Nitrogen deficiency (N)
Nitrogen deficiency is recognizable by the plants’ lighter colour and their delayed development. In contrast to a deficiency of sulphur and many micronutrients, a lack of nitrogen will initially affect older leaves. These leaves will show chlorotic spots, which will later turn necrotic, and which in case of a prolonged deficiency will also spread to younger growth. Chlorosis will begin along the outer leaf-edges and will intensify as it spreads towards the main leaf veins.
Nitrogen deficiency in bell peppers will typically be characterised by the formation of long, retarded and bent fruits, with very little flesh. Cucumber plants will respond by producing only bent, thin and pale fruit. Depending on the anthocyanin-content of the variety, cabbage may exhibit lilac-coloured discolorations in addition to a generally lighter green colour. Tomato plants will show reduced longitudinal growth as well as fewer lateral shoots and fewer tomatoes. Cabbage and lettuce will form considerably smaller, lighter heads.
The nitrogen requirement of vegetable crops should be met by a combination of starter fertiliser and top dressings. For cabbages and cucumbers, organic fertilisation prior to cultivation has shown to be beneficial. Foliar fertilisation with N-containing fertilisers may be very effective; however, this treatment should only be considered in case of minor deficiencies. In general, we recommend mineral starter dressings in combination with one or more top dressings, in order to prevent or alleviate deficiencies.