How to prevent stem (heart) cracking in vegetable brassica
Hollow stem is a physiological disorder in cabbage, cauliflower and broccoli - frequently linked to calcium and boron deficiency or over-supply of nitrogen.
Fast growing conditions often brought on by heavy rainfall and warm weather after a cold period - tend to favor the occurrence of hollow stem. During these conditions, growth is rapid, but levels of both calcium and boron will be diluted in new tissues. As a result, cell walls lack strength and elasticity, leading to cell breakdown and cracking of stems.
Stem brassicas have hollow stems due to tissue cracking accompanied by a browning, corking or rotting of the damaged pith tissue. Brassicas are tolerant to high levels of boron and toxicity is rare.
Crop nutrition
Calcium and boron supplies are essential for the production of strong but elastic cell walls and to minimize crop disorders. Both nutrients have a key role to play in minimizing cracked stems, hollow heart and in providing good long term storage characteristics.
In addition, too much forced growth through over-application of nitrogen - especially if this is out of balance with calcium and potassium availability - may create an inadequate supply of these elements and result in hollow stem.
Stem brassicas have hollow stems due to tissue cracking accompanied by a browning, corking or rotting of the damaged pith tissue. Deficiencies are most common on low pH and sandy soils. Brassicas are tolerant to high levels of boron and toxicity is rare.
Other crop management practices
Poor soil moisture availability, followed by sudden growth spurts in higher temperatures, or after strong rainfall periods, can result in significant stem cracking and tissue damage. Irrigation scheduling should take into account high, late season needs for water, but not create environments where disease can flourish.
