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Copyright 2005, Board of Trustees, University
NFREC, Quincy Research Report 86-1
EFFECT OF TILLAGE AND WATER
MANAGEMENT ON SOIL-WATER
DEPLETION AND GRAIN YIELD
OF CORN ON A SANDY SOIL
BY F.M. RHOADS AND R.S. MANSELL
SFlorida Agricultural Experiment Stations
Institute of Food and Agricultural Sciences
University of Florida, Gainesville
Effect of Tillage and Water Management on Soil-Water Depletion
and Grain Yield of Corn on a Sandy Soill/
F. M. Rhoads and R. S. Mansell2/
Tillage pans are present in many of the soils of the southeastern U.S. on
which large yield increases of corn have been observed with irrigation. This
raises the question of whether or not benefits would be incurred if both
irrigation and subsoiling were combined. The objective of this experiment was
to determine if corn would respond to subsoiling in the presence of irri-
gation. Water management treatments were applied with and without subsoiling
in a two-year experiment on a Troup sand (Grossarenic Paleudult). Water
management treatments in 1976 consisted of 1) natural rainfall, 2) application
of water.with a trickle system when soil-water pressure (SWP) at the 15 cm
depth reached -0.01 MPa and 3) -0.02 MPa. In 1977, natural rainfall was
compared with irrigation from a sprinkler system when SWP reached -0.015 MPa
at the 15 cm depth. One-half of the plots were in-row subsoiled to a depth of
45 cm both years.
Irrigation significantly (P < 0.01) increased grain yield of corn each
year with widely varying rainfall distribution between years. Subsoiling
in-row increased yield significantly (P < 0.01) with irrigation, only when
rainfall was sufficient to cause downward movement of plant nutrients. Yield
increase from irrigation ranged from 0.5 to 1.5 Mg/ha (7.8 to 23.8 bu/A) in
1/North Florida Research and Education Center Research Report 86-1.
?/Professors of Soil Science, North Florida Research and Education Center,
Quincy, and Department of Soil Science, Gainesville, respectively. University
1976. The average response to subsoiling in 1976 was 1.4 Mg/ha (22 bu/A).
Irrigated plots produced about 10 times as much grain as non-irrigated plots
in 1977 but there was no response to subsoiling. Subsoiling in-row reduced
soil strength and increased soil-water depletion in the 30 to 60 cm depth
Additional index words: Subsoiling, Soil strength, Maize, Zea mays L.,
Effects of subsoiling on crop yield under irrigation have not been studied
extensively because subsoiling is generally considered a dry-land farming
practice to increase root depth and available water for crop plants. Grain
yield of corn was increased in two out of 14 experiments by subsoiling in
Illinois from 1955-57 while no yield increases were observed at eight
locations in Iowa (4). The absence of response was attributed to annual soil
freezing to considerable depth which would tend to minimize traffic pan
development. Tillage pans have been identified and characterized in some of
the Coastal Plain soils occurring throughout the southeastern United States
(3). New Jersey studies using subsoiling on a Collington sandy loam soil did
not show significant yield increases of several vegetables (2). Subsoiling
increased soybean yields in seven of 16 experiments in Georgia (5). In-row
subsoiling increased seed cotton yields as much as 41% in Georgia (1).
Soybean yields were consistently increased in a 3-year Florida study by in-row
subsoiling on a Coastal Plain soil (Orangeburg loamy sand) where a tillage pan
had developed (7). Rainfall amount and distribution were observed to
influence the response of crop yield to subsoiling in earlier studies in
Florida (9). Maintaining high soil-moisture levels in the plow layer with
irrigation was effective in increasing corn yields on a variety of soil types
Variability of crop response to subsoiling between locations and soil
types indicates that tillage recommendations should be based on research
conducted under local conditions. The objectives of this experiment were to
compare the yield response of corn grown on a Troup sand (Grossarenic
Paleudult) to in-row subsoiling with and without irrigation, to measure the
effect of subsoiling on soil strength and to determine the effect of
irrigation and subsoiling treatments on soil-water depletion.
