ISHS Acta Horticulturae 178: Symposium on Nutrition, Growing Techniques and Plant Substrates
NITRATE IN LETTUCE ON RECIRCULATING NUTRIENT SOLUTION |
| Authors: | J. van der Boon, J.W. Steenhuizen |
| Abstract:
Lettuce (Lactuca sativa L.) was grown on recirculating nutrient solution with a view to obtain a crop with an acceptable nitrate content, high levels being considered undesirable from the standpoint of human health. This culture method permits instant changes in the form and amount of nitrogen supplied to the roots. The effect of a solution with a high ammonium/nitrate ratio or a solution without nitrogen, introduced a few days before harvest, on the nitrate concentration of lettuce was studied. A solution without nitrogen can only be used for a short period without seriously affecting yield and quality, although it considerably decreases the nitrate content of the crop. The effect of a high ammonium/nitrate ratio in the solution on the nitrate content of the lettuce was relatively small in early summer and more pronounced in early spring, while yield was scarcely affected in both experiments. In separate experiments the effect of heating the nutrient solution and lowering the glasshouse air temperature (favourable from the viewpoint of saving energy) on the nitrate content of lettuce was investigated. Heating of the solution did not significantly raise the nitrate content of lettuce, while growth was stimulated. | |
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