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CHAPTER 5. YIELDS AND CULTURAL ENERGY REQUIREMENTS FOR CORN AND SOYBEANS WITH VARIOUS TILLAGE–PLANTING SYSTEMS
C. B. RICHEY ET AL.
man. The object of tillage was to prepare an adequate seedbed and to control
weeds. A good job of plowng with complete inversion of the soil aided in both
respects, There was limited time for secondary tillage operations but cultivation
for weed control became increasingly important as the weed population multiplied.
When row-crop tractors with efficient equipment became available, farmers
had the capacity to perform more tillage operations than in the past, particularly
on small farms in years with good spring weather. They were able to disc corn
stalks before plowing to aid in complete coverage of trash and they could disk,
roll, and drag until they had the fine, uniform seedbed they had always desired.
They could also cultivate up to five times in check-rowed corn to control weeds.
Although most corn belt farmers had reached this point in mechanization by
1940, the average corn yield in the United States for the period 1937-1941 was
1824 kg/ha (29 bu/A), only 183 kg/ha (2.9 bu/A) higher than for the period
1867-1871. During the intervening period the high yield was 1994 kgfhg (31.7
bu/A) in 1906 and the low was 994 kg/ha (15.8 bu/A) in 1934 (USDA
Agricultural Statistics, 1900, 1942). Thus, increased tillage was not the answer,
and only as hybrid seed and increased fertilization came into use did corn yields
begin their rapid advance to present levels.
One of the earliest projects to evaluate tractor-powered tillage methods for
corn was started in Ohio in 1938 (Willard et d.,1956). In a cornwheat-hay
rotation on fairly level fine-textured Miami-Brookston soil, sod ground was
prepared for planting corn by:
1. Spring plowing and several diskings.
2. Spring plowing with a prairie-breaker bottom which smoothly inverted the
sod strip, followed by a smoothing harrow or straight disk.
3. Rotary tillage.
4. Surface tillage with sweeps or disk to kill the sod.
5. Surface tillage only to kill sod.
6. Treatment 1 with the addition of 4.4 tonnes/ha (2 tons/A) straw mulch
after the first cultivation.
Over the 14-year period 1938-195 1, the yields of plowed treatments were not
significantly different and averaged about 3400 kg/ha, (54 bu/A); rototilled,
2956 kg/ha (47 bu/A); treatment 4, 281 1 kg/ha (44.7 bu/A); and treatment 5,
2528 kg/ha (40.2 bu/A). Stand, sod regrowth, and weeds were problems in
treatments 4 and 5 .
It was stated that “The results show conclusively that there is no advantage for
corn in more working of plowed land than is necessary to insure a good stand,
and there are indications that such working may be detrimental.”
The advent of chemical weed control made it possible to control weeds
without tillage in many cases. This greatly increased tillage-planting options and
brought us into the present era of experimentation to find the optimum
YIELDS AND REQUIREMENTS FOR CORN AND SOYBEANS
combination of tillage, planting, and weed control practices to give maximum
yields at minimum cost with minimum soil erosion.
The purpose of this chapter is to review the tillage system effect on yield for
corn and soybean production in the United States corn belt, and to estimate
cultural energy requirements for various systems and soil types, including energy
requirements for herbicides but not for fertilizer, harvest, and drying.
II. Tillage-Planting Systems
A. DEFINITION OF TILLAGE-PLANTING SYSTEM
Since the condition of the soil dictates the type of planting which is necessary
t o secure a good stand, tillage and planting must be considered together. The
type of cultivator required and its effectiveness in controlling weeds also depends
on the condition of the soil. Thus the tillage-planting system includes preplant
tillage, planting, and weed control by cultivation, herbicides, or both. The tillage
system also affects methods of fertilizer and insecticide application.
The tillage-planting system encompasses the operations needed to produce the
crop ready for harvest.
