Guidelines and Practice problems for 2011 State FFA Agronomy CDE
The team activity will consist of a given scenario regarding establishment of an agronomic crop.
There will be calculations pertaining to lime and fertilizer requirements, herbicide formulation,
and unit costs of various fertilizer ratios. Participants will be given sample soil lab results for a
check soil and a specific agronomic crop with a specific target yield; multiple lime tables for
various target pHs, and nutrient management guidelines for an agronomic crop with a target
yield. The recommendations at the bottom of the sample will be removed and be determined by
participants. The goal was to make problems as practical as possible.
Here are some types of problems that participants should know.
Problem 1
Participants will be given a target pH. They must find the appropriate lime table for the target
pH, use the buffer pH and the soil pH from the soil lab results to determine if lime is necessary,
and if so, the amount.
* Please note that recommendations are not removed from the attached practice soil
analysis, but will be removed for the actual team activity.
Lime tables may be found at:
http://www.clemson.edu/public/regulatory/ag_svc_lab/soil_testing/lime.html
For example: Using the attached soil lab analysis and a target pH of 6.5, determine whether a
lime application is necessary, and if so, how many lbs per acre?
Locate the lime chart with a target pH of 6.5; read the soil pH of 5.7 and Buffer pH of 7.7 from
the soil analysis. Read from the chart that lime is necessary at the rate of 2,100 lbs per acre.
Problem 2
When given pounds of Active Ingredient (AI) of specific herbicides, they will need to calculate
the amount by volume (liquid formulation) or weight (dry formulation) of the herbicide to be
used per acre.
For example: The labeled rate of Gramoxone is .75 lbs AI per acre. It is an emulsifiable
concentrate formulation of 2 lbs AI per gallon. How many pints per acre is this?
2lbs/gallon = 2lbs/8 pints = .75 lbs/x pints; x = 3 pints/acre
For example: The labeled rate of FirstShot 50 SG (50% AI in a dry formulation) is .25 lbs AI /
acre. How many ounces by weight per acre should be applied?
.25 lbs * 16 ounces = 4 ounces / .50 AI = 8 ounces / acre
Problem 3
Participants will need to refer to the soil lab results (see attached sample), reading levels of
Phosphorus and Potassium, find the corresponding nutrient management guideline table for the
given CROP and the TARGET YIELD. They will then need to interpret the data and find the
correct recommended N P, and K in lbs/acre. Those tables may be found at:
http://www.clemson.edu/public/regulatory/ag_svc_lab/soil_testing/downloads/agronomic_crops.
pdf
* Please note that recommendations are not removed from the attached practice soil
analysis, but will be removed for the actual team activity.
For example: Using the attached soil lab results and nutrient management guidelines, determine
the N-P-K recommendations for soybeans with a target yield of 50 bushels per acre.
Phosphorus (P) is in the low range and Potassium (K) is in the medium range. Use this
information, find the correct chart for soybeans (they are in alphabetical order) with a 50
bu/acre target yield, you see that 0-100-80 is the recommended pounds per acre. *This would be
a good time to note that soybeans are leguminous and why no nitrogen is necessary in this case.*
Problem 4
Participants should be able to use nutrient recommendations of N-P-K per acre and determine
correct amounts of given fertilizer products
For example:
How many pounds of 19-19-19 are required to supply 80-40-20 lbs per acre of N,P,K?
Since N requirements are the highest and fertilizer ratio is equal, use 80 and divide by the % of
N in the fertilizer product given.
80 ÷.19 = 421 lbs /acre
For example:
How many pounds of 0-20-10 should be applied to supply 0-100-30 lbs per acre of N,P,K?
Since Phosphorus requirement is highest, divide 100 lbs required by 20% in fertilizer product
given.
100 ÷.2 = 500 lbs / acre
Problem 5
Participants should be able to calculate per acre application costs of various products when given
prices of fertilizer products.
For example:
10-10-10 is $400 per ton, and a farmer needs to put out 600 lbs/ acre based on soil test
recommendations. What is the application cost per acre?
$400 / 2000 lbs = 0.20 cents per pound * 600 lbs = $120 per acre
or
600 lbs / 2000 lbs = .3 tons * $400 = $120 per acre
Problem 6
Participants should be able to figure seeding rate when given desired plant population and
germination rate.
For example:
If the desired plant population per acre of soybeans is 102,000, and the germination rate of the
seed is 88%, what should the seeding rate in lbs per acre be? Assume there are 2,700 seeds per
pound and round to nearest whole number.
102,000 ÷.88 = 115,909 seeds ÷2,700 seeds per lb = 43 lbs per acre of seed
What is the seed cost per acre if a 50 lb bag of seed is $48?
$48 / 50 lb bag = x / 43 lbs; 50x = 2064; x = $41.28