Keywords: Fertilizer spreading, Fertilizer application.

This paper concerns the application of mineral fertilizers on agricultural soils. Influencing factors like the operator, the field, the weather, machine design and fertilizer are accounted for. Future and present ways of improving the spreading result are discussed.

It is shown that measurement of the spreading pattern and the evenness of distribution poses problems. It is concluded that care must be taken when comparing spreader tests. Comparison of the same individual spreader between years, with different settings, in different fields etc. are safer to do than comparison between different machines.

The operator is the overall regulator when spreading fertilizer. The operator’s lack of information characterises today’s working situation, while an excess of information may pose a problem in the future. The operator needs information concerning the position of his vehicle and the local need for nutrients in the field.

The field will influence losses by deposition of fertilizer outside the field and by gaps and overlaps. The slopes in the field generate mass flow or spreading pattern changes depending on the type of machine. Impacts and vibrations due to ground undulations can be handled.

Weather influences do not pose a severe problem provided the wind stays below 10 m/s and the fertilizer is properly stored and handled before spreading.

Although the machine design influences mass flow and spreading pattern variations, it is concluded that those inconveniences can be handled. The biggest improvement possible in fertilizer spreading today seems to be positioning aides.

The fertilizer is often characterised by several, up to 30, physical properties. Among those properties, particle size and size distribution, internal and external friction, density and aerodynamic resistance are those influencing the working result the most. Particle strength is also of importance, especially for broadcasters.

J E T Svensson, Swedish University of Agricultural Sciences, Dept. of Agricultural Engineering, Uppsala, Sweden.

38 pages, 12 figures, 4 tables, 48 refs.