Fertiliser is a key input that drives productivity in most enterprises that incorporate improved pastures. It generally leads to increased pasture production, allowing for increased stocking rates and increased profitability.
In most production systems, improved pastures can be more productive than local native varieties. This production, however, comes at a cost to the soil nutrient profile. Unless soil nutrients are replaced, pasture performance will decline, and pasture rundown will occur. A well-considered fertiliser management plan is required to make the most of the investment in improved pasture through protecting against pasture rundown.
When soil nutrient reserves are very high, additional fertiliser applications may not provide any benefit. In these cases, it may be better to apply a lower rate of fertiliser and utilise the soil reserves.
Soil condition (e.g. acidic soils or those prone to water logging) may limit the benefit that can be realised from the application of fertiliser. These constraining factors should be addressed before, or in parallel with, a nutrient program.
Choosing the right fertiliser
Fertilisers come at a cost. Through reduced production, however, the cost of not fertilising is usually far greater. It is important to know which nutrient is limiting production and apply fertiliser strategically.
Fertiliser comes in many forms. These range from products formulated to meet plant needs for macro-elements such as nitrogen, phosphorus, potassium and sulphur, to high analysis fertilisers that address trace or micro-element requirements such as molybdenum, copper and zinc. Liquid and organic fertilisers are also available.
Which fertiliser will best suit a particular production system and addresses plant requirements is not always obvious.
Plant requirements can be identified through visual assessment, plant tissue tests and soil tests. Some soil nutrient deficiencies are expressed through obvious signs on the foliage, while others are less obvious and may only be detected through laboratory testing. While soil tests provide a useful objective assessment of a soil's nutrient profile, these results require interpretation and it is often advisable to seek professional assistance through a local FertCare accredited agronomist or consultant to develop a fertiliser management plan for your enterprise.
Soil acidification is a problem in some regions and lime can be used to correct this issue. Payback periods can be reduced by ensuring that a high value enterprise is used on limed pastures.
Timing the application
It is important that fertiliser application occurs at the right time in the production cycle – usually when the nutrient will be rapidly taken up by the plants. For example, the application of super phosphate to cold, wet soil will result in much of the phosphorus being locked up in forms not available to the plants.
It is important to ensure that applied nutrients stay on site and do not leach though the soil profile or run off into water ways. The farm nutrient loss index tool provides a simple method to ensure that applied nutrients stay on site.
A well-planned fertiliser application will usually deliver a significant increase in pasture production if other factors, such as moisture, are not limiting growth. It is important that this increased pasture production be utilised to maximise the return on the investment in fertiliser.
Financial budgets and feed budgets are a good way of ensuring that livestock are present to utilise increased pasture following a fertiliser application.
Where there are insufficient animals to utilise the pasture, consideration may be given to fodder conservation.
MLA's phosphorus tool assists producers in calculating:
- the amount of phosphorus required
- the additional number of stock that may be carried
- the time taken to return a positive cash flow after fertiliser application.
It is important to note the payback period from a fertiliser program can be greatly reduced by using a high value enterprise on the pasture and using high genetic merit animals.
Soil tests should influence your fertiliser decisions. Local FertCare accredited agronomists or consultants should be consulted to determine the correct methodology and frequency of soil testing. The composition of the pasture should also be considered in determining an appropriate fertiliser program.
It is important to determine if there are sufficient desirable species in the pasture that may respond to fertiliser or if a renovation program should be considered. The pasture health kit can assist by providing a method for species mix assessment in a paddock.