Tidsåtgång för maskinarbeten på små fältNilsson, Daniel; Rosenqvist, Håkan; Bernesson, Sven
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 2:1 (length: width), was 36 min/ha when the field area was 1.0 ha, 26 min/ha when the field area was 5.0 ha and 24 min/ha when the field area was 15.0 ha. Thus, it was concluded that the field area was important to consider also for ‘regular-shaped' rectangular fields. Simulations were also carried out for elongated rectangular fields (e.g. headlands and border strips). The results showed that the time for non-productive work (e.g. for in-field transports) can be considerable if the machinery work width is not well-adapted to the field width.
The time demand for the mowing of grass (machinery width 2.25 m, driving speed 10.0 km/h, field area 1.0 ha) was compared for different 'irregular-shaped' fields. Using a rectangular 2:1-field as a reference, the time needed varied from -4% (trapezium-shaped field) to +16% (a polygonal field with a circular impediment). The number of turnings (machine not in work) had a crucial impact on the results, but the extent to which the machine was driving in curves (machine in work but with a limited driving speed) was also an important factor.
In the project, a simple method for calculating transport distances has been developed. The method was based on the fields' block numbers.
KeywordsSmå fält, oregelbundna fält, maskinkapacitet, tidsåtgång, simulering, small fields, irregular-shaped fields, machine capacity, time demand, simulation
Published inRapport (Institutionen för energi och teknik, SLU)
2014, number: 072
Publisher: Institutionen för energi och teknik, Sveriges lantbruksuniversitet
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