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Influence of irrigated agriculture on soil carbon and microbial community structure
Get PDFIncreasing the amount of carbon (C) in soils is
one method to reduce the concentration of carbon dioxide
(CO2) in the atmosphere. We measured organic C stored in
southern Idaho soils having long-term cropping histories that
supported native sagebrush vegetation (NSB), irrigated moldboard
plowed crops (IMP), irrigated conservation-chisel-tilled
crops (ICT), and irrigated pasture systems (IP). The CO 2 emitted
as a result of fertilizer production, farm operations, and
CO2 lost via dissolved carbonate in irrigation water, over a
30-year period, was estimated and used to calculate net C
fixation. Organic C in ecosystems decreased in the order
IP>ICT>IMP> NSB. In February 2001, active fungal, bacterial,
and microbial biomass was greater in IP soils than all
other soils. Active fungal, bacterial, and microbial biomass
was least in ICT soils at the 15-30-cm depth than all other
soils. In August 2001, active bacterial biomass was greater in
IMP soils than IP, ICT, and NSB soils. Active fungal biomass
was greater in IP soils than all other soils. Whole-soil fatty acid
profiles differed among management regimes and sampling
dates and, to a lesser extent, with soil depth. FAME profiles
from the NSB soils were distinct from the agricultural treatments
and contained greater amounts of total fatty acids than
the other treatments. The IMP and ICT soils yielded fatty acid
profiles that were similar to each other, although those at the
15-30-cm depth were distinct from all other treatment-depth
combinations. The IP FAME profiles suggest that arbuscular
mycorrhizal fungi are more common in these soils than soils
from the other treatments. Differences in carbon substrate
utilization patterns (BIOLOG) among treatments were more
variable and less pronounced that FAME results. In general,
irrigated arid soils can both increase C storage while increasing
microbial biomass and changing microbial diversity
A variable flow rate sprinkler for site-specific irrigation management
Get PDFA variable flow rate sprinkler applicable to center pivot and lateral–move irrigation systems was constructed and
tested in the laboratory. Sprinkler nozzle size was reduced a fixed amount using a retractable concentric pin in the nozzle bore.
Cycling insertion of the concentric pin in the sprinkler nozzle bore provided a time– averaged variable flow rate over a range
of 36% to 100% for the nozzle sizes tested. The application pattern radius of the sprinkler tested was reduced approximately
15% under variable flow conditions. Sprinkler drop size distribution was also reduced by engagement of the pin in the
sprinkler nozzle bore. Measured flow rates compared well with theoretical flow rates below 28 L/min (7.4 gpm). Results from
laboratory testing indicate the variable flow rate sprinkler could potentially be used for site–specific irrigation management
with center pivot and lateral–move irrigation systems
Phosphorus composition of manure from swine fed low-phytate grains: Evidence for hydrolysis in the animal
Get PDFIncluding low-phytic-acid grains in swine diets can reduce P concentrations
in manure, but the influence on manure P composition is
relatively unknown. To address this we analyzed manure from swine
fed one of four barley (Hordeum vulgare L.) varieties. The barley types
consisted of wild-type barley (CDC bold, normal barley diet) and
three low-phytic-acid mutant barleys that contained similar amounts
of total P but less phytic acid. The phytic acid concentrations in the
mutant barleys were reduced by 32% (M422), 59% (M635), and 97%
(M955) compared with that in the wild-type barley, respectively. Phosphorus
concentrations were approximately one-third less in manures
from animals fed low-phytic-acid barleys compared with those fed the
wild-type variety. Phytic acid constituted up to 55% of the Pin feed, but
only trace concentrations were detected in NaOH–EDTA extracts of all
manures by solution 31P nuclear magnetic resonance (NMR) spectroscopy.
