3.03 - Pasture growth estimates

The mid-monthly estimates of pasture growth rates (kg DM/ha/day) below are for average seasonal conditions for a range of localities and regions across southern Australia. They are from state PROGRAZE manuals, available from your state department of agriculture and based on a combination of research results, growth predictions and practical experience.

Although there is a large variation in rainfall pattern and feed supply within any year, when put together, these monthly values reflect pasture growth in a ‘typical’ year for the locality or region without a reference to what growth occurred in the previous month. Also included are two tables demonstrating that there is a significant difference between varieties within species. The examples given are Meridian perennial ryegrass compared to Victorian perennial, and Holdfast GT phalaris compared to Australian phalaris.

These estimates provide a basis to assist with the calculations for short- to medium-term decision making in the beef business. They are intended as a guide and will assist with the calculations in Tool 3.5. It is recommended that the MLA Pasture Ruler (or equivalent) is used to generate similar estimates of pasture growth rates for selected paddocks or the whole farm.

Assumptions

The following assumptions are made for the range of pastures/pasture mixes unless otherwise stated in the estimates:

• Pastures are of moderate to high density.
• Soil has good moisture holding capacity, such as a clay loam.
• Pasture is maintained in an active growth phase at all times during the growing season.
• Pastures are well managed and fertilised to avoid nutrient deficiencies. This is key to having good pasture production and persistence. A well fertilised pasture in a low rainfall situation will grow significantly more pasture than a low fertility pasture of the same type.

For example: 1kg phosphorus (P)/ha applied in a typical season grew 6.70t of pasture at 12DSE and in the drought of 1982, grew 4.14t of pasture, a reduction of 40%. The pasture receiving 15kg P/ha grew on average 14.00t of pasture at 12DSE and in the drought year of 1982, grew 9.38t of pasture a reduction of 30%. This demonstrates that a fertile pasture grows more pasture regardless of rainfall, but most importantly is more resilient in dry years and can be considered a risk minimisation tool.

• Estimates are for the middle of each month.

The following important variables need to be considered and adjusted against the expected local, district or regional patterns and practical experience:

• climate (rainfall and temperature)
• soil type and variability
• pasture species
• fertiliser (nutrient) requirements (ie adequate or limiting); adjustments for expected pasture growth may be required (see Module 2: Pasture growth)
• grazing management.

Estimates of pasture growth rate

Unless otherwise stated, the estimates are for expected availability of feed of adequate quality and are based on:

• pastures or pasture mixes with a good balance of legumes, grown on suitable soils
• pastures that are well managed to be maintained in the active growth phase so that quality is at a high level
• soil fertility is non limiting (Module 2: Pasture growth outlines adequate nutrient levels)
• using some form of rotational grazing to enable pastures to rest and grow between grazing events
• growth rate of the pasture, stocking rate, degree of wastage through trampling and fouling and the previous management of the pasture.

In any period, the pasture type is capable of growing pasture mass of adequate quantity and quality to suit the requirements of seasonal conditions.

In the following tables, estimates are presented for localities or regions in NSW, Victoria, Tasmania, South Australia and Western Australia.

More detailed pasture growth rates are available from the look-up tables for cattle from the MLA Feed Demand Calculator

Feed year growth rate patterns:

• New South Wales
• Victoria
• Tasmania
• South Australia
• Western Australia

With species pasture growth variations

* Data from CSIRO/AWI/Seedmark (2008), Phalaris Breeding Program Holdfast GT Technical Report