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More Information:

	Cornell Extension Service  Handbook.
	Dr. Howard Resh Lettuce Production
	University of Georgia

 

Growing with less internal tipburn. (information courtesy of Nunhems, Holland)

Tipburn is one of the most important disorders in lettuce cultivation. As a result of disturbances in the balance between water uptake through the roots and transpiration through the leaves, cells near the leaf margin collapse. This results in discoloration and eventual necrosis of the leaf margins.

Of the different types of tipburn, internal tipburn accounts for the biggest losses in yield. Internal tipburn occurs inside the head of the lettuce and in general, problems are more severe as you get nearer to harvest. Head lettuce is also more susceptible than open types. 

Internal tipburn is a result of a lack of Calcium uptake by the younger, inner leaves caused by high transpiration through the outer leaves at low air humidity. As a result there is a high flow of fluid to the outer leaves, which in turn slows down and limits the transport of Calcium to the inner leaves. Because Calcium is needed for cell structures, the deficiency causes cells to collapse and as a esult tipburn develops.

Solutions for minimizing the risk of internal tipburn depend on creating a well balanced growing environment. In general one should avoid factors that reduce water uptake by the roots or stimulate the transpiration through the leaves.  You should avoid high EC levels in the growing medium, high a air temperatures, low air humidity during the heading stage and take care with nitrogen levels. In general it is better to reduce the use of ammonium nitrogen and apply a slow release fertilizer and at the same time keep a careful eye on Calcium levels while building a strong root structure.

During trials more tipburn was caused by higher temperatures, above optimum irrigation and higher nitrogen while extra applications of Calcium limited the occurrence of tipburn.

The General advice is:   

1.) Reduce the speed of growing ............."GROW SLOWLY"

2.) Reduce Nitrogen levels. Use low %N fertilizer or slow release fertilizer.

3.) Reduce irrigation levels.

4.) In general, growing slowly improves head/base shape and creates a stronger plant which is less susceptible to disease.

 

Lettuce -  color intensity.

Whether you are talking about Green or red leafed varieties, Butterhead to Oakleaf, color is a factor. Mostly our enquiries regarding color intensity apply to the Red leafed crops ie Red Oak, Lolla Rossa's, Red butterhead etc.

The intensity of the red coloring of leaves is primarily a varietal factor but the environment will also have an influence.  Temperature and nutrition will effect quality but light intensity is the a key factor.  Shading affects Chlorophyll A and Chlorophyll B, responsible for the green pigments and the Anthocyanins (Antho) , responsible for the Red.  Shading can, and does significantly reduce the concentration of the Antho  especially when combined with sub optimum temperatures. Monitor nutrition, temperature and light intensity.

Choose suitable varieties (triple reds) and adapt for time of plantings.

Buy a light meter and keep records.

Remove shade cloth during periods of low light intensity.

Add artificial light IF possible ($$!!).