Phosphate was the major P fraction in the manures (86-94%
extracted P), with small concentrations of pyrophosphate and simple
phosphate monoesters also present. The latter originated mainly from
the hydrolysis of phospholipids during extraction and analysis. These
results suggest that phytic acid is hydrolyzed in swine, possibly in the
hind gut by intestinal microflora before being excreted in feces, even
though the animals have little phytase activity in the gut and derive
little nutritional benefit from phytate P. We conclude that feeding
low-phytic-acid grains reduces total manure P concentrations and
the manure P is no more soluble than P generated from normal
barley diets
Conservation tillage effects on sediment and phosphorus losses from a furrow irrigated field
Get PDFDry beans are often grown after alfalfa in southern Idaho, which conventionally involves four or more
tillage operations before planting. The objective of this three year study (1998-2000) was to
determine the effects of conservation tillage on runoff, soil erosion and phosphorus loss from dry
beans following small grain under furrow irrigation. Tillage treatments were direct seed, spring disk,
fall disk and fall chisel plow. Polyacrylamide (PAM) was applied to half of the furrows during the last
two years of the study. Direct seeding increased residue in furrows, which tended to reduce runoff
volume and soil loss but increased soluble P loss. Applying PAM significantly reduced soil loss for
only 4 of 11 irrigations, but significantly decreased total annual soil loss 63% in 2000. Direct seeding
did not significantly reduce dry bean stand, but weed competition and other factors reduced bean
yields from direct seed by 39% and 47% the last two years of this study. The three tilled treatments
had similar crop yields, residue amounts and phosphorus losse
Using soil texture to guide variable-rate nitrogen fertilization
Get PDFVariable-rate fertilization is becoming a common practice in the US. Many
producers are applying phosphorus and potassium at site-specific rates that take into
account local factors that affect nutrient availability, crop growth and yield potential.
Phosphorus and potassium are relatively immobile in the soil and soil testing can be
effectively used to map the plant available concentration in the soil. Fertilizer spread
maps are created from interpolations of these samples. Nitrogen, however, is very mobile
in the soil. Sampling is only meaningful until the next rain or irrigation. Nitrogen is
highly affected by soil moisture and rainfall. It is more difficult to create fertilizer spread
maps based on soil N test values.
Nitrogen availability for crop growth is related to many soil factors. These factors
include organic matter, soil texture, topography, aspect, residues and previous crop. Of
these, soil texture has a large effect on N availability because it effects water holding
capacity. Nitrogen movement in the soil is highly related to water movement. Coarse
textured soils have higher infiltration rates and lower water holding capacity. Fine
textured soils have lower infiltration rates but high water holding capacity. The
combination of irrigation management and soil texture greatly affects the N availability to
a crop. In a site-specific management study by Machado et al. (2002), it was pointed out
that although the spatial variability of crop yields depends on the interaction between
many physical and biological factors, the effects of soil physical properties on crop yield
is predictable and therefore useful in variable rate technology.
Nitrogen is an important factor in the growth of most crops, especially in sugar
beets where it directly affects yield, sugar content and quality. With many crops the cost
of applying too much nitrogen is the cost of the excess fertilizer and application as well
as the environmental impact that is not a direct cost to the grower. However, applying
too much nitrogen to sugar beets will reduce sugar content and quality, which is a direct
cost to the grower. (Humburg and Stange, 1999).
