CONSIDERATION OF NITROGEN MINERALIZATION FROM HARVEST RESIDUES IN THE CALCULATION OF FERTILIZER RECOMMENDATIONS

A field experiment was carried out in order to test if nitrogen (N) mineralization of harvest residues is considered correctly in the fertilizer recommendations given by the decision support system ‘N-Expert’. Kohlrabi (Brassica oleracea convar. acephala var. gongylodes L.) was grown with 4 levels of mineral nitrogen and 4 levels of lettuce (Lactuca sativa L.) harvest residues.
For each level of harvest residues a recommendation for mineral fertilization was calculated by N-Expert.

As the amount of harvest residue increased, recommended N fertilizer decreased from 200 to 100 kg/ha N. Calculation of nitrogen balance showed that the amount of nitrogen that mineralized from harvest residues was less than estimated by N-Expert.
Despite this estimation error no fertilizer recommendation of N-Expert resulted in significant yield losses in this experiment.
This was shown by regression models, which were fitted to yield of kohlrabi in dependence on mineral fertilizer.

Ecological aspects of Vegetable Fertigation in Integrated crop Production in the Field

M. Fink

vegetables, model, decision support system, N-Expert

https://doi.org/10.17660/ActaHortic.1996.428.24