378 research outputs found
CQESTR Simulation of Management Practice Effects on Long-Term Soil Organic Carbon
Management of soil organic matter (SOM) is important for soil productivity and responsible utilization of crop residues for additional uses. CQESTR, pronounced “sequester,” a contraction of “C sequestration” (meaning C storage), is a C balance model that relates organic residue additions, crop management, and soil tillage to SOM accretion or loss. Our objective was to simulate SOM changes in agricultural soils under a range of climate and management systems using the CQESTR model. Four long-term experiments (Champaign, IL, \u3e100 yr; Columbia, MO, \u3e100 yr; Lincoln, NE, 20 yr; Sidney, NE, 20 yr) in the United States under various crop rotations, tillage practices, organic amendments, and crop residue removal treatments were selected for their documented history of the long-term effects of management practice on SOM dynamics. CQESTR successfully simulated a substantial decline in SOM with 50 yr of crop residue removal under various rotations at Columbia and Champaign. The increase in SOM following addition of manure was simulated well; however, the model underestimated SOM for a fertilized treatment at Columbia. Predicted and observed values from the four sites were signifi cantly related (r2 = 0.94, n = 113, P \u3c 0.001), with slope not signifi cantly different from 1. Given the high correlation of simulated and observed SOM changes, CQESTR can be used as a reliable tool to predict SOM changes from management practices and offers the potential for estimating soil C storage required for C credits. It can also be an important tool to estimate the impacts of crop residue removal for bioenergy production on SOM level and soil production capacity
On the Structure of the Fusion Ideal
We prove that there is a finite level-independent bound on the number of
relations defining the fusion ring of positive energy representations of the
loop group of a simple, simply connected Lie group. As an illustration, we
compute the fusion ring of at all levels
Wheat Straw Decomposition in the Field
Wheat (Triticum aestivium) varieties 'Nugaines' and 'Lemhi'
were grown on Portneuf silt loam soil with three nitrogen and
three irrigation treatments in 1967. After harvest, 84 kg N/ha
was applied to half of each plot before plowing. Uniform
straw samples were enclosed in fiberglass cloth bags and
buried in the plots September 7. The straw placed in N-treated
plots received sufficient N in solution to increase the straw N
from about 0.29 to 1.5%. Straw samples were recovered November
15, after the soil had cooled below 4C, and at three
later sampling dates to October 3, 1968, after a bean crop
(Phaseolus spp.) was harvested. Weight loss and total N were
determined on all samplings and total C on the first sampling.
Decomposition was greater with N than without it for the
November sampling and the March sampling for Nugaines but
not at other samplings for both varieties. The weight of N in
both N-treated straw varieties decreased 55% by November 15,
while in the non-N-treated Nugaines and Lemhi straw, N
weight increased 12 and 32%, respectively, by March 22. Later,
N moved out of all the straw samples when the N percentages
were much lower than the theoretical equilibrium value
Microbiological Quality of Surface Drainage Water from Three Small Irrigated Watersheds in Southern Idaho
The irrigation waters applied to and the surface drainage waters
leaving three small watersheds in southern Idaho were analyzed for
coliforms and other microorganisms and for biochemical oxygen
demand (BOD). Numbers of coliforms and fecal coliforms tended
to be greater in the drainage than in the irrigation water, but the
differences were generally within the confidence limits for Most
Probable Numbers analyses. Fecal streptococci numbers were higher
in the drainage than in the irrigation water on two of the three
small watersheds. The numbers of fecal streptococci and microorganisms
incubated at 20C were higher in the drainage than the
irrigation water; otherwise, the bacteriological quality of the irrigation
water was not significantly changed by irrigation use. BOD in
the drainage water samples averaged 4 mg/liter oxygen demand
compared with 2 mg/liter oxygen demand in the irrigation water
Influence of Residual Nitrogen on Wheat Straw Decomposition in the Field
Plant material decomposition appears to be
mainly controlled by the C/N ratio of the plant
