Yield Reduction Resulting from Uneven Fertilizer Distribution

Fertilizer should be distributed as evenly as possible over crop areas with uniform soil and vegetation so that an optimum net profit (plant yield minus variable fertilizer costs) is achieved. Standard laboratory tests have proved very high uniformity of spreading for the best centrifugal spreaders under laboratory conditions. The coefficient of variation is as low as 5%, or even less. In this article theoretical calculations are made with the aim of determining the increase of net profit to be achieved by further improvement of the properties of the fertilizer spreaders under laboratory conditions. From the calculations it can be seen that in theory, the highest increase of net profit to be achieved will be around 0.5%. It can therefore be concluded that instead of focusing mainly on laboratory tests, as is the case today, future research into and development of centrifugal spreaders should rather aim at improving the abilities of the fertilizer spreaders under realistic field conditions. External influence, such as field irregularities, drift of the fertilizer grains due to wind, etc., are thus responsible for most of the variations in the rate of application of fertilizer and the resulting yield losses.