Using Fuel Price as a Factor in Tillage System Selection

Using Fuel Price as a Factor in Tillage System Selection

March 20, 2009

This is one in a series of publications on Meeting the Challenge: Farming in Uncertain Times, written by specialists at the Panhandle Research and Extension Center. For more go to http://www.panhandle.unl.edu/meeting_challenge.htm

Choice of a tillage system is based on a number of factors, and fuel price is certainly one of the important issues. Fuel consumption can be highly variable for a specific tillage operation and for a particular tillage system, depending on tillage depth, soil type, soil moisture, field speed, and design of the soil-engaging tool.

Setting these variables, you can compare potential differences among tillage systems. Assume, for example, the following operations and associated fuel consumption for several tillage systems for planting corn after corn under a pivot irrigation system in western Nebraska.

Table 1. Comparison of fuel use and the resulting input cost for fuel priced at both a low ($1.80/gal) and a higher ($3.00/gal) rate.
 
Diesel
Fuel Use

(gal/ac)
Fuel Cost
at $1.80/gal
Fuel Cost
at $3.00/gal

($/ac)
Difference
in Fuel Cost

($/ac)
Moldboard Plow
Disk stalks, plow, rollerharrow twice
3.90
$7.02/ac
$11.70/acre
$4.68
Double Disk
Disk two times
1.15
$2.07/ac
$3.45/acre
$1.38
Zone Tillage
Apply herbicide, zone till
1.23
$2.21/ac
$3.69/acre
$1.48
No Tillage
Apply herbicide only
0.18
$0.32/ac
$0.54/acre
$0.22
Table 2. Fuel costs for component operations of two tillage systems, calculated at both a low ($1.80/gal) and a higher ($3.00/gal) rate.
Tillage System Field Operation

Typical Diesel
Fuel Use
(gal/ac)

Fuel Cost
at $1.80/gal
($/ac)

Fuel Cost
at $3.00/gal
($/ac)

Difference in Fuel Cost
($/ac)

Moldboard Plow

Disk stalks
0.50
0.90
1.50
0.60
Plow
2.40
4.32
7.20
2.88
Rollerharrow
0.55
0.99
1.65
0.66
Rollerharrow
0.45
0.81
1.35
0.54
Total
3.90
7.02
11.70
4.68
Double Disk
Disk
0.60
1.08
1.80
0.72
Disk
0.55
0.99
1.65
0.66
Total
1.15
2.07
3.45
1.38

Although actual fuel consumption will be different for each producer and each field, these typical values demonstrate two points relative to the question of whether fuel price should influence tillage system selection.

  1. When fuel price increases as much as it did in 2008, this increase alone is significant. Fuel use for the moldboard plow tillage system increased $4.68 per acre in 2008; fuel costs for the double disk system increased $1.48 per acre (Table 1).

     

  2. There are substantial differences in fuel cost and fuel-cost increases between tillage systems with different amounts of tillage inputs. Spread over hundreds or thousands of acres, these costs will add up. Using a fuel cost of $3.00 per acre, the cost per tillage system ranged from $11.70 per acre for the moldboard plow system to $3.69 for zone tillage or $0.54 for no tillage (Table 1).

While important, fuel costs for tillage operations cannot be the only, or even most important factor for deciding which tillage/production system to use. Sustainable crop yield, weed control, soil erosion control, labor availability, management style, soil water conservation, and crop rotation are as or more important criteria.

Also keep in perspective the relative contribution of the cost of fuel for tillage operations with the cost of fuel for the entire production system (planting, harvesting, spraying, hauling), and the relative contribution of the selected tillage system to net crop income. Saving $15 per acre to eliminate a critical tillage operation is not a good choice if it reduces corn yield by 10 bushels per acre or sugarbeet yield by 1 ton per acre, for example. When deciding whether to perform a particular tillge operation, consider how it contributes to the overall crop production system, and where applicable, eliminate that operation. Table 2 shows the estimated costs of the component operations for two tillage systems — moldboard plow and double disk. Use it to estimate how much you can save by eliminating one tillage operation.

Reducing Fuel Costs

In addition to eliminating or combining field operations, look for other ways to reduce fuel costs.

  • Does the implement power requirement match the tractor power?
  • Can you gear up and throttle back?
  • Is the tractor ballast or tire slippage in the correct range?
  • Can you reduce the depth of tillage without decreasing the effectiveness of the operation?

Match Tractor to Task. Using a 250-horsepower tractor to pull an implement requiring 100 horsepower will not use fuel effectively. The weight of the oversized tractor requires additional power and fuel just to move the tractor through the field, and the high axle weight might contribute to soil compaction. If the implement operation does not require full tractor power, consider gearing up and throttling back to find an engine rpm that has more fuel efficiency.

Balance Ballast with Load. Use a reasonable balance of tractor ballast with the load being pulled to achieve a 10%-15% tire slip in most typical soil conditions. Lower slip increases power train wear and reduces traction efficiency. Higher slip increases tire wear and wastes power and fuel. Experiment with tillage depth to find a minimum depth that will still allow desired tillage performance. Generally a change in tillage depth is not proportional to the resulting change in power and fuel input - as you double tillage depth you more than double, probably triple, power and fuel input.

Summary

When fuel prices change it is a good time to evaluate tillage systems. Examine how the fuel price affects input cost and how each tillage operation contributes to the outcome of the cropping system. Also look at how the tillage operation or tillage system contributes to other important goals of your overall production system, including soil and water conservation.

John Smith
Machinery Systems Engineer, Panhandle REC