Farm scale study: Results from 2008
In 2008 we grew corn, soybean, sweet potato, and sweet sorghum organically at three different farming scales:
- Biointensive plots were managed according to methods recommended by John Jeavons, in his book How to Grow More Vegetables…, using only human labor and hand tools. Each biointensive plots covered 20 m2 (215 sq. ft.).
- Market garden plots were managed with hand tools and walk-behind tractors. Each market garden plot covered 126 m2 (1356 sq. ft.).
- Small farm plots were managed primarily with conventional 4-wheeled tractors, supplemented with hand tools and walk-behind tractors for tasks that weren’t suited to the larger machines. Each small farm plot covered 836 m2 (9000 sq. ft.).
We recorded the labor used to manage each plot through the season, and divided this figure by the plot size. The biointensive plots used the most labor (26 minutes per square meter) and the small farm plots used the least (3.7 minutes per square meter.).
We recorded the intensity of our labor in order to estimate the metabolic (food) energy needed to support the laborer while working. We multiplied the volume of fuel used for machinery by the energy density of the fuel to estimate the fossil fuel energy consumed. The small farm plots used the most energy (0.75 megajoules per square meter) and the biointensive plots used the least (0.10 megajoules per square meter).
Metabolic energy accounted for all of the energy invested in the biointensive plots. Fuel energy accounted for most of the energy invested in the market garden and small farm plots.
Plot preparation (cultivation) accounted for most of the energy use at all farm scales.
Plot preparation (“double digging“) accounted for most of the labor use at the biointensive scale, but weed management and post-harvest processing accounted for the largest components of labor use at the market garden and small farm scales. Hand tools were frequently used for in-row weed management at all production scales. Post-harvest processing tactics differed little between treatments because we did not have access to the combine harvestors or threshing machines that would typically be used at the small farm scale.
Soybean yield was highest at the market garden scale. Sweet potato yields were similar across scales. Field corn and sweet sorghum yields were highest at the small farm scale.
Small farm plots used land and labor most efficiently; biointensive plots were the most energy-efficient.
These results are from the first year of a four-year study. 2008 was a drought year. Our corn and soy yields were well below national averages at all scales, but sweet sorghum yield for the fuel variety (M81E) was well above the national average at the small farm scale.
We plan to make some changes in 2009, based on the results in 2008:
- We will try different varieties of corn and soybean;
- We will transplant corn and sweet sorghum into biointensive plots, instead of direct seeding;
- We will not double dig biointensive plots, but will incorporate compost with a broadfork;
- We will use a smaller tractor to cultivate the small farm plots.
For more information see:
- Kentucky State University’s Organic Agriculture Working Group website
- Previous blog posts
- Energy and labor use in field preparaton (May 22, 2008)
- KSU project update and photos (July 8, 2008)
- Energy and labor use in KSU energy farm study through July (July 31, 2008)
- KSU energy farm in August (August 29, 2008)
Thanks to Tony Silvernail for managing the study, as well as Brian Geier, John Rodgers, Joelle Johnson, the KSU farm crew, and student volunteers from the CASS program for their many hours of help. Comments and feedback regarding this study are most welcome.