required nutrients before any lack of nutrients can have a negative impact on yield. Tissue tests are taken by carefully cutting plants off at ground level, but be sure to not contaminate the samples with soil. Select a number of different sites within the field for analysis, or you can select good areas to sample and compare them separately to bad areas. This latter suggestion can help if you are looking to isolate specific nutrient deficiencies within different regions of fields. Contact your local Extension office or consulting agronomist for more direction on how to mail in your samples for testing.
Seeking sound agronomy assistance from a certified crop adviser is money well spent. After all, if you don’t compare your varieties to others, how can you be sure you’re planting the best ones?

What Is the Value of Aerial Imaging?

Jan 13, 2012

Question: I’m hearing more about aerial imaging and wonder if I should consider it this year on some of my acres?

 Answer: Aerial imaging, or Normalized Difference Vegetation Index (NDVI) mapping, can give you an in-season snapshot of your crop. Knowing the level of detail provided by the map will determine how you use the tool. NDVI is a good tool to use in developing management zones. Make sure you know what you want to learn from the maps before you take the plunge. For instance, if you want the map to act like a yield monitor, a 15-meter or 30-meter map will suit your needs. If you want a map with a higher level of detail than a yield map so you can see smaller management zones or pinch rows behind the planter, then you probably need a higher resolution. Your local retailer can probably tell you how to go about getting the mapping process done, your potential costs and ROI.
In 2010, the Farm Journal Test Plots crew went to the field with all of the commercially available technologies to create NDVI maps. There are multiple ways to collect data for the maps: equipment-mounted sensors, images taken from airplanes and satellite imagery.

Would you recommend starter fertilizer for corn?

Jan 08, 2012

Question: Would you recommend starter fertilizer in corn?

 Answer: Starter fertilizer can definitely help you gain more bushels in the field, but the response can and does vary year-to-year. In our test plots, on average, we’re seeing a 7 bu. to 10 bu. per acre response when we use starter. Bear in mind that success with starter fertilizer is very dependent on optimum timing and good placement. In addition, you may want to consider incorporating some zinc into your starter as zinc can help improve consistency of response. If you add zinc, make sure you buy a good quality zinc and mix according to the label. We’re seeing about a 7 bu. average response to adding 9% EDTA chelated zinc at the rate of 1 qt. per 20 lb. of phosphorus. 
Want to bump those yields this year, then look into the opportunities available with starter fertilizer.

How Do I Minimize Nitrogen Tie-up in Corn on Corn?

Jan 04, 2012

Question: If you don't have access to sidedress equipment, what is the best alternative in a corn-on-corn rotation to minimize nitrogen tie-up and grow the best corn crop possible?

Answer: Residue breakdown varies depending on what part of the country you are located in. In general, in corn on corn from the mid-U.S. to the North, residue breakdown is slower due to cool temperatures. In the South, it is less of an issue, since warm temperatures help to break down the corn on corn residue. In central Illinois and the eastern and northern Corn Belt, we typically recommend applying 100 lb. N/acre (may be different in your area) up front to handle the carbon penalty in corn on corn. These 100 lb. should be a mix of broadcast N and starter fertilizer; the remainder of the N needed for the corn crop is then sidedressed.
In your situation, where sidedress is not possible, starter fertilizer could play a more important role for applying N (in addition to P). Applying N in a 2x2 band along with your P will help. Depending on your soil type (rates will vary), consider applying a portion of the N with the corn planter in a band at least 2x2 away from the seed. I would still recommend some broadcast N preplant in addition to the starter to help break down residue. The remainder of your N needs could be applied preplant broadcast or banding, depending on the source. Consider using a stabilizer product for this application. Another option would be applying UAN with the corn planter between 3" and 4" away from the seed at higher rates; however, you would want a closer placement for the P. Some growers who do not have a sidedress bar have applied UAN sidedress with a sprayer setup with drop nozzles in between the rows. A stabilizer to prevent volatilization is very important here. 
Although they aren’t needed in large quantities, micronutrients play a big role in plant health.
With many nitrogen inhibitors and products on the market, Ken Ferrie has some easy-to-follow tips to make sure you are getting the correct response to your fertility program.
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