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Answers to last weeks problems listed
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First, last week there were some simple ag-related math problems with answers promised this week. Here are the problems with the solutions. Remember you should have only needed pencil and paper for one of them.
1. You are applying 100 lb. nitrogen/acre as urea. Urea is 46 percent nitrogen. How much urea fertilizer must you apply per acre: 46 lb. or 217 lb.? The fertilizer, urea, is less than 50 percent nitrogen so you will need more than twice as much urea so 217 lb.
2. You have two sources of the same fertilizer. Shipping costs are equal. Here are the two prices; $1000/ton and 60 cents/pound. Which is a better deal? $1000/ton is the same as $1000/2000 lb. or $1/2 lb. or 50 cents/lb.
3. Your sprayer has 60 nozzles spaced 20 inches apart with a per nozzle output of 8 ounces over 30 seconds and you want to apply 10 gallons per acre. Could you set up and answer the following questions. What is you nozzle output in gallons per minute per nozzle and total output of all the nozzles? 8 ounces in 30 seconds equals 16 ounces/minute or one pint/minute. There are 8 pints in a gallon so the output/nozzle is 1/8 gallon per minute or 0.125 gallons/minute. Take 0.125 gallons/minute and multiple by the number of nozzles (60) and your total output is 7.5 gallons/minute. What speed do you need to drive to apply 10 gallons per acre? The nozzle spacing is 20 inches (1.67 ft.). Multiply 1.67 feet by the number of nozzles (60) - 100 ft. An acre is 43,560 sq. ft. so take 43,560 sq. ft. and divide it by the boom width 100 ft. so 435.6 ft. is the distance you need to drive to cover an acre. Your output is 7.5 gallons/minute. To determine how long it will take you to apply 10 gallons do the following: 10 gallons/(7.5 gallons/minute) or 1.33 minutes. That means you need to drive 435.6 feet in 1.33 minutes or 435.6 ft./1.33 minutes or 327 ft./minute. To shorten this up a bit, just convert this to miles per hour. There are 5280 ft./mile and 60 minutes/hour. So 435.6 ft. equals 0.0825 miles. We need to drive 0.0825 miles/minute so multiply by 60 minutes/hour or 4.95 mph.
4. You are administering an injection to a steer. The label says to administer 5cc per 1000 lbs. of weight. You approximate the weight as 700 lbs. What is your dosage? 5 cc/1000 lbs. equals 0.5 cc/100 lbs. Multiply 0.5 cc/100 lbs. by 7 or 3.5 cc.
5. The cost of a wheat fungicide treatment is $15/acre and you are told to expect a 3 bushel/acre yield benefit. What is the minimum price of a bushel of wheat that allows you to break even? Three bushels of wheat must return at least $15 so take $15 and divide by 3 so the answer is $5/bushel.
The sprayer problem is really much easier than it looks written out and all of this becomes second nature the more you do it. The key for our students is providing them with a foundation in math and critical thinking to develop these skills. Next week we’ll take a look at the initial weather outlook for 2012 and wheat acreage.
Dr. Victor L. Martin is the agriculture instructor/coordinator for Barton Community College. He can be reached at 620-792-9207, ext. 207.