159 research outputs found
Winter rapeseed performance in the southeastern Coastal Plain
Fifty-five rapeseed (Brassica napus L.) cultivars were evaluated between
1982 and 1987 on a Norfolk loamy sand (fine, loamy, siliceous, thermic Typic Paleudult)
near Florence, South Carolina. The average seed yield (1,590 kg/ha or 1,420 pounds/acre)
was comparable to that at other southern locations where rapeseed is grown as a winter
annual, but it was lower than in the Pacific Northwest, where the crop is grown as a
true biennial. Assuming a contract price of 0.09/pound), estimated gross returns
for rapeseed would be about $320/ha 0130/acre). For conservation purposes, the crop
may be more valuable because of its potential to reduce soil erosion; rapeseed provides
soil surface cover at an earlier date than winter wheat (Triticum aestivum L.). Results
of this evaluation suggest that additional research is needed to evaluate rapeseed as a winter
forage and/or cover crop for soil erosion control
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
Soil quality improvement through conversion to sprinkler irrigation
Conversion from furrow to sprinkler irrigation is a recommended conservation practice for improved water use efficiency (and/or erosion control), but effects on soil quality indicators were unknown. Several soil quality indicators were therefore quantified within a northwestern U.S. Conservation Effects Assessment Project (CEAP) watershed after changing from long-term furrow to sprinkler irrigation. Four on-farm sites were identified where producers were growing irrigated barley (Hordecum vulgare L.) using both irrigation practices. Climate, soil type, and management were similar between sites. Soil samples were collected from the upper and lower ends of furrow irrigated fields at three in-field positions (bed, shoulder, and furrow); fields converted to sprinkler irrigation were sampled where the upper and lower ends were when the field was furrow irrigated. Soil quality indices (physical, chemical, biological, nutrient, and overall) were computed using the Soil Management Assessment Framework (SMAF). Regardless of in-field position, furrow irrigated field bottoms had higher soil quality index scores than field tops due to long-term erosional deposition. Within sprinkler irrigated fields, soil quality indices for field tops and bottoms showed minimal differences. Overall, when all sampling locations and in-field positions were combined, soil quality was similar for both irrigation methods. However, as compared to furrow irrigation, sprinkler irrigation had greater soil quality indices in the field tops, suggesting that sprinkler irrigation improved soil quality of historically eroded furrow irrigated fields
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
Planting geometries and the efficient use of water and nutrients
In nature and in the most primitive agricultural systems, seed distribution
is broadcast across the landscape. Such a distribution results in nearly uniform
spacial interaction of the developing phytomass. With the development of
agrarian civilization has come an implement-dependent systemization of crop-
planting patterns. This has brought about the planting of crops in uniform
rows—from the drilling of small grains at inter-row spacings of 0.1 to 0.2
m and plant intra-row spacings of i to 5 cm, to the staking of horticultural
and vine crops at 2- to 3—m inter-row spacings and typically 0.3- to l-m intra-row spacings.
The implement dependence of agricultural cropping strategies has
resulted in row cropping. The staple crops regarded as most suited to this
approach are commonly called row crops, and this review will concentrate
largely on how row crops interact with plant geometry, water, and nutrients
to in?uence sustained productive capacity
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
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