Land management practice trends in South Australia's broadacre cropping industries
Introduction
Broadacre cropping (includes cereals, oilseeds, lupins, sugar cane, legumes, hops, cotton, hay and silage) is an important industry in South Australia, contributing almost $1.7 billion (37 per cent) of the gross value of agricultural production for the state and 4.2 per cent to the gross value of Australia's agricultural production in 2009 — 10 (ABS 2011). According to national land use mapping, about 4.2 million hectares (4.3 per cent) of the total area of the state (Figure 1) was cropped in 2005-06 (ABARE-BRS 2010). As there is a small number of agricultural businesses in the Alinytjara Wilurara and South Australian Arid Lands regions the data have been combined for reporting purposes below.
Improving soil condition is important to agricultural productivity and the quality of ecosystem services provided to the community from rural lands. Wind and water erosion, soil carbon rundown and soil acidification processes reduce the land's ability to provide clean air and water and productive soils, protect biodiversity and maintain the resilience of the landscape to climate change, while producing food and fibre. The impact on soil condition of some land management practices used in broadacre cropping industries is summarised in Table 1.
Caring for our Country—the Australian Government's $2 billion flagship natural resource management initiative—is funding projects in the sustainable farm practices national priority area under the improving management practices and landscape scale conservation targets. These projects provide information to farmers in the broadacre cropping, dairy, horticulture and beef cattle/sheep industries about land management practices that will help improve soil condition and contribute to maintaining a healthy environment.
By 30 May 2012, $448 million had been approved for projects across Australia to improve soil and biodiversity management practices on farm. On farm practice change is being monitored using the biennial Australian Bureau of Statistics (ABS) Agricultural Resource Management Survey (ARMS), which surveys 33 000 of Australia's 135 000 agricultural businesses (farmers). Results are reported at the national, state and natural resource management region levels (ABS 2009).
Cropping industry profile
According to ABS estimates, in 2009-10 South Australia had 7685 broadacre cropping businesses in South Australia, a decrease of about 11 per cent since 2007-08. During this time the estimated area of broadacre crops decreased by about 12 per cent.
In 2009-10 the average age of managers of South Australian crop businesses was 53 years; on average they had managed their holdings for 25 years and farmed in their local region for 32 years. An estimated 11 per cent (846) of crop businesses had a Landcare group member.
Figure 1. Cropping in South Australian natural resource management regions, 2005-06.
Source: ABARE-BRS 2010.
Table 1. Cropping management practices expected to improve soil condition.
Practice / Increases carbon / Reduces wind erosion risk / Reduces water erosion risk / Reduces soil acidification risk /No cultivation apart from sowing / Indirectly / Y / Y / N
Crop residue left intact / Y / Y / Y / Indirectly
Soil pH testing / Indirectly / Indirectly / Indirectly / Y
Soil nutrient testing / N / N / N / Y
Lime or dolomite applied to reduce soil acidity / Indirectly / Indirectly / Indirectly / Y
Land management practices
Caring for our Country provided project funding to encourage farmers to better manage ground cover by reducing tillage and increasing crop residue retention, to test and lime soils regularly where required and to build soil carbon, has complemented the activities of state agencies, industry and community groups. Data from the ABS 1995-96, 2000-01 and 2010-11 agricultural censuses (which surveyed all agricultural businesses) and the 2007-08 and 2009-10 ARMS help track trends in adoption of these practices. The percentage of farmers reporting using particular practices can exceed 100 where more than one method (such as crop residue retained in some areas, burnt in others) is used on a holding.
Tillage practices
Farmers have been encouraged to move to one-pass sowing systems to reduce the risk of soil loss through wind and water erosion, lower greenhouse gas emissions and improve water use efficiency. The estimated number of broadacre cropping businesses in South Australia using no cultivation apart from sowing when preparing cropping land increased from 56 per cent to 67 per cent from 2007-08 to 2009-10 before decreasing to 53 per cent in 2010-11 (Figure 2). Longer-term ABS data (not shown) indicate that the current number of broadacre cropping businesses in South Australia using no cultivation when preparing cropping lands is more than three times greater than in 1995-96.
The area prepared for crops and pastures without cultivation apart from sowing was estimated to have increased state wide from 67 per cent to 73 per cent between 2007-08 and 2009-2010, followed by a small decrease in 2010-11. Most regions followed a similar pattern, except for the South Australian Murray-Darling Basin, where the estimated area prepared without cultivation increased from 50 to 61 per cent between 2007-08 and 2010-11 (Figure 3). The area prepared without cultivation in South Australia was estimated to have increased from 9 per cent to 70 per cent between 1995-96 and 2010-11 (Figure 4).
