Integrated farming systems for a sustainable future - what is the role of mixed farming in sustainable agriculture?

Author: | Date: 18 Sep 2014

Dr Andrew Moore,

CSIRO Agriculture Flagship, Canberra.

Keywords:

integrated farming systems, sustainability, flexibility, resilience.

Take home messages

  • Unlike other southern states, livestock numbers on cropping farms in NSW have increased since the end of the last drought, even though they are being supported by less land.
  • Soil organic matter is the main long-term sustainability concern for which the only practical solution is to include forages in the land use mix.
  • Maintaining a mixed farming system instead of a specialized cropping or livestock farming system provides a greater range of possible future land use pathways.

Trends in mixed farming - the big picture

Over the last 30 years, there have been major shifts in land use on wheat and mixed farms in southern Australia. Average farm size has increased by about 60% over that time, with a corresponding decrease in labour inputs per hectare (Australian Agricultural and Grazing Industries Survey). This consolidation of farms appears to have accelerated since about 2002. A second national trend; which has been under way since at least 1980, has been toward greater areas of land under crop (Figure 1a). During the 1980s, this change should be seen more as an intensification of mixed farming systems than a shift away from them.  That is, the number of dry sheep equivalents per farm hectare remained fairly stable even though more land was being allocated to crops.

Since about 2000, however, livestock numbers have dropped sharply. Meat production has become relatively more important than wool as a source of income for mixed farmers, partly because of price changes and partly because of the changes to flock structure caused by the price changes.  That is, the ratio of wethers to ewes has dropped from about 40% in 1990 to about 8% today. Stocking rates expressed in dry sheep equivalents (Figure 1b) have, therefore, not fallen as much as raw livestock numbers. Over this time there has not been much change in the balance between sheep and cattle, nor in the overall importance of Merino breeds of sheep.

Figure 1 also shows that patterns of land use change on wheat and mixed farms in New South Wales continue to be different to those in Victoria, SA and WA. The increases in cropped area in NSW are smaller and are much more recent.  That is, the area under crop has only gone up appreciably since the “Millenium drought” of the 2000s, to about 30-35% rather than the current 45-55% in the other states. It remains to be seen whether cropping areas will continue to rise. Unlike the other southern states, livestock numbers on cropping farms in NSW have increased since the end of the last drought, recovering about 20% of the reduction since 2000 even though they are being supported by less land.

It is hard to tell how much of the shift toward cropping in the southern states is a result of specialization by some farms through abandonment of livestock, and how much is a change in the enterprise mix within farms that remain diversified. A recent GRDC farming practices survey, which was weighted toward larger crop producers, found that 14% of farms in the NSW-Victorian slopes zone had no livestock and in the northern WA zone it was 27%.

Figure 1. Land use change on cropping (i.e. ‘wheat and other crops’ plus ‘mixed livestock and cropping’) farms in New South Wales and in Victoria, South Australia and Western Australia combined.  Data are from AAGIS and are updates from Bell & Moore (2012).

Figure 1. Land use change on cropping (i.e. ‘wheat and other crops’ plus ‘mixed livestock and cropping’) farms in New South Wales and in Victoria, South Australia and Western Australia combined.  Data are from AAGIS and are updates from Bell & Moore (2012).

Another significant trend has been a migration of mixed farming into higher-rainfall areas. Over the last 20 years, the proportion of farm area that is cropped has expanded from 10% to 20% in southern Victoria, from 13% to 18% in south-east SA and from 12 to 25% in south-west Western Australia.  

Drivers of land use change in the cereal-livestock zone

The land use trends in Figure 1 are the product of a range of economic, technological and social factors. The increase in stocking rates in the 1980s and the initial decrease after 1990 are clearly responses to the rise and fall of the wool price during that period. Over the longer term, however, productivity gains in crop production due to a combination of improved plant genetics, increased fertilizer inputs and more-efficient machinery have combined with price changes to make cropping more profitable on average.

At the same time, major elements of the longstanding ‘fit’ between cropping and livestock production are becoming less relevant. Use of fertilizer N has reduced farmers’ reliance on the N fixed by pasture legumes, and in Mediterranean environments the smaller areas of pasture mean that less N is being fixed anyway. There is a mismatch between the large paddock sizes that are optimal for cropping machinery and the smaller paddocks that allow control of grazing livestock. Control of summer weeds and earlier sowing reduce the amount of summer feed available from crop residues. Perhaps most importantly, however, crop and livestock enterprises now compete for severely limited labour time (Figure 2).  In a world where the average farmer has to manage nearly twice the area than a generation ago, simpler farming systems have a real attraction (McGuckian 2006).
Figure 2. The inexorable increase in labour efficiency on Australian cropping farms.  Data are from AAGIS and are updated from Bell and Moore (2012).

Figure 2. The inexorable increase in labour efficiency on Australian cropping farms.  Data are from AAGIS and are updated from Bell and Moore (2012).

The initial increases in cropping in the higher-rainfall areas (above about 600mm rainfall) were driven by new technologies such as raised beds and longer-season cultivars. These have been reinforced by a run of lower-rainfall years that have reduced waterlogging constraints, and by the opportunity to graze crops during the winter and so relieve a major feed gap (Moore et al. 2009).

Mixed farming versus continuous cropping – the sustainability dimension

Soil organic matter

Soil organic matter is the main long-term sustainability concern for which the only practical solution is to include forages in the land use mix. Results from the SATWAGL long-term-experiment (Chan et al. 2011; Table 1) confirm that pasture-crop rotations can rebuild soil carbon but crop-only rotations will not, even when combining no-till, stubble retention and high frequencies of grain legumes.

