Fertiliser and grazing management for Autumn sown perennial pastures.

Rob Harborne- AusWest Seeds Southern NSW

Optimising the potential of autumn sown pastures in the tablelands pasture systems can be critical in overcoming the winter feed gap, leading to better livestock performance and profitability.

Grazing systems need to identify several key factors in order to maximise the grazing benefits from autumn sown pastures.

  1. Know the fertility status of the paddocks
  2. Have a pasture that is going to suit the class of livestock that is in the operation
  3. Understand and be able to apply optimal grazing management in order to maximise grazing benefit from those pastures
  4. Fertilise at the right time with the right product in order to maximise production

Key nutrients

Nitrogen (N) - Nitrogen is the most common fertiliser used to increase pasture production and this is mainly applied by the product called Urea. When applying nitrogen to pastures, it is important to consider the following factors such as; that the pastures need to be actively growing, that the soils should not be waterlogged and that the fertiliser is best applied within three days of grazing or slashing. (NSWDPI, 2006).

Phosphorus (P) - Phosphorus is frequently a limiting nutrient to the growth of pastures. Phosphorus fertilisers can be applied to dry soil and split applications are preferable when using heavy rates. Highly productive temperate pastures require a soil test Colwell P of at least 75 mg/kg, for medium production the result should be 50 mg/kg (NSWDPI, 2006). Having low Colwell P levels may create favorable conditions for weeds and less productive pasture plants therefore limiting pasture production.

Potassium (K) - A large store of potassium is available in most soils. Potassium deficiency usually arises when plant removal is high. Hay and silage production removes large amounts of potassium from the soil. Potassium is relocated around the farm in dung and urine and should be replaced in areas of depletion. (NSWDPI, 2006).

Sulphur (S) – Sulphur can be the forgotten nutrient as many fertilisers have small amounts available. Single superphosphate is the most common fertiliser to supply sulphur to pastures and Gypsum supplies sulphur and calcium (Ca) to the soil.


Nutrient removal

Depending on how nutrients are removed determines how much and what type of fertiliser needs to be applied to maintain production. Nutrients removed from paddocks through milk by dairy cows are different to those removed by wool production or live weight gain in sheep and beef.

Key Tips:

  • The use of the correct fertiliser at planting down the seeding tube will increase DM (drymatter) production usually by double compared with broadcasting the same fertiliser. Therefore placing fertiliser with the seed is critical.
  • Applying Nitrogen to a pasture is the most cost effective way to fill your feed gap. On average there will be at least 10kg’s of drymatter produced for every 1kg of nitrogen applied. So
    50 kg/ha of urea equates to 23kg N/ha and this will grow approximately 230 kgs DM/ha additional feed (depending on base soil fertility and timing of urea application).

Good pasture production requires good soil fertility and achieving this means applying fertilisers that have the correct nutrients for the pasture you are growing and that replaces the nutrients removed by your farming system.

For more information please contact our Stephen Pasture Seeds or AusWest Seeds team.

Incitec Pivot, 2011. http://www.incitecpivotfertilisers.com.au/en/Products%20and%20Services/Agriculture%20Industry/~/media/Files/Productive%20Pastures%2012pp%207870proof12.ashx
NSWDPI, 2006
University of Georgia

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