Pioneer brand '3369A' corn was planted March 18, 1976 and Funk's 'G-4507'
corn was planted March 29, 1977. Two seeds per hill were planted by hand and
thinned after emergence to a population of 71,700 plants/ha ( 29,000
plants/A). Row spacing was 91 cm with distance between plants approximately
15 cm. Plot rows were 7.6 m long in 1976 and 6.1 m long in 1977 with four
rows per plot each year. Two center plot rows were harvested, starting about
0.6 m from each end of plots to minimize border effects, for grain yield.
Grain yields are reported at 15.5% moisture content.
A total of 336 kg/ha of N, 98 kg/ha of P, and 279 kg/ha of K were applied
each year. Fertilizer was applied each week in amounts shown in Fig. 1. Rate
of application was increased during the first 8 weeks of growth in 1977 as
compared with 1976 because of slight chlorosis observed in 1976. Fertilizer
application was completed in 12 weeks in 1977 rather than 14 as in 1976.
Three water management treatments were imposed in 1976: natural rainfall,
irrigated when soil-water pressure reached -0.01 MPa at 15 cm depth, and
irrigated when soil-water pressure reached -0.02 MPa at 15 cm depth. Two
water management treatments were applied in 1977 as follows: natural rainfall,
and irrigated when soil-water potential at 15 cm depth reached -0.015 MPa.
Trickle irrigation was used in 1976 and sprinkler irrigation in 1977. Two
tillage treatments were applied each year within each water management
treatment: conventional tillage consisting of disc harrowing to provide a weed
free seed bed, and conventional tillage plus subsoiling in-row to a depth of
Soil resistance to penetration was measured with a C-700 pocket penetro-
meter. Holes 30 cm in diameter were dug in the row and penetrometer readings
2 4 6 8 10 12
Accumulative percentage of fertilizer applied to corn in
weekly amounts (total N, P, and K) for the growing seasons
of 1976 and 1977.
Rainfall and irrigation distribution for
and 1977. Day 0 was the planting date:
March 29, 1977.
corn plots in 1976
March 18, 1976 and
(PR) were taken horizontally at 5 cm depth intervals to a depth of 45 cm.
Penetration measurements were taken in the same location and direction of the
slot made by the subsoiler. Soil resistance values are based on a regression
analysis of readings taken from the same field location with a cone type
penetrometer versus the C-700 pocket penetrometer rather than the factory
calibration values of the pocket penetrometer (8).
Tensiometers with mercury manometers were installed at 15, 30, 60, and 90
cm depths in one plot of each treatment in both years.
A split plot experimental design with water management as main plots and
tillage as sub-plots was used in 1976, while a randomized complete block
design was employed in 1977. There were four replications each year. Appro-
priate statistical analysis were made to evaluate the data.
RESULTS AND DISCUSSION
Rainfall amount and distribution were extremely different between 1976 and
1977 (Fig. 2) from 0 to 110 days after planting each year. Plots irrigated
when soil-water pressure (SWP) declined to -0.02 MPa received 6 irrigations
(total of 6.9 cm) in 1976 and plots irrigated at a SWP of -0.01 MPa received
17 irrigations (total of 17.2 cm). An extreme dry season occurred in 1977 and
28 irrigations (total of 44.8 cm) were required to maintain SWP above -0.015
in irrigated plots at the 15-cm depth. Total rainfall for the 110 day growing
seasons in 1976 and 1977 was 56.8 and 26.2 cm, respectively.
Tensiometer readings at 41 days after planting in non-irrigated plots
indicated that corn roots were extracting water at the 30 cm depth to a
greater degree in subsoiled plots than in non-subsoiled plots (Fig. 3). Water
extraction at the 60 cm depth was considerably greater in subsoiled plots 48
days after planting. Subsoiling made very little difference in water
extraction at these depths in irrigated plots. Similar results were observed
SOIL WATER PRESSURE (MPa)
)f I I / /'/ 1 I ) / I / 1
Soil-water pressure values as affected by subsoiling at
four depths in non-irrigated corn plots 41 and 48 days
after planting in 1977.
