Over the past two weeks we prepared the land in the Kentucky State University Energy Farm Study for planting. We started with a freshly-cut hay field that has grown an alfalfa and grass mixture for the past three years. It is rich in organic matter and naturally-fixed nitrogen, so we chose not to add additional fertilizer in the first year of the study. The soil preparation process differed between our three production systems:

1. Biointensive plots were cleared with a hoe, then double dug with a spade, spading fork, and broadfork. All labor was done by hand over the course of a week.
   
   
2. Market garden plots were prepared with two passes of a roto-tiller attached to a 13 hp BCS 852 walk-behind tractor, fueled by gasoline. The roto-tiller passes were spaced two weeks apart to allow sod to decompose after the initial cultivation.
   
   
3. Small farm plots were prepared with a single pass of a moldboard plow attached to an 89 hp John Deere 5520 tractor, fueled by diesel. The plow was followed, two weeks later, with two passes of a roto-tiller, pulled by the same tractor.
   
   

The following charts show the amount of labor and energy used to complete the soil preparation process at each of the three farm scales. Labor use is in minutes per square meter of land. Energy use is in megajoules per square meter of land (1 megajoule = 239 food calories). Error bars show the standard error, which is a measure of the variability between plots that were treated the same way.

The small farm plots cover about 40 times as much land as the biointensive plots, and 6.5 times as much as the market garden plots. (A previous blog post showed relative plot size on an aerial photograph of the site.)

We spent 20 hours clearing sod and double digging the biointensive plots, 2.5 hours using the walk-behind tractor in the market garden plots, and 3.0 hours on the 4-wheeled tractor in the small farm plots. The walk-behind tractor consumed 3.7 liters (1.0 gallon) of gasoline and the 4-wheeled tractor consumed 34.5 liters (9.1 gallons) of diesel fuel.

Michael Bomford provides research and extension services related to organic agriculture and small-scale renewable energy production through Kentucky State University's Land Grant Program. He thanks Brian Geier, John Rodgers, Hank Schweickart and Tony Silvernail for their help with preparing the land for planting.