Following the 2004 Workshop in Lincoln, NE, the regional corn trial below was proposed to address local, and regional development of Nitrogen Fertilization Optimization Algorithms (NFOA) for wheat, corn, and rice.   This trial will include collaborative work with scientists from Canada, Mexico, Argentina, Minnesota, Missouri, Nebraska, Iowa, Oklahoma, Illinois, Kentucky, Kansas, Colorado, and Texas.

GPS Capture Program (follow this link)

Robert Mullen
 Extension Specialist/Assistant Professor
 OARDC - School of Natural Resources
 1680 Madison Ave.
 Wooster, OH 44691
 330.263.3785
mullen.91@osu.edu

Greg Schwab
 UK Department of Agronomy
 N-106 Agricultural Science Bldg.-North
 Lexington, KY 40546-0091
 gjschw2@uky.edu

Wade Thomason
 Crop & Soil Environmental Sciences
 Blacksburg, VA
 580 465-4378
 wthomaso@vt.edu

Method of Application: 

1. Nitrogen Sufficiency-USDA-ARS, UNL

a. Minolta SPAD meter readings collected from treatment 2 (t2) and treatments 7 (t7) and 8 (t8)
b. 30 lbs N/ac applied to treatments 7 and/or 8 whenever whenever t7/t2 or t8/t2 SPAD meter readings result in a value <0.95
c. N should be applied in a continuous stream using 50-200 ml syringes (all 4 rows treated the same)
d. Treatments 2, 7, and 8 monitored throughout the cycle and N applied (30 lb N/ac) whenever the sufficiency (t7/t2 and/or t8/t2) was less than 0.95.

2. NFOA

a. NDVI sensor readings (and CV) collected from treatments 2 (t2), treatment 9 (t9) and treatment 10 (t10) between the V8 and V10 growth stages.  Readings should be collected from the center 2 rows, the entire length of the plot.
b. Using the Sensor Based Nitrogen Rate Calculator that is available on the web, use either the "Corn Rainfed" or "Corn-Irrigated" algorithm depending on your growing conditions.

http://www.soiltesting.okstate.edu/SBNRC/SBNRC.php

c. Enter the number of days from planting to the day of sensing
d. Enter NDVI values for treatment 9 in the "Farmer Practice"
e. Enter NDVI values for treatment 2 in the "N Rich Strip"
f. Enter CV value (for each plot) for treatment 9 and 10 in the "Coefficient of Variation (CV)" (this will be the average CV value displayed on the Hand-Held GreenSeeker once complete sensing the center 2 rows)
g. Enter a Maximum Yield for the Region (generally 2 times the average yield for a field, usually not less than 300 bu/ac)
h. Enter the Plant Population in either plants/ac or plants/ha depending on what units you are using.  Preferably this should be the plant population at sensing, but you can use "planted" population even though it will be a bit higher.
i. Click "Submit" to obtain N Rate Recommendation (available in English or Metric Units by clicking appropriate buttons below)
j. Repeat steps c-i substituting treatment 10 for treatment 9.
k. N should be applied at the base in a continuous stream using 50-200 ml syringes (all 4 rows treated the same)

Comments: note the Response Index will be different for treatment 9 and 10, because the N Rich Strip is divided by the NDVI value in these respective treatments.  In general, you should expect less topdress N to be applied topdress in treatment 10 versus treatment 9.  Details on how the N rate is calculated (step h) are available at http://www.nue.okstate.edu/RI_CV_Discussion.htm

An excel file that can be used in the field with your PDA (does everything the SBNRC does) .... follow this link (EXCEL file)

3. Missouri

Instructions for VR N Using Active-Light Sensors: Missouri 2004 version

For this algorithm, you’ll be using the ratio of the visible to NIR (i.e., VIS/NIR).

IN each case where VIS/NIR is included below, this is the simple ratio (last output value on the GreenSeeker sensor).  SR = (VIS/NIR)

Collect sensor reflectance readings on treatments 2, 11, and 12 (t2, t11, and t12) sometime between V8 and V10 (preferably closer to V10) at approximately 53 cm above the height of the corn canopy.

Treatments t11 and t12 are designated as the “target”, and treatment t2 is designated as the “reference.”

Calculate the N rate for t11 and t12 as follows: N rate (lbs/acre) = -200 + 250 x [ VIS/NIR(target) / VIS/NIR(reference). Using this equation, corn that looks exactly like the reference will still receive 50 lbs N/acre.

Apply N as close in time to when senor readings are taken as possible.

N source and placement methods should follow the same procedure as the listed for the other treatments being tested

4. Virginia

Follow guidelines in the on-line spreadsheet.

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Issues for ALL TRIALS

Replications: 3-4
Plot size:  4 rows wide x 20 - 30 ft long
Row Spacing: As per equipment used (30" or 36")

P and K applied preplant to local sufficiency levels
Nitrogen to be applied between V8 and V12

Nitrogen Sources: 
1. Pre-Plant: Urea or UAN
2. Topdress: UAN

Sensor/Chlorophyll Meter Readings
Active Sensor readings taken weekly, Greenseeker RED
Chlorophyll meter readings (SPAD) taken weekly
 

Pre Plant Soil Tests (0-12, and 12-24")
NO3-N, and NH4-N
Total N
Organic C
pH