Abstract A field experiment was carried out in sugar beet with a wide-span (12.2 m) tractor and laser guided implements. By means of a side-shift facility, implements were mounted on this vehicle for seedbed preparation, drilling, fertilizing, spraying and hoeing. Automatic laser guidance was possible with an accuracy of 0.6 cm on a track length of 220 m on arable land. No inputs (soil cultivation, fertilizer, herbicide) were made at places where they were not needed, or even would potentially pollute the environment. The aim of the experiment, which was carried out in 2 successive years on fields of the same farm, was to investigate the influence on weed occurrence and efficiency of weed control. Leaving out seedbed preparation between the future crop rows left already germinated weeds alive. In 1 year pre-emergence application of paraquat-diquat was necessary to stop growing of well developed weed plants. A crumbling operation had to be carried out to break the clods, otherwise inter-row hoeing was impossible. From the viewpoint of weed control restricting seedbed preparation to the future sugar beet rows was not of advantage. Precision guidance allowed enlargement of mechanical weed control, i.e. interrow hoeing to 80% (40 cm wide at a row distance to 50 cm). Savings on herbicides were 75%, because little overlap was necessary of chemically and mechanically treated areas. The absence of fertilizers in these inter-row bands did not diminish the number of weeds, and speed of emergence of weeds. The effect of seedbed preparation and drilling the sugar beet crop in complete darkness (at night), made possible by the automatic guidance, on weed infestation was not different from daylight treatments. In these experiments this so called photo-control of weeds was only demonstrable after hoeing.