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LCF Australia

Crop guide

Pasture nutrition

Nutrient needs, seasonal growth, common deficiencies and why nutrients go missing in Australian grazing pastures.

Nutrient needs

In many southern Australian pastures, phosphorus is the nutrient that most often limits growth, followed by sulphur, and potassium on some soils. Pasture legumes such as subterranean clover, medics and lucerne fix nitrogen, which feeds the grasses growing with them.

Grass-dominant pastures, and pastures needed for winter feed, can respond to strategic nitrogen. Molybdenum can be short on acidic soils and limits nitrogen fixation in legumes. Soil pH and liming affect how well both legumes and nutrients perform.

Every tonne of hay, grain or livestock product removes nutrients. Hay cutting removes large amounts of potassium in particular, so cut paddocks run down potassium faster.

Key nutrients

Growth stages and when nutrients matter

  1. Stage 1

    Autumn break and establishment

    Maintenance phosphorus and sulphur are commonly applied around the autumn break, so nutrients are available as pasture starts growing.

  2. Stage 2

    Winter

    Growth slows in the cold. Strategic nitrogen on grass-dominant pasture can lift winter feed when it is short.

  3. Stage 3

    Spring

    The main growth flush, when pasture uses most of its nutrients. Shortages show up most clearly now.

  4. Stage 4

    Summer and the dry period

    Growth stops in most dryland systems, and little is taken up until the next autumn break.

Common deficiencies and signs

Symptoms of different problems can look alike. Disease, herbicide damage, waterlogging and frost can all produce signs similar to a deficiency.

Nutrient What to look for Where it is more likely
Phosphorus Slow growth, small leaves and reddish or purplish tints in clover. Low-phosphorus soils and paddocks with little recent fertiliser.
Potassium In clover, small pale spots around the leaf margins that join and turn brown. Sandy soils, higher-rainfall areas and paddocks cut for hay.
Sulphur General yellowing of the whole plant and slow growth, easily mistaken for nitrogen deficiency. Sandy and low organic-matter soils and higher-rainfall areas.
Nitrogen Pale, slow-growing grasses, especially where legumes are sparse. Grass-dominant pastures and cold, wet conditions.

What deficiencies look like in pasture

Photos of deficiency symptoms. Where we do not yet have a suitable photo, we will add our own trial photo. Symptoms vary with crop, variety, soil and season.

  • Phosphorus deficiency in subterranean clover. We will add our own trial photo here.
  • Potassium deficiency in clover. We will add our own trial photo here.

Photos may show other crops with the same symptom. Full credits: Image credits.

Why nutrients go missing

Not everything applied to a pasture crop ends up in it. These are the main ways nutrients are lost or become unavailable.

Removal in product
Hay, grain, meat, milk and wool all carry nutrients off the paddock. Hay removes large amounts of potassium in particular.
Runoff and erosion
Phosphorus attached to soil particles, or fertiliser still on the surface, can be carried off in runoff after heavy rain on sloping or saturated ground.
Phosphorus fixation (lock-up)
Phosphorus reacts with calcium in alkaline soils, and with iron and aluminium in acidic soils, forming compounds plants cannot easily use. It also moves very little in soil. Calcareous soils and soils with a high phosphorus buffering index (PBI) bind more of it.
Leaching
Nitrate and sulphate dissolve in soil water and move down with it. On sandy soils, heavy rain can carry them below the root zone.
Volatilisation
Urea left on the soil surface is converted to ammonium and then to ammonia gas, which can escape to the air. The loss is greater on warm, moist soils with no follow-up rain, on alkaline soils and under heavy surface stubble.
Soil acidity
As soils acidify, molybdenum becomes less available and legume nodulation declines, while aluminium released in acidic soils restricts root growth.

LCF offers fertiliser technology matched to your use case, whether that is drilled urea or top dressing before or after planting. Advanced inhibitor technology is added in the compounding process at our manufacturing partner Lardmee (LDM).

How we match technology to your use case

How LCF products fit

LCF Australia supplies compound fertilisers made by our manufacturing partner Lardmee (LDM), including Urea Plus and zinc and manganese sulphates, on enquiry. We also supply the Field Spears soil testing kit, which reads soil N, P, K and pH in the paddock. Which product suits, how much and when depends on the soil, the crop, the season and how you apply it.