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IV. Yield Factors Influenced by Tillage–Planting System
Mean Daily Maximum Soil Temperature in Row at 10 cm (4 inches) Depth for the 8 Weeks Following Planting Corn in Indiana, in "C ( O F )
Tracy silt loam Runnymede loam Blount silt loam Pewamo silty clay loam Bedford silt loam silty clay loam
No-till coulter plant
Fall ridge with residue in furrow
YIELDS AND REQUIREMENTS FOR CORN AND SOYBEANS
Mean maximum daily soil temperatures in the row at a depth of 10 cm (4
inches) during the 8 weeks following planting in various Indiana soils are shown
in Table IX.
Fall plowing with conventional spring tillage showed the highest soil temperatures. The loosened soil dried well in the spring and there was little surface
residue to shade the soil.
Chiseling was slightly lower due to the residue left on the surface.
Ridges with residue mostly in the furrow averaged slightly warmer than
chiseling but below plowing, perhaps because soil in the ridges was not loose,
except for the reshaped soil thrown up in the fall.
With no-till planting in shredded corn stalks, the soil was not loosened t o aid
drying and the residue shaded most of the surface, resulting in temperatures
around 2.5'C (4.5'F) below plowing treatments. This definitely slowed early
growth in central and northern Indiana.
Crusting impedance to emergence can result from a heavy rainfall after
planting on vulnerable soils. A finely worked surface and soil firming over the
seed increases the tendency to crust. The till-planter technique of pressing the
seed into firm moist soil and covering it with uncompacted loose soil results in
high germination and minimum crusting. In 1972 a heavy rain immediately
following planting caused severe crusting on the Bfount and Pewamo soils in
eastern Indiana. All stands were severely reduced from the 59,300 kernels per
hectare (24,000 kernels per acre) planted but the till-planter plots and the ridge
plots (also planted with the till-planter) averaged 39,000 plants per hectare
(15,800 plants per acre) compared with an average of 27,675 plants per hectare
(1 1,200 plants per acre) for all other plots.
B. SOIL COMPACTION
Soil managed for minimum compaction will have increased water infiltration,
reduced erosion, and increased aeration and will allow greater root penetration.
It has often been difficult to obtain direct effects of compaction on yield
because plants are quite adaptable. A plant with a small root system having
access to adequate water and nutrients may yield as much as one with a large
Experiments in Illinois (Bateman, 1962) compared medium compaction by
plowing and two diskings with several treatments designed to produce high
a. Plowed, six tandem diskings.
b. Plowed and two diskings, also compacted by two passes of tractor tires over
all the plot after planting and between rows after the last cultivation.
C. B. RICHEY ET AL.
c. Two pass tire compaction in bottom of each furrow and on the land,
plowed, two diskings.
The 1960 and 1961 results for the means of the high compaction treatments
versus medium compaction are shown in Table X for two soils. It was concluded
Corn growth may be expected to be retarded when the air voids at field capacity
moisture are near the 10% value.
Many results have indicated that tractor tire traffic can reduce air voids to the critical
value of 10% or less in many soil types, and the low values are easier to develop at the
higher soil moisture contents.
The Drummer silty clay loam appeared to be more susceptible than the Thorp silt
loam to compaction. Important factors in the difference are the higher clay content of
Drummer and its normally higher moisture when the soil is tilled.
Experiments in New York (Free and Bay, 1964) found that nine diskings and
harrowings compared to one reduced corn yields only 5.2 hl/ha (6 bu/A) in the
fourth year of treatments but the difference increased t o 19.1 hl/ha (22 bu/A)
the fifth year and 27.8 hl/ha (32 bu/A) in the sixth year.
