Early spring is a good time to assess your soil fertility and prepare paddocks to get the most
out of your silage and or hay.
With improved genetics from new ryegrass varieties (e.g. Amass and Astound), and the added use of annual clovers, hay yields for maximised forage production now often exceed 6 t/ha.
Hay and silage production – if not well managed – can mine nutrients from the soil.
Soil nutrient tip: Assessing your nutrient requirements is more than just calculating how much nutrition is removed in hay and silage and simply replacing that amount. Other factors like leaching and mineralisation also come into play. The soil will have a reserve of nutrients including nitrogen and sulphur in the form of organic matter. These stored nutrients become plant-available in spring through mineralisation as soils warm up and stay moist.
Phosphorus is vital for the establishment of new plants, root development, photosynthesis and the movement of energy within the plant. In Victoria, Olsen P is the most common test used to determine plant available phosphorus in the soil. Colwell P is traditionally used more in NSW.
Potassium is one of the most important nutrients heading into spring, particularly for paddocks that will be used for hay or silage. An average hay or silage crop will remove between 15 and 30kg of potassium per tonne of dry matter harvested. Ensure potassium levels are adequate for silage growth and are replenished after cutting.
Nitrogen and sulphur
When soil temperature is below 8-10°C, it is often advisable to apply sulphate of ammonia (SOA) in conjunction with urea as a nitrogen source. The two different forms of nitrogen help improve uptake into the plant. SOA also applies sulphur which can become limiting over winter due to leaching and locking up in the soil.
As the weather warms up, urea will likely become the most economical option for nitrogen and the pasture will be in higher demand. Economic rates of nitrogen are between 25 kg/ha and 40 kg /ha. In early spring, nitrogen response of perennial ryegrass is likely to be around 15-20kg DM/kg of N applied.
Moisture must be available. Ideally, apply before a
heavy rain event to reduce the loss of nitrogen due
to leaching through the soil.
Generally, silage and hay fertilizers(e.g. NPK blends) are used at rates of up to and not beyond 250 kg/ha in one application.
In some situations (e.g. in high production systems or where the season is favourable) some growers choose to apply fertiliser at higher rates. If this is the case, and you are applying more than 250 kg/ha, split your fertilizer application into two, for example 2 x 150 kg/ha applications three to four weeks apart.
Pictured below: silage from Amass at Samaria in NE Victoria with a yield of 19 bales / hectare