Phosphorus (P) was discovered in 1669 by Hennig Brand when he extracted it from buckets of urine and because the substance glowed in the dark, he initially called it “cold fire”. Due to its reactive nature, and its use in poisons and nerve agents, and because it was the thirteenth element discovered, it was sometimes called the ‘Devil’s Element’. Typical phosphorus is a waxy, white solid and when white phosphorus is heated to 250°C it forms a vapour which is then collected underwater and forms red phosphorus. Red phosphorus is used on the side of matchboxes. (Helmenstine, 2019)
Both plants and animals, in fact, all living things, require a continual supply of energy to function. Plants obtain their energy by trapping the sunlight using chlorophyll, animals do so by the oxidation of foods they eat. However, before any of this energy can be utilized it has to first be transformed into a form which the organism can handle. Adenosine triphosphate (ATP) is an energy-carrying molecule found in the cells of all living things. Chemical energy is captured by ATP obtained from the breakdown of food molecules and then this chemical energy is released to fuel other cellular processes (Encyclopaedia Britannica, 2020). ATP is a nucleotide that consists of three main structures with one being a chain of three phosphate groups that is the actual power source which the cell taps. As a result of phosphorous being an important component of ATP, it means it is a vital ingredient in the diet of all living organisms (May, 2019).
Phosphorus is Essential for Animals
Phosphorus (P) has more known functions than any other mineral element in the animal body. It has a close association with calcium (Ca), and is a structural component of bone, with between 80-85% of the total body phosphorus being found in bones and teeth. The remainder is found in soft tissues and fluids where it serves essential functions in energy metabolism, protein synthesis, transport of fatty acids, amino acid exchange, growth and cell differentiation (DNA), maintenance of osmotic pressure and acid/base balance, appetite control, the efficiency of feed utilisation and fertility. Phosphorus is also required by microorganisms of the gastrointestinal tract for their growth and cellular metabolism.
An adequate supply of phosphorus in a form that can be absorbed by the animal to support these physiological processes is essential for optimum livestock health and production. If it is in an available form, phosphorus is well absorbed even when there is an excess to requirements. However, when calcium intake is high in an animals’ diet, there is a consequent reduction in the absorption of phosphorus.
Most Australian soils are derived from parent material which is low in phosphorus. When soils are naturally deficient in phosphorus, the pastures growing on them are similarly deficient in this vital mineral. Deficient areas are commonly Coastal and Meat & Livestock Australia (2006) report that about 70% of northern Australia has some degree of phosphorus deficiency. McDonald (2011) states that phosphorus deficiency can be regarded as the most widespread and economically important of all the mineral disabilities affecting grazing livestock.
What Does Phosphorus Deficiency Look Like in Livestock?
Phosphorus deficiency causes an economic loss for cattle by reducing the ability to withstand drought, reducing fertility and stunting the development of young stock, it also causes decreased production and deaths from secondary conditions such as Botulism and Osteomalacia. Signs of phosphorus deficiency are summarised by Hungerford (1990) as:
- Demineralisation of bone, un-thriftiness, fragile skeleton, fractures, lameness;
- Bone-chewing, depraved appetite (pica),
- Poor appetite, poor feed conversion, poor growth
- Poor fertility, reproductive failure, reduced milk yield;
- Dull, dry hair coats and listless behaviour
- Increased mortality.
When an animals’ diet is deficient in phosphorus, it will utilise phosphorus from its bones which become frail, porous and brittle. When bone reserves are exhausted, bodily functions that are reliant on phosphorus including reproduction, growth and lactation tend to fail. Growing and lactating animals are the first and worst affected.
Anyone grazing livestock on country that has phosphorus deficient soils should be aware of the potential risk of deficiency to their animals and provide a phosphorus supplement to stock. Supplementing stock with phosphorus works best when pasture quality and quantity is high and when protein and energy needs are being met.
A soil test will reveal phosphorus levels. If they are below 10ppm (Colwell P), this indicates that an immediate response may be achieved with phosphorus supplementation.
Indicators of phosphorus status (ppm)
| ‘Acute’ | ‘Deficient’ | ‘Marginal’ | ‘Adequate’ | |
| Soil phosphorus | <2 | 3–5 | 6–8 | >10 |
The Importance of Phosphorus for Soil and Plants
Just as is the case for livestock, having adequate phosphorus is vital for plant growth. Phosphorus makes up about 0.2% of a plant’s dry weight and is essential for vigorous early root growth, good shoot growth, effective pollination, seed formation and viability. After Nitrogen (N), P is the second most frequently limiting macronutrient for plant growth.
It is quite common for Australian soils to not have enough phosphorus for sustained pasture and crop production. To make matters more difficult, a lot of the phosphorus in the soil is present in unavailable forms. When testing for phosphorus content in soils it is important to look at available P (Colwell phosphorus test) as this is more useful than total phosphorus.
Mycorrhizal fungi, in particular, perform an important function in improving the phosphorus nutrition of plants by taking up phosphorus from a larger volume of soil than is possible for uninfected plants. (Menzies, 2019)
What Does Phosphorus Deficient Country Look Like?
Phosphorus deficiency in plants can be difficult to identify visually, but the following list gives some indicators to look for:
- Stunted growth, stunting of shoots and root systems
- Leaf distortion, dull leaves (sometimes yellowing)
- Blue/green or purple/red leaves
- Phosphorus is highly mobile in plants and when deficient it may be translocated from old plant tissue to young, actively growing areas. Symptoms appear in older leaves first.
Nearly all country with termite mounds is deficient in phosphorus, however, not all phosphorus deficient soils have termite mounds. The type of vegetation growing in an area is often a useful indicator of phosphorus deficient country, some are listed below:
- Mulga
- Wattle
- Spotted gum
- Spinifex grass
How AgSolutions Can Help
A good place to start in order to determine the phosphorus status of your land is by getting a soil test done. AgSolutions can assist your operation by taking a soil test and working with you to develop a soil management program. The NatraMin range including NatraMin Hi-Phos is formulated to restore bio-activated broad spectrum minerals to your soil, assisting to improve the three aspects of soil fertility – nutritional, biological and structural.
MegaMin Livestock Supplements have a number of blends suitable to assist in providing stock grazing phosphorus deficient country with adequate phosphorus levels. This in turn can help to promote production and get a return on investment. Look for MegaMin Extra Phos 8, MegaMin SulPhos, MegaMin Extra Phosphorus and MegaMin USDA/NOP Extra Phosphorus at your preferred rural store.
For further information on AgSolutions phosphorus products contact Head Office on 1800 81 57 57.
By Shannon Godwin (BAppSc GDTL)