143 research outputs found
Implement and soil condition effects on tillage-induced erosion
Water, wind, or tillage-induced soil erosion can significantly degrade soil quality. Therefore, understanding soil displacement
through tillage translocation is an important step toward developing tillage practices that do not degrade soil resources. Our
primary objective was to determine the effects of soil condition (i.e. grassland stubble versus previously tilled soil), opening angle, and harrow speed on soil translocation. A second field study also conducted on a Lixisol but only in the stubble field, quantified displacement effects of mouldboard ploughing. The field studies were located 12 km South of Évora, Portugal. Soil displacement or translocation after each tillage operation in both studies was measured using aluminium cubes with a side length of 15mm as ‘tracers’. Offset angles for the harrow disk were 20◦, 44◦ and 59◦; tractor velocities ranged from 1.9 to
7.0 km h−1 and tillage depth ranged from 4 to 11 cm. The depth of mouldboard ploughing was approximately 40 cm with a wheel speed of 3.7 km h−1. The translocation coefficients for the two implements were very different averaging 770 kgm−1 for the mouldboard plough and ranging from 9 to 333 kgm−1 for the harrow disk. This shows that the mouldboard plough was more erosive than the harrow disk in these studies. All three variables (soil condition, opening angle, and tillage velocity) were critical factors affecting the translocation coefficient for the harrow disk. Displacement distances were the largest
for compacted soils (stubble field), with higher opening or offset angles, and at higher velocities. The results also showed
significant correlation for (a) mean soil displacement in the direction of tillage and the slope gradient and (b) soil transport
coefficient and the opening angle. Our results can be used to predict the transport coefficient (a potential soil quality indicator for tillage erosion) for the harrow disk, provided tillage depth, opening angle, and tool operating speed are known
Alternative N fertilizer management strategies effects on subsurface drain effluent and N uptake
Demonstrating positive environmental benefits of alternative N fertilizer management strategies, without
adversely affecting crop growth or yield, was a major goal for the Midwest Management Systems Evaluation Areas
(MSEA) program. Our project objectives within this program were to quantify the effects of split- and single-N
fertilization strategies on NO3-N concentration and loss in subsurface drain effluent and N accumulation and yield of
corn (Zea mays L.) and soybean [Glycine max (L.) Merr.]. The study was conducted on glacial till derived soils in
northeast Iowa from 1993 through 1995 using no-till and chisel plow tillage treatments. One-third of the 2,611 effluent
samples had NO3-N concentrations greater than 10 mg L-1 . Split applying fertilizer N based on pre-sidedress soil nitrate
test (PSNT) results significantly increased corn yield for both tillage treatments in the extremely wet 1993 without
increasing NO3-N loss in drain effluent. Increased grain yield also resulted in significantly more N removal. When
fertilizer N was applied based on the PSNT, no-till and chisel treatments had similar NO 3-N losses and concentrations.
Average flow-weighted NO3-N concentrations in drain effluent were not increased when larger amounts of fertilizer were
applied based on PSNT. However, prior crop and tillage practices and differences in drain flow volume caused significant
differences in NO3-N losses and concentrations. These results suggest that spatial differences in flow volume are a major
factor determining NO3-N loss in drainage effluent. Significant differences suggest that combining no-tillage practices
with split N fertilizer management strategies can have positive environmental benefits without reducing corn yield
A conservation tillage research update from the Coastal Plain Soil and Water Conservation Research Center of South Carolina: A review of previous research
In the U.S. Southeastern Coastal Plains conservation tillage (CT) became useful as a management
system with the development of in-row subsoiling systems capable of planting into heavy residues.
Research priorities associated with the development of CT included: reducing cover crop water loss,
improving stand establishment, assessing nutrient and water management requirements, determining
optimal subsoiling strategies, understanding long-term conservation tillage effects on soil properties,
evaluating the interaction of crop residue removal with tillage systems, and documenting tillage impact
on pests and beneficial organisms. Since the late 1970s the Coastal Plains Soil and Water Conservation
Research Center in Florence, SC has made a concerted effort to study these interactions and
alleviate them as obstructions to the use of CT management. These studies showed that for Coastal
Plain soils such as Norfolk sandy loam ( fine-loamy, siliceous thermic, Typic Paleudults ) winter cover
crops such as rye (Secale cereale L.) desiccated the soil profile by evapotranspiration in the spring.