B. HIGH-ENERGY SYSTEMS
In these systems the soil is thoroughly loosened at least 12 cm (5 inches)
deep, either by moldboard plow, chisel, or heavy-duty disk harrow. Current corn
belt practice is to plow about 20 cm (8 inches) deep if power and soil condition
permit. The average depth of chiseling is usually comparable to plowing depth,
with the points penetrating the old plow sole. This is considered to be an
advantage for chiseling because it improves water infiltration. Chiseling is also
considered less likely to develop a “sole” or impenetrable layer than is plowing.
Heavy-duty disk harrows with 61-cm (24-inch) diameter blades can cut up to
15 cm (6 inches) deep with a draft per unit of cross section tilled comparable to
that for a chisel plow, or about 80%of that for a moldboard plow. They also cut
and cover most of the residue.
Plowing and chiseling are preferably done in the fall on level fine-textured soils
which are not subject to winter erosion. Chiseling after corn leaves more residue
on the surface than plowing and thus does not leave the soil as vulnerable to
water and wind erosion as does plowing. Residue effects are minimal after
Corn stalks are often shredded or disked to avoid clogging, although high-
C. B. RICHEY
clearance plows and chisels can often operate without stalk treatment. Some
chisels use a gang of straight coulter-blades across the front to cut the stalks and
prevent clogging. One chisel uses an opposed pair of disk gangs across the front
with the angle of cut adjustment controlling the proportion of residue left on
the surface for erosion control.
Secondary tillage operations are performed in the spring and usually include an
early disking to level the soil and a disking or field cultivation just ahead of the
planter to lull weeds, break any crusting, and secure a finer, firm seedbed.' The
disk may also be used to incorporate broadcast herbicides and insecticides where
In some areas special mulching tools have become popular for the final
preplant operation. They consist of various combinations of spring teeth, rollers,
spike teeth, and leveling blades to break up clods and obtain a very level, firm
Planting is helped by high-energy tillage because there is little surface residue,
allowing the use of runner openers rather than disk openers, and the level
seedbed facilitates uniform depth of seeding.
Major plant nutrients can be applied in a variety of ways with high-energy
systems. Phosphorus (P) and potassium (K) for corn are normally bulk spread
before primary tillage or before the final secondary tillage operation. Volatile
forms of N (NH,) can be knifed in separately or in combination with tillage
operations. Nonvolatile forms of N can be broadcast on the surface or applied as
starter fertilizer along with P and K by the planter.
Insecticides are often band-applied by the planter and preemergence herbicides
can also be banded or broadcast as spray or granules if they have not been
previously applied. Planters of more than eight rows are sometimes not equipped
with fertilizer or herbicide attachments in order to reduce lost time during
High-energy systems also facilitate mechanical cultivation because there is little
surface residue to clog, and the soil is loose enough for shovels and sweeps to
operate effectively. If the herbicide is effective no cultivation may be necessary.
Many farmers plan to cultivate corn once and soybeans twice, with more
cultivation being done if needed.
In general, the high-energy systems provide a greater factor of safety than
low-energy systems because extra operations can be done if needed. An extra
The practice of wheel-track planting completely eliminates secondary tillage. The ground
is plowed only a day or so ahead of planting and then the rows are planted in tractor and
planter wheel tracks. In spite of good yield response this system has lost favor as acreages
increased because of the economic handicap of having enough plowing capacity to keep
ahead of today's large planters. It is also not compatible with incorporation of broadcast
YIELDS AND REQUIREMENTS FOR CORN AND SOYBEANS
preplant tillage operation can be done if a heavy rain causes crusting, or an extra
cultivation if the herbicide is not effective. The high-energy systems also provide
more options for fertilization and pest control.
C. MODERATE-ENERGY SYSTEMS
In these systems the soil is usually tilled less than 10 cm (4 inches) deep, with
a total energy requirement for tillage and planting two-thirds or less of that with
hgh-energy systems. Specialized equipment may be needed and there are fewer
options for fertilization and pest control.
The most popular moderate-energy system is disking with a conventional
tandem disk, although surface residue makes necessary a disk-opener planter.
