Kale
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3 min read
Kale is a winter feed crop with a deep root system, making it drought-resistant. It's tolerant to many pests and is often grown after swedes due to its resistance to club root and dry rot. You should decide on the type of kale to plant based on yield and quality, with short, intermediate, and giant cultivars offering different benefits. To maximise kale's energy value, focus on the leaves and top third of the stems. For the best yields, prepare a fine, moist seedbed, and consider soil nitrogen tests before fertilising. Kale requires specific amounts of N, P, and boron. Stay alert for pests like springtails and aphids, and always use certified seeds to avoid unwanted weeds.
Kale is normally used as a winter feed crop. With a deep root system; it has good drought tolerance.
Kale also has good tolerance to most insect pests and can be used as a second brassica crop, especially after swedes, because of its tolerance to club root and dry rot. It is usually sown in November or December.
What type of kale should I plant?
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SHORT CULTIVARS |
INTERMEDIATE CULTIVARS |
GIANT CULTIVARS |
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Potential yields around 12 t DM/ha* Good quality with high leaf: stem ratio |
Potential yields around 15 t DM/ha* Balanced leaf: stem ratio |
Potential yields around 17 t DM/ha* Lower leaf: stem ratio so often lower in quality |
These yields can be achieved under good growing conditions.
The yield will vary depending on soil type, fertility, and available moisture. Soil moisture is usually the main cause of yield variation - in some areas it can be the lack of moisture during summer, while waterlogging can be a problem in wetter areas. Regardless of cultivar, yields as low as 6-8 t DM/ha can result if kale is grown on light, infertile soils, or experiences water stress. Kale has no ripening requirements, but maximum yield is around 150 to 220 days.
What is the energy value of kale?
Kale leaves and the top third of kale stems are generally high in energy, and will test at an ME of 12 MJ/kg DM or more. Lower portions of the kale stems have reduced ME, with feed quality dropping off as the stem gets closer to the ground. All stems will become increasingly hard and fibrous with time.
How should I prepare the soil to maximise kale yield?
To maximise yield, a fine, firm, moist seedbed with good soil-seed contact and uniform plant population must be established. Full cultivation often produces the best seedbed for kale establishment, however, if done correctly, sowing method does not affect yield.
If spray and drill (direct drilling) is being used the sowing rate is 3-5 kg seeds/ha, and if the seeds are being broadcast and rolled then the sowing rate is 5 kg/ha. The optimum sowing depth is 1-1.5 cm.
What fertiliser should I apply?
Kale responds strongly to N application; it is advisable to do an available soil nitrogen test before sowing to determine how much fertiliser N will be needed. Depending on soil moisture levels and potential crop yield, a typical recommendation for kale is 250-350 kg DAP/ha at sowing, followed by two topdressings of 100 kg urea/ha at 4-6 and 8-12 weeks after emergence. Too much N, or late applications can lead to nitrate poisoning and excess crude protein in the leaf and upper stem. Surplus crude protein during grazing will increase urinary N excretion and the risk of nitrate leaching.
While the requirement for P is quite low, sufficient P is vital for the establishment of seedlings. The P requirement for a second crop is likely to be higher. The ideal pH is 5.8 to 6.2; this should be corrected with lime a year before sowing. Kale seldom responds to S or K fertiliser.
Brassicas have a high boron requirement - applications of up to 400 grams B/ha can be required, but the amount should be adjusted depending on soil test results.
What pests, diseases, and weeds should I look out for?
The main insect pests are springtails, diamondback moth, white butterfly, and aphids. Nysius fly can cause major problems by allowing dry-rot (black leg) to enter; this causes weak bases in the plants. Inspect young crops regularly by walking well into the paddock and if necessary, apply the appropriate insecticide. If the spray and drill method is being used, slug control and checks for grass grub and porina are recommended, as these pests can cause the death of new seedlings.
A healthy, well-fertilised crop will usually outgrow weeds but yields may be reduced if weed pressure is high. To compete with weeds, ensuring a good start for the crop is essential. Spray applications prior to sowing depend on the method of establishment. Always use certified seed to reduce the risk of introducing weed species to your farm.