Nitrogen fertigation of flue-cured tobacco in a Mediterranean environment

Abstract

Nitrogen fertilizing significantly affects yield and quality of tobacco. Under Mediterranean conditions, irrigation, too, is a critical factor that can influence yield and quality of flue-cured tobacco. The combination of trickle irrigation and N fertilizing (N fertigation) should enable more efficient use of N and water to be made, and facilitate the management of the crop. This hypothesis was tested in two field experiments on a clay soil. Yield was the same with one irrigation line for every plant row or one irrigation,line for every two plant rows. Leaf DM yield was the same (4 t ha^-1) over the range of 70–160 kg N ha^-1, although fresh yield slightly increased over this range from 25 to 30 t ha^-1.

In contrast to other studies, topping the plants increased DM yield by 19% but fresh yield by only 8%, irrespective of N rate. Nicotine content increased in leaves of topped plants as the season progressed, but decreased in leaves of untopped plants. Application of 70–115 kg N ha^-1 did not differentially affect the nicotine content of the leaves, but proportionally decreased their reducing sugars content. However, 160 kg N ha^-1 applied over a longer period (with the first four irrigations) markedly increased the nicotine content. It is concluded that nitrogen should be liquid fed with the first two irrigations. As DM yield was the same with 70–160 kg N ha^-1 and only fresh yield increased with 160 kg N ha^-1, the N rate to be used will be decided on the basis of the desired leaf quality.