Feasibility and economic analysis of improved nitrogen fertilization measures for vegetables in Germany

Optimization of nitrogen (N) fertilization in order to reduce the risks of nitrate leaching into the ground water is an important challenge in open field vegetable production. The intensity of vegetable production is very high, compared to other arable crops, and optimal N-supply is essential to produce adequate yields and quality. However, many vegetable crops leave high levels of nitrate (N_min) in the soil as well as significant amounts of organic N in crop residues at the time of harvest. This study presents an analysis of the practical feasibility and economic assessment of costs and benefits of measures to improve N-efficiency in vegetable production. The results are based on a project, financed by the Ministry of Agriculture and implemented in collaboration between farmers and advisory and research services in three major vegetable producing regions in Germany. In the project, improved N-fertilization strategies were tested on-farm, practical experiences as well as costs and benefits were analyzed and results were transferred to the vegetable producing sector. The fertilizer strategies presented in this paper are based on splitting the N-amount into more and smaller applications than the standard practice of one application at planting and one top dressing. Based on repeated N_min soil samples to minimize risk, these strategies can be implemented in different ways, e.g. using different spreading equipment or combining fertilizer and pesticide applications. Potential N-fertilizer reduction depends on many factors, e.g. residual N from the previous crop, soil type and organic matter, as well as mineralization conditions (temperature, humidity). Hence, practical feasibility varies according to conditions on the farms. To assess economic outcomes, scenario analysis is applied for different farm conditions, crop sequences and application techniques. The results show that in many scenarios, a major part of costs for additional soil samples, labor and machinery costs are compensated through savings in fertilizer costs.