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Fertiliser requirements should be based on soil testing. High yielding brassica crops have a large nutrient requirement. The nitrogen (N) requirements can range from 250 to 500kg N/ha. While total crop requirement for phosphorous (P) is quite low, it is vital during establishment and for shallow rooting brassicas. The application of P in a base dressing and down the spout at planting will provide good response particularly on low P soils. Growing brassicas on effluent ground may allow significant reduction in fertiliser inputs but again this should be on the basis of soil testing and knowledge of crop requirements.
Fact File
FERTILISER
The soil pH level should be at least 5.6 and ideally between 5.8 and 6.2 for most brassicas. Crops should have at least 40-60 kg phosphate/ha available at sowing.
Paddocks should have low soil sulphate levels. After grazing, a light application of nitrogen will greatly increase yields of subsequent growth. Use of nitrogen may increase problems of high crop nitrate content; test levels before grazing.
KEY ACTIVITIES:
- Allow the paddock to get a pasture or weed cover of 2000 kgDM/ha.
- Spray out with glyphosate at the correct label rate.
- Three days later, hard graze to remove vegetation prior to cultivation or drilling.
- If cultivating, use conventional farm practices that result in a fine, firm, residual free seedbed.
- In cultivated situations, seed can be broadcast, then harrowed and rolled.
- Best practice for direct drilling is to use a double spray programme. The initial spray out with glyphosate and usually a broadleaf herbicide occurs about 6 weeks before sowing. A second spray with glyphosate occurs prior to sowing to remove germinating seedling weeds and usually includes an insecticide and may require slug bait. Seed is sown at approximately 10 mm depth and then rolled. Seek advice for the appropriate use of chemicals.
- Once the crop is sown, it is important to monitor the crop and apply the appropriate herbicides and insecticides to remove any weed or insect problems.
