Fast growing types (e.g. cauliflower and broccoli) require a high nitrogen supply as they have high nitrogen uptake rates and a high nitrogen requirement, particularly during early growth
Slower developing types (e.g. cabbages) – particularly those growing at lower temperatures and lower radiation conditions – take longer to utilise the N needed for high yields
By ensuring a good supply to the outer leaves, they will develop strongly and support later growth by providing assimilates and also redistributing nitrogen needed for high brassica yields. Failure to get nitrogen into these leaves by using inadequate low rates in early fertiliser applications will result in lower brassica yields. Later applications cannot make up for this.
Potassium plays a crucial role in the energy status of plants. Brassicas have a relatively high potassium requirement, and up to 2.7-5.1 kg of potassium is required per tonne of crop. Uptake follows growth, so it is essential that potassium supply mirrors key growth needs.
Potassium rates of 225 kg/ha and above produce responses on high yielding sites, increasing both plant biomass and resultant head weight and yield.