EFFECTS OF PLANT DENSITIES AND NITROGEN SUPPLY ON YIELD HARVEST DATE AND QUALITY OF CARROTS

In northern Germany near Hannover carrots (small spherical cultivars) are produced for the processing industry.
Carrots are grown on loamy sand using bed systems consisting of eleven rows per 1.35 m.
The carrots are processed as whole ones.
Thus, only carrots of a diameter from 18 to 32 mm are marketable with the consequence of short potential harvest periods.

In field experiments the influence of plant density and nitrogen supply on yield, size distribution and harvest date were determined.
The N-supply – that means the amount of mineral nitrogen in the root zone (0 – 60 cm) and N-fertilizer application two weeks after emergence – necessary for highest yield is 80 to 140 kg N/ha depending on N-mineralization during growing season.
There is no need of a rest of mineral nitrogen in the root zone at harvest time.
The determination of the nitrate content in petioles by a rapid nitrate test, using diphenylamine diphenylbenzidine, was very useful to rate top-dressing accurately.
Low N-supply kept the crop in marketable size for a longer period and resulted in low nitrate content (< 300 ppm) in the roots.

For earlier harvest dates densities of about 500 plants/m² were the best, but for later harvest dates 600 to 800 plants/m² gave higher yields.
The higher the plant density the lower was the percentage of marketable carrots of

Symposium on the Timing of Field Production of Vegetables

H.-J. Wiebe

https://doi.org/10.17660/ActaHortic.1987.198.24