One or two spring diskings often provide a good seedbed following soybeans,
since there is little residue and the soil tends to be loose. More disking may be
required following corn.
Disking is often a wise choice when wet weather has delayed high-energy
spring tillage, because deep tillage of wet soil can result in large hard clods if the
weather turns dry. It also facilitates incorporation of fertilizer, herbicides, and
The ridge system developed in Iowa (Buchele et al., 1955) has moderate
energy requirements. After the permanent ridges have been initially formed,
they are maintained by cultivation. Stalks are shredded in the spring before
planting and tend to settle in the furrows. A conventional planter is guided by
large disks bearing against the ridge sides and plants on the old ridge top,
disregarding the old stubs.
A fall ridging system requiring somewhat more energy has been developed
in Indiana (Richey e l al., 1973). Ridges are reshaped in the fall after harvest
by a combined flail shredder and disk bedder. The stalk residue is picked up
by the shredder, elevated over ridging disks located just behind the shredding
rotor, and funneled into the open furrows between ridges. The ridges are
smoothed in the early spring by a rolling cultivator when necessary, and planting
is done directly on the ridge top in the mellow soil which was thrown u p in
the fall. The planter is guided on the ridges by disks bearing against the ridge
sides or by wide furrow-fitting tires on the planter transport wheels.
Ridge systems provide a warmer seedbed than other tillage systems having
surface residue, and the residue in the furrows helps t o control runoff and
erosion. There is reduced inundation of seedlings in wet weather compared to
The fall furrow-mulch ridging system provides winter erosion protection and
does not require cultivation to reshape the ridge. Fertilizer broadcast in the fall
before ridging is concentrated in the ridge. Anhydrous ammonia can be knifed
C. B. RICHEY ET AL.
into the furrows in the spring by using coulters to cut the trash ahead of the
D. LOW-ENERGY SYSTEMS
Strip or slot tillage of the seed row in combination with planting requires only
about one-fourth the tractor energy required for high-energy systems, although
herbicide costs may prevent an overall saving.
The till-plant system, which was developed in Nebraska (Wittmuss and Lane,
1973) and is widely used in the western corn belt, requires minimum energy for
planting but requires at least one ridge-shaping cultivation to maintain the ridges.
In this system, a 25- to 35-cm (10- to 14-inch) wide flat sweep preceding the
planter opener slices about 6 cm (2.5 inches) from the top of the ridge, pushing
stalk residue and root clumps into the middles. Shredding the stalks ahead of the
planter eases cultivation, although it is not necessary for planting.
Till-planting evolved from an experimental design by Poynor (1950) and
further development in Nebraska (Lane and Wittmuss, 1961). One till-planter
forms a V-furrow in the exposed moist soil, drops in seed, presses it down with a
narrow seed press wheel, and covers the seed with loose soil from two small disk
coverers. Uniformity of depth and moisture content is good and the loose
covering soil is not as likely to crust as when compacted by a large press wheel
such as used on conventional planters.
After planting, the row area is usually slightly lower than the loose material in
the middles. Clearing the row area of residue aids soil warm-up, resulting in
better germination and better early growth than with the no-till system where
the residue is left in place.
Rolling cultivators are often used because they do not clog easily, and the
gangs can be tilted to rebuild the ridges. Disk cultivators are also popular.
Herbicides may be broadcast at planting or banded since a cultivation wiIl be
needed to rebuild ridges. If not cultivated the depressed row area causes
increased stubble loss when harvesting soybeans.
The “no-till” coulter system is the most popular lowenergy system and has
had wide acceptance for corn in the southern corn belt and for doubre-cropping
of soybeans after small grains. Coulters with flutes ranging from 6 cm (2 1/2
inches) down to about 1 cm (1/2 inch) wide are used to cut a path through the
residue and loosen a slot in the soil for the planter opener. Since the pressure of
the coulter tends to depress the soil, the planter press wheel usually has a rib in
the center to aid in firming the soil over the seed.
