Posted 6/29/2008 08:56 (#406633 - in reply to #406601) Subject: Calibrating Drills
Ashburn, GA, (very close to Heaven!)
I just finished setting a couple of no till drills this week for soybeans.
Set your "cups" levers to match the size seed you have, according to the manual. Smaller seed set it close to the top, more "closed" and further down for larger seeded stuff like soybeans for example. I had a farmer trip a couple of his down last fall on wheat, and it made a mess across a few fields, dropping lots more seed than necessary in a few rows. This is a common mistake I think I have seen farmers make.
Figure out how many seed you want per foot of row. I count out 250 soybeans and, using a funnel, drop them into a 100 ml graduated cylinder. This tells me how many milliliters I have per 250 seeds in that seed lot; 250 is pretty close to the number I am going to plant per 50 feet of row in 15 inch rows. Nevertheless, depending on your desired drop rate, use the ml/250 seed amount to determine a factor to find out how many milliliters of seed you need on 50 feet of your row.
Get about two quarts of seed and pour them into the drill over two rows that you choose to calibrate. Believe me, it is better to do this above only two rows at the shelter. I have actually ridden grain drills in the field down 50 feet of row, and am not sure that is too smart...
Jack the drive wheel of the drill up, and engage the drive wheel. Measure the circumference of the drive wheel, and calculate the number of revolutions required to travel 50 feet.
Set the drill chute opening close to what you think it might be, probably some pretty accurate suggested settings in the manual. Disconnect two of the drop tubes and put a couple of drink cups under them. Have somebody rotate the drive wheel and "charge" the drill cups and start the drop down the tubes, stopping the valve stem at a good reference point. Empty your drink cups, you're ready to check calibration.
Next have the person rotate the tires the number of revolutions required to travel 50 feet of row while you catch the seed in your drink cups. Pour the seed through a funnel into your calibration tube and see how close you are to the number of milliliters you need. Adjust until you get the desire drop. I always calibrate both sides of the drill, as they are not always uniform. Whenever I change the chute width setting, I recharge the drill cups and tubes to adapt to the new setting. Once you get the rate you want, it's good to run two or three times to verify you are getting a good and accurate average drop rate.
I learned how to do this from Dr. Dewey Lee, corn and small grains specialist with the University of Georgia in Tifton. It has been a valuable addition to my services with small grains and drilled soybeans. It takes a little while to do, but at today's prices, we need to do everything possible to be sure we are using the optimum drop rate for seed, both for seed costs and agronomic performance.
I have a crude Excel spreadsheet set up to do some calculating for me. Email address is in my profile, if you want it.