Field experiments with the South American grain crop, quinoa, were carried out at two sites in Denmark in 1988–90 in order to study the effects of varying the nitrogen fertilization rate, seed rate, row spacing, harvesting method and harvest date. Although there was a significant yield increase when the amount of nitrogen fertilizer was increased from 40 to 160 kg N/ha, quinoa seems to be well adapted to poor soils. Yield decreased by 24–1% when the nitrogen supply was reduced from 160 to 40 kg N/ha, while the yield decrease was 120 and 2–7% when the nitrogen supply was reduced to 80 and 120 kg/ha, respectively.

A model expressing yield as a function of plant density, for three experiments analysed as one, showed an optimal plant density with respect to yield of 327 ± 220 plants/m2. This plant density was the top point of the curve relating yield to plant density. However, the large standard deviation indicates that apparently a rather wide range of plant densities would provide similar yields. When the row spacing was varied, it was shown that plots with a row spacing of 50 cm, which were hoed, gave a higher yield than plots with 25 or 12·5 cm row spacing, which were unhoed. There was an overall increase in yield when changing from combined harvesting to swathing; however, when comparing the yields from the optimal harvest dates for the two methods, no yield differences could be detected. The optimal harvest date for swathing was found to be the stage when the inflorescences start to turn brown, whereas for combining, the optimal harvest date was the stage when most of the inflorescences are already brown.