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The influence of high application rates of polyacrylamide on microbial metabolic potential in an agricultural soil
Get PDFWater soluble anionic polyacrylamide (PAM) is a highly effective erosion preventing and infiltration enhancing polymer, when
applied at rates of 1-10 g 111-3 in furrow irrigation water. PAM greatly reduces sediment, nutrients, pesticides and coliform bacteria
in irrigation runoff. There has been some concern about the potential for PAM accumulation to affect microbial ecology. We ran a
long-term study applying massive quantities of PAM to soil and monitored its impact on soil microbial potential. In June, July and
August, we measured active soil bacterial and fungal biomass and microbial diversity in soils receiving 0 (control), 2691 and
5382 kg active ingredient (ai) PAM ha-1. Active bacterial biomass in soil was 20-30% greater in the control treatment than in soil
treated with 2691 or 5382 kg ai PAM ha -1- in June and August, but not July. Active fungal biomass in soils was 30-50% greater in
the control treatment than soil treated with 2691 or 5382 kg ai PAM ha -1- in June and July, but not August. Active microbial biomass
in soil was 27-48% greater in the untreated control than soil treated with 2691 or 5382 kg ai PAM ha-1- except in June. Whole soil
fatty acid profiles showed no discernible change in the soil microbial community due to either of the PAM treatments at any
sampling time. Analysis of nutritional characteristics using Biolog GN plates, however, yielded an apparent separation of the non-amended
control soils from those plots receiving the high PAM application rate in June, but not in July or August. In contrast,
comparisons of the three sampling times by both the fatty acid and Biolog analyses indicated that the microbial metabolic potential
present in June were different from those sampled in July and August. Although PAM application to soil or irrigation water in some
cases may reduce active bacterial and fungal biomass it does not seem to appreciably affect the soil microbial metabolic potential
Solute response to changing nutrient loads in soil and walled ceramic cup samplers under continuous extraction
Get PDFThis report evaluates a vacuum-assisted walled percolation sampler
preconditioned in soil, and examines the dynamic response of leachate
solutes. The 20-cm walled percolation sampler extracted soil water
under continuous tension via a ceramic cup collector embedded in a
silica flour layer, whose upper surface interfaced with field soil. In
the laboratory, alternating solutions with high and low NO3-N (232
or 3.6 mg L-1), molybdate-reactive P (MRP) (1.75 or 0.0 mg L -1), K+
(568 or 3.6 mg L-1), and Br- (9.6 or 0.0 mg L-1) concentrations
were delivered directly to the (i) sampler ceramic cup; (ii) silica flour bed
surface, or (iii) 12-mm soil layer placed over the silica flour bed. For
alternating input solutions delivered to the silica-flour bed surface, (i)
solute breakthrough (95% equivalency) occurred in 4 pore volumes and
was the same for both the high and low concentration input phases of the
application, and (ii) concentrations of NO 3-N, Br-, and MRP in cumulative
extracted water volumes were within 5% of those in corresponding
input volumes. Alternating nutrient loads from high to low
levels in the fixed flow rate input waters caused excess MRP (L6 times
that in the high concentration MRP solution) to leach from the calcareous
soil. The dynamic character of P transport in K-fertilized soils deserves
further study and may have important environmental implications
Comparison of site-specific and conventional uniform irrigation management for potatoes
Get PDFSite-Specific Irrigation Management (SSIM) can be defined as irrigation management (depth, timing) based on
crop need to defined sub-areas of a field referred to as management zones. Implementation of SSIM will require additional
irrigation system hardware, labor, and information on soil and/or plant water status in each management zone. Costs
associated with these additional requirements will need to be offset by increased receipts from improved crop yield and quality
in order for the technology to be adopted by producers. The potential for SSIM to increase crop yield, quality, and economic
return has not been evaluated in field studies. Crops such as potatoes, for which yield and quality are highly sensitive to soil
water availability, are most likely to show an economic benefit from site-specific irrigation management. A two-year field
study was conducted to evaluate the potential for SSIM to increase yield and quality of potatoes relative to Conventional
Uniform Irrigation Management (CUIM). Near real-time soil water content was used to schedule irrigations under both
irrigation management treatments. Field average water application was nearly the same for the irrigation management
treatments, 503 mm (19.8 in.) in 2001 and 445 mm (17.5 in.) in 2002. In both study years, tuber yield distributions trended
4% greater under site-specific irrigation management but were not significantly different (p < 0.05). Total tuber yield per
unit of water applied from irrigation and precipitation was 4% greater in 2001 and 6% greater in 2002 under SSIM. Based
on a local tuber quality adjusted potato processing contract price structure, the trend in gross income averaged across the
