Brassica Establishment & Management

Planning is the key to success. Your planning checklist should include the following:

 

 Paddock selection

Questions to ask when selecting paddocks:

  • Which paddocks have poor performing pastures? Have undesirable species? Low legume content?
  • Has fertility status been limiting pasture production?
  • Will this need addressing to ensure a good brassica crop and a successful renovation phase?
  • Is the paddock selected in close proximity to a run-off paddock, supplementary feed source and water supply?
  • How easily will the paddock be subdivided?
  • Is the right farm equipment available for successful subdivision or paddock water supply requirements etc.?
  • What is the proposed crop sequence for this paddock?
  • Do any other issues need addressing prior to a permanent sow-down, e.g. elimination of volunteer ryegrass before AR37/AR1 endophyte ryegrass establishment?

Pre-sowing preparation

  • Successful weed control starts with careful identification of species, growth stage and vigour. This will determine herbicide selection. Seek advice from a technical representative for specific recommendations
  • Early workings should aim to stimulate weed germination (ideally 2 months pre-sowing)
  • Aim for a moist, fine, firm seedbed, allowing the small brassica seed to be planted at an even 1 cm depth
Conventional cultivation
Conventional cultivation is generally the most reliable way of eliminating weeds and establishing brassicas. Best practice is the broadcasting of fertiliser prior to planting. For a minimal pass operation, pull hoses out of coulters and drop fertiliser in a surface band, with incorporation by light harrowing and rolling.

Direct-drilling
Direct-drilling is suitable if spray control of weeds is successful and fertiliser applications are considered carefully. For detailed information on no-tillage and direct-drilling refer to “Successful No – Tillage in Crop and Pasture Establishment”, Ritchie et al. (2000). Nitrogen (N) applications are a key component of successful establishment from direct-drilling. Under no-tillage regimes, crop residues are broken down by microbial activity (not burning, oxidation or mineralisation as in tillage systems) that temporarily
locks up nitrogen. Therefore N will not be available at the time of the brassica establishment, and hence this delay in N availability needs to be compensated for at sowing time.

Ridging
Ridging effectively provides a raised seedbed for establishment away from excess moisture. It is best suited to use in wetter climates.

Broadcasting
Broadcasting, (the scattering of seed onto a worked seedbed), can be successful, but a higher sowing rate and subsequent light harrowing and rolling is recommended.
Typically, less productive pastures are sown out into brassicas, often meaning they are established into less than optimum conditions. Brassicas tend to differ from other crops in certain aspects of their fertiliser requirements. Brassica yields are sensitive to nitrogen and phosphorus status. In addition, boron deficiency may impact on plant health, especially in the bulb brassicas. The seed is particularly prone to germination injury if soluble fertiliser or boron is placed too near the seed. Inappropriate levels of certain nutrients can induce animal disorders e.g. the sulphur compound S-Methyl Cysteine Sulphoxide (SMCO).

For specific fertiliser recommendations please contact your local fertiliser representative or contact your local Agricom Sales Manager.

The successful grazing of livestock on brassicas requires farmers to be aware of a number of factors that may impact on the productivity and health of animals. To successfully achieve the desired outcome (e.g. body condition score gain, liveweight gain or maintenance feeding) from grazing brassica crops, farmers should be aware of a number of factors which may impact on the productivity and health of animals.

Allocation
In many cases, where animal performance does not meet the expectation of farmers, reduced feed intake through poor allocation of feed is a common cause. Fast growing animals require high intakes and where feed is restricted high intakes are not possible. Restricted intake may occur as a result of the daily break in a strip grazing situation being too small for the number of animals or animals spending too long in a paddock in
a rotationally grazed situation. Stocking rate being too high in a set stocked system can also restrict intake. Correct allocation is critical for highly productive systems.

Feed Quality
Quality parameters of feed influences stock performance. For young growing animals adequate intakes of energy, protein, macro and trace elements are important for healthy
and productive livestock. Specific requirements will depend on liveweight, pregnancy status and desired performance level (e.g. growth rate). Table 10 gives typical values for energy, protein and DM% of a range of feeds to help determine specific requirements.

Crop Utilisation

Break feeding (strip grazing) is the best practice for manipulating utilisation rates, diet quality, crop life, and crop regrowth potential. Generally, as crop utilisation increases, animal intake per head decreases.

Transitioning onto a Crop

Transitioning is allowing time for the rumen microbial populations to reach a new equilibrium capable of dealing with a new feed. Theoretically this process takes 21 days to be fully complete but practically the transition is well enough advanced to minimise
issues by 10-14 days. The process usually entails a gradual increase in the proportion of the crop in an animal’s diet. This can be achieved by:
a) the time they are left on the crop each day, or
b) the daily crop allocation.

The following guidelines help to limit the effect of diet change through the transition period:

  • Introduce animals slowly to a crop, from an initial 2-3 hours to full allocation by 10-14 days. This allows rumen microbes to adjust and may reduce the “grazing check” effect
  • Do not introduce hungry animals to the crop. Gorging may occasionally lead to bloat or nitrate poisoning problems
  • Offer an alternative source of feed, pasture, hay or silage, during introductory stage and throughout grazing of crop
  • Stock performance will be improved if transitions from grass to brassica and back to grass are minimised as much as possible, e.g. use appropriate stocking rates so animals stay on brassicas for the desired time

Why is Fibre Important?

Brassica crops typically are highly digestible, have high ME and protein content but are often low in fibre. Fibre (NDF and ADF) is required for efficient rumen function and it:

  • Helps maintain rumen pH by encouraging saliva production through chewing
  • May dilute any possible anti-nutritional plant chemicals and therefore reduce their effect on livestock
  • Extends the number of grazing days on the crop, as it supplements animal intake
  • Must be palatable so stock can consume it
  • May be detrimental to animal performance if there is excessive use of low quality fibre

NOTE: Always ensure that stock have ready access to a good supply of drinking water.

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