Compared to other vegetable crops, cauliflower and broccoli are extremely perishable and should be stored for relatively short periods. Leafy brassicas are less demanding in terms of harvest timing. Here, leaf nutrition is the key: ensuring good green, strong plants will help secure good quality and a long shelf life.
Nitrogen is important for yield, but if optimum rates are exceeded it can have a negative impact on storage quality.
Excess nitrogen can result in low dry matter content – which reduces the storage quality of cabbage, and can lead to greater disease in the stored crop, particularly in susceptible varieties.
Adequate potassium supply ensures a more marketable crop and with a healthy longer shelf life and less moisture loss during storage.
The form of potassium can also influence storage with SOP (sulphate of potash - potassium sulphate) leading to higher dry matter than MOP (muriate of potash - potassium chloride).
Calcium is probably the third most important nutrient needed by brassicas and has an important role in maintaining crop quality.
Calcium is responsible for the structural and physiological stability of plant tissue. It helps form strong cell walls and is vital to cell membrane integrity, both of which are important to achieve improved storage and longer shelf life.
Typical disorders caused by calcium deficiency include tip burn on leaves, glassiness of cauliflower curds and internal browning in Brussels sprouts
Magnesium improves brassica crop storage characteristics.
Magnesium uptake can be depressed by an excess of other cations (K+; NH4+; Ca2+), so it is important to maintain a correct balance to avoid compromising Mg uptake. Magnesium salts (e.g. carbonate, nitrate and sulphate) are more soluble than calcium salts but also more prone to leaching losses. Foliar sprays can be used to correct acute deficiencies.
Sulphur also has a major role to play in brassica crop quality.
As seen above, application of sulphur in the form of SOP (potassium sulphate or sulphate of potash) increases dry matter content of white cabbage, which gives better storage quality.