field site was 65/acre) greater with SSIM. This increase in gross income is likely about half the actual cost of
commercial site-specific irrigation technology. The required 3- to 5-year crop rotation for potato disease management means
that the site-specific irrigation system needs to be mobile or an economic benefit must also be realized from other crops in
the rotation. The economic benefit of SSIM needs to be increased or realized for other crops in the rotation for it to be an
economically viable technology in potato production systems in Idaho
Yield response of corn to deficit irrigation in a semiarid climate
Get PDFIrrigation water supplies are decreasing in many areas of the US Great Plains, which is
requiring many farmers to consider deficit-irrigating corn (Zea mays L.) or growing crops like
winter wheat (Triticum aestivum L.) that require less water, but that are less profitable. The
objectives of this study were to: (1) quantify the yield response of corn to deficit irrigation,
and (2) determine which of several seasonal water variables correlated best to corn yield in a
semiarid climate. Eight (T1-T8) and nine (T1-T9) deficit-irrigated treatments (including
dryland), were compared in 2003 and 2004 in North Platte, Nebraska. The actual seasonal
crop evapotranspiration (ETd) (calculated with procedures in FAO-56) for the different
treatments was 37-79% in 2003 and 63-91% in 2004 compared with the seasonal crop
evapotranspiration when water is not limited (ETw). Quantitative relationships between
grain yield and several seasonal water variables were developed. Water variables included,
irrigation (I), total water (W ) rain + irrigation (WR+1), evaporation (E), crop evapotranspiration
(ETd) ; crop transpiration (Td), and the ratios of ETd and Td to evapotranspiration and
transpiration when water is not limited (ETw and Tw). Both years, yield increased linearly
with seasonal irrigation, but the relationship varied from year to year. Combining data from
both years, ETd had the best correlation to grain yield (yield = 0.028ETd-5.04; R2 = 0.95),
and the water variables could be ranked from higher to lower R 2 when related to grain
yield as: ET d(R2=0.95) > Td(R2=0.93) > ETd/ETw(R2=0.90) = Td/Tw(R2=0.90) > Wall(R2=0.89) > E(R2 =0.75) >
WR+I(R2=0.65) > I(R2=0.06). Crop water productivity (CWP) (yield per unit ETd) linearly increased
with ETd/ETW (R2 = 0.75), which suggests that trying to increase CWP by deficit-irrigating corn
is not a good strategy under the conditions of this study
Automated system for collecting multiple, sequential samples from soil water percolation samplers under continuous vacuum
Get PDFManually collecting a series of sequential, discrete water samples from
soil water percolation samplers, or similar devices that withdraw water from unsaturated
porous media under continuous vacuum, is a logistical challenge, though the
resulting collection can provide valuable information on the dynamics present in
both laboratory and field studies. This article describes a sequential tension autosampler
(STAS) that executes such sampling automatically. The STAS operates on 12
volts direct current (VDC) and can be adapted for laboratory and field applications.
A data logger was programmed to operate a series of solenoid valves, which direct
soil water collected under tension to seven individual collection bottles. The number
of sequential samples, sample period, start time, and between-sample interval are
specified by the user. The operator only need to attend the system periodically to
transfer water samples to storage vials and program the next sampling sequence.
In a laboratory study, the apparatus successfully collected samples overnight or
over several days
Influence of solid dairy manure and compost with an without alum on survival of indicator bacteria in soil and on potato
Get PDFWe measured Escherichia coli, Enterococcus spp. and fecal coliform numbers in soil and on fresh potato skins after addition of
12 solid dairy manure and dairy compost with and without alum (Al 2(SO4)3) treatment 1, 7, 14, 28, 179 and 297 days after application.
13 The addition of dairy compost or solid dairy manure at rates to meet crop phosphorus uptake did not consistently increase E. coli
14 and Enterococcus spp. and fecal coliform bacteria in the soil. We did not detect E. coli in any soil sample after the first sampling day.
15 Seven, 14, 28, 179 and 297 days after solid dairy waste and compost and alum were applied to soil, alum did not consistently affect
16 Enterococcus spp. and fecal coliform bacteria in the soil. We did not detect E. coli in any soil, fresh potato skin or potato wash-water
17 at 214 days after dairy manure or compost application regardless of alum treatment. Dairy compost or solid dairy manure
18 application to soil at rates to meet crop phosphorus uptake did not consistently increase Enterococcus spp. and fecal coliform
19 numbers in bulk soil. Solid dairy manure application to soil at rates to meet crop phosphorus uptake, increased Enterococcus spp.
20 and fecal coliform numbers in potato rhizosphere soil. However, fresh potato skins had higher Enterococcus spp. and fecal coliform
21 numbers when solid dairy manure was added to soil compared to compost, N and P inorganic fertilizer and N fertilizer treatments.
