17 research outputs found
Changes in infiltration under alfalfa as influenced by time and wheel traffic
Infiltration rates were measured for alfalfa, (Medicago saliva L.,
cv. WL514) subjected to treatments where wheel traffic was varied
in terms of area covered and time of application on a Wasco sandy
loam (coarse-loamy, mixed, nonacid thermic Xeric Torriorthent).
Traffic treatments were (i) No-traffic, (ii) Preplant, (iii) Repeated,
and (iv) traffic similar to what a grower would apply. Infiltration
rates increased for all treatments, with increases being 240% for
treatments without harvest traffic and 140% for treatments with harvest
traffic Increases in infiltration were related to decreases in
stand density. Slight packing (traffic) applied before the soil was
flood-irrigated in 1983 increased infiltration rates 20% compared to
flooding loosened soil (no traffic). Harvest traffic resulted in slower
water movement in the soil
Bulk density of a sandy loam: traffic, tillage, and irrigation method effects
Modern crop production creates a cycle between soil compaction
caused by traffic and alleviation of this condition by tillage or natural
processes such as freezing and thawing. The objective of this study
was to evaluate important management practices as they relate to
changes in bulk density of a tilled sandy loam soil. Practices evaluated
were irrigation method, time between tillage and traffic, tire pressure
and wheel load of applied traffic, and controlled traffic. Relationships
among bulk density, penetration resistance, and infiltration rate were
determined. Experiments were conducted in the San Joaquin Valley
of California, on a sandy loam soil (Entisol) with an organic-matter
content of <1%. After tillage, settling and trafficking of a soil resulted
in rapid changes in its bulk density until a new equilibrium was reached.
Tire pressure of 408 kPa and wheel weight of 2724 kg applied at
moisture contents near field capacity resulted in a bulk density of 1.92
Mg m-3 , compared with a value of 1.67 for no traffic. The time
interval between tillage and traffic did not affect final bulk density.
Drip irrigation, which did not saturate the soil, resulted in a bulk
density of ?0.1 Mg m-3 lower than flood irrigation, which saturated
the soil surface. Wheel traffic in the furrow resulted in only small
changes in the bulk density within the row. When tillage did not occur
between cropping seasons, traffic caused high bulk densities in the
furrow but only small changes in the row. An increase in bulk density
from 1.7 to 1.89 Mg m-3 decreased the infiltration rate by four times
and increased resistance to penetration at the end of the season by
three times. Knowledge of how management practices affect bulk density
can aid growers in reducing recompaction following tillage
Fine root development of alfalfa as affected by wheel traffic
Root development in alfalfa (Medicago satire L.) is dependent of
many factors including the soil environment which is influenced by
crop management procedures. Soil compaction, which is unavoidable
under current management procedures, can have a detrimental effect
on root development. The purpose of this field experiment was to
compare the effects of controlled and conventional traffic management
on alfalfa fine root growth in a Wasco sandy loam (coarse-loamy,
mixed, nonacid thermic Typic Torriorthent). No wheel traffic
and traffic only before planting were compared to two conventional
systems that varied in the amount of traffic applied during crop
production. Twenty months after planting, there was a significant
decrease in fine root density (FRD) from single passes of traffic after
each harvest down to a 0.45-m depth while several passes after each
harvest significantly decreased FRD down to 1.8-m depth. Regardless
of treatment, root density was greatest in the upper 0.1 m of
soil decreasing to 1.8 m in the first summer. By the second summer
FRD showed bimodal distribution with significantly fewer roots at
0.3 to 0.6 m compared to layers above and below this depth. Seasonally
there was a significantly higher root density during the winter than the summer in the upper 0.3 m of soil. The results of this
study shows that alfalfa fine roots more thoroughly exploit the soil
volume in the absence of wheel traffic and that compaction from
traffic diminished root growth to different depths depending on its
intensity
Alfalfa (Medicago sativa L.) water use efficiency as affected by harvest traffic and soil compaction in a sandy loam soil
Traffic during alfalfa harvest operations can
cause soil compaction and damage to newly growing
stems. Root exploration for soil water and nutrients,
forage growth dynamics, and final yield can all be affected.
The objectives of this study were to determine the
long-term effects of harvest traffic and soil compaction on
water-use efficiency (WUE) of alfalfa grown in a Wasco
sandy loam (coarse-loamy, mixed, nonacid, thermic Typic
Torriorthents). Alfalfa was planted into tilled soil and
managed with or without harvest traffic. Plants subjected
to traffic during harvest had a significantly lower WUE
two out of the three years studied compared to plants that
were never subject to traffic. The second experiment examined
whether planting alfalfa into compacted soil and
managed with or without harvest traffic altered WUE.
Soil compaction had no affect on alfalfa WUE. It was
significantly lower when grown in compacted soil and
subjected to harvest traffic. It is suggested that the decrease
in WUE caused by harvest traffic may be explained
by plants allocating carbohydrates to damaged shoots
and crowns instead of to above ground forage production.
The area of the field affected by harvest traffic, which
damages newly growing stems, should be minimized to
increase crop water use efficiency
Alfalfa yield as affected by harvest traffic and soil compaction in a sandy loam soil
Harvesting alfalfa (Medicago saliva L.) results in plants
being subjected to traffic at different times during the growth
cycle with equipment having different wheel sizes and loads.
The affect of this traffic could have important ramifications
on yield. The objectives of this study were to determine the
long-term effects of harvest traffic and soil compaction on
alfalfa yield. In the first experiment, two conventional traffic
systems were compared to alfalfa production with no traffic.