material under soil moisture, temperature, and
aeration conditions that support plant growth
in the field. Harmsen and VanSchreven (4) reported,
"Numerous earlier papers were devoted
to the study of this problem .... Fairly
close agreement was obtained by all these investigators
as to the N content limits of the
added material, below which no N mineralization
may be expected. This is 1.5 to 2.0 per
cent of the dry matter, corresponding to a C/N
ratio of 20 to 25." Similar values were also
reported by Broadbent (2) from laboratory
studies; and Allison (1), in a recent review,
cited several reports that are in general agreement
The relationship of particle size and nitrogen content to decomposition of wheat straw in soil
Straw samples of different particle size and N content
were selected from three spring wheat (Triticum aestivum)
varieties; added to Walla Walla, Palouse, and Portneuf silt
loam soils at 0.5 and 2.0% rates; and incubated. At the 0.5%
addition rate, straw samples containing 0.2 to 0.7% N decomposed
at the same rate. When 2.0% straw was added to
soil, the decomposition rates increased with increasing N
percentage. The N- supplying capacity of the soil apparently
influenced decomposition at the higher straw rates. After
incubation, considerable nitrate was found in the soil with 0.5%
straw but little was found in the soil with 2.0% straw. Different
particle sizes of straw with the same N contents decomposed
at approximately the same rate. Soil nitrate concentrations
were lower for each successively smaller straw particle size
after incubation
Influence of Silica and Nitrogen Contents and Straw Application Rate on Decomposition of Gaines Wheat Straw in Soil
'Gaines' and 'Nugaines' varieties of soft
white winter wheat (Triticum aestivum)
yield straw ranging up to about 7 tons per
acre (2). Growing row crops such as dry edible
beans (Phaseolus vulgaris) or sugarbeets (Beta
vulgaris) following such heavy straw production
poses special management problems. Straw
layers that result from plowing down a large
amount of straw may result in reduced bean
yields (supposedly because of nitrogen immobilization),
abnormal sugarbeet root growth,
and tillage and water movement problems.
Much of the tremendous acreage of the irrigated
wheat grown in the Pacific Northwest
is in rotation with sugarbeets, potatoes, beans
and other crops. Therefore, straw residue
management is a major problem with great
economic implications
Families index theorem in supersymmetric WZW model and twisted K-theory: The SU(2) case
The construction of twisted K-theory classes on a compact Lie group is
reviewed using the supersymmetric Wess-Zumino-Witten model on a cylinder. The
Quillen superconnection is introduced for a family of supercharges parametrized
by a compact Lie group and the Chern character is explicitly computed in the
case of SU(2). For large euclidean time, the character form is localized on a
D-brane.Comment: Version 2: Essentially simplified proof of the main result using a
map from twisted K-theory to gerbes modulo the twisting gerbe; references
added + minor correction
Microbiological Quality of Subsurface Drainage Water From Irrigated Agricultural Land
Irrigation and subsurface drainage waters sampled from an
82,150-hectare (203,000-acre) irrigation district in southern Idaho
were evaluated for bacteriological quality. The soils in the district
are wind deposited over fractured basalt, calcareous, and have a pH
near 7.8. Drainage, where needed, is provided by horizontally
mined tunnels or by tile drains connecting shallow relief wells that
flow the year around. For the 12 months ending September 30,
1969, a 2-meter (6.5-foot) depth of water for the entire irrigation
tract was diverted, and 50% of the water passed through the soil
becoming subsurface drainage. The irrigation water and seven subsurface
drains were sampled at 2-week intervals during the summer
of 1969. Coliform, fecal streptococci, starch hydrolyzers, and
bacteria able to grow at temperatures from 0 to 55C were counted.
The diverted irrigation water contained from 140 to 3,300 coliform
per 100 ml, but 86% of the subsurface drainage samples contained
5 or fewer conforms per 100 ml. Numbers of other microorganisms
were also low in the drainage waters. The outflow samples were
oxygen saturated and the temperatures were 13.0 ± 1.1C for all
samples. Percolation through the soil improved the water quality
almost to domestic water standards
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