Nitrate content of lettuce on nutrient film. 4. Ammonium/nitrate ratio. External quality as affected by raising the ammonium-to-nitrate ratio and by omitting nitrogen 15, 12, 8 and 4 days before harvest

Steenhuizen, J.W.

Rapport, Instituut voor Bodemvruchtbaarheid, Netherlands 6: 85


In trials with greenhouse lettuce in spring 1984 and summer 1983, plants were grown using the nutrient film technique with nitrate or 80% nitrate and 20% ammonium nitrogen and near harvest were transferred to solutions with a higher ammonium:nitrate ratio or to solution with no nitrogen. In spring the effect of heating the nutrient solution was also investigated. The higher ammonium:nitrate ratio increased sulphur and chloride uptakes and decreased nitrate, potassium and calcium uptakes.