Jason Bradford and I left Willits, late Thursday and set off
toward the Sacramento
valley, set to return with all the necessary equipment and supplies to initiate
the Dryland Grain demonstration with ET-7, a scratch-built electric tractor. We
had a strong truck and an eleven foot long trailer that would be able to carry any
implement we found that would be appropriate. As you may know, the Sacramento valley is considered to be the northern heartland
of California
agriculture. Thus, it is rich in used agricultural equipment and plenty of
conventional wisdom related to various large-scale agricultural operations.
Before setting out, we had spent the week calling various grain distribution outlets
and equipment dealers, trying to narrow the number of stops on our trip.

There are many options for a farmer as they “open the field”
(i.e., begin to turn over the soil for the first tilling and planting). Typical
practice includes using a moldboard plow that is capable of turning over soil
at a depth of about 14 inches, using a roto-tiller to incorporate and shred the
first 4-6 inches into a fairly fluffy and uniform seedbed, and using a single
ripping tooth to dig and rip into the soil from 8-36 inches. Each of these soil
cultivation practices are energy intensive and disruptive to the microbiology
in the soil. The PTO driven roto-tiller uses much of the available horsepower
from a tractor and runs at a high RPM, burning diesel and shredding microbes
and organic matter in its wake. The moldboard plow runs deep into the soil, uses
a fair amount of energy as it flips the topsoil to the bottom thereby
disrupting natural soil strata and creating a plow-pan. Finally the ripping
tooth requires multiple passes, again disrupts the fungal web of the soil, and
requires more diesel energy the deeper you go.

In light of these observations we have chosen to use a
disc-harrow to open the soil. This implement will be used to penetrate the soil
4-6 inches and incorporate sod and organic matter gently into the land. While it
may not be as effective in the first pass as a roto-tiller or moldboard plow,
it is a long-term practice that will eventually cut into the land gently without
making a drastic hard-pan, severely disrupting the biology, or utilizing
significant energy from the tractor to prepare a seedbed

Since we are working with an electric tractor (an admittedly
rare item) we had a difficult time getting any clear answers from equipment
dealers as to what the actual size of the disc they would recommend. As you
might expect, there was not a lot of experience in the field of electric
tractors. We, therefore, had to do the math for ourselves. I knew from my conversations with Steve Heckeroth that the
tractor with two 2Hp electric hub motors, geared at 50:1 ratio would have
enough “guts” to pull any heavy implement, but we wanted to find the appropriate
sized implement or we would not be making efficient use of the on-board battery
banks. Sure, it could pull something big, but if it drained the battery too
fast what good was the implement. In fact, over-sizing the implement is one of
the biggest wastes of energy with tractors in agriculture and also limits a tractor's life expectancy.

The key for the electric tractor is to run slow. The slower the machine runs
the deeper the disc will sink into the ground. Also the slower the machine runs
the more drawbar horsepower (ability to tow) will be available to the implement. The Drawbar
horsepower needed to pull an implement is given by the weight of the implement (including
the average pounds of force applied per disc in the soil) F and the speed that the implement is pulled through the soil S. The equation to find the necessary
horsepower to pull an implement is FS/375.
Each 18 inch disc is about 38 pounds of weight load into soil and most
disc-harrows have 16-20 discs. Initial test data related to ET-7 suggested that
it could provide 20Hp of continuous operation with a tops speed of about 8 MPH. This was our goal; match a disc
to operate smoothly at around 20Hp. We found a 5 foot wide disc-harrow that
had 16 blades and weighed 628 pounds. To see if this disc would fit we
performed the calculation described above:

F= [628 pounds + (38 x 16)] = 1236 pounds S=6mph

1236 x 6=7416 7416/375=19.78
Hp required to pull implement

Ok, so now we had the range. We called some dealers and
looked on craigslist for used tools and made our way toward the Sacramento Valley. We checked in at Woodland
Tractor. These gentlemen were friendly, but unfortunately they did not have the
any implements that would be ideal for our application. We told the salesman
that we were headed to Grass
Valley for the 2^nd
Annual Sierra Nevada Small Farm Progress Day and he suggested a dealer in that
town. We thanked him and made our way to the Small Farm Progress Day.

When we arrived at the Small Farm Progress Day, we saw the
Electric Tractor on display. This convention was to demonstrate and showcase
tools suited to small farms and included horse drawn equipment, small scale implements,
and food and livestock production workshops. We manned the Electric Tractor
booth with Steve Heckeroth and used the opportunity to talk about issues of
energy usage in the total food system, localized food production, and the way in which
the electric tractor confronts the food vs. fuel issue. Overall it was a fun
day and we felt proud that while many people got to look at the machine, we
were the folks who would begin to put it through its paces.

After the Small Farm Progress Day we visited the local equipment
dealership in Grass
Valley. They had a 4.5
foot Gearmore disc-harrow that weighed about 480 pounds and had 16, 18 inch disc-blades. Given the equation we worked above:

F= [480 pounds + (38 x 16)] = 1088 pounds S=6mph

1088 x 6=6528 6528/375=17.4
Hp required to pull implement

This disc seemed to be well within the acceptable range for
the size of the implement we are using. Like the disc, the measurement to the
outside of the wheels is 4.5 feet wide. Pretty close to a perfect fit. Since
this disc is so light we will have to find a method to add a little weight over
the blades. To do this we will add scrap steel and/or a water tank to help
drive the blades deeper into the soil. With the disc on the trailer we were off to Adams Grain Company to pick up wheat seed.

--Want to learn more about sizing farm impliments click here

--Want to learn more about tractor horsepower and torque click here

Steve Discussing ET-7 at the Small Farm Progress Day in Grass VAlley, CA

Small Scale Farmers Looking on at ET-7 Workshop

Gearmore 4.5 Foot Disc-Harrow (Semi-Stubble)

Front View of the Disc-Harrow Loaded on The Trailer