This delayed emergence and early season growth of corn (Zea mays L.) but not full-season soybean
(Glycine max ( L. ) Merr. ). Conservation tillage helped manage soil strength by gradually increasing
soil organic matter content, restricting traffic patterns and maintaining higher soil water contents.
Laboratory studies demonstrated a negative correlation (R2=0.85 ) between proctor soil strength and
organic matter content. Conservation tillage affected nematode, Bradyrhizobium japonicum and Heliothis
species populations. Alternate cropping systems using rapeseed (Brassica napus L.) as a winter
crop or sunflower (Helianthus annuus L.) either before soybean or after corn provided crop cover
against potential soil loss from late autumn through early spring, when bare soil is exposed to intense
rainfall. Water quality questions associated with CT have been raised but remain unanswered. Although
CT can reduce runoff and erosion, the crop residues can support higher insect populations and
pathogen inoculum levels, and thus prompt greater pesticide use. Quantifying relationships between
soil strength, macropore formation and persistence, and water infiltration with surface and subsurface
water quality is the focus of new long-term evaluations. The findings of these studies, published to
date, are summarized in this paper
Bragg soybeans grown on a Southern Coastal Plain soil. IV. Seasonal changes in nodal N and P concentrations
Determinate soybean [Glycine max (L.) Merr.] has been
characterized by few detailed nitrogen and phosphorous partitioning
studies. Knowledge of the variation in N and P concentrations with
plant part, nodal position, and plant age is needed for a better
understanding of plant functions. In this field study, 'Bragg'
soybean was grown on an Aquic Paleudult soil (series Goldsboro loamy
sand). Plants were sampled at 10 to 14 day intervals beginning 44
days after planting (July 7) until harvest. Maximum observed N
concentrations were 3.1, 2.8, 5.8, and 5.4% for stem internodes,
petioles (+branches), leaf blades, and pods, respectively. Maximum
observed P concentrations were 0.34, 0.48, 0.78, and 0.52 for the
same respective plant parts. Nodal and temporal mean N and P
concentrations varied considerably with plant age and nodal position
in all plant parts. These data show that mean N and
concentrations in all four plant parts can vary several fold,
depending upon plant age and nodal position for the sample. This
suggests caution should be exercised in tissue sampling and
interpretation of plant analysis. Concentrations of N and P
generally decreased with time for stem internode, petioles
(+branches), and leaf blades, but increased with time for pods.
Except for N concentration in stem internodes, which increases with
internode number, the N and P concentrations remain nearly constant
throughout the growing season. The relationships provide insight
for developing accurate plant models depicting N and P
concentrations and translocations over time and among plant parts
in determinate soybean
A decade of progress in conservation tillage in the South Carolina Coastal Plain
Stream discharge measurements with chemical dilution techniques have
been proposed in several forms since the beginning of this century (Groat4).
Early techniques consisted of introducing a chemical, usually brine, at a
known rate into flowing water and determining the resulting concentration
of the chemical in the stream at a section far enough downstream to assure
adequate mixing of the chemical with the water. A variation of this method,
and the technique used in the present study, was described by Barbagelata5
in 1928. In that method, a known quantity of tracer was added, as a slug, to
the stream to be measured. At a sampling station sufficiently far downstream
for adequate lateral mixing, the tracer concentration-time curve was determined.
The stream discharge was then calculated from the amount of
tracer added and the area measured under the curve
Soil and plant response to three subsoiling implements
Many Southeastern Coastal Plain soils require deep (>0.45 m)
inrow tillage or subsoiling to disrupt dense tillage/traffic pans and/
or eluvial (E) horizons. Three subsoiling implements [Super Seeder
(SS), ParaTill (PT), and Kelly (KE)] were compared on Norfolk
(Typic Paleudult) loamy sand to assess their effectiveness in developing
and maintaining a proper rooting environment for corn (Zen
mays L.). Soil strength (cone index) for the implements was evaluated
with and without conventional surface tillage (disking). All three
subsoiling implements effectively disrupted the E horizon regardless
of surface tillage, but the 67% stand establishment in nondisked
treatments was significantly lower than for disked treatments (92%).
