Laggan grazing demonstration

Local Land Services supported producer Shannon Arnall in the Crookwell region on a grazing demonstration to determine fertiliser use on pastures and productivity.

• Location: ‘Carinya’, Laggan
• Property size: 606ha
• Soils: Quartz based, pH 4.0 (unlimed) with increasing Al to depth
• Pastures: mainly native perennial grasses (weeping grass and wallaby grass) with annual grasses and subterranean clover
• Enterprises: Merino breeding, mostly to Merino sires 

Project background

This on-farm demonstration began in January 2015. Shannon Arnall had purchased a new block of ‘native’ country that hadn’t received fertiliser for over 13 years and was keen to increase profitability from the existing pasture in the most cost-effective way. 

A simple nutrient trial showed that phosphorus (P) was the major nutrient limiting pasture growth. This was not surprising given the history of the paddock, however the question then became: does it still pay to put fertiliser out in a wool operation?

Project objectives

To investigate the level of pasture and animal production that can be sustainably achieved on a native-based pasture in the Crookwell region.  

Specifically, the project investigated the effect of applying fertiliser (single superphosphate) and lime on: 

• stocking rates and overall farm profitability (using a fully-costed economic analysis)
• soil fertility and pH
• pasture composition
• soil carbon levels.

Project delivery

Treatments 

Paddock 1

Lime + Single superphosphate (L+S): fertiliser applied annually to increase soil P over time to a targeted level. Lime applied as a one-off application (2.5 t/ha) to reduce aluminium levels (by raising soil pH).

Paddock 2

Control: a native pasture of low fertility (that is, the “do nothing” approach).

Paddock 3

Single superphosphate (SS): fertiliser applied annually to increase soil P over time to a targeted level. 

Project outcomes

After 10 years of investigating the impact of fertiliser and lime on pasture and livestock production. 

Results showed carrying capacity and profitability more than doubled through regular, targeted fertiliser inputs and a one-off application of lime.

Trial findings

Native perennial pastures can respond to fertiliser

The results from the Laggan grazing demonstration showed a similar response in fertiliser application to native pastures, to a previous a long-term grazing demonstration in the Bookham NSW district, despite being almost twice the elevation (1000 m vs 520 m). 

Over the 10 years of the Laggan grazing demonstration, stocking rates for the 3 paddocks have averaged:

• Control: 4.0 wethers/ha
• Single Superphosphate: 7.2 wethers/ha
• Lime+Single superphosphate: 8.2 wethers/ha

These stocking rates shows a clear link between fertiliser application and pasture response allowing for a higher stocking rate. 

Native pastures are often made up of a range of native grass species, and some species are more responsive to nutrients than others. Weeping Grass (Microlaena stipoides) is one native pasture species which the trials have shown responds well to increasing soil fertility and is found both at Laggan and Bookham trial sites.

Pasture research has shown that some Wallaby Grass species (but not all) are also very responsive to fertiliser while Red Grass (Bothriochloa) and Kangaroo Grass (Themeda) are less responsive to soil fertility.

Therefore, many factors will affect fertiliser response in a native pasture, including pasture species, environment and soil type/depth. Read more about fertilising native pastures.

Nutrients drive production; lime is the ‘cream on the cake’

The grazing demonstration has shown that when P and S is applied at this site, stocking rates on average have had an 81% increase from 4.0 wethers/ha to 7.2 wethers/ha. 

• A one-off surface application of lime in early 2015 increased stocking rate by a further 1.0 wether/ha on top of the SS treatment.
• The biggest increase in livestock production and profitability has come from addressing P and S deficiencies. Lime was the ‘cream on the cake’, further increasing legume production, stocking rate and overall profitability.
• When averaged over the 10 years, an economic comparison shows that SS increased net profit by $218/ha/yr above the control. The application of lime with fertiliser increased returns by a further $105/ha above the SS treatment (Table 1).
• While the difference in stocking rate between the SS and L+S paddock is relatively small (average of 1.0 wethers/ha), there have been periods over the last 10 years where wool and mutton markets have been very strong. When markets are favourable, small increases in carrying capacity and livestock production per head (wool cut and liveweight gain) can make a big difference to the bottom line (Figure 1).

The increase in production between the paddocks has gone hand-in-hand with legume production – the stronger the legume component, the higher carrying capacity and overall profitability. 

Interestingly, despite lime only having an impact on soil pH and aluminium down to a depth of 2.5 cm, the L+S paddock has consistently had a stronger legume component, carried more livestock and generated higher returns than the SS paddock. 

As expected, legumes performed poorly in the Control paddock due to low soil fertility (Table 2).

The Laggan grazing demonstration shows what can be achieved by simply addressing P & S deficiencies to stimulate the legume component. 

Legumes in a pasture increase production in two ways:

• directly through providing grazing animals with highly digestible forage; and
• by fixing atmospheric nitrogen and releasing into the soil, which in turn increases pasture growth and quality.

Regular soil testing enables you to ‘fine tune’ your fertiliser program

The aim of any fertiliser program should be to apply the minimum amount of fertiliser required to grow the grass you need. This process involves:

• identifying your starting point (through a soil test)
• setting appropriate nutrient targets
• gradually working towards your target using modest applications of fertiliser and increase in livestock numbers to match feed supply.

The Laggan Grazing Demonstration is an example of how to apply this approach (Figure 2). 

• Initial soil testing showed major deficiencies in P and S.
• Initially it was decided to apply 125kg/ha/yr of single superphosphate, however after the first three years of the demonstration it became apparent that this rate was sufficient to address maintenance P, but not enough to build soil P levels.
• Based on this information it was decided to increase the application rate to 160kg/ha. This higher rate resulted in the soil test results slowly heading towards the identified Colwell P target range.
• Stocking rate increased over time with increasing soil P levels.

Soil test results can vary significantly from year-to-year depending on the amount of fertiliser applied, seasonal conditions and when samples are taken. 

Regular (annual) soil testing is the key to identifying trends and checking the appropriateness of fertiliser application rates.

Funding and partnerships 

Thank you to Shannon Arnall for providing the land to run the demonstration and for the on-going support.  

Local Land Services’ Laggan Grazing Demonstration received financial support from the Australian Government through the National Landcare Program.