A single traffic event, that covered 100% of the plot area 3
to 5 d after each swathing, compared to no traffic significantly
decreased yield by 20% in the 1st yr, 16.5% in the 2nd yr,
14% in the 3rd yr, with no significant difference the 4th yr.
There was no difference in total yield between nontrafficked
and a typical grower's traffic pattern the 1st yr, but in the
succeeding 3 yr there was a 5 to 17% reduction. The effects
of soil compaction and harvest traffic on yield were separated
in the second experiment. Alfalfa grown in moderately and
heavily compacted soil had a 12 and 26% decrease respectively
in seasonal total yield compared to the yield from
plants grown in noncompacted soil the 1st yr. Annual yields
were the same regardless of the degree of soil compaction in
the 3rd yr. When harvest traffic was applied to alfalfa grown
in extremely compacted soil there was an additional decrease
in yield. It was not statistically significant the 1st yr, but in
the following 2 yr, 1987 and 1988, yield was significantly
reduced by 17.8 and 19.1%, respectively. Alfalfa yields were
significantly reduced both by harvest traffic and compacted
soil. To achieve optimum long-term alfalfa yields compacted
soil must be tilled before planting and operations that reduce
the area of the field subjected to traffic must be implemented
Infiltration rate of a sandy loam soil: effects of traffic, tillage, and plant roots
Settling and trafficking of a soil after tillage causes rapid changes
in the soil physical condition until a new equilibrium is reached. In
the soil studied, a Wasco (coarse-loamy, mixed, nonacid, thermic Typic
Torriorthent) sandy loam, soil compaction reduces infiltration rates,
which under grower conditions could result in inadequate infiltration
of irrigation water to supply crop requirements. Our objective was to
evaluate important management practices as they relate to changes in
the infiltration rate of a sandy loam soil. Factors evaluated were traffic,
tillage between crops, and the formation of channels by roots of perennial
crops. Tillage between crops increased the infiltration rate during
the first part of the season in trafficked soils but decreased or had
no effect on nontrafficked soil. Alfalfa (Medicago sativa L.) increased
the infiltration rate fourfold during a 2-yr period in a heavily compacted
soil. An increase in bulk density from 1.6 to 1.8 Mg m-3
decreased infiltration rate 54% in the field. Hydraulic conductivity of
undisturbed cores was at least seven times larger than that measured
in columns of disturbed soil (same bulk density). This difference is
believed to be the result of natural channels in the undisturbed soil
that are destroyed when the soil is disturbed. Under controlled traffic,
when surface seal is not a problem, tillage will not be necessary to
obtain adequate infiltration rates except in the wheel paths
Infiltration rate as affected by an alfalfa and no-till cotton cropping system
Previous studies measured a long-term increase in infiltration rate
in a sandy loam soil with time when alfalfa (Medicago saliva L., cv.
WL514) was grown. Cotton (Gossypium hirsutum L.) was direct-planted
into alfalfa to determine if the high infiltration rates measured
under alfalfa culture could be maintained in cotton under either
a till or no-till system. Treatments were no-till or tillage to the 0.15 -
m depth just before the cotton was planted. Prior compaction levels
created by harvest traffic applied to the alfalfa made the soil loose
or compacted. Cotton was planted flat and irrigated as a basin. Infiltration
rates measured 2 h after water was applied and averaged
for the season were 101 (no-till, loose), 56 (till, loose), 82 (no-till,
compacted), and 42 mm/h (till, compacted). All the infiltration rates
were much higher than normally measured for cotton in these soils.
Water flow in the 5-yr-old alfalfa was determined to be mainly
through the soil macropore system. High infiltration rates measured
in the no-till cotton were also probably the result of flow through
the macropores
Crop coefficients and water use for cowpea in the San Joaquin Valley of California
To improve irrigation planning and management, a modified soil water balance method was used to determine the crop coefficients and water use for cowpea (Vigna unguiculata (L.) Walp.) in an area with a semi-arid climate. A sandy 0.8-ha field was irrigated with a subsurface drip irrigation system, and the soil moisture was closely monitored for two full seasons. The procedure used was one developed for cotton by DeTar [DeTar, W.R., 2004. Using a subsurface drip irrigation system to measure crop water use. Irrig. Sci. 23, 111-122]. Using a test and validate procedure, we first developed a double sigmoidal model to fit the data from the first season, and then we determined how well the data from the second season fit this model. One of the results of this procedure was that during the early part of the season, the crop coefficients were more closely related to days-after-planting (DAP) than to growing-degree-days (GDDs). For the full season, there was little difference in correlations for the various models using DAP and GDD. When the data from the two seasons were merged, the average value for the crop coefficient during the mid-season plateau was 0.986 for the coefficient used with pan evaporation, and it was 1.211 for the coefficient used with a modified Penman equation for ET0 from the California Irrigation Management and Information System (CIMIS). For the Penman-Monteith (P-M) equation, the coefficient was 1.223. These coefficients are about 11% higher than for cotton in the same field with the same irrigation system. A model was developed for the merged data, and when it was combined with the normal weather data for this area, it was possible to predict normal water use on a weekly, monthly and seasonal basis. The normal seasonal water use for cowpea in this area was 669Â mm. One of the main findings was that the water use by the cowpea was more closely correlated with pan evaporation than it was with the reference ET from CIMIS or P-M.Cowpea Black-eyed peas Crop coefficients Evapotranspiration Irrigation Subsurface drip irrigation Crop water use