This paper will present the results of a variable rate N study and the importance of
texture in determining the N rate and yield and yield quality
Irrigation increases inorganic carbon in agricultural soils
Get PDFInorganic C reactions are among the most important
chemical reactions that occur in irrigated soils and
may contribute to the total amount of C sequestered in those
soils. Because CO2 can escape from soils to the atmosphere
or return to precipitate carbonate minerals, soils are open systems
with regard to inorganic C. We measured inorganic and
organic C stored in southern Idaho soils having long-term
land-use histories that supported native sagebrush vegetation
(NSB), irrigated moldboard plowed crops (IMP), irrigated conservation
(chisel) tilled crops (ICT), and irrigated pasture systems
(IP). Inorganic C and total C (inorganic + organic C) in
soil decreased in the order IMP>ICT>IP>NSB. We use our
findings to estimate that amount of possible inorganic and
total C sequestration if irrigated agriculture were expanded by
10%. If irrigated agricultural land were expanded by 10%
worldwide and NSB were converted to IMP, a possible 1.60
x 108 Mg inorganic C (2.78% of the total C emitted in the
next 30 years) could be sequestered in soil. If irrigated agricultural
land were expanded by 10% worldwide and NSB were
converted to ICT, a possible 1.10 x 109 Mg inorganic C
(1.87% of the total C emitted in the next 30 years) could be
sequestered in soil. If irrigated agricultural land were expanded
worldwide and NSB were converted to IP, a possible gain of
2.6 x 108 Mg inorganic C (0.04% of the total C emitted in the
next 30 years) could be sequestered in soils. Inorganic C sequestered
from land-use changes have little potential to make
a significant impact on the concentration of atmospheric CO2.
However, when coupled with organic C and altering land use
to produce crops on high-output irrigated agriculture while
selected less productive rain-fed agricultural land was returned
to temperate forest or native grassland, there could be
reductions in atmospheric CO2
Managing soil quality: Challenges in modern agriculture
Get PDFThe editors of this book, P. Schjonning, S.
Elmholt, and B.T. Christensen, have succeeded in
compiling perhaps the most focused technically
based book on soil quality published to date. The
chapters they have brought together are predominately
the work of European, Australian, and Canadian
authors who, to a greater degree than in previous
texts, have taken a data-based analytical
approach to concept demonstration and testing.
This is refreshing for a topic that has been largely
dominated in the American literature by philosophical
semantics and institutional proselytizing,
more often than not in the absence of specific data
collected or applied to the proposed conceptual
framework. Even the nonempirical opening and
closing chapters by Schjonning et al., which are intentionally
philosophical, consider some new conceptual
refinements and are at least somewhat open
to the possibility that critiques of the soil quality
concept offered to date have merit worth pondering.
Nevertheless, as one of us communicated to
Per Schjonning during the preparation of the
book, we feel an opportunity was missed by failing
to include more objective assessments of the concept
directly from concept-skeptics. Although a
few chapters cite the existence of concept criticisms
superficially, none deal substantively with any
of the twenty or more specific technical reservations
about the soil quality concept that have been
specifically and repeatedly articulated in several
high-profile critiques in the literature. Fewer than
ten sentences in Schjonning et al.'s book deal with
these specific reservations, and none substantively
Some unique benefits with Sudangrass for improved U.S. #1 yields and size of Russet Burbank potato
Get PDFThree studies provided additional knowledge of
beneficial effects of sudangrass for yield and quality
increases of the Russet Burbank potato. Thro of these
studies showed significant 'increases of both U.S. #1 and
smooth tubers >280 g following green manures of sudangrass.
These sudangrass (HS-33) effects did not differ
from a sorghum-sudan hybrid (Trudan-8). When a sudangrass
green manure was compared with a fallow treatment,
results of the first study showed mean yield
increases of 36% for U.S. #1 tubers >280 g and yields of
a second study by 34% for U.S. #1 tubers. This same
sudangrass treatment outperformed green manures of
either Austrian winter pea, barley, or sweet corn by
increased U.S. #1 yields that ranged from 27% to 61%.
By several lines of evidence, these benefits were found
to extend beyond the effect of Verticillium suppression.
