How to prevent black petiole in vegetable brassica

Black petiole or black midrib is an internal disorder of cabbage, which occurs as the head approaches maturity. It is thought to be caused by an imbalance of potassium and phosphate and excess nitrogen.

An imbalance of potassium and phosphorus causes black petiole

Black Petiole is due to a collapse of the cytoplasm in the parenchyma cells and believed to be associated with a potassium and phosphorus imbalance when the potassium level in the soil is low and the phosphorus concentration high.

The dorsal side of the internal leaf petioles or midribs turns dark grey or black at or near the point where the midrib attaches to the core. The affected area may be quite limited or may extend for 5 to 8 cm along the midrib.

High rates of nitrogen may contribute to black petiole

High rates of nitrogen may also contribute to the problem. Black petiole tends to become more evident when cabbage has been stored for a period of time. Soft rot can become a problem in broccoli when optimum nitrogen is exceeded.

Vegetable brassica agronomy and fertiliser advice
Vegetable brassica agronomy and fertiliser advice

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