Fertilizer advice and nutrient balances for outdoor vegetables

Many horticultural crops have a high nitrogen requirement and a short cropping time compared to agricultural species. Therefore, a large amount of N must be available in comparatively short time for these crops to ensure high yields and good quality.

The estimation of the necessary fertilization with nitrogen (N) is always based on predictions of the N-requirement of the plants and the N-supply of the soil. Since both are strongly influenced by weather conditions and site characteristics, prediction errors can not be ruled out in principle. An overestimation of the need for fertilizer poses only a low business risk, since the fertilizer costs are comparatively low. On the other hand, underestimation of the need for fertilizers poses a considerable risk for vegetable growers, as even small nutrient deficiencies in some vegetable crops can mean that marketing is not possible, or only partially possible, and that considerable revenues can thus be lost. Therefore, it is customary practice to compensate for uncertainties in the prognosis of the fertilizer requirement by safety margins. This leads in many cases to excessive fertilizer inputs. Investigations by IGZ and independent field trials have shown that by using the N-Expert fertilization advisory system developed at IGZ, safety supplements can be reduced and – compared to fertilization according to rules of thump – nitrogen losses are reduced without sacrificing yield.

The computer program “N-Expert – Fertilization Advice and Nutrient Balancing in Field Vegetable Farming” supports farmers and fertilizer consultants in determining the fertilization requirements of vegetable crops and in preparing nutrient balances according to the German Fertilizer Ordinance.
The program published by the Leibniz Institute of Vegetable and Ornamental Crops (IGZ) computes fertilizer recommendations in accordance with the Fertilizer Ordinance 2017.

For farms that are not covered by the German Fertilizer Ordinance (eg small farms or farms in other countries), the fertilizer recommendations and nutrient balances can also be calculated according to purely scientific criteria and good professional practice.

The database provided contains up-to-date information on nutrient requirements (N, P, K, Mg) of all important vegetable species and many other plant species, which can be grown in rotation with vegetables.