Winter freezing and thawing ameliorates compaction, at least down to plowing
depth, in most of the corn belt. In the warmer southern states compaction is
more serious. Research in Alabama (Dumas et al., 1973) found that plow sole
compaction and tractor wheel compaction between the rows left about 25% of
the soil profile to 46 cm (18 inches) depth loose enough for good cotton root
development by midsummer. With 46 cm (18 inches) deep tillage and controlled
traffic where all operations were performed with a 3-m (120-inch) wheel tread
tractor running on untilled paths, 55% of the soil profile was available for root
penetration away from the wheel tracks and 44% including the wheel tracks. The
deeptilled controlled-traffic plots yielded up to 37% more cotton than the
Inasmuch as wheels are the primary source of compaction, it is possible to
reduce compaction by (a) reducing tractor and machine weight, (b) reducing the
number of trips, and (c) reducing the area compacted by practicing controlled
Moderate- and lowenergy tillage systems should reduce compaction because
lower-powered lighter tractors can be used and fewer trips are made across the
field. Also, there is less disturbance of the favorable soil structure which
develops under grassland with its continuous macropores, due to root and worm
channels which facilitate infiltration (Van Doren et al., 1976; Baeumer and
Controlled traffic is not presently practical with plow or chisel systems where
the old rows are obliterated. The ridge and no-till systems allow maintenance of
row position and should be amenable to controlled traffic. With equipment for
eight 76-cm (30-inch) rows, for instance, the wheel track area would occupy only
Compaction Effects on Corn Yields in Two Types of Soil in Central Illinois'
Corn yields in kg/ha (bu/A) for nitrogen rates of:
Air voids 0-30 cm
(0-12 inches) (%)
Drummer silty clay loam
Thorp silt loam
'From Bateman (1962).
bSignificant difference from the medium density level.
44.8 kg/ha (40 Ib/A)
134.5 kg/ha (120 Ib/A)
C. B. RICHEY ET AL.
about 17% of the total area, leaving 83% uncompacted except for implement
action. The harvester should use the same wheel tracks and harvest eight 76-crn
Soybeans are considered to be more sensitive to compaction than corn,
although there has been little research in this area. The current interest in deeper
chiseling in the corn belt could be primarily due to farmer awareness of
reduction in soybean yields due to compaction.
The advent of 130 kW (175 hp) two-wheel drive tractors and combines
weighing up to 13,500 kg (30,000 Ib) loaded provides capability of deeper soil
compaction than previously experienced. Additional tire area does not greatly
reduce deep compaction because the pyramid of support is principally affected
at the surface.
Gill (1971) states:
Soil compaction is a national problem of significant consequence in that it cannot be
economically assessed accurately at this time. Compact soil conditions can naturally
decrease the yields of crops over vast areas of tilled land. Increase in machinery size and
use increase the seriousness of this problem. . . .
The maintenance of a low degree of soil compaction must be undertaken by the
development of complete crop production systems. The recompacting actions of operations subsequent to initial soil loosening operations, in excess of any desirable firming
operations, must be eliminated from the crop production system when economically
justifiable in order to prevent a gradual degeneration of a desirable loose condition.
C. WEED CONTROL
Tillage can help control weeds by:
1. Burying weed seed and delaying perennial weeds.
2. Leaving a rough surface to discourage weed seed germination.
3. Providing enough loose soil to permit effective row cultivation.
4. Leaving a clean uniform surface for efficient herbicide action.
5. Incorporating herbicides when necessary.
Plow tillage systems are the most effective in controlling weeds since they
comply with items 1, 2, and 4 above. Several herbicide-resistant perennial weeds
such as milkweed (Asclepias syriacu L.) which are kept under control by
plowing, may become serious pests when plowing is omitted for several years
(Williams and Wicks, 1976).
Chisel systems do not bury weed seed as well as plow systems and leave more
residue on the surface. Field experiments in Indiana (Bauman, 1976) found that
corn plant residue covering 85% of the soil surface resulted in only 70% of
atrazine spray reaching the soil surface for weed control. Not only was 30% of
the herbicide intercepted by the residue but many areas under residue were
YIELDS AND REQUIREMENTS FOR CORN AND SOYBEANS
In the dry spring of 1976, some farmers in Indiana and Illinois noted that corn
following soybeans showed less trifluralin carry-over damage where plowed than
where chiseled. Presumably chiseling did not dilute and bury the old surface soil
as well as plowing and there was not enough rainfall to carry the herbicide down
away from the young plants.
Conventional disks cutting only 10 cm (4 inches) deep leave a fme seedbed
which encourages weed germination and do not bury weed seeds. Herbicide rates
must approach those for no-till to obtain good weed control.
The till-plant system provides rough inverted middles which tend to discourage
weed growth. Weed germination is high in the smooth row area but herbicides
are effective. The row weeds can also be controlled by a rolling cultivator w h c h
can work through the rough middles without clogging.
The ridge system with residue in the furrow has allowed reasonably good weed
control. Ridge reshaping in the fall provides some inversion of weed seed, a clear
row area for herbicides and some loose soil for cultivation.
