In the face of rising hay prices, high demand for spreading contractors and an expected shift to a drier weather pattern, the need to maximise good early pasture growth will be front of mind for many.
With pasture research demonstrating no downside to yields when applying phosphorous fertilisers in summer instead of autumn, Incitec Pivot Fertilisers pasture technical agronomist Lee Menhenett said applying superphosphate early was a good option for farmers wanting to avoid delays and ensure their phosphorous is on the ground before the autumn break.
“To ensure a wedge of quality feed leading into winter, legume growth needs to be maximised through immediate access to good soil-P levels,” Mr Menhenett said.
“Fertiliser application prior to the autumn break is often a logistical challenge for farmers, and it’s almost a perfect storm this year with a wet spring, late harvest and difficulty getting on to paddocks delaying spreading already.
“Light rain and even morning dews are enough to move P into the soil within a few days. The granule left behind is basically gypsum (calcium sulfate), which will dissolve and move into the soil with the next rain event.
“Once in the soil, phosphorus is immobile, meaning leaching losses are generally small.
“So, unless the soil type is a light sand, or a paddock has little ground cover, early season application can be made with confidence.”
Soil testing is another tool farmers can use to ensure they’re only applying fertiliser where they need to.
“The adequate Olsen P range to achieve 95 to 98 per cent potential yield for a legume-based pasture system for dairy should be 15 to 20mg/kg, and to achieve 90 to 95 per cent potential yield for a beef/sheep production system it’s 12 to 15mg/kg,” Mr Menhenett said.
“At these soil-phosphorus levels, fertiliser is applied at maintenance rates. Regular soil testing is the only method available to determine soil nutrient levels and importantly trends over time.”
When applying fertiliser early in the season, farmers need to be mindful to avoid applying in areas where groundcover is less than 70 per cent, as bare soils are prone to shedding water leading to erosion and run-off taking valuable soil holding P and other nutrients.
“Paddock topography is relevant, as steeper slopes are more prone to wind and water soil erosion,” Mr Menhenett said.
“Things like leaving buffer zones around waterways and storages to prevent run-off is also important, as is avoiding applying fertiliser if heavy rain is forecast within four days.”
