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Site-specific management of pH-induced iron chlorosis of maize
Get PDFA study was conducted over nine site/years in Nebraska, USA between 2004 and 2005 to evaluate
the potential to predict chlorosis-prone areas within fields which are relatively stable in space
and time. The study also investigated the potential benefits of site-specific cultivar management
according to chlorosis pressure. Sites were mapped for soil apparent electrical conductivity (ECa)
at two depths (0-30 cm and 0-90 cm), and soil pH at a depth of 10 cm. Sites were also sampled by
hand on a regular grid to a depth of 20 cm and analyzed for a range of soil properties. Sites were
evaluated in-season with natural color and near-infrared imagery, and at the end of the season by
yield mapping. In all or a portion of each field, replicated paired strips of two maize cultivars were
planted, one considered susceptible to iron chlorosis (P34N42), another with similar characteristics
but tolerant to iron chlorosis (P34B99). Detailed evaluation of the ability to predict iron chlorosisprone
areas was conducted over 3 site/years. Management zones were delineated using combinations
of yield data, biCa and vegetation indices derived from aerial imagery. Across all locations, grid
sampled pH ranged from 6.1 to 9.1; on-the-go pH ranged from 4.9 to 9.2; shallow ECa ranged from
0.1 to 39 InSini: deep ECa ranged From 0.2 to 152 mS/rn. For one field, planted to maize one year
and soybean the next, two chlorosis management zones were consistently delineated both years,
with similar spatial relationships. For another field, soil water holding capacity was a larger yield
limiting factor than iron chlorosis and management zones for iron chlorosis could riot be delineated.
For 8 site/years where paired strips of chlorosis-prone or tolerant cultivars were planted, no distinct
advantage of site-specific maize cultivar management was found based on yield response of the
two cultivars evaluated. Generally P34B99 yields were superior to P34N42 regardless of the level
of chlorosis pressure. This study found spatial information on factors conducive to iron chlorosis
can be useful in delineating chlorosis-prone areas within fields_ However, other yield limiting
[-actors may confound delineation of zones strictly for chlorosis management. Successful spatial
cultivar selection for iron chlorosis management will require the use of cultivars with response
characteristics which differ more than those used in this study
The importance and challenge of modeling irrigation-induced erosion
Get PDFIrrigation-induced erosion and rain-induced erosion result from very different
systematics. Therefore, both cannot be predicted effectively using the same models. The
average two-fold yield and three-fold economic advantage of irrigation over rain-fed agriculture,
coupled with the fragility of irrigated land and the strategic importance of irrigation
development to meet world agricultural production needs, has raised the urgency for the
development of robust, accurate, and precise irrigation-induced erosion models. This paper
details the rationale for separate irrigation-induced erosion models, presents essential aspects
unique to irrigation that must be accounted for in the models, and summarizes the progress
(to date) toward the goal of irrigation-induced erosion model development
Management of irrigated agriculture to increase carbon storage
Get PDFFossil fuel burning at the present rate, will double atmospheric carbon dioxide (CO 2 ) in this
century, raising air temperature 1.5 to 5 °C. Sequestering carbon (C) in soil can reduce
atmospheric CO2 concentration. We measured inorganic and organic C in southern Idaho
soils having long term land use histories of native sagebrush vegetation (NSB), irrigated
moldboard plowed crops (IMP), irrigated conservation- (chisel) tilled crops (ICT) and
irrigated pasture systems (IP). Soil Organic C (SOC) decreased in the order
IP>ICT>NSB>IMP. We used our findings to estimate potential amounts of organic C
sequestered if irrigated agriculture expanded. If irrigated agricultural land was expanded
by10°/0 worldwide and NSB was converted to ICT, 2.5 x 10 9 Mg organic C (4.38 °A of the
total C emitted in the next 30 yr) could potentially be sequestered in soil. If irrigated
agricultural land were expanded by 10% worldwide and NSB were converted to IP, a possible
9.3 x 109 Mg organic C (16.32 % of the total C emitted in the next 30 yr) could be sequestered
in soil. Irrigated agriculture produces twice the yield compared to non-irrigated land.
Irrigation increases soil C relative to native semi arid or arid sites. Since irrigated agriculture
produces higher yields, less land area needs to be put into production compared to rainfed
agriculture. Altering land use to produce crops on high output irrigated agriculture, while
returning less-productive rainfed agricultural land to temperate forest or native grassland,
could further reduce atmospheric CO2 . Inorganic carbon increases with irrigation were less
consistent and much smaller than SOC. Irrigating these soils also increased microbial
biomass and changed microbial diversity
What aspect of dietary modification in broilers controls litter water-soluble phosphorus: Dietary phosphorus, phytase, or calcium?