Corn stalks are usually shredded to obtain a uniformly distributed mulch. No
residue preparation is necessary in the case of a chemically killed sod crop or
YIELDS AND REQUIREMENTS FOR CORN AND SOYBEANS
Strip rotary tillers have been used to till strips about 20 cm (8 inches) wide
and slightly deeper than planting depth. A conventional planter is trailed behind
or unit planters are mounted on the tiller for a once-over operation. Stalk
shredding can often be omitted because the residue in the row is well chopped.
Energy requirements are very similar to the no-ti11 coulter system, as is plant
Cultivation is difficult with either the coulter or strip rotary system because of
the lack of loose soil. Cultivators in general are not adapted to work in firm untilled soil, so herbicides must be relied upon for weed control.
Bulk applications of P and K should be made before planting. Nitrogen may be
applied in bulk as a nonpressure solution with or without herbicide. Anhydrous
ammonia (NH,) may be knifed in, although a residue cutting coulter must
precede the knife, and extra sealing wings may be needed on the knife to prevent
loss because of the firmness of the soil.
Starter fertilizer is desirable to help overcome the initially adverse environment.
Ill. Influence of Tillage-Planting System on Yields
1, Indiana Experiments
An interdisciplinary project to compare various tillage planting systems for
continuous corn was initiated in 1967 (Richey et al., 1973). The chemical and
mechanical analysis of the soils is shown in Table I (Griffth et al., 1973).
The results for northwestern Indiana are shown in Table 11. On the Tracy sandy
loam (typic hapludalf) there was little difference between systems. In the
1967-1971 period, the till-plant system had significantly higher yields but this is
thought to be primarily a result of the single cultivation needed t o build up a
ridge for the following year. In subsequent years cultivation was found to also
increase yields with the other tillage systems on this soil.
On the heavier Runnymede loam (typic argiaquoll) fall plowing showed a 942
kg/ha (15 bu/A) advantage over spring plowing and more over the other
treatments for 1969-1971. The no-till coulter system was at a considerable
disadvantage, yielding substantially less than the other systems and almost
one-third less than fall plowing in 1969-1971.
The results for east central and southern Indiana are shown in Table 111. On
the heavy Blount silt loam (aeric ochraqualf) and Pewamo clay loam (typic
argiaquoll), conventional plowing was superior to the other treatments with
disking, no-tiU, and rotary strip tillage decidedly inferior.
C. B. RICHEY ET AL.
Chemical and Mechanical Analysis of Indiana Soils to 15 cm (6 inches) Depth, 1967'
Soil type and location
Tracy sandy loan (typic
Runnmede loam (typic
Blount silt loam (aeric
ochraqualf) East central
Pewamo silty clay loam
(typic argiaquoll) East
Bedford silt loam (typic
fragiudult) South central
Total Total Total Organic
pH kg!ha (lb/A) kg/ha (lb/A) (%)
20.67 58.64 20.67
14.07 47.40 38.50
'Griffith ef al. (1973).
bMedium range for P 46-80 kg/ha (41-71 lb/A).
CMediumrange for K 151-210 kg/ha (135-187 Ib/A).
On the Bedford silt loam (typic fragiadult) in southern Indiana, all systems
averaged about the same for 1967-1971, except for the till-plant which again
showed an increase possibly due to its cultivation, Residue on the surface
appeared to provide a slight yield advantage. Moisture conserved in the summer
may have overbalanced the lower soil temperature early in the season.
2. Ohio Experiments
Studies comparing corn yields of conventional plow tillage with no-till coulter
planting under several crop rotation combinations on several typical Ohio soils
were conducted in the 1962-1973 period. The results are summarized in Table
IV (van Doren et al., 1976). Plots were thinned to achieve a common plant
population. No-till gave significantly higher yields than plowing under continuous corn and a corn-soybean rotation on Wooster silt loam but significantly
lower under continuous corn on Hoytville silty clay loam.