Pasture Management Factsheet

December 2016

Best practice pasture management is essential to cow performance, milk solids production and the operating profit of a grazing dairy business model.  Every effort should be taken to implement procedures that will optimise both growth and utilised tonnes of dry matter per hectare.

So how do I do that?  We look at options to consider at different times of the year. Included are simple tools that give accurate results.  These make it easy to work out how much forage our cows are actually getting, as well as explaining factors that can affect dry matter intake, like neutral detergent fibre (NDF).

When we really understand how to manage our pasture and what it is actually delivering to the cow, it becomes a lot easier to make decisions on next steps.

3 Leaf stage

Perennial ryegrass tillers grow by leaf emergence. When the first leaf has reached maturity, the second leaf commences growing and so on. However, once the third leaf reaches maturity and a fourth leaf appears, the first leaf will begin to decay. Therefore, the optimal time for grazing is when ryegrass tillers reach the 2.5 – 3 leaf stage.

Leaf emergence changes with the seasons. During spring, leaf emergence may be as rapid as 6 days but come winter, this may be 20 days. Leaf emergence is a great tool to use when setting grazing rotations for optimum pasture utilisation. Ryegrass tillers should never be grazed at or below the two leaf stage, nor should they be grazed at 4 or 5 leaf stage.

Post grazing residuals

Over grazing during periods of low daylight hours and reduced soil temperature will effectively slow total growth rates. Conversely, under grazing during early spring will allow stem elongation to occur which results in falling pasture digestibility at the next grazing. Post grazing residuals therefore become a key target that must be measured and monitored throughout a season.

Month

Target post-grazing residual

January

1,600kg DM/ha

February

1,600kg DM/ha

March

1,600kg DM/ha

April

1,650kg DM/ha

May

1,700kg DM/ha

June

1,700kg DM/ha

July

1,700kg DM/ha

August

1,600kg DM/ha

September

1,500kg DM/ha

October

1,500kg DM/ha

November

1,550kg DM/ha

December

1,600kg DM/ha

Conservation of surplus

Any genuine surplus of pasture grown in spring or autumn should be conserved as high quality silage. This surplus must not be ‘manufactured’, as the first objective of pasture grown is to support grazing intake. Paddocks may be considered for conservation when there are more than 5 days of grazing that could be utilised on one given day. Paddocks should not be out of the rotation for more than 7-10 days before mowing begins in order to maintain silage quality and achieve optimal regrowth.

Pasture walks

Plate metering needs to occur on a weekly basis. All individual paddock measurements must be recorded and entered into a pasture management diary or program (eg. Farmax, Pasture.io) to further aid pasture management decisions. Average pasture cover targets will be set each season via Farmax models and every effort must be taken to keep on track with these targets. Supplements may be considered for use at times of APC deficit in order to get back on target when seasonal conditions may cause complications.

Pre-graze topping

This strategy may be used from time to time in order to stimulate daily pasture intake per cow. For this strategy to be effective, topping must start early, before there is stem elongation in the pasture in order to avoid cows consuming low digestibility pasture that they would have otherwise left behind. This may be beneficial for one or two rounds during the months of September and October. It may also help reduce the risk of sporulation in autumn that leads to facial eczema.

Feed testing

It is beneficial to send pasture samples off to an accredited laboratory on a regular basis to gain further insight into pasture nutrient quality. This is beneficial for total ration balancing and may also give insight into soil fertiliser requirements. Suggest a minimum of 4 per annum.

Nitrogen fertiliser usage

Should be applied for best advantage to increase total pasture available for harvest. Nitrogen fertiliser is best applied either 2 days prior to grazing or immediately post-grazing. Urea is still the most cost effective form of nitrogen available and should be applied at the rate of 50-60kg per hectare. Consultation with the management team should be taken at times when soil moisture may limit nitrogen fertiliser efficacy.

Capital fertiliser

Should always be applied according to the management plan, which is at the discretion of the business owner. Soil testing should be undertaken with the fertiliser company of choice to determine which nutrients and at what levels need to be applied.

Quadrant cutting

This is a simple process to help ensure that rising plate meter (and your eye) calibrations are in line with seasonal pasture variation.

  1. Make yourself a quadrant that measures 50cm x 50cm. It can be made from any material eg. wood, plastic, metal. Some use a piece of string that is 2 metres in length and 4 tent pegs…
  2. Choose random sites in your paddock to be measured that are representative of what you are observing. Site your quadrant and using a pair of shears/secateurs, proceed to cut the grass within the quadrant right down to ground level
  3. Place all of your clippings into a suitable bag for collection and seal it off when you are finished
  4. Establish the net weight of the clippings using a kitchen scale that has 1 gram calibrations, record the net weight of the clippings (if you weigh the clippings in a bag or container, don’t forget to subtract the weight of the bag/container to obtain the net weight)
  5. If required, ask permission to commandeer the microwave oven for the purpose of drying your clippings (it does give off a slightly strong odour). Place your clippings into a microwave proof dish (you may want to re-weigh your sample at this point while it is in the container and record your starting weight) and place into the microwave along with a mug of water, which will stop your sample from catching fire in the later stages of this process…
    Pasture factsheetPasture factsheet
  6. Cook on medium-high for 5 minutes, remove your sample and re-weigh. Record the new weight, which you will note is lower than your starting weight. Check your water level and repeat this step 3-4 more times
  7. As you start noticing smaller weight changes per cooking interval, reduce the cooking time to 2 minute periods. Continue the process until you have two post cooking weights the same, as this means that your sample is now completely dry. Record your final dry weight.
  8. To establish your dry matter content, simply divide your final net weight by your starting net weight
  9. To calculate kg DM/ha from your sample, simply multiply your final net weight by 40
  10. Repeat for multiple samples to add rigor to your data. And I’m sorry, but if you do start a small fire in your microwave, you will have to start again…

 

Example:

Sample net weight final   X   100  =  % dry matter content
Sample net weight start

Sample net weight final   X   40  =  Kg DM/ha

 

Sample net weight (start), 514 grams. Sample net weight (final), 86 grams.

(86 ÷ 514) x 100 = 16.7% dry matter content

86 x 40 = 3,440kg DM/ha

 

Watch our helpful video on doing your own herbage mass assessment.


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