Laggan Grazing Demonstration – latest results are in!

12 Aug 2024

The livestock production and financials have been crunched for another year and the results for 2023-24 are in!

While wool and sheep meat prices struggled during the 2023-24 period, above average rainfall through the 2023-24 summer/autumn period (Figure 1) resulted in above average wool production and profitability in the fertilised paddocks (Table 1). In contrast, the control paddock (nil fertiliser) couldn’t capitalise on the good growing conditions and once again carried a relatively low stocking rate (Table 1).

	L+S	Cont	SS
Wethers/ha	8.2	4.1	7.1
Wool cut (kg wool/ha, clean)	34.7	15.3	28.0
Wool income ($/ha/yr)	607	294	511
Meat income ($/ha/yr)	183	59	122
Total income ($/ha/yr)	790	353	633
Total costs ($/ha/yr)	245	82	195
Profit ($/ha/yr)	545	270	434
Difference to control	+ 275 (102%)		+ 168 (62%)

Table 1: Livestock and economic data - average annual results from January 2015 – June 2024.

Figure 1: Monthly rainfall totals (mm) recorded at the Crookwell Post Office (BOM station 70025). Total rainfall for 2023-24 was 981 mm. The annual long-term median rainfall for this site is 869 mm.

Background

The grazing demonstration commenced in 2015 and consists of three treatments:

single superphosphate (SS)
lime + single superphosphate (L+S)
control (Cont).

Lime was surface applied as one-off application (2.5 t/ha) at the start of the demonstration and single superphosphate is applied annually. Treatments are continually grazed by Merino wethers. Wethers are regularly weighed and stocking rates adjusted to achieve similar average body weight across treatments. The financial performance of each treatment is based on wool returns plus meat income when wethers are sold.

Project aim

To investigate the effect of applying fertiliser and lime on:

stocking rates and overall farm profitability
soil fertility and pH
pasture composition
soil carbon levels.

Pasture production and economics

These results show that when Phosphorus (P) and Sulphur (S) is applied at this site, stocking rates on average have increased by 3 wethers/ha above the Control (72% increase). The surface application of lime at 2.5 t/ha has increased stocking rate by a further 1.1 wethers/ha above the SS treatment (Table 1). The biggest increase in livestock production has come from addressing both P and S deficiencies, with lime lifting production to a lesser degree.

An economic comparison shows that SS has on average increased net profit by $154 - $168/ha/yr above the control (depending on what method of analysis used). The L+S treatment has increased net profit to a far greater extent, boosting returns by $272 - $275/ha/yr above the control (Table 1).

While the effect of lime on soil pH was limited to the top 2.5 cm of soil, lime appears to have had a positive effect on legume production at this site. The increase in legume production in the L+S paddock has increased stocking rate by 1.1 wethers/ha and overall profit by $111/ha above the SS paddock (Figure 2). However, applying lime is still a considerable up-front cost to the producer and any potential benefit will only be realised if major nutrient deficiencies are addressed.

Figure 2: Gross margin comparison between treatments ($/ha). This economic analysis is based on (wool income + annual change in mutton value during the 12 month period.

Soil nutrients

Regular applications of single superphosphate between 2015 and 2024 have increased P and S levels in the two fertilised paddocks (Figure 3). This has led to a significant increase in the amount of sub clover in the fertilised paddocks, especially in the L+S treatment. The increase in stocking rate has been a function of both increased pasture quantity and quality. Note: fertiliser was not applied in 2022 and 2023 due to wet conditions.

Figure 3: Fertiliser application history and results of annual soil testing on Colwell P (* indicates the years in which superphosphate was applied with molybdenum).

Soil pH

Soil testing to 20 cm shows that the lime has only had an impact on the top 2.5 cm of soil, lifting pH (CaCl2) from 4.2 to 5.0 and reducing aluminium from 16 % to 0 %. This was achieved within the first 16 months of application.

Despite the lime only having an impact to a depth of 2.5cm, the application of lime has had a positive effect on pasture growth, sub clover performance and overall economics.

Soil carbon

Baseline 0-10 cm soil testing at the end of 2014 showed that soil carbon levels were already high at this site, ranging between 4.0 and 5.0 %. Annual soil testing shows a declining trend in the first two years, before a notable increase in soil carbon levels in 2017. However, this increase was short-lived due to drought conditions in 2018 and 2019 (Figure 4).

Soil carbon levels in all paddocks increased in 2020 on the back of an extremely strong season, however the last three years there has been a declining trend across all treatments.

At this stage there is no clear effect on soil carbon levels due to the different paddock treatments. The measured changes appear more related to seasonal conditions.

Figure 4: Results of annual soil testing on Total Carbon % (Dumas Combustion method).

Acknowledgments

Thank you to Shannon Arnall for providing the land to run the demonstration and for the on-going support. Financial support from the Australian Government through the National Landcare Program is also gratefully acknowledged.