Case studies in soil acidity management

Page last updated: Monday, 17 September 2018 - 11:22am

In this section you will find detailed information on various case studies highlighting the long-term benefits of liming and different options used by farmers for incorporating lime.

Alan and Helen Hawley, King River: long-term monitoring and liming program

Alan Hawley at his computer
Alan Hawley from King River assessing records of his liming and monitoring program.

Property information

Average rainfall: 762 millimetres (mm)
Enterprise: Short horn beef cattle
Dominant soils: Deep sandy and gravelly duplexes and clay loams

Background

Alan Hawley has tried a number of different innovations to improve his profitability and soil management however the two that have given the biggest benefits have been planting kikuyu and liming.

Alan was aware that he had a pH problem on the farm. This was evident through soil testing and the pasture composition. As a result he was on the lookout for something that would help deal with the issue.

In the early 1980s Alan went to a department field day in the South Stirlings area. It was demonstrating the yield increase in crops from applying lime. From this Alan decided to give it a go and applied lime to one of his most acidic paddocks.

The response was fantastic with an increase in clover content and size which motivated him to continue. There was also the potential that he would be able to decrease phosphate applications due to the increase in pH.

Monitoring

Alan uses Microsoft Excel to record a range of data including his soil test results, fertiliser applications, lime applications and stocking rates. He also uses critical levels to determine nutrient and pH status and has mapped these since 2001. As a result it is possible to see the changes in soil nutrients and pH over many years (Figure 1).

Alan Hawley’s mapping of the pH status of his farm shows a clear improvement from 2001 to 2011.
Figure 1 Alan Hawley’s mapping of the pH status of his farm shows a clear improvement from 2001 to 2011

Alan maps his farms by soil/land management unit. He then takes 30-50 cores from each unit, which he then combines and mixes before taking a subsample for analysis. This makes it easier to sample and analyse by combining similar soil types that are managed in the same way.

In 2013, Alan’s farm was mapped under the whole farm nutrient mapping project run by the department (Figure 2). This project funded the sampling and analysis of Alan’s entire farm, paddock by paddock for macro nutrients, pH and Phosphate buffering Index. This provided an excellent opportunity to compare the current 2013 mapping results with data from Alan’s innovative mapping and data storage, which goes back to the mid 1980s.

The pH status of Alan Hawley’s farm as mapped by DAFWA whole farm nutrient mapping project in 2013.
Figure 2 The pH status of Alan Hawley’s farm as mapped by DAFWA whole farm nutrient mapping project in 2013

Implementation

Allan’s approach was to apply lime fairly regularly. He aimed to treat the entire farm at least every five years. Rates did vary but they were around 2.5 tonnes per hectare (t/ha). This meant that every paddock got one and sometimes two applications in five years, which is roughly the strategy he has been using since the late 1980s.

Over the last five years Alan ramped up his application of lime. He applied an average of 4.3t/ha of lime over the five years across the farm. This did however vary with between 2.5 and 5t/ha applied across the different paddocks. Rates were based on economics, the pH at the time and future activities such as hay cropping.

In the late 1980s the pHCa of the farm was low with paddocks ranging between 3.8 and 4.4. Alan then started to lime the farm regularly and by 2001 the average pHCa across the farm was 4.6 though this did vary between 4.1 and 5.1 (Figure 1). By 2011 the average pHCa across the farm was 4.8 with at least 50% of the property between 4.4 and 4.8 (Figure 1). This was encouraging, however the pH was still too low.

By 2013 the average pHCa was 5.3 with paddocks ranging between 4.8 and 5.7. On average the pH increased by 0.5 units over three years with the increase in pH varying from 0.2 to 0.9 pH units across the property.

If we look at one area in particular, Hazard Rd paddocks 9 and 10, the pHCa in 1985 was 4.3. Over the next few years the pHCa gradually increased with fairly regular applications of lime to 4.6 by 2011. The cumulative effects of continued liming started to pay dividends and by 2013 the pHCa had reached 5.5 (Table 1, Figure 2).

Table 1 The pH of Hazard Rd paddocks 9 and 10 over time. *Measurement was 5.3 in water
Year pHCa
1985 4.3*
2011 4.6
2013 5.5

Total lime application in Hazard Rd paddocks 9 and 10 between 1985 and 2011 was 12.35t/ha which was applied usually in lots of 2.5t/ha using two main lime sources. A further 2.47t/ha was applied in 2012 which brought the total up to 14.8t/ha since 1985.

The other factor that Alan has considered is the quality of the lime. From 1985-2008 he used lime that had a neutralising value of around 83%. From 2008-2011 he used another source that had a lower neutralising value of approximately 60%.

Despite the rates being applied, Alan felt that the lime was not ameliorating the acidic soils adequately, which was supported by the apparent drop in average pH from 2008-2011. In 2008 the average pHCa across the farm was 5, however by 2011 it had dropped to 4.8. Alan then swapped back to his normal source of lime and the pH in 2013 was up on average to 5.3, with paddocks ranging from 4.8 to 5.7 (Table 2).

Table 2 Improvements in the soil pH (CaCl) on Alan Hawley's King River cattle farm over time
Year Average pH Highest pH Lowest pH % of paddocks above pH 5
2001 4.6 5.1 4.1 8
2008 5.0 5.3 4.8 50
2011 4.8 5.3 4.5 23
2013 5.3 5.7 4.8 91

Summary

Alan has seen a dramatic change in the quality of his pasture. While there are many factors that can influence this, Alan is sure that part of the change can be attributed to the improvements in soil pH. He now has more clover and rye grass in his sward, which is better able to persist amongst the kikuyu pasture. This has been especially evident on the flats where he had bare areas and large amounts of lotus minor, which has now been almost completely replaced by rye grass and clover.

The other benefit is the greater availability of nutrients with higher pH. He is able to produce the same amount of feed with less fertiliser and now that the whole farm has been sampled he is more certain of being able to cut back on fertiliser applications by halving current rates, except for paddocks producing hay.

Now that the pH has reached the target levels Alan is planning to drop lime applications back to maintenance levels. He will still follow the same methodology of liming the entire farm every five years but will drop application rates back to between 1-1.5t/ha and will continue to monitor the soil nutrient and pH levels and adjust rates accordingly.

The increases in pH have occurred due to a long-term program of liming. Some amount of variability has occurred, however since the 1980s there has been a general upwards trend. This has shown that even in paddocks with pHCa as low as 3.9 it is possible to bring them up to an acceptable level and reap the rewards.

Regular monitoring has been the key to success. He has been able to identify the issue, apply the solution and where necessary adjust his approach. This would not have been possible without regular rigorous soil testing, information storage and management.

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Contact information

+61 (0)8 9690 2256
Gaus Azam
+61 (0)8 9690 2159