Nitrogen fuels brassica crop development and good supplies are required in wrap or guard leaves so that these can provide sufficient assimilates and nutrients for the curd or head. Good leaf/curd ratios and the highest quality compact curds can only be produced by applying optimum high rates of nitrogen.
Improving vegetable brassica compactness, size, weight and colour
Brassica compactness, size, weight and colour vary depending on the market needs and also on the different brassica types. There are, however, some common quality attributes. A uniform size, weight and colour, plus freedom from soil and disease are important characteristics desired by the retailer and consumer.
Crop nutrition and vegetable brassica compactness, size, weight and colour
Nitrogen improves brassica yield and appearance
Correct nitrogen nutrition also improves crop colour and reduces the incidence of brown head in broccoli, which improves marketability.
Potassium influences size and weight
Potassium boosts plant biomass and resultant brassica head weight and yield. Supplies need to be balanced alongside those of nitrogen. Potassium also helps to reduce variability on crop grade at harvest and maintain head and curd compactness.
Sulfur needs to be balanced with nitrogen to avoid deficiences
Sulfur is an important component of enzymes and other proteins, and is required for chlorophyll formation. A steady supply of sulfur throughout the season is needed. Care needs to be taken however, to match sulfur and nitrogen supply. Increasing nitrogen supply can restrict sulfur uptake. This is either a dilution effect due to better growth or a direct competition for uptake.
Iron
Iron is the micronutrient needed in greatest quantities within brassicas – between 80- 90g/t Fe – and over four times as much iron is needed compared to boron or zinc. It is important to plant metabolism as a component of enzymes and proteins, in order to increase brassica size and weight.
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