Soil N was significantly increased following green
manures of sudangrass, and these increases were in turn
negatively correlated with wilt incidence and positively
correlated with yields of both U.S. #1 tubers and tubers
>280 g. Additional benefits also included significant
increases of tuber grade percentages for marketable
tubers and of smooth tubers >280 g. Benefits from
sudangrass green manures beyond the effects of Verticillium
suppression became further evident following a
greenhouse study that involved field soil and sudangrass
that had been grown in the same field. This study corroborated both field experiments by showing increased
yields with green manures of sudangrass that approximated
5.5 t ha-1 dry wt. As with the field studies, these
yield benefits also extended beyond the effects of Verticillium
suppression and were closely associated with significant
increases of Fusarium equiseti, F. oxysporum,
and F. solani. Throughout all studies, sudangrass green
manures significantly increased microbial activities with
increased populations of Fusarium spp. and increased
concentrations in soil of mineralizable N, organic P, K,
Mn, along with the percent soil organic matter — all factors
that could have contributed to significant increases
of yield and quality
Optimizing phosphorus characterization in animal manures by solution phosphorus-31 nuclear magnetic resonance spectroscopy
Get PDFA procedure involving alkaline extraction and solution 31P nuclear
magnetic resonance (NMR) spectroscopy was developed and optimized
for the characterization of P in animal manures (broiler, swine,
beef cattle). Inclusion of ethylenediaminetetraacetic acid (EDTA) in
the alkaline extraction solution recovered between 82 and 97% of
the total P from the three manures, which represented a significant
improvement on recovery in NaOH alone. Low concentrations of
paramagnetic ions in all manure extracts meant that relatively long
delay times (>5 s) were required for quantitative analysis by solution
31P NMR spectroscopy. The manures contained inorganic orthophosphate,
orthophosphate monoesters, orthophosphate diesters, and inorganic
polyphosphates, but results were markedly influenced by the
concentration of NaOH in the extractant, which affected both spectral
resolution and the apparent P composition of the extracts. For example,
extraction of swine manure and broiler litter with 0.5 M NaOH +
50 mM EDTA produced remarkable spectral resolution that allowed
accurate quantification of the four signals from phytic acid, the major
organic P compound in these manures. In contrast, more dilute NaOH
concentrations produced considerable line broadening that obscured
individual signals in the orthophosphate monoester region of the
spectra. Spectral resolution of cattle manure extracts was relatively
unaffected by NaOH concentration. Improvements in spectral resolution
of more concentrated NaOH extracts were, however, compromised
by the disappearance of phospholipids and inorganic polyphosphates,
notably in swine and cattle manure extracts, which indicated
either degradation or a change in solubility. The optimum extraction
conditions will therefore vary depending on the manure type and the
objectives of the study. Phytic acid can be accurately quantified in
swine manure and broiler litter by extraction with 0.5 M NaOH +
50 mM EDTA, while a more dilute NaOH concentration should be
used for complete P characterization or comparison among different
manure types
Elemental uptake in relation to root characteristics of tall fescue
Get PDFHiMag, an accession of tall fescue (Festuca arundinacea Schreb.), was
selected for high magnesium (Mg) concentration in leaves to reduce
grass tetany risk to ruminants. However, the mechanism for enhanced
Mg uptake in HiMag leaves has not been determined. The objective
was to investigate if increased Mg uptake in HiMag could be explained
by differences in elemental distribution among plant parts, root
characteristics, or organic acid concentrations compared to its
parental cultivars, "Kentucky 31" (KY31) and "Missouri 96"
(M096). The study was conducted on a surface-irrigated calcareous
Portneuf silt loam (coarse-silty, mixed, mesic, Durinodic Xeric
Haplocalcid). Vegetation and soil cores of 7.6-cm diameter were
sampled to a 45-cm soil depth in 15-cm increments. Mass and ash were
determined for leaves, crowns, and roots. Leaf area, root length, root
area, root length density, elemental concentration, and uptake
[potassium (K), calcium (Ca), Mg, sodium (Na), and phosphorus
(P)], and malate and citrate concentrations also were determined. Leaf
Mg concentration was higher in HiMag than parental cultivars.
HiMag generally did not differ in crown and root elemental
concentrations from its parents. Risk of causing grass tetany,
indicated by leaf Ki(Ca + Mg), was lower in HiMag than KY31 and
M096 in both 1994 (P = 0.03) and 1995 (P= 0.01). Root length, area,
and mass were not related to cation concentrations in the three tall
fescue accessions, suggesting that HiMag may have an active uptake
or transport mechanism for Mg