Estimating the Field Ag Decision Maker

Capacity of Farm Machines File A3-24

T
he field capacity of a farm machine is can be used to find an average field capacity in
the rate at which it performs its primary differing terrain and weather conditions.
function, i.e., the number of acres that
can be disked per hour or the number of tons of Effective field capacities for many implements
hay that can be baled per hour. Measurements are estimated in Table 1. Average field conditions
or estimates of machine capacities are used to are assumed. Not all implements are shown,
schedule field operations, power units, labor, and particularly the wide range of combination tillage
to estimate machine operating costs. tools (strip till, vertical till, disc-subsoiler/ripper,
rotary harrows, etc.). If your implement differs
The most common measure of field capacity markedly in size, speed, or field efficiency from
for agricultural machines is expressed in acres those listed, effective field capacity should be
covered per hour of operation. The effective field calculated by using the information and equations
capacity (EFC) of a machine in the field can be shown at the end of this publication. Deeper or
easily calculated by dividing the acres completed more aggressive tillage, high-yielding crop, or
by the hours of actual field time. Recording acres adverse field conditions slow travel speed.
and hours for several fields over the whole season

Table 1. Average field speeds, field efficiencies, and effective field capacities for Iowa farm
machines
Speed Field Efficiency Effective
Machine Size (mph) (%) Field Capacity (A/hr)
Fertilizer spreader 40' 6 70 20.4
60’ 6 68 29.7
60’ 12 68 59.3
80’ 6 68 39.6
80’ 12 68 79.1
Manure spreader – box or liquid 15' 5 63 5.7
20' 6 63 9.2
30' 6 60 13.1
– liquid inject 36' 5 60 13.1
45' 5 60 16.4
Anhydrous ammonia applicator 15 knife 6 65 17.7
17 knife 6 63 19.5
23 knife 5 63 22.0
Moldboard plow 6–16" 5 85 4.1
8–18" 5 85 6.2
10–18" 5 83 7.5
Continued

PM 696 Revised May 2016

Page 2 Estimating the Field Capacity of Farm Machines

Table 1. Average field speeds, field efficiencies, and effective field capacities for Iowa farm
machines (continued)

Speed Field Efficiency Effective

Machine Size (mph) (%) Field Capacity (A/hr)
Subsoiler 5–30" 5 85 6.4
7–24" 5 83 7.0
7–30" 5 83 8.8
9-24” 5 83 9.1
Chisel plow 11’ 6 85 6.8
17’ 6 83 10.3
21’ 6 83 12.7
42’ 5 83 21.1
Disk, primary 21’ 5 83 10.6
24' 5 83 12.1
30’ 5 83 15.1
36’ 5 80 17.5
40’ 5 80 19.4
44' 4.5 80 19.2
Disk, secondary 21’ 6 83 12.7
24' 6 83 14.5
30’ 6 83 18.1
36' 6 80 20.9
40’ 6 80 23.3
44’ 5.5 80 23.5
49' 5 80 23.8
Field cultivator/seedbed, 20' 7 85 14.4
conditioner 24' 7 85 17.3
36' 7 83 25.4
45' 7 80 30.5
50' 7 80 33.9
65' 7 78 43.0
Planter, row-crop 6–30" 5.5 65 6.5
8–30" 5.5 65 8.7
12–30" 5.5 65 13.0
16–30" 5.5 63 16.8
24–30" 5.5 60 24.0
36–30" 5.5 58 34.8
48–30" 5.5 55 44.0
Grain or soybean drill 10' 6 70 5.1
15’ 6 70 7.6
20' 6 70 10.2
25' 6 68 12.4
30' 6 68 14.8
Air drill 25' 6 70 12.7
30' 6 70 15.3
40' 6 68 19.8
50' 6 68 24.7
60' 6 68 29.7
Continued
Estimating the Field Capacity of Farm Machines Page 3

Table 1. Average field speeds, field efficiencies, and effective field capacities for Iowa farm
machines (continued)

Speed Field Efficiency Effective

Machine Size (mph) (%) Field Capacity (A/hr)
Sprayer – pull type 30' 7 65 16.5
60' 7 63 32.1
80' 7 63 42.8
– self-propelled 90' 12 60 78.5
100' 12 60 87.3
120' 12 58 101.2
Mower conditioner, rotary 8’ 7 83 5.6
10' 7 83 7.0
13' 7 80 8.8
14' 7 80 9.5
16' 7 78 10.6
19' 7 78 12.6
Rake 16' 7 80 10.9
20' 7 80 13.6
25' 7 78 16.5
Combine, soybeans* 25' 4.5 78 10.6
30’ 4.5 78 12.8
35' 4.5 75 14.3
40’ 4.5 75 16.4
45' 4.5 75 18.4
Combine, corn* 4–30" 4.5 82 4.5
6–30" 4.5 82 6.7
8–30" 4.5 80 8.7
12–30" 4.5 78 12.8
16-30” 4.5 75 16.4

