Steiger Green,.........Here are some good examples of why to color of Corn should be Steiger Green....Not John Deere Green.
Corn on Corn, Corn on Cotton, A good corn ear is 18 kernels around the ear and 52 kernels up the ear. Ear and kernel size was statistically the same for the included pictures of N application....TAPPS application was made just prior to planting with a 20 inch tool bar. Texas Tech and Texas A&M provided the corn stalks and ears in Exactrix test plots at Plainview.  The N in the TAPPS application was 100 pounds N to 180 pounds N....we are pretty confident about 140 N, 30P, 20S and 1 pound Zn....any more or any less is risky in corn on corn or corn on cotton.  Obviously solution 32 through the pivot will raise cost another 150 dollars per acre and may not reach the same yield level.
The infrared pictures included show dark red at 180 pounds N per acre and spotty light red and pink at 140 and 100 pounds N per acre.  The best returns are 140 in TAPPS.
Variable Rate Application....The Economic Method should be applied once the producer has established 3 years of test plots.  The producer has confidence that his general application rate based on the current economics is correct and typically the entire pivot has no more than 12% invested of the gross.  Take a good yield map for the pivot and design an application map that runs at 12% of the gross with the Exactrix.  Low yield areas have much less invested and only 12% of the gross for low yield areas. The controller should readout out in percent of Gross....we can set it up that way if necessary to understand the importance of economical application........no more than 12% of the gross.  
You can have up to 15 Exactrix management zones.....because the application CV is 1% and full response is 3 seconds. The optimum machine width is probably 30 feet....and 40 feet is still practical.  But if there is turning like the Palouse the narrow machine is the winner.
It is important to realize that nutrients are toxic when overapplied.  Yes there is a downward slope back side to the yield curve....The important point is to apply at the point of diminishing returns for every site specific area of the field. You must know the efficiency of the application....The Process Management Engine has different levels of efficiency....and Exactrix Engine runs at .6 of the soil lab recommendation in pre-plant and .5 of the soil lab recommendation in side dress.
You can not economically build soils with nutrients.  Soil building and testing or building soils for lack of P...this is based on cheap nutrients of the past.  J.R Simplot Soil Builders....True in 1955.
You can apply nutrients based on a historical yield of the field.....This is the most reliable means.....that works today.
A good corn plant has only one ear....does the second ear hurt yield and efficiency if it begins to show up?
Irrigating and adding 2 feet of water is probably not a good idea in today's energy sensitive world. But some producers still do it....when 18 inches or less might be better.  Don't forget a Center Pivot is really a poor applicator of water.....this is why there are Lateral Move Irrigation Systems for high value crops such as potatoes....Center Pivots have water application problems.....a high CV of application.....There is nothing like a good rainstorm.
SDI might be a lot better and you can see cotton with SDI on 60 inch centers in the pictures included....Plainview, Texas.  Notice the soil is wet to the surface in the foot path.
A typical nutrient investment in a corn crop should be 12% of the gross....not 24% and not 30% of the gross.
Never focus on Nitrogen in feeding corn....Always focus on Nitrogen, Phosphate and Sulfur plus Zn in a uniform, balanced and timed application when feeding corn.  Potash or K must also be considered and when, where, and what method should be used to apply K and Cl.
So if you must focus on all nutrients in feeding corn utilizing VRT and Economics .....It is economically impossible to VRT top dress the corn(salvage and convenience)....right.   Confirming.....it might be a really good idea not to fertigate and not to top dress commodity corn..........It is important to band the balanced nutrients in the soil and drive the efficiency of the nutrients and the plant to much higher levels.
The nitrogen credit (nutrient credit should be considered) for soybean and alfalfa is huge....Why?....because a good uniform stand of a legume is crop equivalent to applying 2 times and some cases 3 times the synthetic units of NPKS.  Even though the soil scientist is able to measure the soil available nutrient value....The scientist seldom makes allowance for uniform vertical plane and horizontal plane  distribution of organic nutrients....Something a nutrient applicator with an Exactrix system can not duplicate.
A Nutrient Credit should be considered for Legumes.....A nutrient credit would include N, P, K and S for a legume.....too much focus on N when P has been trans-located by the Alfalfa roots....Not all is lost through the top growth removal..........what about the alfalfa roots and how do they improve the nutrients......all the nutrients must be considered for the legume.
Timing of nutrients rates in the top 5 factors in Process Management of Corn production.....do you know the 5 critical factors.
There are 3 long term factors that does improve the knowledge of the application rate....do you know the 3 long term factors.
Selection of tillage practice is critical for good economic returns.
Type of rotation and length of rotation is critical to reduce risk.
Legumes may not be required in rotation to make good economic gains....but good land values are often found where legumes are in rotation.
High soil test P......TAPPS may not be economical.....However, Thio-Sulfate and Zn is still required.....Manured Soils with 80 ppm Bray 1 soil test and it is practical to switch to NH3, ATS and AZn....and form TATS with Zn.  The Acid Base reaction is critical to solubulize the micro nutrients, stabilize the band and provide sulfur.....NH3 should never be placed as single product....Molasses can be placed with NH3 to stabilize the band....Get a carbon source with the NH3....Powdered Sugar might work pretty good....but never place NH3 as a single product.
A note about N removal.
I doubt that if try to use N removal or P removal rates to develop application maps that you can develop a system that  will work economically.........trying to use N removal or P removal....Larry Murphy and I agree....the statistical data developed in the last 60 years.... is a Scientific Wild Ass Guess.  Walter McClure would agree....You can not alter soil test P economically on the Great Plains.
You might want to call Carlos Crovetto.....and find out how he does it.....
Dave....the critical point to remember.....Nutrients were Dirt Cheap at one time.   Nutrients are expensive polluters today.  Take Carlos' approach....learn a new language and learn how to do it with the check book....with very little input cost.  Close your eyes to the past....dealing in the past approaches is the killer.  Nutrients must be applied economically.


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