e I/ // // / // //// /Y 11 1117
Penetrometer resistance versus soil depth indicated that the traffic pan
was located in the 15 to 25 cm zone (Fig. 4). However, data from subsoiled
plots showed soil resistance to be relatively low in the slot made by the
subsoiler throughout the growing season. Conventional tillage following
harvest increased soil strength in the subsoiled slot a considerable amount
(Nov. 15 date). Soil strength was the same in subsoiled as non-subsoiled
plots at the end of the second growing season after subsoiling (data not
shown). Kashirad et al. (3) reported that root growth was drastically reduced
in several Ultisols when PR was greater than 20 kg/cm2
Grain yield response to irrigation (averaged over tillage treatments) was
significant (P < 0.01) with water applied at -0.01 MPa SWP in 1976 (Table 1).
The highest single treatment yield was 10.0 Mg/ha (159 bu/A) which resulted
from in-row subsoiling and irrigation at-0.01 MPa SWP. In-row subsoiling
increased yield from 1.1 to 1.6 Mg/ha with or without irrigation with an
average increase of 1.4 Mg/ha (22 bu/A). Yield was not increased by
subsoiling in 1977 where irrigation was applied (Table 2). Grain production
under irrigation without subsoiling was 10.0 Mg/ha (160 bu/A) and with
subsoiling 10.2 Mg/ha (163 bu/A). Irrigated plots produced about 10 times as
much grain in 1977 as non-irrigated plots. Efficiency of irrigation water
measured in terms of kg of grain/ha-cm was about 2.5 times greater in 1977
than in 1976. Irrigation efficiency was 81 kg/ha-cm (3.3 bu/A-in) for the
-0.02 MPa treatment and 78 kg/ha-cm for the -0.01 MPa treatment in 1976.
Efficiency in terms of grain per unit of water input in 1977 was 205 kg/ha-cm
(8.3 bu/A-in) of irrigation water applied at -0.015 MPa SWP and averaged about
36 kg/ha-cm of rainfall with no irrigation. Total water input efficiency
(including rainfall and irrigation) in 1977 was 143 kg/ha-cm (5.8 bu/A-in).
Penetrometer resistance in subsoiled and control plots in June and
November of 1976.
Maximum yield under irrigation was approximately 10.0 Mg/ha each year which
shows the possibility of maintaining consistent yield levels from year to year
on sandy soils with extreme variation in rainfall by using appropriate water
and nutrient management practices.
Table 1. Effect of irrigation and tillage on grain yield of corn in 1976.
Tillage none -U.U2 MPa -0.01 MPa Average
Conventional 7.3 7.8 8.8 8.02/
in-row-subsoil 8.7 9.4 10.0 9.4
Average 8.1a 8.6ab 9.4 b/
1/Irrigation (1.3 cm of water per application) applied with drip system when
soil-water pressure reached specified value at the 15 cm soil depth.
LSD.01 (tillage) = 1.1 Mg/ha.
/Means followed by same letter are not significantly different according to
Duncan's Multiple Range test (P = .01).
Table 2. Effect of irrigation and tillage on grain yield of corn in 1977.
Tillage None -0.015 MPa-/
Conventional 0.7 10.0
in-row-subsoil 1.2 10.2
/ Irrigation applied with sprinkler system when soil-water pressure at 15 cm
depth reached -0.015 MPa.
Wilt ratings in the rainfall plots taken during the first half of the 1977
growing season indicated that plants in subsoiled plots were not stressed as
much as plants in conventional tilled plots. However, during the last half of
the season plants in subsoiled plots were as severely stressed as those in
conventional tilled plots. Severe drought occurred during 1977 rendering
subsoiling ineffective for increasing crop yield on the Troup soil.
Subsoiling can compensate to some extent for poor rainfall distribution and
slightly deficient amounts but not for extremely low amounts. The increase in
yield (Table 2) from 0.7 to 1.2 Mg/ha with in-row subsoiling and no irrigation
was not significant (P < 0.10) because of a large standard deviation in the
Response to subsoiling in irrigated plots during 1976 might be attribu-
table to recovery of nutrients that moved below the traffic pan as a result of
excessive rainfall between 40 and 80 days after planting. Plants in subsoiled
treatments may have recovered more of these nutrients because of deeper
rooting (Fig. 3). Rainfall and irrigation were not applied in sufficient
amounts to cause leaching of plant nutrients in 1977 (Fig. 2). Two cm of
irrigation did not increase the soil-water content at the 60 cm depth (Fig.
