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Steve Peterson - Wheatfield, Indiana
November 17, 04,
1. Yield Goal
2. Residual nitrogen based on soil sampling or soybean yield maps.
3. Soil type.
4. Organic Matter contribution or CEC of the soil and soil pH.
5. Tillage Systems having compacted soil layers or No-tillage systems having well drained soils.
6. Manure credits
7. Seed Row N
9. Uniformity of Application
10. Timing of Application.
11. Variety Selection.
12. Dual product application.
13. Availability of the nitrogen source
14. Cost of the nitrogen source.
15. The need for other major and minor nutrients.
16. Stable nitrogen vs. mobile nitrate solution fertilizer.
Scientific evaluation factors that affect the algorithm for pounds of N per bushel using NH3 as the nitrogen source. After two years of testing Exactrix is .7 to .8 pounds of total N per bushel…the university recommendation in the corn belt varies from 1.1 to 1.2 pounds of total N per bushel.
1. Uniformity of the application. A 1% C to a 50% CV
2. Timing of the application. Fall vs. spring pre-plant, planter applied or side dress.
3. Band spacing. 60” to 10”
4. Depth of the band. 2.5” to 12”
5. Positional relationship of the nitrogen band with the corn row. Directly under, to the side or mid-row, indexed and double side banded to the row.
6. Tillage system. Shank application to single disc application.
Factors that affect the machinery selected to apply NH3.
1. Soil type
2. Tillage system or a No-till, Ridge-till system. Strip tillage considered.
4. The temperature at the time of application.
5. The width of the applicator.
6. The desire to side dress and pre-plant apply.
7. The desire to apply NH3 with VRT.
8. Dual application techniques improving NPK and S efficiency, which requires narrow band spacing.
9. Other crops in the rotation such as wheat that requires narrow band spacing.
10. Injection of Nitrogen stabilizers into the NH3 flow.
There are three key factors that affect the economic risk of applying NH3. Several types of application variability do occur in the application management of nitrogen as NH3. Field Rate, Band Rate, and the Lineal Sinusoidal Rate.
First Key Factor: Regarding the field applied rate as indicated by the controller.
1. The bulk density is changing constantly. A 30 degree F spread between early morning and late afternoon means a 7% change in the actual N rate per acre.
2. The first 2/3 of tank will have a small temperature variation. The last 1/3 of the tank will have a significant temperature drop. A volumetric application will have a 3% to 7% variation due to the change in the bulk density from the top of tank to the bottom of the tank. Since NH3 must be pushed out the tank energy is required. The energy required can be measured in the change in bulk density or the temperature of the material in the tank.
3. The turbine type flow meters have a +-3% variation across the flow range. If the application is made primarily in one flow range then the calibration number can be adjusted but VR-N becomes very difficult.
4. Because the tank valve began to close at a high flow rate or the cooler could not keep up at the high flow rate. Stretched NH3 of a lighter bulk density or partial gas flow state through the turbine flow meter indicated liquid flow…..But a much lower bulk density.
5. Defective tanks with broken siphon tubes or damaged tank valves with poor excess flow internal valves. Blocked or plugged tank siphon tubes are common. Poor tank valves and cracked welded delivery siphon tubes are common creating tremendous variability in the per acre applied rate.
Second Key Factor: Regarding the band rate which is masked in the operators mind as the per acre rate. The band rate is the most critical rate.
1. The band rate can be measured with buckets of water. The CV can be as high as 50% as per Hnatowich in Saskatchewan.
The shank is installed into a 5 gallon water bucket complete with the delivery tube. The bucket should have about 25 pounds of water. Since 90% of the pressure reducing systems have a cooler the vent tubes are also installed into the dedicated band buckets. About 6% of the total NH3 flow is vented through the cooler. Aqua Ammonia is formed in the water buckets as the metering system is activated delivering NH3. Guess Row Return side dress buckets at 50% rates are also captured in the bucket. After about 5 minutes the application of NH3 into the buckets is stopped and buckets are weighed with a very accurate counting scale.
A CV calculator is used to develop the system application CV. Thus the system has been measured… not just the manifold. The Coefficient of Variation is a dimensionless number made with an exponential calculation. The calculation is a measurement of variability, uncertainty with a 95% chance that the event measured will occur again. It is a measurement of economic risk once a dollar value is added to total amount of N applied e.g. $40 per acre of N is applied with a 30% CV indicates that $12 per acre is wasted and only $28 per acre applied was effective.
