Sustainable Livestock Production on the Frontier: Plant and Soil Responses to Simulated Managed Grazing in Sub-Arctic Alaska

View the project final report

• 2015 annual report

Commodities

• Agronomic: corn, wheat, grass (misc. perennial), hay

Practices

• Animal Production: feed/forage, grazing management, grazing - rotational, pasture renovation, pasture fertility, stocking rate
• Crop Production: nutrient cycling
• Education and Training: extension, on-farm/ranch research
• Production Systems: agroecosystems, holistic management
• Soil Management: nutrient mineralization, organic matter, soil analysis, soil microbiology, soil physics, soil quality/health

Alaskans live at the end of a very long, vulnerable food chain. The Alaska Food Policy Council Strategic Plan, 2012 estimated that only 5% of food consumed in Alaska was produced in-state. The growing awareness of food insecurity and the impact of food systems on state economy, health, and security has renewed interest in agricultural production with a goal of developing a more sustainable and diverse agricultural model. Even though grazing is a natural system for Alaska, agricultural production in the state has remained largely undeveloped due to limiting factors such as extreme climactic conditions, expensive farm inputs, and a lack of research into regionally specific farming practices.  At USDA and SARE sponsored conferences and workshops, Alaskan livestock producers have emphasized the need to develop sustainable grazing strategies that are appropriate for high latitudes 1. Developing flexible livestock management systems not only enhances the sustainability of current farming operations but also provides producers with essential tools to manage risks associated with global climate change 2. We need to start collecting baseline information now and initiate monitoring programs if we are to understand and adapt to changes in sub-arctic agricultural systems. The goal of this research is to evaluate the response of pastures to an intensively managed rotational grazing (IMRG) regime. Managing a robust pasture ecosystem and optimizing available forage in sub-arctic conditions is a challenge. The region is characterized by a short growing season, slow decomposition rates, and undeveloped soils that are sensitive to compaction and erosion. Although grazing practices in Alaska are frequently characterized as continuous, they are largely unmanaged. Here, as elsewhere, unmanaged grazing results in a heterogeneous pattern of pasture use, with animal feeding preferences creating patches of both over- and under-utilization and degradation. To evaluate the impacts, a full factorial experiment of simulated trampling, manure/urine deposition, and forage removal will be conducted, mimicking the intensity and frequency of an IMRG. The simulations will be conducted on plots in two established pastures over the 2014 and 2015 grazing seasons. Changes in soil biota, physical soil characteristics, plant biomass, and plant community composition will be used to evaluate the suitability of IMRG for livestock farms in interior Alaska. This research provides a twofold benefit to stakeholders; it evaluates site-specific responses to IMRG and provides insight on the relative roles of grazing disturbance mechanisms on sub-arctic soil and plant health. References:  1) Rowell, J. E. et al. 2013. UAF Agricultural Forestry Experiment Station,  misc. - 1304.  2) Joyce, L. A. et al. 2013. Rangeland Ecology & Management 66, 512-528.

The goal of this study is to evaluate the effects and interaction of simulated herbivory, manure/urine deposition, and trampling in response to IMRG methodology.  The research will provide regionally specific baseline information and address some crucial knowledge gaps through the following objectives:

1. 1. Determine how an intense but brief simulated grazing disturbance affects the physical structure of pasture soils and plant communities.

1. 1. Measure changes in abundance and community structure of soil organisms and consequent effect on decomposition.

1. 1. Evaluate the relative and interactive roles of the three grazing mechanisms: herbivory, manure/urine deposition, and trampling in sub-arctic pastures.

The following hypotheses address the objectives stated above:

a) Soil organic matter will increase in response to manure/urine application, root sloughing from herbivory, and incorporation from trampling.

b) Plant species composition will become more diverse and percentage of bare ground will decrease as a response to managed herbivory.

c) Soil biota abundance and activity will increase in response to additional nutrients from manure/urine applications, root sloughing, and incorporation through trampling.

d) Soil bulk density and penetration resistance will remain unchanged as plant cover and soil organic matter compensate for compression due to trampling.