22 We did not find any E. coli, Enterococcus or total coliform bacteria on the exterior of the tuber, within the peel or within a whole
23 baked potato after microwave cooking for 5 min
The influence of manure phytic acid on phosphorus solubility in calcareous soils
Get PDFManure characteristics can influence the potential for P transfer in
runoff following land application of manures. This research assessed
the influence of manure characteristics on P solubility in calcareous
soils using manures from poultry (Gallus Domisticus) fed a variety
of grain-based diets with the manures containing a range of total P
(5.6-16.4 g P kg-1), water-extractable P (WEP, 0.9-4.7 g P kg -1),
phytic acid P (0.1-7.6), total N/P ratios (2.6-5.1), and total C/P ratios
(19.5-75.7). In addition, mono-ammonium phosphate fertilizer and
reagent grade inositol hexaphosphate (phytic acid [PA]), were included,
as well as a control treatment with no P additions. Treatments
were incorporated into two soils (Portneuf [Coarse-silty, mixed,
superactive, mesic Durinodic Xeric Haplocalcids] and Millville
[Coarse-silty, carbonatic, mesic Typic Haploxerolls]) at three rates
(10, 20, and 40 mg P kg -1) and incubated for a total of 18 wk with
subsamples taken at 2, 5, 9, and 18 wk. Soil samples were analyzed for
inorganic and organic NaHCO3 (Olsen) extractable P and select soils
were analyzed at 0 and 12 wk by 31P nuclear magnetic resonance
spectroscopy (NMR) for soil P characterization. The percentage of
WEP and PA (of total P) in the manures were linearly related (r 2 =
0.94). Increases in Olsen P over time were positively related to the
percentage of monoester P in the treatments. At 2 wk, there was a
strong negative correlation between the amount of PA added in the
treatments and increases in Olsen P. However, by 18 wk, Olsen P was
more closely related to the amount of C or N added with the treatments.
Changes in PA content of manures due to dietary modification may
influence P sorption on calcareous soils in the short-term while other
characteristics such as C/P ratio may exert a stronger influence over
changes in soil test P over longer time periods
Dairy manure/compost N release for sugarbeets and subsequent wheat
Get PDFThere is frequently more manure generated than can be environmentally applied in a sound
manner within the limited land resources of the growing number of Idaho dairies and feedlot
operations. There is considerable incentive to export manure or compost from these operations
to nearby farmer fields. Manure composting is currently used to reduce the volume of material
hauled. But the slower release nature of organic N sources could be problematic for sugarbeets
if the timing of N release interferes with late season sugarbeet growth and sugar content. A
better understanding of the N release dynamics from manures and composts is needed to know
how best to use these resources without causing excessive available N at the end of the season,
the associated higher brei nitrate and conductivity, reduced sugar content and recoverability.
Marketing of manures and composts to sugarbeet producers is limited by a lack of information
regarding sugarbeet response to the applications.
Sugarbeet production in southwest Idaho involves fall application and shallow incorporation
of broadcasted fertilizers prior to fall bedding. The bedding process essentially concentrates
broadcasted fertilizers, composts or manures over the row to be planted the following spring.
Precipitation can move soluble and mobile salts to the soil depth at which sugarbeet seed must
germinate.
The objective of this study was to compare fall applied manure and compost N sources with
conventional fertilization. Depth of organic N incorporation was also of interest
Sprinkler droplet energy effects on soil penetration resistance and aggregate stability and size distribution
Get PDFSprinkler droplet energy degrades surface soil structure. Modifying
sprinkler irrigation systems to reduce droplet energy may reduce surface
sealing and crusting, thereby increasing emergence. From 1997 to 2001,
we evaluated the effects of sprinkler droplet kinetic energies of 0, 8, and
16J kg-1 on in situ surface penetration resistance (PR, a measure of crust
strength), aggregate stability (a measure of a soil's resistance to breakdown),
and water-stable aggregate size distribution, expressed as a mean
weight diameter (MWD). Each year near Kimberly, ID, we planted
sugarbeet (Beta vulgaris L.) into an initially tilled field of structurally weak
Portneuf silt loam (Durinodic Xeric Haplocalcid), then irrigated two to
four times using a lateral-move sprinkler system with spray heads having
either smooth or spinning, four-groove deflector plates. After the first
and last irrigation each year, we measured PR in situ and collected soil
samples at the surface, 0 to 6 mm. When measured after one irrigation,
PR increased, and aggregate stability generally decreased as droplet
energy increased, although the magnitude of the response differed from
year to year. After multiple irrigations, PR decreased linearly with
increasing droplet energy, likely due to erosion of the crusted surface.
Five-year average MWD after multiple irrigations decreased by 10%, to
0.42 mm, with droplet energies of 8 J kg-1 or more. Trend analysis of
soils data from 1998 to 2001 revealed that droplet energies ~10.6 J kg -1
decreased MWD most. Producers should reduce sprinkler droplet kinetic
energy to <10.6 J kg-1 to minimize surface structural breakdown of
recently tilled soil
Water management practices: Irrigated Cropland
Get PDFIrrigation is practiced on about 17 percent of
the world's arable land. Irrigated land accounts
for 33 percent of the world's food production
(FAO, 1988) and contributes greatly to the economy
in many agricultural regions. In developing
countries, nearly 60 percent of rice and wheat
production used for food is grown on irrigated
cropland. The United Nation's Food and Agriculture
Organization (1988) estimates that about
two-thirds of the increase in arable land needed
to produce food crops by 2050 will be irrigated.
Along with the significant economic impact of
irrigated agriculture, however, come significant
environmental and natural resource impacts.
U.S. Department of Agriculture (USDA)
conservation programs commonly are used to
improve irrigation systems and their management
in an attempt to reduce the impacts of irrigation
on the environment and natural resources