Economic and Environmental Performance of Mixed Crop-Livestock Farming Systems on the Palouse
Wachter, Jonathan Malina
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The global trends of simplifying cropping systems and segregating livestock from cropping enterprises have generated high yields while exacerbating environmental problems globally. To examine the potential for organic and mixed crop-livestock farming systems to reduce environmental impacts and diversify revenue in the Palouse region of eastern Washington State, long-term research plots were established in April 2012 representing 4 farming systems: a conventional 3-yr winter wheat/spring wheat/spring pea rotation (CONV); a mixed crop-livestock 3-yr rotation of winter wheat/spring wheat/grazed winter pea (MIX ); an organic mixed crop-livestock rotation of perennial alfalfa/grass hay (3-yr)/grazed spring pea/winter wheat (ORGcrop); and a continuous organic hay system (5-yr) with grazing (ORGhay). This dissertation consists of 3 main chapters: (1) a 40-yr global review assessing the performance of organic and conventional farming systems in the context of sustainability metrics; (2) a 5-yr study of the CONV, MIX, ORGcrop, and ORGhay systems in terms of their productivity, economic performance, and impacts on soil biological indicators; and (3) an examination of N2O and NH3 emissions from these four farming systems in years 4 (2015) and 5 (2016) of the experiment. The review found that organic farms produce lower yields, are more profitable and environmentally friendly, and deliver equally or more nutritious foods that contain less pesticide residues compared with conventional farms. Significant barriers exist to adopting organic and other alternative farming systems, however, and a diversity of policy instruments will be required to facilitate their development and implementation. In the 5-yr field study, ORGcrop and ORGhay plots were more profitable and showed increases in organic carbon, nitrogen mineralization, and biological activity in the soil compared to CONV and MIX plots. Emissions of N2O and NH3 were mainly influenced by specific management and weather events such as fertilization, rainfall, grazing, and cutting hay, and were not consistent between years and farming systems. Organic mixed crop-livestock and hay systems have great untapped potential to improve soil quality and increase revenues in the Palouse region. Moreover, integrating perennial alfalfa and forage grasses into other cereal cropping systems would likely deliver many of these benefits as well.