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November 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.

When Is The Best Time To Apply Phosphorus?

Nov 27, 2012

Question: What is the difference between phosphorus loss from fall-applied fertilizer versus spring-applied?

Answer: If your question is about high pH soils that tend to tie up phosphorus, then you’re better off to wait until spring. In the spring, you’re applying phosphorus closer to plant up-take and limiting the risk of tie up in the soil. When we talk about phosphorus loss from the soil through the tile it usually means the soil already has above adequate levels of phosphorus—essentially excessive amounts—and it wouldn’t be a good idea to be applying more. An example of this problem is the Chesapeake Bay area which is fighting the problem in groundwater.

Focus on the Phosphorus Cycle in Corn Production
Farm Journal Field Agronomist Ken Ferrie explains how soil microbial activity unleashes phosphorus to the plant.

The Value of Phosphorus in Starter
Our agronomist tells how much phosphorus is needed in the blend for starter fertilizer. Starter fertilizer is one tool farmers use to help get their corn crop off to a strong start.

What Factors Help Determine Nitrogen Rates?

Nov 21, 2012

Question: What is the deciding factor in varying the rate of nitrogen? Is it relative to CEC?

Answer: There are multiple factors that have to be put into play. Are you dealing with a high-yield or low-yield environment (both of which can be in a single field)? What is the plant density--are we pushing for high yields? What is the soil’s ability to supply nitrogen?

Traditionally that is a factor dealing with organic matter CEC. The healthier the soil, the more nitrogen it usually supplies. But, it can also depend on field history such as whether it’s been in corn-on-corn, or if manure has been applied to it. One of the things we’re looking at is testing for organic nitrogen followed up with nitrate testing, trying to predict high, medium or low mineralization rates.

The last thing we need to tie into this is the potential for nitrogen loss through nitrification or leeching. An example of this would be a high-yield environment with the ability to supply sufficient nitrogen that it would allow us to reduce our input of nitrogen. Yet that environment could be a high-risk area due to drainage, or, under wet conditions the nitrogen could be lost and we’d have to rescue those areas with more nitrogen.

Can Tillage Practices Reduce Organic Matter in Wheat Ground?

Nov 13, 2012

Question: I have been 100% no-till in my farming operation for 26 years. I am wondering if spreading wheat and using shallow vertical tillage to incorporate will lessen organic matter; which in return over a period of time will reduce crop yields? My thinking is any time you bring soil to the surface enabling contact from the sun you are destroying a percentage of organic matter, if you believe my thoughts to be correct, can you please give me your opinion on how much damage to soil structure you feel is occurring from shallow vertical tillage?

Answer: I'm not sure what region you farm in, and that will have a big impact on the relevance of my response. When I first moved from England to Kentucky 23 years ago, I began working with about 25 growers. My primary responsibility was to help them increase their yields and profits by introducing some of the European crop management practices which had helped some of the western European growers reach or exceed 200-bushel-per-acre wheat yields.

Initially, many of these growers were broadcasting wheat with spinner trucks and working it in with a disc or field cultivator. The standards of emergence, uniformity and plant populations across their fields were entirely too variable for maximum yields, so an important step the following year was to talk all of these clients into buying new or well-maintained, older model drills. This turned out to be a good strategy, as their stands improved and yields quickly climbed.

Based upon these and other experiences across the United States, and depending on the number of acres you expect to plant on a regular basis, I would strongly encourage you to buy or rent a good, well-maintained, no-till drill. The operating costs per acre will be similar as running a vertical tillage tool, but I think your stands will be more consistent and the soil disturbance will be reduced. I also believe with the improved seed placement provided by the drill, you could lower your seeding rates between 10% and 20%, compared to broadcasting seed, to save money.

I don't have any data to suggest how much damage you’re doing to organic matter by cultivating the soil with vertical tillage, but I can tell you that most of my growers are making +/- twice the yields they were 20+ years ago, and by using no-till their soil quality and organic matter is increasing slowly.

More from Ask An Agronomist: 

What Causes No-Ear Corn?

Nov 12, 2012


Question: This year we had spots in the (corn) field that were black and dead early with no ears on them. What would have caused these?
Answer: There could have been multiple issues.  One that we would look at is corn nematodes. They could have put enough stress on the plants, along with the drought, that the plants died early.  You can verify this with a soil sample, and evaluate corn nematodes in particular if you’re in a corn-on-corn area.  Some of the problem could be soil-type related. What is your ground’s water-holding capacity level? Some soils are able to hold more water than others. Did you notice whether you had any pockets of ground (size-wise, approximately the size of a pickup to a house) that had barren stalks?  We saw this problem, and we excavated three different pockets of ground like this. There was a noticeable difference in the soil moisture at approximately 18" to 20" deep in those pockets. When we got to a depth of 4 to 5 feet under the dead areas we were finding a band of sand or gravel in the soil. Those bands of sand and gravel restrict water from moving up to where corn roots could access it causing a perched water table. Under normal rainfall years the normal water table is high enough, but when it’s pulled below a certain level, like this year, the corn burns up.  That is our preliminary finding this year.  Here are some additional resources for your consideration.
Nematologists are seeing higher rates of nematode pressure in corn in recent years.
Knowing your soil’s water-holding capacity is essential to setting realistic yield goals.


How Does USDA Report Corn Losses from Drought?

Nov 02, 2012

Question: I am wondering if the 3 to 8 percent loss most corn suffered from being too dry on the later harvested corn (I heard as low as 10 percent @ local elevator) is factored into the latest  (USDA) report? My last field of irrigated corn I harvested on October 4, tested 12.2% moisture, it was 112-day corn and had been sprayed with a fungicide, so it would have been wetter in the beginning. I figured I had a 6 % reduction in yield at least, maybe more. Irrigated yields were fantastic--230 to 270 bushel/A here in North east Nebraska. But a 6% reduction to that means a 13 to 16 bushel/A decrease. Just saying it will show up down the road depending on the number of acres that where harvested after late September here in Nebraska.
-- Thanks Alan Hoehne
Answer: The report contains harvestable acres, so I don’t think that loss is calculated, as you suspect.  I also doubt whether the fields that were condemned this year because of aflatoxin were calculated either. When that last report was done, it was based on expected yields and not any calculated future loss.

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