There is no doubt that modern cropping systems with minimum tillage, stubble retention and high fertilizer N inputs have much greater primary productivity, and so carbon inputs, than well-managed pastures. They have also become more efficient at converting fertilizer nitrogen and phosphorus into exported product. Most of the N and P consumed by livestock, on the other hand, is recycled to the soil via faeces and urine. Recent research (Kirkby et al. 2014) suggests that in Australian farming the inputs of organic matter into the long-lived soil pools are limited by nutrients such as N, P and S rather than carbon supply. Doing nutrient budgets is therefore likely to be a good way to get an appreciation of the likely future direction of soil organic matter change of alternative land use systems.

Table 1. Long-term rates of soil organic carbon change (0-300mm) in no-till rotations of the SATWAGL experiment near Wagga Wagga (Chan et al. 2011).

Rotation

Rate of SOC change
(t C/ha/decade)

Significantly different from zero?

Wheat-lupin, stubble retained

-0.5

No

Wheat-lupin, stubble burnt

-1.0

No

Wheat-clover, stubble retained

+2.6

Yes

Soil erosion

Soil erosion risks are driven by rainfall patterns, by soil texture and surface structure, and by the ground cover at times of water runoff or high wind speeds. Of these, ground cover is the main factor under farmers’ control. The most important factors determining ground cover in summer and autumn are firstly the amount of biomass left standing at the end of the previous growing season, and secondly whether it is removed by tillage or burning. No-one has made a long-term comparison because it is so obvious that modern minimum-tillage systems and higher fertilizer rates have increased ground cover compared to once-conventional crop management. A recent modelling study (Moore 2014) concluded that wind erosion risk is now concentrated on the grazing land on mixed farms in medium and low rainfall environments, even where stubbles are grazed and livestock are confined to a feedlot during droughts; it is entirely possible that a shift to continuous cropping will reduce overall erosion risk.

Soil structure decline

Soil structure decline due to livestock trampling is sometimes cited as a reason not to graze stubbles. Stubbles can contribute 8-10% of annual livestock energy requirements in southern NSW, so removing them from the feedbase will reduce the sustainable stocking rate and hence the profitability of a livestock enterprise. A recent review of the literature (Bell et al. 2011) and experimental measurements by Hunt et al. (2011) make it clear that, at least for sheep, the effects of trampling on soil structure are relatively small and short-lived, and that ensuring adequate ground cover after grazing is more important than direct trampling effects.

Mixed farming and long-term resilience

Price relativities, between grain, meat and wool or between inputs and products, have changed in the past and are likely to change in future, and a mixed producer will be better equipped to track such changes if they take an unexpected direction. Present-day cropping practices depend critically on the availability of herbicides, high levels of mechanization and on access to reasonably cheap fertilizer. The last two of these, in turn, depend on readily-available and cheap sources of energy. Livestock enterprises rely much less on these inputs.

Herbicide-resistant weeds are already a significant problem (Kirkegaard et al. 2014) and having livestock available to manage them through grazing can be one part of an integrated management system to control them. While energy prices are not expected to rise sharply over the next 10 years or so, political and military risks make their future extremely uncertain (Figure 3).

Figure 3. Oil price rises are not expected for the next decade, but the forecasts are highly uncertain (Source: U.S. Energy Information Administration Annual Energy Outlook 2014).

Figure 3. Oil price rises are not expected for the next decade, but the forecasts are highly uncertain (Source: U.S. Energy Information Administration Annual Energy Outlook 2014).

Maintaining a mixed farming system instead of a specialized cropping or livestock farming system has an ‘option value’, because it provides a greater range of possible future land use pathways. Depending on individuals’ assessment of these uncertainties and their attitude to future versus present profitability, this option value may be high enough to make continuing with integrated crop-livestock systems worthwhile despite their greater complexity and labour demand.

References

Bell LW, Kirkegaard JA, Swan A, Hunt JR, Huth NI, Fettell NA (2011) Impacts of soil damage by grazing livestock on crop productivity. Soil & Tillage Research 113, 19-29

Bell LW, Moore AD (2012) Integrated crop-livestock systems in Australian agriculture: trends, drivers and implications. Agricultural Systems 111, 1-12

Chan KY, Conyers MK, Li GD, Helyar KR, Poile G, Oates A, Barchia IM (2011) Soil carbon dynamics under different cropping and pasture management in temperate Australia: Results of three long-term experiments. Soil Research 49, 320-328

Hunt JR, Swan A, Kirkegaard JA, Breust P, Peoples MB (2011) Do livestock reduce crop yields in conservation farming systems? , In: ‘Resilient food systems for a changing world’. Proceedings of the Fifth World Congresson Conservation Agriculture, Brisbane, Australia, 26–29 September 2011, pp. 382–383

Kirkby CA, Richardson AE, Wade LJ, Passioura JB, Batten GD, Blanchard C, Kirkegaard JA (2014) Nutrient availability limits carbon sequestration in arable soils. Soil Biology & Biochemistry 68, 402-409

Kirkegaard JA, Conyers MK, Hunt JR, Kirkby CA, Watt M, Rebetzke GJ (2014) Sense and nonsense in conservation agriculture: Principles, pragmatism and productivity in Australian mixed farming systems. Agriculture, Ecosystems & Environment 187, 133-145

McGuckian N (2006) ‘Social dimensions of managing mixed farming systems: discussion papers’. Report to the Grain and Graze program.

Moore AD (in press) The case for and against perennial forages in the Australian sheep-wheat zone: modelling livestock production, business risk and environmental interactions. Animal Production Science

Moore AD, Bell LW, Revell DK (2009) Feed gaps in mixed-farming systems: insights from the Grain & Graze program. Animal Production Science 49, 736-748

Contact details

Dr Andrew Moore,

CSIRO Agriculture Flagship, Canberra

Andrew.Moore@csiro.au