Maximising forage yield
- Feed budget to determine your livestock needs, 3 to 12 months in advance.
- Forage brassicas will handle a broad pH range from 5.5 -- 6.5.
- Soil test well before planting (6 months) to determine nutrient levels. Aim to supply the crop with enough plant available nutrients to achieve your target yield, as well as increase base fertility if required.
- Carefully consider the plant growing window and select the appropriate cultivar accordingly e.g. turnips 70 -- 120 days to maturity, kales 150 -- 180 days to maturity.
Weed and pest prevention
- Provide pest protection to emerging seedlings e.g. seed treatment.
- In summer dry areas where moisture retention is critical, a late winter spray can be used to remove pasture/weeds that will compete for moisture in the spring.
In direct drilled situations it is important to be extra vigilant for pests such as slugs, grass grub, Nysius and Argentine stem weevil. A number of options exist to control these pests.
Seek specialist advice from your local retailer.
- Apply herbicides to control weeds prior to or post establishment. Seek specialist advice from your local retailer.
- If cultivating, aim for a fine, firm, moist seedbed free of weeds and pests.
- Provide a fine firm seed bed to enable brassicas to be shallow sown at 5 - 10mm. Use press wheels with light chain harrows in direct drilled situations, or a light roller. Generally, for cultivated soils plant when you can just see your heel indent on the soil surface. Ensure good firm seed to soil contact and moisture retention post sowing.
- Brassica sowing rates vary according to species used, ploidy or if sown as part of a pasture mix. Use higher rates when broadcasting, or if seed bed preparation is difficult due to slope or soil conditions. General sowing rate guide per hectare: forage rape at 3 - 4kg, forage rape in pasture mix up to 1.5kg, turnips 1 - 3kg, turnips in pasture mix up to 0.75kg, leafy turnips 3 - 5kg and kale 4 - 5kg. Talk to your retailer about your specific requirements.
- Brassicas respond well to the macro nutrients, phosphorus and nitrogen. Ensure these nutrients are not limiting to the crop during early growth. Due to associated animal health issues, minimise the use of sulphur containing fertilisers.
- Address any trace element deficiency, such as molybdenum and boron. Monitor and treat for pests.
- Brassicas are susceptible at emergence to a number of pests which need to be controlled when they reach trigger levels. Seek specialist advice from your local retailer.
There are some points to consider after you have selected the appropriate cultivar for your situation that will help ensure you get the best animal performance from your crop when grazing.
Know how much crop is available to graze
- Take quadrant cuts from several areas of crop and weigh to find out wet tonnage per ha. Send crop to feed testing lab to find out dry matter % (DM %). Multiply wet tonnage/ha x DM% to get dry matter per ha yield. Allow for wastage during crop grazing, as stock cannot utilise 100% of crop grown.
- In an ideal situation there is generally 10% wastage (firm, dry conditions underfoot, break feeding).
- In less than ideal situations there can be more than 50% wastage (muddy conditions, no break feeding).
- Take the tonnes of DM/ha and wastage factors into your feed budget.
- Often if stock do not perform on crops, it is due to overestimates of crop on offer and/or underestimates of crop wasted. These have to be adjusted to allow stock to perform well on crop.
- Low levels of neutral detergent fibre (NDF).
- Brassica NDF is very quickly digested.
- Protein levels are moderate provided ample green leaf is present.
- Levels of non-structural carbohydrates (NSC) are high.
Gradual adaptation to crop
Types of rumen microbes in brassica-fed stock differ to those in pasture-fed stock.
Ratios of volatile fatty acids (VFAs, the end products of microbial fermentation) are different for stock on crop vs. pasture. Time is needed for the rumen microbes to change from a pasture fermentation to a brassica fermentation.
- Allow a minimum of 10 days for stock to adapt to crop.
- Start at low levels of brassica/head/day.
- Balance of diet as standing pasture, hay, silage and/or straw.
- Stock going straight onto high rates of brassica crop may lose body condition, and risk of brassica bloat, rumen acidosis, nitrate toxicity and abortion is high.
Use electric fencing to provide daily feed breaks for optimum livestock allowances and to reduce fouling and trampling losses. Ideally provide long narrow breaks to ensure all stock have good access to crop. Front and back fence for regrowth crops such as forage rape or leafy turnips.
Grazing forage brassica crops in conjunction with pastures or crop stubbles is a good practice to help maintain balance in the diet.