2. With the best pressure reducing manifolds available as tested at ISU in one ideal flow range…. The application CV is between 27% to 35%. Why? Because of the cooler contribution to the CV at 8% to 10%…. The shank delivery tube CV at 10% to 12% and the Guess Row return CV at 9%…. Plus the manifold CV which you can select from the ISU manifolds tested chart which can be from 7% to 23%.
As the flow range changes the ISU tested pressure reducing manifolds are volume sensitive and not pressure sensitive because of the two state flow. Thus as the flow changes the regulation CV of the manifold changes…. Making VRT impossible since the CV is not predictable in all flow ranges. The tests did indicate high variability in all flow ranges. Application rates in VR-N are adjusted in several management zones by a factor of 6 times the lowest rate. So application can be from 40 pounds of N to 240 pounds of N per acre.
3. The condition of the shank drilled outlet ports are constantly changing. A 10% CV is considered good when new. Measurements made at ISU indicate the CV can be above 50% when the shanks are used. Thus the gas state and liquid state flow or two phase flow follows the path of least resistance contributing to a greater application CV.
4. Delivery tubes do plug since the NH3 is freezing the shank. Mud builds up around the ports and changes the application CV. A partially plugged delivery tube allows other delivery tubes to receive more flow. Since pressure reducing systems are only volume sensitive systems…. Flow can not be controlled to the high degree of accuracy required for VRT and reduced use of the material.
5. NH3 pressure reducing systems deliver NH3 steady by jerks. This can be easily observed by watching the bouncing needle of the manifold pressure gauge or installing a pressure gauge in the shank delivery line. This is due to the constant change of equilibrium in the two state flow system. A steady pressure gauge needle would be a good indication of non-interrupted flow as created by the shank.
Third Key Factor: Regarding the lineal band rate (sine wave) is hidden from the operator, the scientist, the agronomist. Over the length of a 100 foot band the variation of NH3 can be as high as 50% CV. The sinusoidal, pressure reducing NH3 application geometry or location is only known to the growing crop. Some areas of the lineal band are too hot (high pH, oxidizer) and some areas are not adequate.
1. The application sine wave at high CV means that the concentration of NH3 can be 4 to 5 times higher in one column area of a lineal band as compared to an adjoining column area in the same band. Micro core samples can be taken to confirm this, Circa, John Moraghan, NDSU. If the NH3 column is too concentrated the fine hair roots are damaged (oxidized) and colonize around the hot spot which has a stable pH of 9.5. The damaged (oxidized) hair roots never penetrate into the core of the high NH3 concentration. This small amount of placed NH3 is lost to the environment.
2. The best way to measure the NH3 application sine wave in a lineal band is to use a growing crop such as corn. Scientists can compare this by using Aqua Ammonia and compare it to Anhydrous Ammonia. Aqua Ammonia always outperforms NH3 since up to 30% less Aqua Ammonia 20-0-0 is required as tested in the PNW. This also explains why placed P is more efficient with Aqua Ammonia since the hot spots in the lineal band are reduced. Aqua ammonia is always delivered with flooded manifolds using orifice plates that have a 6% to 10% CV. Excellent pictures showing stranded nitrogen and damaged (oxidized) hair roots due to excessive NH3 band concentration are available from the Ron Rickman of the USDA-ARS-Pendleton.
3. Another way to test lineal band variation (sine wave) is to apply with a pressure reducing NH3 system at a low, mid and high rate and then cross compare to a liquid, high pressure injection, of NH3 using an Exactrix system.
Stated and understood by the writer and reader…..It would be better to test pressure reducing NH3 improved manifold systems that have non tested system CV’s by comparing to an Exactrix system with a tested system CV.
As we progress in our understanding that the only way to test and compare any NH3 delivery system is to set up a series of crop plots using the same applicator, tractor, and operator to compare high pressure liquid injection of NH3 with the improved pressure reducing manifolds. Thus the variability of two application machines is taken away.
This has been done in Indiana this year. Producer Steve Peterson used a Hiniker control and a Hiniker cooler system to meter NH3 through an Impellicone developed by Iowa State and licensed to John Blue. The Impellicone or Equa-flow has an ISU tested 6% CV to 6.9% CV in two flow ranges.
System Applying, NH3 Application,Yield, Nutrient Cost, CostN/Bu, Gross Return, Gross Margin % of Gross Marginal Dollar Return
Pounds N/A. Bu./A $.25 N, $/A centsN/Bu. $/Bu@$1.75/Bu N-Gross $N/$Gross MRP, MEY
180 189 45
23.80 330.75 285.75 13.60 $5
invested lost $6.00 at MEY
2KM Liquid Dual Placement
2KC Coriolis Mass Flow
2KM Mini-Man Manifold