Proper Calibration of Fertilizer Spreaders Reduce Uneven Application

Alternating strips of pale green and dark green are not an uncommon sight in wheat fields in May. Often these strips match the route traveled by a fertilizer spreader and are an indication that the application of nitrogen a few weeks earlier was not uniform. While not always easy to spot from the road, walking your fields may reveal subtle changes in plant color and vigor that follow the pattern.

This is not just a problem in wheat. Fertilizer applications can also be problematic in other crops – such as potash applications on alfalfa – but are not as easy to see without careful measurement.

As producers prepare for spring planting, Michigan State University Extension recommends calibrating spreaders and making sure operators are well-trained and familiar with the equipment they will soon be using. Fertilizer applications can be improved by paying attention to several areas:

Common operator errors
Before you hook onto the spreader, check the operator’s manual. In particular, check for proper hitch height. If the spreader is hitched too low or too high on the tractor, it will change the angle of the spinners in relation to the ground surface and it will affect the distance individual fertilizer particles are thrown. Run the spreader at its intended operating speed (RPMs) and be sure this speed can be maintained over the field terrain. While spreading, be sure to maintain proper overlap distance from one pass to the next.

Material matters
Check the density and quality of fertilizer to be spread. Density of fertilizer changes from product to product, and these changes in density will affect the rate of flow of the material and potentially the spread pattern. Fertilizer that has been handled several times, especially thru augers, may have a high amount of fine particles and dust. Dust and fine particles can impact the rate of flow through the spreader as well as the ultimate distribution of the nutrient because fine particles tend to not be thrown as far as larger particles.

Equipment maintenance
Check equipment for worn or corroded parts, rusted sagging spinner frames, loose components and sticking bearings. These can all contribute to erratic machine operation and poor performance.

Equipment adjustment
While occasionally equipment is out of adjustment, more often operator errors, material quality and equipment maintenance are associated with poor spread patterns. Consult the equipment operator’s manual before attempting to adjust your equipment.

Check uniformity with a calibration kit
Calibration kits contain a series of pans with baffles, which are laid out across the path of the spreader. The spreader is then operated by spreading fertilizer over the pans, and a sample of which is caught over the width of the spread pattern and the compared. The baffles inside the pans are important because they keep fertilizer particles from bouncing out of the pan. While it is tempting to attempt to access uniformity in the field by observing material on the soil surface, this can be misleading. Crop debris, soil surface cracks, soil surface color and clods can make it difficult to see and compare particle distribution. Calibration kits can be purchased from many application equipment suppliers and may also be available though some fertilizer retailers.

Calibrating spreaders, having a good knowledge of equipment and checking uniformity of fertilizer to be applied to the fields will help producers avoid over and under fertilized sections of their fields.

Source: Michigan State University Extension 

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