Figure 2. Percentage of businesses in South Australian natural resource management regions using different cultivation intensities to prepare land for broadacre crops, 2007-08 to 2010-11.
Note: The 2007-08 numbers include businesses preparing land for pasture. Results for the number of businesses not cultivating (apart from herbicide spraying or sowing) were not publishable for the Alinytjara Wilurara/South Australian Arid Lands (2009-10) and Kangaroo Island (2009-10) regions.
Figure 3. Percentage of crop area in South Australian natural resource management regions prepared by broadacre cropping businesses using different cultivation intensities, 2007-08 to 2010-11.
Note: The 2007-08 numbers include areas prepared for pasture. Results were not publishable for the Alinytjara Wilurara/South Australian Arid Lands (2007-08 and 2009-10) and Kangaroo Island (2009-10) regions.
Crop residue management
Retaining residues between crops not only affords protection from soil loss through wind and water erosion, but also helps to improve soil organic matter (soil carbon). Between 2007-08 and 2009-10 there was an estimated increase from 42 per cent to 50 per cent in the number of farmers retaining crop residues in South Australia, followed by a decrease to 46 per cent in 2010-11 (Figure 5). The regions for which data were publishable show a similar pattern. Longer-term ABS data (not shown) indicate that the number of broadacre cropping businesses in South Australia retaining crop residue after harvest in 2010-11 was more than three times greater than in 1995-96.
Over the period 2007-08 to 2009-10, the area where crop residue was retained after harvest was estimated to have increased from 60 per cent to 66 per cent in South Australia, declining to 61 per cent in 2010-11. Most regions (except the South Australian Murray-Darling Basin) for which data were publishable show a similar pattern (Figure 6). Since 1995-96 the area of crop residue retention state wide was estimated to have increased from 14 per cent to 61 per cent (Figure 7).
Figure 4. Percentage of crop area in South Australia prepared by broadacre cropping businesses using different cultivation intensities, 1995-96 to 2010-11.
Note: The 2007-08 numbers include areas prepared for pasture.
Figure 5. Percentage of broadacre cropping businesses in South Australian natural resource management regions using different crop residue management practices, 2007-08 to 2010-11.
Note: Results for businesses leaving crop residue intact were not publishable for the Alinytjara Wilurara/South Australian Arid Lands (2009-10) and Kangaroo Island (2009-10) regions. Results for businesses modifying (ploughing or mulching) crop residue were not publishable for the Alinytjara Wilurara/South Australian Arid Lands (2007-08 and 2009-10) and Kangaroo Island (2009-10) regions. Results for businesses removing (baling, burning or grazing heavily) crop residue were not publishable for the Kangaroo Island (2009-10) region.
Figure 6. Percentage of crop area in South Australia natural resource management regions reported by broadacre cropping businesses with different crop residue management practices, 2007-08 to 2010-11.
Note: Results were not publishable for the Alinytjara Wilurara/South Australian Arid Lands (2007-08 and 2009-10) and Kangaroo Island (2009-10) regions.
Figure 7. Percentage of crop area in South Australia that broadacre cropping businesses reported as having different crop residue management practices, 1995-96 to 2010-11.
Note: The 1995-96 numbers include the area where pasture stubble was managed.
Managing soil acidity
It is estimated that about half of Australia's agricultural land has a surface soil pH of less than or equal to 5.5, which is below optimum for extremely acid-sensitive agricultural crops and below the optimal level to prevent subsoil acidification (National Land and Water Resources Audit 2001). Where soil acidity moves further down the soil profile, damage may be irreparable. Very acid soils are unlikely to support good ground cover, increasing the risk of soil loss through wind and/or water erosion and reducing input to soil carbon.
About 7 per cent of South Australia's cropping land is thought to have a high risk of soil acidification, 25 per cent is at moderate risk and 68 per cent at low risk (Figure 8, Table 2). Areas at high risk are where the soil pH is low, the soil has a low capacity to buffer against pH decreases and the dominant (current and/or past) agricultural practices are highly acidifying. Of the major areas under cropping, an estimated 45 per cent in the Eyre Peninsula region and 35 per cent in the Northern and Yorke region are thought to be at moderate to high risk of acidification.
Regular testing of soil pH and applications of lime and/or dolomite can be used to manage surface soil pH. Testing soil nutrient levels to better match fertiliser applications to crop requirements can also help slow soil acidification. The number of broadacre cropping businesses in South Australia undertaking pH and nutrient testing was estimated to have declined between 2007-08 and 2009-10, from 19 per cent to 17 per cent for pH testing and from 22 per cent to 19 per cent for nutrient testing (Figure 9). Estimated increases in soil pH testing and soil nutrient testing, from 12 per cent to 16 per cent and 13 per cent to 16 per cent respectively (Figure 9), occurred in the South Australian Murray-Darling Basin region. Most of the other regions for which data were available had decreases in the estimated percentage of businesses testing soil pH and soil nutrients (Figure 9).