The weed problem builds up year after year with continuous no-till coulter
and rotary strip tillage systems. Herbicide-resistant weeds, such as milkweed
(Asclepias syriaca L.), fall panicum (Panicurn diehotomiflorurn Michx.), and
briars are naturally selected. A no-till coulter plot was plowed the fourth year in
the Indiana experiments and then continued with no-till. During the fifth and
sixth years it showed a noticeable reduction in weed population compared t o the
continuous no-till plot.
In Ohio experiments (Van Doren et al., 1976) “Most of the weed control
problems occurred in the no-tillage plots of the corn-oats-meadow rotation.
During the first six years, about 40% of all no-tillage plots had problems
compared to 10% for plowed plots. Problems were cut in half during the
remaining years, indicating improved, but not yet perfect ‘state of the art,’
especially for no tillage .”
In Table VII, weed weights are shown for Illinois soybean plots in 1974
(Siemens and Oschwald, 1975). Plowed plots showed a great advantage over the
other plots, although all plots were rated as having good weed control.
The no-till system has a serious handicap in that mechanical cultivation is
usually ineffective because of the firm soil. Thus total reliance must be placed on
herbicides, whereas cultivation can “back stop” herbicide failure in the other
systems. This problem should be minimized as more effective herbicides are
D. FERTILIZER PLACEMENT
Obviously, nutrients must be available at locations in the soil accessible to
plant roots. With the no-till coulter system, broadcast fertilizer tends to stay
C. B. RICHEY ET AL.
near the surface. Due to the firm soil and moisture available near the surface
under the mulch, roots tend to feed closer to the surface than with conventional
tillage, with consequent vulnerability to dry weather.
In the Indiana experiments cited earlier, nitrogen deficiency was noted, both
visually and by leaf analysis, in certain years prior to 1971 in strip-tillage plots
on poorly drained soils.
In 1971-1972, conventional, chisel, and coulter plots on poorly drained Runnymede loam were split three ways. One-third of each plot received NH3 d e e p
placed, one-third received liquid N on the surface plus a knife through the soil
with no N deep-placed, and one-third received surface N only. The same rate of N,
168 kg/ha (150 lb per acre) was used with each treatment. Special adaptations to
apply NH3 in no-till coulter plots included a separate independently mounted
coulter to cut through trash and sealing wings welded to each knife at two levels.
Deep-placed N brought no-till yields up to conventional tillage for the 2 years
of this study. Tillage effect of the NH3 knife also appeared to increase yields
when N was surface applied on noncultivated no-till plots. There was some
indication of improved yield for deep-placed NH3 in chisel plots, but stand
variability also influenced yield. Maturity of no-till corn was not improved by N
placement. Grain moisture at harvest was 2% higher in 1971 and 5% higher in
1972 for no-till versus conventional corn with all N placement treatments.
In Illinois experiments comparing plow, chisel, disk and no-till treatment for
corn (Siemens et d.,1971) soil tests for pH, P, and K were made at 0- to 8-, 8to 1.5, and 15- to 23-cm (0- to 3-, 3- to 6-, 6- to 9-inch) levels. Total nutrients
did not vary significantly. The plowed plots were fairly uniform in the first two
levels, dropping to 73% in the third level. The no-till plots had only about
one-half the nutrients in the second level and about 40% in the third level of
those in the first level. The other treatments were similar to the no-till.
It was concluded that: “Moldboard-plowing and subsequent mixing of the soil
to plow depth may be necessary for high corn yields in years when the surface
soil is extremely dry and plants are obtaining the majority of their phosphorus
and potassium from lower depths.”
With conventional tillage, phorphorus and potassium can be broadcast and
worked in by subsequent plowing or chiseling. Ridging after broadcasting tends
to concentrate the fertilizer in the ridge. This would seem to be advantageous,
especially for starting young plants, but has not been evaluated by experiments.
Nitrification inhibitors make possible fall application of nitrogen fertilizers
without overwinter leaching losses. Indiana experiments (Warren et al., 1975)
with fall application of nitrogen found that the addition of the inhibitor
nitrapyrin increased corn yields 24% for a rate of 85 kg/ha (76 lb/A) and 12%
for a rate of 170 kg/ha (1 52 lb/A) and gave yields equal to the same amount of
nitrogen applied in the spring.
