According to the ‘Theory of Minimum’ all nutrients need to be available in the right proportions. Therefore, a homogeneous nutrient distribution is crucial for high nutrient use efficiency and high yields. Only COMPLEX fertilizers containing all nutrients in each granule can ensure the best nutrient distribution in the field and thus maximize yields.
Figure 1: Figure: Twenty-three field trials with different crops in Germany, Austria, Belgium, Denmark and France (1988-1992) show higher yields with COMPLEX compound fertilizers compared to blends. On average 400 kg more yield per hectare with COMPLEX fertilizers was achieved. Ref: E. Schöningh, Limburgerhof, BASF, 1993
Unlike mixed/blended fertilizers, COMPLEX fertilizers do not get segregated when being stored, transported to the field and spread. Segregation leads to uneven spreading, and nutrition disparities. The difference can be up to 30 to 40% variation in mixtures with different physical properties. Irregular spreading is made visible by alternate light and dark strips in the field, which lead to yield losses. Furthermore, the compound fertilizer facilitates a denser distribution (more granules per plant) in the field compared to fertilization with straights or bulk blends.
Uniform distribution depends on even fertilizer output from the disc and overlapping between two passes (out and back) of the broadcasted fertilizer granules.
To test the regularity of fertilizer spreading, the actual dose of fertilizer spread over the projecting distance is measured and the curve of the spreading profile is plotted. Spreading regularity is expressed in coefficient of variation (CV), which quantifies the average deviation of doses applied in relation to the mean dose, and is stated as a percentage. CV as defined in European Standard 13739 is the ratio between the standard deviation and the mean total distribution.
The lower the CV, the better the distribution. The quality of fertilizer distribution is expressed as follows:
Imprecise spreading can have serious consequences. It is often visible in strips or waves, showing 30% over or under-dosing. Uneven and imprecise distribution of fertilizer leads to nutrition deficiencies of the plants, and thus a reduction in yield and protein content. Fertilizing more than the economic optimum causes loss in revenue and increases the risk of unproductive nitrogen loss.
It is a false assumption that uneven spreading would even out on a field. Higher yields due to more fertilization do not balance the lower yields due to less fertilization because of the flattening dose-response curve. This is true at any yield level and without crop damages.
Illustration of the gains and losses due to more and less fertilization than specified (200 kg N/ha). The dose-response-curve flattens; therefore, yield losses (red) are always larger than the gains (green).