21 research outputs found
Crop and Soil Response to Long-Term Tillage Practices in the Northern Great Plains
Summer fallow is the most common cultural practice in the northern
Great Plains. With proper cultural management, however, annual cropping
may be feasible and economical. Our objective was to determine
crop and soil response to nontraditional annual cropping practices (till
and no-till) in lieu of conventional fallow-crop rotation for the production
of spring wheat (Triticum aestivum L.) and barley (Hordeum vulgare
L.) in the northern Great Plains. The study, initiated in 1983, was
on a Dooley sandy loam (fine-loamy, mixed Typic Argiboroll) 11 km
north of Culbertson, MT. Tillage practices on annually cropped treatments
included sweep tillage in autumn and disk tillage in spring; sweep
tillage in spring; and no-tillage. Conventional fallow-spring wheat rotations
were included as the control. With three exceptions, there were
no statistical differences among treatments in soil P, soil nitrate N, and
pH. Phosphorus and N were nonlimiting in all years; pH decreased about
0.06 units per year in the 0- to 8-cm layer because of N fertilization.
Bulk density differences in the 0- to 10-cm layer appeared after 7 yr,
with the lowest bulk density for the no-tillage annual crop treatment.
Grain and straw yields with the no-tillage treatment were both 80%
of yields with the fallow-crop treatment. Total water use efficiency, based
on soil water differences between harvest of one crop and harvest of
the next, was significantly greater with no-tillage than with the fallow-crop
treatment. Soil organic C decreased nearly 0.4 g kg I per year with
the fallow-crop treatment; there was a negligible decline with the no-tillage
annual crop treatment. No-tillage annual spring wheat crop production
was the most efficient crop and soil management practice from
the standpoint of yield, water use efficiency, soil organic C, and bulk
density
Lentil green manure as fallow replacement in the semiarid northern Great Plains
Green manures (GM) may offset inorganic N needs and improve
soil quality. Study objectives were to determine effects of green manure
on soil-N fertility, water use, soil quality, and yield of spring wheat
(Triticum aestivum L.). On two treatments, lentil (Lens culinaris
Medikus cv. Indianhead) was green manured in a green manureāspring
wheat rotation. Lentil was killed by disking (GMMF) or chemicals
(GMCF). Additional treatments were annually cropped wheat (AW)
in a mechanical fallow (MF) or chemical fallow (CF) sequence. No
inorganic N was used on GMMF and GMCF. Experiments were
started in 1991 on a Williams loam (fine-loamy, mixed Typic Argiboroll)
near Culbertson, MT. Green-manure treatments used 56 mm
more water than fallow treatments when lentil was grown to lower-pod
set. When lentil was killed at full bloom, there were no differences
in water use among GM and fallow treatments. There were no differences
among treatments in soil water at wheat planting. Wheat yield
was 25% less on GM than on MF and CF. Soil NO 3āN (0-0.6 m) was
35% less on GM than MF and CF rotations. There were no differences
in soil quality indicators of bulk density, organic C, pH, electrical
conductivity, and deep NO3āN (0.6 ā1.8 m) among treatments after
two cycles of GM. Potentially mineralizable N was 66% greater on
GM treatments than on fallow treatments. Short-term results (5 yr)
show that available N limited wheat production more than did soil
water on the GM treatments. Soil improvement using green manures
may require many additional cropping cycles
Sprinkler irrigation runoff and erosion control with polyacrylamide - laboratory tests
Many semiarid and arid soils are prone to irrigation-induced erosion.
Polyacrylamide (PAM) greatly reduces erosion from furrow
irrigation. We hypothesized that PAM applied via sprinklers will
provide erosion control and benefit water infiltration and aggregate
stability. Screened (6.4 mm) Rad silt loam (coarse silty, mixed, superactive
mesic Durinodic Xeric Haplocambid) was placed in 1.5 by 1.2
by 0.2 m steel boxes with 2.4% slope. An oscillating nozzle, 3 m above
the soil, produced a median drop size of 1.2 mm diameter. We applied
0, 1, 2, 4, and 6 kg ha-1 PAM in 20 mm of water in the first irrigation,
followed by two 20-mm water-only irrigations. In a second test, we
applied 0, 2, and 4 kg ha-1 PAM in 8 mm of water in the first irrigation,
followed by two 20-mm water-only irrigations. Two kilograms per
hectare PAM in the first 20-mm irrigation reduced runoff 70% and
soil loss 75% compared to control. Polyacrylamide in 8 mm of water
was less effective. Polyacrylamide in the 20-mm irrigation did not
affect tension infiltration; PAM in the 8-mm irrigation doubled tension
infiltration following the third irrigation. Wet aggregate stability following
the first irrigation was greater in all PAM treatments than on
the check. With 2 kg ha-1 PAM in the 20-mm irrigation, it was 55%;
in 8 mm, 77%. Polyacrylamide applied in the first irrigation at low rates
effectively reduced runoff and erosion. Erosion was more effectively
controlled than runoff
Bowen-Ratio Comparisons with Lysimeter Evapotranspiration
Water use in agriculture by different cropping systems is of interest
in determining crop water use efficiency of different tillage practices
that will lead to reduced crop production risk. Lysimeters are considered
the standard for evapotranspiration (ET) measurements; however,