YIELDS AND REQUIREMENTS FOR CORN AND SOYBEANS
Application of nitrogen before fall tillage should result in less soil compaction
than spring application as well as in reduction of spring work, although coulters
and extra sealing wings may be needed to apply anhydrous ammonia through
surface residue into firm soil.
E. MOISTURE CONSERVATION
Tillage affects soil moisture content by:
1. Facilitating drying by loosening the soil, thus enabling earlier planting.
2. Facilitating water intake by loosening the soil and leaving residue on the
surface to reduce sealing and runoff.
3. Reducing evaporation by leaving residue on the surface.
4. Controlling weeds which use soil moisture.
When tillage loosens soil but buries residue, the net effect is usually reduced
soil moisture. This is evidenced by the advantage of no-till coulter planting over
conventional tillage in sod-planted corn (Smith and Lillard, 1976; Blevins et aZ.,
1971) and in double-cropping soybeans or grain sorghum after small grain, where
moisture for germination is critical.
Experiments in Indiana (Mannering er al., 1975) determined that residue cover
after planting corn following corn was 0.6-1.8% of the total surface for conventional plow tillage, 4-14% for till-plant, 10-18% for disk, 6-29% for chisel,
38-89% for strip rotary, and 59-82% for no-till coulter.
Runoff from artificial rainstorms of 10 cm (2.5 inches) per hour was greatest
on plowed plots and least on chiseled plots with no-till plots in between. Water
content in the top 19 cm (27 inches) of soil throughout the season was usually
greatest for the no-till plots and least for the plowed plots.
The results from these tests show limited tillage systems to be effective in moisture
conservation for two principal reasons:
(1) Those systems that leave the surface rough and porous or create ridges at right
angles to major slopes effectively increase infiltration, thus reducing runoff. In addition,
the rougher the surface the more tortuous the runoff path and the slower the velocity of
runoff thus allowing more time for infiltration. The roughness factor disappears with
time during the season-the rate being dependent upon the stability of the soil material.
(2) Those systems that leave large portions of the soil surface covered with residues
offer surface protection from raindrop detachment of soil particles and surface sealing
which limits water intake. The residues also serve as barriers to runoff thereby decreasing its velocity, again allowing more time for infiltration. Systems that rely on
surface residues for protection are likely to be more permanent than those dependent on
soil roughness. Several systems such as the chisel and till plant contain the roughness
factor plus some residue effect. . . .
These results support previous work showing those tillage systems that leave a large
portion of the soil surface covered with residue to be very effective in reducing
C. B. RICHEY ET AL.
evaporation losses, thus conserving soil moisture. This serves as a distinct advantage for
crop production on droughty soils, while on poorly drained sites the greater soil
moisture content under residue in the spring results in delayed planting because of
wetness and reduces plant growth because of cooler soil temperatures. (Mannering el
As can be seen from Table 111 the clean-tilled plow systems have not yielded as
well on the light-colored droughty Bedford soil in southern Indiana as have the
other systems, all of which leave varying amounts of residue on the surface and
do not loosen and dry out the soil as much. The yields of the strip tillage
systems rank near the top rather than at the bottom as in northern Indiana. This
is apparently because the early-season temperature depression is less serious and
is outweighed by the later moisture conservation effects.
F. SOIL EROSION PREVENTION
It has been well established that soil erosion tends to be inversely proportional
to the percent of the soil surface covered by plant-residue mulch (Wischmeier,
1973). A mulch cover facilitates infiltration by protecting the soil surface from
raindrop impact and consequent sealing over. It also reduces runoff velocity
which both increases infiltration and reduces transport of soil particles.
In Ohio studies (Harrold and Edwards, 1974) soil erosion was monitored from
1949 to 1969 on two comparable watersheds of about 1.5 ha (0.6A), each under
a corn, wheat, meadow, meadow rotation. Soil loss averaged about 2250 kg/ha
(2000 lb/A) per year on each throughout the period. Continuous corn was then
grown for the next 4 years, one plot with conventional plow tillage and the
other with no-till coulter planting. Soil loss averaged 5980 kg/ha (5340 lb/A) per
year on the conventionally tilled plot and 64 kg/ha (58 lb/A) on the no-till plot.
Experiments in Indiana (Meyer and Mannering, 1961) compared infiltration
and soil loss on conventional plowed and disked plots with plowed and wheeltrack planted plots. Rainulator (artificial rainfall) tests totaling 13 cm (5.2
inches) at a 6.5-cm (2.6-inch) per hour rate shortly after planting gave a soil loss
of 37.4 tonnes (t)/ha (16.7 tons [TI /A) for the conventional and 19.5 t/ha (8.7
T/A) for the reduced tillage plots.
