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CHAPTER 5. YIELDS AND CULTURAL ENERGY REQUIREMENTS FOR CORN AND SOYBEANS WITH VARIOUS TILLAGE–PLANTING SYSTEMS

CHAPTER 5. YIELDS AND CULTURAL ENERGY REQUIREMENTS FOR CORN AND SOYBEANS WITH VARIOUS TILLAGE–PLANTING SYSTEMS

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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



143



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

soybeans.

Corn stalks are often shredded or disked to avoid clogging, although high-



144



C. B. RICHEY



ET AL.



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

needed.

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

seedbed.

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

planting.

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

herbicides.



YIELDS AND REQUIREMENTS FOR CORN AND SOYBEANS



145



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

insecticides.

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

flat planting.

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



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C. B. RICHEY ET AL.



into the furrows in the spring by using coulters to cut the trash ahead of the

knives.



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

soybean stubble.



YIELDS AND REQUIREMENTS FOR CORN AND SOYBEANS



147



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

growth.

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



A. CORN



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.



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C. B. RICHEY ET AL.



TABLE I

Chemical and Mechanical Analysis of Indiana Soils to 15 cm (6 inches) Depth, 1967'

~~



Soil type and location

Tracy sandy loan (typic

hapludalf) Northwestern

Indiana

Runnmede loam (typic

argiaquoll) Northwestern

Indiana

Blount silt loam (aeric

ochraqualf) East central

Indiana

Pewamo silty clay loam

(typic argiaquoll) East

central Indiana

Bedford silt loam (typic

fragiudult) South central

Indiana



~



Total Total Total Organic

KC

sand

silt

clay matter

Pb

pH kg!ha (lb/A) kg/ha (lb/A) (%)

(%)

(%)

(%)



6.1



113(101)



317(283)



59.36 38.93



2.64



1.41



6.3



104(93)



240(214)



47.48 44.79



7.73



2.99



6.7



lOl(90)



323(288)



20.67 58.64 20.67



1.74



6.5



226(202)



306(273)



14.07 47.40 38.50



3.28



6.4



64(57)



204(182)



10.02 83.75



1.71



6.22



'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.



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