However, yields were not significantly different. Significant differences
in soil strength were measured among subsoiling implements
at the beginning of each growing season. In 1985 mean profile soil
strength was lower (P 0.10) for SS and PT than for KE. In 1986,
soil strength was lower (P 0.10) for SS than either PT or KE.
The consistent difference between SS and KE occurred because SS
disrupted a larger area than the thinner-shanked KE. Nondisked
treatments had mean soil strength that was 0.32 MPa lower within
the row than disked treatments, but disked treatments had mean
soil strength that was 0.37 MPa lower between the rows. Soil strength
results suggest that Coastal Plain soils, which have been subsoiled,
are less likely to restrict root development regardless of implement
with, or without, prior surface tillage
Irrigation management for double-cropped fresh-market tomatoes on a high-water-table soil
Two tomato (Lycopersicon esculentum, Mill.)
experiments were conducted for two years on a southeastern
Coastal Plain soil that has a high, fluctuating water
table. In one experiment, two methods for managing
microirrigation were compared to a treatment that received
only rainfall by measuring marketable fruit yields for
spring and fall cropping seasons. Irrigation increased yields
for both seasons in the second year because of low rainfall.
Measurements among seven shallow wells on the site
showed no consistent differences for either water table
depth or gradient between adjacent wells. Two cultivars
were evaluated in the second year, primarily because frost
severely damaged the tomato plants about three weeks
after transplanting. In the second experiment, two
excessively irrigated treatments were evaluated in an effort
to induce a "soft-fruit" storage and shipping problem
experienced by many growers in this region. Although
extremely large quantities of irrigation water were applied,
these symptoms were not observed in this study. There
were no differences in fruit yield between the two water
management treatments in either spring or fall. Fruit
quality measurements showed no significant differences.
The 'Sunny' cultivar performed better than 'Walter' during
the fall season for the extremely wet soil condition. A
double-crop, microirrigation management system has
higher input costs but provides increased profitability for
fresh-market tomato production, particularly where
markets are available for both spring and fall crops
Morphological, temporal, and nodal accumulation of nutrients by determinate soybean
Crop growth models that account for nutrient accumulation offer
insight into soil fertility and plant nutrition interactions. This understanding
provides opportunities to develop improved management practices. During the
1980s, several process-level growth models were developed for soybean [Glycine
max (I..) Merr.). Model validation and application to different locations and
weather require detailed, independent data sets. An extensive data set describing
the nutrient status of a determinate soybean ('Bragg') was collected in 1979 on
a Goldsboro (Aquic Paleudult) loamy sand near Florence, SC, USA. Because of
its importance to subsequent model development, we concluded that providing this
entire data set in a readily accessible form was a logical step in the course of this
experiment. We report here, in tabular form, mean and standard deviation data
for aerial accumulation of dry matter and eight nutrients (N, P, K, Ca, Mg, Mn,
Fe, and Zn) for 10 dates, for four plant components (stems, leaves, petioles,
pods, and total), and for each node (and whole plant). We will provide, upon
arrangement, these same data on diskette for use in simulation models or other
applications
Experiences with microirrigation for agronomic crops in the southeastern USA
Microirrigation offers several advantages over sprinkler irrigation in humid areas, including
ease of automation; lower water pressure and flow rate; improved management of water and
nutrients; and easy seasonal start-up, especially for subsurface placement. Microirrigation
system cost could be reduced and made more profitable for agronomic crops by using wider
spacing and subsurface placement of microirrigation laterals. Results are reviewed from five
experiments involving microirrigation of agronomic crops (corn, soybean, and cotton) and
including 14 site-years of data. Agronomic crops can be effectively and efficiently irrigated
in the southeastern Coastal Plain with microirrigation systems. In three experiments involving
nine site-years of data, both normal (0.76 - 1.0 m) and wide (1.5 - 2.0 m) lateral spacings
were used to irrigate corn and cotton; yields were equal except in one year when corn yield
was reduced by about 10% for the wide spacing. With corn, there was no yield difference
between surface and subsurface placement of laterals at the normal spacing (every row).
Other data indicate that wider spacing of laterals in subsurface installations produces cotton
lint yields similar to those for the same spacing in surface placements. Consequently, it
appears that surface or subsurface placement of laterals at wider spacings (alternate furrow,
1.5 - 2.0 m) has significant potential for profitable irrigation of agronomic crops such as corn,
cotton, and soybean in the southeastern USA
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