Nitrogen uptake of table beet – validation of a model.
To reduce nitrogen (N) losses from vegetable fields fertiliser recommendations should be adjusted to the large range in yield and thus in N demand of vegetable crops. Thererfore, Feller and Fink, 1996 developed a generic model to predict total N demand based on expected yield. This model has been validated successfully in a series of studies for Brussels sprouts (Brassica oleracea L. var. gemmifera), white cabbage (Brassica oleracea L. var. capitata) and kohlrabi (Brassica oleracea L. var. gongylodes). The objective of this study was to validate this model for table beet (Beta vulgaris L. var. conditiva), a crop with a large variability in N demand, which is caused by a large potential range for selecting sowing dates, plant densities and cultivars.
Field experiments were carried out over two years where all together 55 combinations of N fertiliser levels, plant densities, cultivars and sowing dates were tested. Plants were sampled at two or three week intervalls, and fresh matter, dry matter and N content of leaves and beets were measured. Crop specific model parameters for table beets were determined from independent data.
The model overestimated N uptake for N-limiting conditions, but for optimally fertilized table beets measured and estimated N uptake showed a close correlation (R² = 0.93) when total yield was used as an input parameter for the model. Although the error of estimation (SE = 35 kg N ha-1) was considerable, studies with other vegetable crops using this model showed this error can be even higher if other tools such as look up tables were used for predicting N uptake.
Feller, C.; Fink, M. 2002. Nitrogen uptake by table beet - validation of a model. Journal of the American Society for Horticultural Science. 127 (6), 1013-1017.