There was no change in the number of cropping businesses in South Australia applying lime and/or dolomite to their holdings to manage soil acidity (8 per cent, Figure 10) between 2007-08 and 2009-10. Longer-term data for cereal businesses (a major component of the cropping business category which excludes cotton, rice, sugar, oilseeds and pulses) show that an estimated 2 per cent applied lime or dolomite in 1995-96. This figure increased to 7 per cent in 2000-01 and then fell slightly to 6 per cent by 2009-10 (Figure 11). South Australian broadacre crop farmers applied a total of 88 082 tonnes of lime and 4766 tonnes of dolomite to their holdings, at rates of 1.81 and 1.60 tonnes per hectare respectively, in 2007-08 (Table 3).
Table 2. Estimated percentage of cropping area at risk of soil acidification.
Region / Low risk / Moderate risk / High risk /Alinytjara Wilurara/South Australian Arid Lands / 100% / 0% / 0%
Eyre Peninsula / 55% / 31% / 14%
Kangaroo Island / 33% / 41% / 26%
Adelaide and Mount Lofty Ranges / 51% / 36% / 13%
Northern and Yorke / 65% / 33% / 2%
South Australian Murray-Darling Basin / 90% / 6% / 4%
South East / 72% / 16% / 12%
South Australia / 68% / 25% / 7%
Source: These estimates were produced by intersecting cropping (dryland and irrigated) from Land use of Australia 2005-06 (ABARE-BRS 2010) with the soil acidification risk map (Wilson et al. 2009).
Figure 8. South Australian cropping areas with low, moderate and high risks of soil acidification.
Note: This figure was produced by intersecting cropping (dryland and irrigated) from Land use of Australia 2005-06 (ABARE-BRS 2010) with the soil acidification risk map (Wilson et al. 2009).
Figure 9. Percentage of South Australian broadacre cropping businesses undertaking pH and soil nutrient testing, 2007-08 and 2009-10.
Note: Results for the Alinytjara Wilurara/South Australian Arid Lands (2009-10) and Kangaroo Island (2009-10) regions were not publishable.
Figure 10. Percentage of broadacre cropping businesses applying lime or dolomite to their holdings, 2007-08 and 2009-10.
Note: Results for businesses applying dolomite were not publishable for South Australia (2009-10) and the Eyre Peninsula (2007-08 and 2009-10) and South Australian Murray-Darling Basin (2009-10) regions.
Figure 11. Percentage of cereal (excluding rice) businesses in South Australia applying lime or dolomite to their holdings, 1995-96, 2000-01 and 2009-10.
Note: 2009-10 data presented here are slightly different from that for Figure 10; there is no direct comparison between cereal cropping businesses and total broadacre cropping businesses.
Table 3. Rates of lime and dolomite application by South Australian broadacre cropping businesses on their holdings, 2007-08.
Region / Tonnes (t) of lime applied / Lime application rate (t/ha) / Tonnes (t) of dolomite applied / Dolomite application rate (t/ha) /South Australia / 88 082 / 1.81 / 4 766 / 1.60
Alinytjara Wilurara/South Australian Arid Lands / 0 / 0 / 0 / 0
Eyre Peninsula / 13 857 / 1.90 / np / 0
Kangaroo Island / 12 362 / 2.12 / 0 / 0
Adelaide and Mount Lofty Ranges / 9 739 / 2.35 / 798 / 1.79
Northern and Yorke / 17 118 / 1.85 / 0 / 0
South Australian Murray-Darling Basin / 6 034 / 1.45 / 227 / 0.98
South East / 28 973 / 1.61 / 3 740 / 1.62
np not publishable.
Conclusions
The data suggest that progress is being made in reducing tillage and increasing crop residue retention, despite the decreases seen in some regions between 2009-10 and 2010-11. Reduced tillage and increased stubble retention could be expected to contribute to reducing the risk of soil loss through wind and water erosion and increasing soil carbon. Cropping industry surveys of tillage practices (Kearns & Umbers 2010, Llewellyn & D'Emden 2010) identify similar trends in the uptake of tillage and crop residue management practices. Given the extensive and insidious nature of soil acidification, with almost 32 per cent of all cropland in South Australia at moderate to high risk of acidification, there may be a need to increase regular testing and where needed, liming of cropping soils, especially in the Kangaroo Island and Adelaide and Mount Lofty Ranges regions.