The tests were repeated when the corn was about 60 cm (24 inches) high and
the conventional tilled and cultivated plots lost 23.3 t/ha (10.4 T/A), the
reduced tillage uncultivated plots 33.4 t/ha (14.9 T/A). The Russell silt loam
soil, 4.5 to 5.0% slope had a tendency to crust. This resulted in highest runoff
and erosion on the uncultivated plots which had a heavy crust resulting from the
previous rainulator tests.
A third series of tests was made in September after harvest with broken over
cornstalks in place. All plots lost less than 2.2 t/ha (1 T/A) with the uncultivated
plots lowest because of a heavy grass cover.
YIELDS AND REQUIREMENTS FOR CORN AND SOYBEANS
Experiments in southwestern Iowa (Moldenhauer et aZ., 1971) compared
second-year corn on conventional plowed plots, till-planted plots, and ridge
plots. In the Iowa system (Buchele et aL, 1955) the ridge is maintained by a
summer cultivation, with planting on the ridge top preceded by shredding the
stalks, which settle into the furrows. Rainulator tests were performed in June
after the first cultivation on rows with slopes of 3.4%, 6.9%, and 9% in order to
evaluate the various treatments for erosion control with off-contour rows. A
total of 19 cm (7.5 inches) was applied by two storms on successive days with a
maximum rate of 12.5 cm (5 inches) per hour. The means for all three slopes
were: conventional, 14 cm (5.5 inches) runoff, 62.5 t/ha (27.9 T/A) soil loss;
till-plant, 13 cm (5.2 inches) runoff, 48.6 t/ha (21.7 T/A) soil loss; and ridge,
15.5 cm (6.2 inches) runoff and 15.5 t/ha (6.9 T/A) soil loss.
The conventional system had the most loose soil and the greatest soil loss.
With the till-plant system the row area was lower than the rough middles,
causing the water to run down the row. With the ridge system, the water ran
down the furrow which had some mulch protection and little loose soil, resulting
in lowest soil loss.
Slope had little effect on amount of runoff but in the conventional and
till-plant plots increasing slope from 3.4% to 9% approximately doubled the soil
loss. Soil loss from the ridge plots was little affected by slope change. “As an
off-contour conservation tillage method, the ridge system was much more
effective than the other two systems because soil and water losses from the ridge
system tended t o be independent of slope within the range tested.”
Rainfall simulator tests on corn after corn plots in Illinois (Siemens and
Oschwald, 1975), after planting showed soil losses ranging from 37.0 t/ha (16.5
T/A) for conventional tillage to 6.3 t/ha (2.8 T/A) for no-till coulter planting
with chiseling averaging 11.O (4.9 T/A), as shown in Table V.
The results for similar spring tests before spring tillage comparing plots
previously in corn with those previously in soybeans gave the results shown in
Table XI (Oschwald and Siemens, 1975).
Runoff starts earliest on the treatment with the smoothest surfaces, such as those
created by the fall plow, disk and chop-plant (no-till) treatments. The rough surface on
the chisel treatments provided more resistance to runoff, so that more time was required
to produce runoff. In addition, the total runoff quantity was smallest with the three
Soil loss was highest with the fall-plow treatment in all three storms. Crop residues on
the surface and a rough stable surface reduced soil loss on the conservation tillage
systems, compared to the fall-plow treatment.
Soil loss was greater after soybeans than after corn with all tillage treatments. The
larger quantity of residue on the surface following corn and the loose, easily eroded soil
following soybeans helps account for the differences in soil loss between corn and
We concluded that conservation tillage systems which provide a protective cover of
crop residues and a rough stable surface also protect the soil from excessive soil erosion.
Runoff and Soil Loss as Influenced by Water Applied, Kind of Fall Tillage, and Crop or Year. Catlin Silt Loam (typic argiudoll), 5% Slope‘
Fall moldboard plow
No fall tillage
Runoff, in cm (inches)
Soil loss, in tonnes/ha (T/A)
Total soil loss:
‘Oschwald and Siemens (1975).
bTime from start of water application.
Smulated rainfall applied at intensity of 6 cm (2.5 inches) per hour after overwinter weathering but prior to any spring tillage.