5). After 7 hours soil-water content was highest at the 15 cm depth following
irrigation. Tensiometer data in Fig. 5 indicate that less than half of the
applied water (2 cm) penetrated to the 30 cm depth. Since rainfall or
irrigation did not exceed 2.5 cm for any 3-day period during the growing
season until about 100 days after planting, less than half of the water
soluble nutrients could have moved below the 30 cm depth. Rooting depth had
reached 30 cm by 48 days after planting in non-subsoiled plots (Fig. 3).
In conclusion, irrigation significantly increased grain yield of corn on a
Troup soil in two consecutive years even though rainfall distribution varied
widely between years. Subsoiling in-row increased yield when rainfall was
sufficient to cause downward movement of plant nutrients. Subsoiling in-row
SOIL DEPTH (cm)
15 30 60 90
TIME AFTER IRRIGATING (hrs)
0 0 70 -0 70 7
-0.005 1 \
Soil-water pressure distribution with depth before
irrigation and 0, 1.5, 3, and 7 hours following 2
cm of sprinkler irrigation in 1977.
reduced soil strength and increased soil-water depletion in the 30 to 60 cm
zone according to tensiometer data. The combination of in-row subsoiling and
irrigation increased yields significantly in a year with leaching rainfall,
but subsoiling did not increase yields on irrigated plots when rainfall was
extremely low. Under rainfed conditions, subsoiling would appear to be of
greatest benefit when the crop experiences slight to moderate levels of stress
on this soil with a low water holding capacity.
1 Boswell, F. C., D. A. Ashley, 0. L. Brooks, G. W. Bird, T. D. Canerday, J.
G. Futral, R. S. Hussey, C. E. Perry, R. W. Ronadori, and J. S.
Schepers. 1977. Influence of subsoiling, liming, a nematicide, and
soil bedding on cotton yield in 'stunt' areas of Georgia. Agri. Exp.
Sta. Univ. of Ga. Res. Bul. 204.
2 Brill, G. D. R. B. Alderfer, and W. J. Hanna. 1965. Effects of sub-
soiling and deep placement of fertilizer on a coastal plain soil and
vegetables. Agron. J. 57:201-204.
3 Kashirad, A., J. G. A. Fiskell, V. W. Carlisle, and C. E. Hutton. 1967.
Tillage pan characterization of selected coastal plain soils. Soil
Sci. Soc. Am. Proc. 31:534-541.
4 Larson, W. E., W. G. Lovely, J. T. Pesek, and R. E. Burwell. 1960.
Effect of subsoiling and deep fertilizer placement on yields of corn in
Iowa and Illinois. Agron. J. 52:185-189.
5 Parker, M. G., N. A. Minton, 0. L. Brooks, and C. E. Perry. 1976.
Soybean response to subsoiling and a nematicide. Agri. Exp. Sta. Univ.
of Ga. Res. Bul. 181.
6 Rhoads, F. M., and R. L. Stanley, Jr. 1975. Response of corn (Zea mays
L.) grown on soils of three textural classes to plow layer water
management. Soil and Crop Sci. Soc. of Fla. Proc. 34:1-3.
7 Rhoads, F. M. 1978. Response of soybeans to subsoiling in North Florida.
Soil and Crop Sci. Soc. of Fla. Proc. 37:151-154.
8 Rhoads, F. M. 1982. Soil resistance to penetration: a comparison between
two types of soil penetrometers. Soil and Crop Sci. Soc. of Fla. Proc.
9 Robertson, W. K., J. G. A. Fiskell, C. E. Hutton, L. G. Thompson, R. W.
Lipscomb, and H. W. Lundy. 1957. Results from subsoiling and deep
fertilization of corn for 2 years. Soil Sci. Soc. Am. Proc.