An Alternative to Traditional Wheat Stubble Management Using Sheep to Control Pests and Improve Soil Nutrient Cycling

An Alternative to Traditional Wheat Stubble Management Using Sheep to Control Pests and Improve Soil Nutrient Cycling

Summary

We monitored wheat-stem sawfly larval populations in grazed, burned, tilled, and control plots at eight Montana sites. Larval mortality was greater in sheep-grazed (67.2%) compared to tilled (50.9%), burned (31.1%) and control (47.6%) plots. Hoof action appears to be the main cause of larva mortality. Grazing did not negatively impact soil compaction. Weed numbers did not differ among treatment. In a second two-year study, we found a 70% reduction in alfalfa weevil larvae numbers in the winter/spring grazed compared to the non-grazed plots. Grazed and non-grazed plots did not differ in quality and quantity of alfalfa hay produced.

Objectives/Performance Targets

Compare burning, grazing, and tilling wheat stubble fields in a multi-farm study on: 1) over-wintering wheat stem sawfly larvae and emergence of adult populations. 2) soil nutrient profiles, nutrient cycling, and soil compaction.3)total biomass including wheat stubble, cheatgrass, volunteer wheat and mustard weed 4) develop an economic model to evaluate long-term cost benefits of the various methods of wheat stubble management and their respective outcomes. 5) develop and conduct large, multiform field demonstrations. Communicate results to producers, students, scientists, and public on advantages of implementing sustainable alternative grain residue management strategies.

Accomplishments/Milestones

We have completed all field data collections. A thesis has been completed. In 2002 and 2003, we published and presented the results at both scientific and producer meetings (see list of publications and presentations). Three journal articles are in progress that address objectives 1, 2, and 3.

We are currently working on objectives 4. We have made good progress on our economic model and are currently analyzing data from large (commercial scale) demonstration/research projects on a number of grain farms with cooperating sheep producers.

Spezzano, Theresa Marie. 2003. The impact of intergrading sheep into wheat farming systems to manage wheat stem sawfly and weeds. MS thesis, Montana State University.

Goosey H. B., T. M. Spezzano, P. G. Hatfield, S. L. Blodgett, P. M. Denke, and R. W. Kott. 2002, Using sheep in grain production systems to reduce pesticide use: I. Control of Wheat Stem Sawfly infestation in wheat stubble. West. Sec. Amer. Soc. Anim. Sci. 53.197-200.

Spezzano, T. M., H. B. Goosey, P. G. Hatfield, S. L. Blodgett, P. M. Denke, and R. W. Kott. 2002, Using sheep in grain production systems to reduce pesticide use:
II. Comparing stubble grazing with tillage and burning on weed and soil characteristics. West. Sec. Amer. Soc. Anim. Sci. 53.208-211.

Spezzano, T. M. H. B. Goosey, P. G. Hatfield, S. L. Blodgett, S. D. Cash, P. M. Denke, R. W. Kott, A. W. Lenssen, and C. B. Marlow. 2003. Managing Insect Pest Damage to Wheat and Alfalfa by Integrating Sheep into Crop Production. Proc. Montana Livestock Nutr. Conf. 52:

Goosey, H., P. Hatfield, S. Blodgett, and D. Cash. “Sheep grazing to control alfalfa weevil” 2003. Montana Woolgrower bulletin, spring issue 2003 page 9.

Impacts and Contributions/Outcomes

Montana ranks 3rd in the nation for wheat production, with $304,497,000 in wheat sales in 2001. Alfalfa is grown on approximately 1.5 million acres in Montana with an on-farm value of $251,370,000. Among disease, weed, and insect pests, insect pests cause the greatest damage to these commodities. Wheat stem sawfly and alfalfa weevil are the most destructive pests to Montana’s grain and alfalfa industries, respectively. Current methods of control are either expensive or ineffective. As part of a long-term project investigating the benefits of incorporate grazing sheep into grain farming systems, we were interested in comparing the impact of sheep grazing, tillage, and a no-input control on over-wintering wheat stem sawfly larval populations. The objective of our alfalfa weevil study was to determine alfalfa yield and quality and alfalfa weevil densities in grazed and non-grazed plots. Over a two-year period at eight commercial grain farms in Montana, wheat stem sawfly larval mortality was greater on grazed compared to tilled plots. Over a two-year period on the same alfalfa field grazed by a large commercial band of sheep, grazing resulted in a lower number of adult weevils without adversely impacting hay production or hay quality. These data reflect the potential of integrating sheep into farming systems for control of insect pest. Additionally, these data indicate that mutually beneficial partnerships between sheep and crop producers could reduce production costs for both enterprises.

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