Spreader.EZ is a computer program that allows you to analyze the patterns from broadcast fertilizer spreaders, determine the uniformity of the patterns and select the effective swath width. This program was originally developed over 25 years ago, but it was recently revised and updated by programmers in LSU AgCenter Information Technology. The original program worked very well but was difficult to use. The current version is designed to run in Windows. It allows easy data input and data storage, as well as provides easily used output.
To use the program, you input some basic data about the spreader, product being applied and test conditions, then type in the weights (or volumes) obtained in the collection pans from a pattern test. The computer program will calculate the skewing in the pattern (amount of material on the left side of center versus the right side) and then mathematically create overlapped patterns for a range of possible swath widths so that you can evaluate those patterns and chose the best width. If the skewing is excessive, you may need to adjust the pattern setting on the spreader and retest. For a typical walk-behind professional rotary spreader, the collection trays are normally on one-foot centers, and the program will provide you with data on possible patterns from 4 feet on up. For each possible width, the computer will provide you with a coefficient of variation (CV) for the overlapped pattern as well as the minimum and maximum points in the overlapped pattern, expressed as percentages of the average rate. In general, you would select the greatest swath width that provides a CV ≤ 20%, a minimum ≥ 80% of the average rate, and a maximum ≤ 120% of the average rate. These guidelines normally work well for fertilizer and herbicide products, but you may want to use tighter guidelines if, for instance, you are preparing golf greens for a tournament. On the other hand, you can select a less-uniform pattern for insect baits since insects are mobile.
The program also tells you the delivery rate at each possible width. You should not rely on those rate figures for your rate calibration. Rates determined from pattern tests are not very accurate due to granules bouncing into and out of the collection trays.
A copy of the program can be obtained from Dick Parish -- dparish@agcenter.lsu.edu.