these units are often not replicated and are few in number at
any given location. Our objective was to determine if a simple Bowen-ratio
system with nonexchanging psychrometers could provide accurate
measurements of ET from lentil (Lens culinaris Medikus) in a
semiarid climate. The study was conducted in 1993 and 1994 on two
adjacent 180- by 180-m fields with weighing lysimeters (1.68 by 1.68
by 1.83 m) located in the center of each field, on a Williams loam
(fine-loamy, mixed Typic Argiboroll) soil near Sidney, MT. A Bowen-ratio
system comprised of two nonexchanging psychrometers and
anemometers at 0.25 and 1.25 m above the plant canopy surface was
placed in the lentil field along with a net radiometer and soil heat
flux plate. Precipitation during the growing season from planting to
swathing was 367 mm in 1993 and 227 mm in 1994. In 1993, soil
water content of the lysimeter was greater than the field after large
precipitation events around Day of Year (DOY) 210, even though
the lysimeter was drained. After this time, the lysimeter ET exceeded
that measured by the Bowen-ratio system. Agreement was closer in
1994, when precipitation was near normal and there was no excess
soil water in the lysimeter. Cumulative ET totals from the lysimeter
were reflective of the seasonal precipitation patterns. Differences
between the lysimeter and Bowen-ratio occurred when there was
excess precipitation and inadequate drainage from the lysimeter. Half-hourly
ET fluxes from lysimeter and Bowen-ratio values agreed to
within 10% throughout the season. Bowen-ratio systems with nonexchanging
psychrometers can provide satisfactory estimates of daily
and seasonal ET and can be used to estimate ET in semiarid climates
Lentil water use and fallow water loss in a semiarid climate
With renewed interest in legumes for green manures or as partial
summer fallow replacement crops, it is important to know water
requirements of these crops in semiarid agriculture. Our objective
was to evaluate seasonal water use by black lentil (Lens culinaris
Medikus cv. Indianhead), a potential fallow replacement crop, and
to relate water use to parameters useful as soil water management tools.
We measured evapotranspiration (ET) from two precision weighing
lysimeters located on a Williams loam (fine-loamy, mixed Typic Argiboroll)
near Sidney, MT. The lysimeters were in adjacent 180- by
180-m fields in a typical strip-crop environment of the semiarid northern
Great Plains. Bowen ratio estimates of ET were also obtained.
Lentil was seeded no-till into wheat (Triticum aestivum L.) stubble on
one lysimeter field in 1993, and the other was left in chemical fallow.
Seeded and fallow fields were rotated in 1994. Water loss by ET from
lentil and fallow lysimeters was the same ( 25 mm) for 3 wk following
seeding. Plant height was related to growing degree days (GDD) in
both years. Cumulative ET was related to GDD for both years until
about 800 GDD, corresponding to nearly 300 mm ET. Deciding how
much water to sacrifice (with hopes of recovery during the noncrop
period) becomes a matter of judgment about probable rainfall. At
full bloom ( 2 Mg ha' dry matter production), the lentil crop used
about 50 to 70 mm more water than fallow. Probably no more than
50 mm of water loss above that from fallow should be sacrificed if a
grain crop is to be seeded the following year. From a practical standpoint,
because plant height was closely related to both GDD and
cumulative ET, it is plausible that a simple measure of lentil height
(about 350 mm maximum) can give sufficient accuracy for determining
when lentil growth, as a partial summer fallow replacement crop in
a semiarid climate, should be terminated
Conservation Tillage
Recent research involving tillage systems has included
studies of responses of crops and soils to
conservation tillage practices. and of the changes in
the rooting patterns of plants that result from different
types of tillage
Sprinkler irrigation runoff and erosion control with polyacrylamide - laboratory tests
Many semiarid and arid soils are prone to irrigation-induced erosion.
Polyacrylamide (PAM) greatly reduces erosion from furrow
irrigation. We hypothesized that PAM applied via sprinklers will
provide erosion control and benefit water infiltration and aggregate
stability. Screened (6.4 mm) Rad silt loam (coarse silty, mixed, superactive
mesic Durinodic Xeric Haplocambid) was placed in 1.5 by 1.2
by 0.2 m steel boxes with 2.4% slope. An oscillating nozzle, 3 m above
the soil, produced a median drop size of 1.2 mm diameter. We applied
0, 1, 2, 4, and 6 kg ha-1 PAM in 20 mm of water in the first irrigation,
followed by two 20-mm water-only irrigations. In a second test, we
applied 0, 2, and 4 kg ha-1 PAM in 8 mm of water in the first irrigation,
followed by two 20-mm water-only irrigations. Two kilograms per
hectare PAM in the first 20-mm irrigation reduced runoff 70% and
soil loss 75% compared to control. Polyacrylamide in 8 mm of water
was less effective. Polyacrylamide in the 20-mm irrigation did not
affect tension infiltration; PAM in the 8-mm irrigation doubled tension
infiltration following the third irrigation. Wet aggregate stability following
the first irrigation was greater in all PAM treatments than on
the check. With 2 kg ha-1 PAM in the 20-mm irrigation, it was 55%;
in 8 mm, 77%. Polyacrylamide applied in the first irrigation at low rates
effectively reduced runoff and erosion. Erosion was more effectively
controlled than runoff