Tidsåtgång för maskinarbeten på små fält : en simuleringsstudie

The machinery costs have an important impact on the economic profitability of crop production in small and irregular-shaped fields. In most cost calculations, the capacity of machinery operations in agriculture is given as a single value, which is assumed to be valid for all types of fields independent of field area, field shape, the presence of field obstacles, etc. This may result in misleading cost calculations for different crops and thus incorrect decision bases for the farmers. The main purpose of this study was to analyze the time demand for different machinery operations in small and irregular-shaped fields with the help of computer simulations. The objective was to get more field-specific capacity data that can be used for calculations of machinery costs. More precise basic data will give the farmers a better basis for decision when choosing crops in such fields. What is meant by the term a ‘small' field is subjective and dependent on where the field is located. In a flat country with large-scale agriculture, a field of 5 ha may be regarded as ‘small', whereas this area may be regarded as ‘large' in forested areas. Of the four Swedish municipalities investigated in this study (Svalöv, Ronneby, Vingåker and Skellefteå), the average lot area was largest in Svalöv (6.7 ha) and smallest in Ronneby (1.9 ha). Furthermore, there is no unambiguous definition of what an ‘irregular-shaped' field is. Often, however, the term is used to describe a field with several corners, narrow tips and ‘islands' with uncultivable land. It is often regarded that the more ‘irregular-shaped' the field is, the more difficult (or costly) it is to cultivate. A comparison of the so-called shape index between the municipalities studied, indicated that fields in municipalities with a higher variability in topography and geographical structure (Ronneby and Vingåker) are more irregular-shaped. The time demand for machinery operations in rectangular fields was simulated using machinery work width, optimal (max) driving speed, field area and field shape as independent input variables. In the simulations, the time needed for turnings, curve driving (limited speed), acceleration/retardation, adjustments, stochastic stoppages, etc. were considered. The results showed, for example, that the time demand for a machine with a working width of 4.0 m, a driving speed of 8.0 km/h and working in a rectangular field with the shape 2