Ground cover, erosion risk and production implications of targeted management practices in Australian mixed farming systems: lessons from the Grain and Graze program

Authors: THOMAS, DEAN - Commonwealth Scientific And Industrial Research Organisation (CSIRO); MOORE, ANDREW - Commonwealth Scientific And Industrial Research Organisation (CSIRO); BELL, LINDSAY - Commonwealth Scientific And Industrial Research Organisation (CSIRO); WEBB, NICHOLAS - New Mexico State University

Submitted to: Agricultural Systems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/1/2018
Publication Date: 2/8/2018
Publication URL: http://handle.nal.usda.gov/10113/5918388
Citation: Thomas, D., Moore, A., Bell, L., Webb, N. 2018. Ground cover, erosion risk and production implications of targeted management practices in Australian mixed farming systems: lessons from the Grain and Graze program. Agricultural Systems. 162:123-135. https://doi.org/10.1016/j.agsy.2018.02.001.
DOI: https://doi.org/10.1016/j.agsy.2018.02.001

Interpretive Summary: Mixed enterprise farming systems are the predominant land use across southern Australia. Managers must operate farms for long-term sustainability as well as shorter-term profitability. This study evaluates management options developed in the Australian Grain and Graze program (an integrated program of research, development and extension) to identify general and/or site specific responses of farm systems to soil erosion risks in the mixed-farming region of southern Australia. Long-term simulation analysis was undertaken, based on regional farm characteristics and enterprise structures. This involved linking the Agricultural Production Systems sIMulator (APSIM) soil water, soil nutrient cycling, annual crop and surface residue simulation models to the GRAZPLAN pasture and ruminant simulation models, using the AusFarm modelling software. Our study presents evidence that the long-term benefits (or costs) to soil conservation associated with the various Grain and Graze interventions will depend on both the region (climate) and type of farming system (land use sequences) being considered. Lessons learned include: (1) Increasing pasture legume content and soil fertility can consistently benefit farm production and environmental indicators, (2) management interventions that target direct management of cover have the greatest potential to affect soil erosion rates, (3) management interventions coinciding with periods of naturally high soil erodibility and wind/water erosivity can substantially increase or decrease erosion risk; timing of management interventions is therefore critical, and (4) careful management of rotational grazing in mixed farming systems is needed to maintain crop stubble and pasture biomass to avoid developing hot spots of erosion and soil degradation. The results make a strong case that increasing pasture productivity and legume content should be carefully considered in mixed farms of southern Australia to increase productivity and to assist in erosion risk mitigation through increased farm ground cover. Conversely, these results flag the potentially heightened erosion risk through the use of bare fallows in rotations for water conservation and weed management in cropping-only farming businesses.

Technical Abstract: Maintaining the productive capacity of the agricultural soils of Australia's broadacre cropping zone requires careful management, given a highly variable climate and soils that are susceptible to degradation. Mixed croplivestock farming systems are the predominant land use across these regions and managers must operate farms for long-term sustainability as well as shorter-term profitability. Achieving profitable and sustainable businesses has required ongoing innovation and productivity gains, of which the integration of crop and livestock enterprises has been an important part. Production-soil erosion trade-offs associated with enterprise integration is critical information that has not been investigated to date at a whole-farm level. The objective of this study as to systematically evaluate management options developed in Grain and Graze (an integrated program of research, development and extension targeting mixed farms) to identify farm systems responses to soil erosion risks across seven regions spanning the mixed-farming area of Australia. To evaluate production-soil erosion trade-offs, we linked the APSIM soil water, soil nutrient cycling, annual crop and surface residue simulation models to the GRAZPLAN pasture and ruminant simulation models, using the AusFarm modelling software. Our results demonstrate that the management options tested in Grain and Graze support the principles of conservation agriculture and inform the sustainable intensification of mixed farming systems. Across the regions considered we found that: (1) Increasing pasture legume content and soil fertility can consistently benefit farm production and environmental indicators, (2) management interventions that target direct management of ground cover have the greatest potential to reduce soil erosion rates, (3) management during critical periods of naturally high soil erodibility and wind/water erosivity can substantially increase or decrease erosion risk; the timing of management interventions is therefore critical, and (4) grazing management to balance use of crop residues and pasture biomass is required to avoid developing hot spots of erosion and soil degradation.