Best management practices for phosphorus (P) fertiliser use

Activity Best management practices

Choice of fertiliser

  • Soluble phosphate fertiliser is used where:
    Fact Sheets 6, 9, 13
    • rapid plant response is required
    • soil P levels are required to be increased rapidly
    • plants are actively growing
    • there is a low risk of runoff
  • Slow release phosphate fertiliser is used when:
    Fact Sheets 6, 9, 13
    • there is a high risk of runoff and/or
    • a rapid plant response is not required and/or
    • soil P levels are adequate and/or
    • soil pH is less than 6.0 and annual rainfall is greater than 800mm

Rate of fertiliser application

  • Nutrient application rates are determined using some or all of the following factors:
    Fact Sheets 5, 6, 7
    • soil and plant tissue analysis
    • nutrient budgets (including any effluent and/or feed imported to the block)
    • crop type, yield/quality/stocking rate targets
    • the need for capital or maintenance applications
    • previous crop and fertiliser history
    • soil moisture conditions and expected future weather patterns
    • local knowledge
  • The amount of phosphate applied per application is limited:
    Fact Sheets 6, 8, 13
    • when high rainfall is anticipated or irrigation is planned
    • on very sandy soils, particularly for soluble phosphate fertilisers
    • when slope is greater than 25º, and/or pasture is less than 25mm high (approx. 1000 kg DM/ha)
    • during winter
  • Soluble phosphate fertiliser must be applied in split dressings if the single application rate would exceed 100 kg P/ha.
    Fact Sheets 6, 13
  • Phosphate is applied in proportion to other nutrients, according to plant requirements. (Adding excessive P when other elements limit crop or pasture growth is inefficient and could lead to P losses.)
    Fact Sheets 5, 6

Application technique

  • Application equipment used is suitable for the conditions and fertiliser type.
    Fact Sheets 3, 4
  • Only Spreadmark accredited spreading companies (experienced operators and calibrated equipment) should be used
    Fact Sheet 4
  • GPS and GIS technology is used for precise application and for a digital record of fertiliser application locations.
    Fact Sheet 3
  • Non-target application of fertiliser is avoided by:
    Fact Sheet 4
    • using fertiliser with larger particle sizes and few or no fine particles (aerial application)
    • application techniques that direct or specifically place the fertiliser appropriately
    • application in bands when sowing crops or pasture seed
    • applying fertiliser only when any wind is blowing away from sensitive areas
    • apply fertiliser only under agreed conditions (e.g. wind speed of less than 15 km/h)

Frequency of application

  • Nutrient availability is matched to plant demand, particularly for soluble P products and liquids.
    Fact Sheets 5, 6
  • Split applications are used where the single application rate would exceed 100 kg P/ha for soluble P or liquid fertiliser.
    Fact Sheet 6

Timing of application

  • Pasture is at least 25mm high (approx. 1000 kg DM/ha) before P is applied.
  • Phosphate fertiliser is not applied after a dry (drought) period until sufficient regrowth has occurred after rain.
    Fact Sheet 5
  • P fertiliser is not applied when the soil is saturated
    Fact Sheets 5, 6

Fertiliser use and management measures

  • P fertiliser is not applied to severely compacted soils. Soil aeration techniques are used on such soils before fertiliser application.
  • To avoid fluoride toxicity to stock, pastures top-dressed with P fertiliser are not grazed for 21 days or until 25mm of rain has fallen.
    Fact Sheet 12
  • Only phosphate fertilisers which comply with the industry limit of 280mg of cadmium per kg of P are used.
    Fact Sheet 12
  • Vegetated riparian buffer strips of sufficient width (10m - adjust for slope) to filter any run-off are maintained adjacent to all waterways.

 

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