Using Simple Relationships to Teach Calibration of Seeders and Sprayers.

With seeders, planting too little seed reduces crop yields and increases weeds while too much seed increases costs and may reduce yields. With a pesticide application, too little product can mean poor control, while too much can mean crop injury, extra costs, and possible residue on the crop and/or carryover. The methods discussed in this presentation are simple relationships and do not require remembering formulas. However, you do need a general understanding of cross multiplication. The important thing is to be consistent: if you put an item on the top of an equation on one side, the same item also goes on the top of the other side. The two factors that determine seeding rate are seeder unit spacing and the amount discharged through the seeding unit over a measured distance at the speed that the equipment will be operated. One must always check to determine if there are variations in discharge rate across the machine and correct those before proceeding with calibration. With sprayers using a pressure gauge to determine if pressure is uniform over the entire spray boom should be performed before sprayer calibration. The three factors that determine sprayer application rate are: (1) Speed, (2) Nozzle spacing, (3) Nozzle output (determined by orifice size, pressure, and density of spray solution). A NebGuide which illustrates this method, G03-1511A "Calibration of Sprayers (Also Seeders)" is available on the University Web Site at: http://www.ianrpubs.unl.edu.epublic/pages/indexhttp://www.ianrpubs.unl.edu/epublic/pages/indexhttp://www.ianrpubs.unl.edu/sendIt/g1511.pdf

To calibrate a seeder using this method first determine how many pounds of seed are needed to plant the number of seed desired per square foot of soil. In this example we use 60 seeds/m in a row with a seeder that has 0.25 m spacing. Seed size in this example is 33,000 seeds/kg and seed is collected for 150 m. We first determine we have 40,000 m of row per hectare (10000 m² ha^-1 / 0.25 m row spacing). Next we determine we need 72.7 kg of seed per hectare - 60 seeds per m of row multiplied by 40,000 m of row in one hectare divided by 33,000 seeds per kg of seed. Our test area is 0.00375 ha (0.25 m multiplied by 150 m of row divided by 10,000 m² ha^-1 . Multiplying 0.00375 ha by 72.7 kg of seed per hectare equals 0.273 kg of seed to collect from each opener in 150 m of row.