Tons/hr**
Small square baler 7
w/accumulator 7
w/bale thrower 6
load/haul/stack 5***
Large rectangular baler 16
Large round baler 16
and move in field 12
and haul/store 10***
Forage harvester
pull-type, 150 hp 18
175 hp 22
200 hp 27
250+ hp 40
self-propelled, 2 rows 30
3 rows 40
4 rows 55

*Capacity in acres/hr may be reduced about 8 to 10 percent for stationary unloading, travel speed
dependent on conditions.
**Material capacity for forage harvester varies with crop size and travel speed.
***Hauling assumes bales are moved one mile from field.
Page 4 Estimating the Field Capacity of Farm Machines

Calculating Effective Field Capacity After you have calculated the machine’s average
Theoretical field capacity (TFC) depends only field speed, TFC can be calculated from equation
on the full operating width of the machine and (1) using the full width of the machine. The FE
the average travel speed in the field. It represents can be taken from the table in this publication
the maximum possible field capacity that can be or estimated using equation (3) if you have a
obtained at the given field speed when the full representative value of EFC.
operating width of the machine is being used. It
(3) FE (%) = EFC/TFC x 100
can be calculated from equation (1).
Conversely, if you need to estimate a machine’s
(1) TFC (A/hr) = width (ft) x speed (mi/hr) x (5,280 ft/
EFC and have an estimate of FE, use equation (4).
mi)/(43,560 sq ft/A) = width (ft) x speed (mi/hr)/8.251
(4) EFC(A/hr) = TFC x FE%/100 =
Actual effective field capacity is less than this due
(width (ft) x speed (mph) x FE%) / (8.25 x 100)
to turns and other delays. The ratio of actual or
effective field capacity (EFC) to TFC is called the The working capacity of harvesting machines
machine’s field efficiency (FE). is often measured by the quantity of material
harvested per hour. This capacity is called the
Field efficiency is expressed as the percentage
machine’s material capacity (MC), expressed as
of a machine’s TFC actually achieved under real
bushels per hour or tons per hour. It is the product
conditions. It accounts for failure to utilize the
of the machine’s EFC and the average yield of crop
full operating width of the machine (overlapping)
per acre, and can be calculated from equation (5).
and many other time delays. These may include
turning, filling with seed, fertilizer, or pesticide, (5) MC(bu or tons/hr) = EFC(A/hr) x crop yield (bu or
emptying grain, traveling to a supply tender or tons/A)
grain cart, cleaning a plugged machine, checking
a machine’s performance and making adjustments, For example, a baler with an EFC of 5 A/hr
waiting for trucks, and operator rest stops. Delay working in a field yielding 3 tons of hay per acre
activities that occur outside the field, such as would have an MC of 5 A/hr x 3 tons/A, or 15
daily service, travel to and from the field, and tons/hr. Harvest travel speed is often adjusted to
major repairs are not included in field efficiency keep a consistent mass flow of crop suitable for
measurement. the harvester.

Average field speed can be easily measured by Points of Interest

marking off a distance of 88 feet in the field, plac- - Although wider equipment operated at the same
ing a stake at each end, and counting the seconds speed covers more acres per hour, measurements
it takes to drive between the stakes. Average field in the field document slightly lower field efficiency
speed can then be calculated from equation (2). of wider equipment. With wider equipment, turns
at headlands are longer with raised implements not
(2) Speed (mph) = 60/seconds to travel 88 feet
in use and headland areas are often larger.
For example, if you traveled between the stakes in
- Wider equipment occasionally results in a smaller
12 seconds, your average field speed was 5 mph.
number of acres covered per hour if travel speed is
slowed due to limited tractor horsepower available
or too much wheel slippage.

1
The factor 8.25 is derived by dividing the number of square feet in an acre, 43,560,
by the number of feet in a mile, 5,280.
Estimating the Field Capacity of Farm Machines Page 5

Other publications that will help make good machinery management decisions are:
PM 709/AgDM A3-27 Fuel Required for Field Operations
PM 710/AgDM A3-29 Estimating Farm Machinery Costs
PM 786/AgDM A3-33 Self-Propelled Harvesting and Spraying: Machinery Ownership Versus Custom Hire
PM 787/AgDM A3-21 Acquiring Farm Machinery Services
PM 952/AgDM A3-28 Farm Machinery Selection
PM 1373/AgDM A3-34 Joint Machinery Ownership
PM 1450/AgDM A3-32 Transferring Ownership of Farm Machinery
PM 1860/AgDM A3-30 Replacement Strategies for Farm Machinery
PM 1874/AgDM A3-25 Fieldwork Days in Iowa

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Issued in furtherance of Cooperative Extension work, Acts of May 8 and July
30, 1914, in cooperation with the U.S. Department of Agriculture. Cathann A.
Kress, director, Cooperative Extension Service, Iowa State University of Science www.extension.iastate.edu/agdm
and Technology, Ames, Iowa.
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