Nitrogen effects on vegetable crop production and chemical composition

Concerns about human health in relation to the intake of food have led to an increasing interest in the nutritional quality of food products. A high intake of vitamins, dietary fibres and some minerals, and a low intake of nitrate, is supposed to protect against several life-style diseases which occur in many industrialized countries. Application of fertilizers may not only influence the yield and quality of field vegetable crops, but also the chemical composition of the marketable product. Therefore, application of fertilizers may be used to control and improve the nutritional quality of products used for human consumption. During the last two decades the chemical composition of field vegetable crops has been monitored in several fertilizer experiments at the Danish Institute of Agricultural Sciences. This paper shows that increased N supply decreased the concentration of dry matter, potassium, sucrose, vitamin C, and dietary fibre in leaf vegetable crops, but increased the concentration of nitrate, nitrogen, and carotene.