Get PDFEnvironmental concerns about phosphorus (P) losses from animal
agriculture have led to interest in dietary strategies to reduce the concentration
and solubility of P in manures and litters. To address
the effects of dietary available phosphorus (AvP), calcium (Ca), and
phytase on P excretion in broilers, 18 dietary treatments were applied
in a randomized complete block design to each of four replicate pens
of 28 broilers from 18 to 42 d of age. Treatments consisted of three
levels of AvP (3.5, 3.0, and 2.5 g kg -1) combined with three levels of
Ca (8.0, 6.9, and 5.7 g kg-1) and two levels of phytase (0 and 600
phytase units [FTU]). Phytase was added at the expense of 1.0 g kg -1
P from dicalcium phosphate. Fresh litter was collected from pens
when the broilers were 41 d of age and analyzed for total P, soluble P,
and phytate P as well as P composition by 31P nuclear magnetic resonance
(NMR) spectroscopy. Results indicated that the inclusion of
phytase at the expense of inorganic P or reductions in AvP decreased
litter total P by 28 to 43%. Litter water-soluble P (WSP) decreased
by up to 73% with an increasing dietary Ca/AvP ratio, irrespective of
phytase addition. The ratio of WSP/total P in litter decreased as the
dietary Ca/AvP ratio increased and was greater in the phytase-amended
diets. This study indicated that while feeding reduced AvP
diets with phytase decreased litter total P, the ratio of Ca/AvP in the
diet was primarily responsible for effects on WSP. This is important
from an environmental perspective as the amount of WSP in litter
could be related to potential for off-site P losses following land application
of litter
Verticillium wilt in experimental sugar beet cultivars in Cassia County, ID, 2006
Get PDFExperimental sugar beet cultivars were evaluated in a commercial sprinkler-irrigated sugar beet field near Heyburn,
ID where winter wheat was grown in 2005. The field trial relied on natural infection of Verticillium dahliae. The plots were
planted on 28 Apr to a density of 142,560 seeds/A, and thinned to 47,520 plants/A on 15-20 Jun. Plots were four rows wide
(22-in. row spacing) and 34.5 ft long. The experimental design was a randomized complete block design with eight
replications per cultivar. The field was cultivated on 8 and 20 Jun. The crop was managed by the grower according to
standard cultural practices. The percentage of plants with leaves that had dead vein delimited sectors was recorded for the
center two rows on 6 Sep. The center two rows were harvested on 25-26 Sep with the aid of a mechanical topper and small
plot harvester. The sugar content of the beets was determined by the Amalgamated Sugar Co. laboratory, and recoverable
sugar was estimated. Data were analyzed using the general linear models procedure (Proc GLM-SAS), and Fisher's
protected least significant difference was used for mean comparisons.
Yields from this trial were below normal for this growing region. Cultivars varied significantly for Verticillium
dahliae symptoms and sugar content but no significant differences were recorded for root yield and estimated recoverable
sugar. Root shape and root hair proliferation indicated that Beet necrotic yellow vein virus (BNYVV) was also present in the
field although the foliar symptoms of this disease were not particularly evident. An interaction between BNYVV and V.
dahliae may have been present and interfered with establishing differences in root yield and recoverable sugar. Based on
Spearman's rank correlation coefficient, the means values for leaf symptoms did not correlate with those for root yield,
sugar, or estimated recoverable sugar (P = 0.3547, 0.6212, and 0.5765, respectively). Good resistance to V. dahliae exists in
some experimental cultivars based on the reduction in foliar symptoms.
Plant Diseas
Verticillium wilt in commercial sugar beet cultivars in Cassia County, ID, 2006
Get PDFCommercial sugar beet cultivars were evaluated in a commercial sprinkler-irrigated sugar beet field near Heyburn,
ID where winter wheat was grown in 2005. The field trial relied on natural infection of Verticillium dahliae. The plots were
planted on 28 Apr to a density of 142,560 seeds/A, and thinned to 47,520 plants/A on 15-20 Jun. Plots were four rows wide
(22-in. row spacing) and 34.5 ft long. The experimental design was a randomized complete block design with eight
replications per cultivar. The field was cultivated on 8 and 20 Jun. The crop was managed by the grower according to
standard cultural practices. The percentage of plants with leaves that had dead vein delimited sectors was recorded for the
center two rows on 6 Sep. The center two rows were harvested on 25-26 Sep with the aid of a mechanical topper and small
plot harvester. The sugar content of the beets was determined by the Amalgamated Sugar Co. laboratory, and recoverable
sugar was estimated. Data were analyzed using the general linear models procedure (Proc GLM-SAS), and Fisher's
protected least significant difference was used for mean comparisons.
Yields from this trial were below normal for the growing region. Cultivars varied significantly in their symptoms of
Verticillium wilt but no differences were recorded for any yield parameter. Root shape and root hair proliferation indicated
Beet necrotic yellow vein virus (BNYVV) was also present in the field although the foliar symptoms of this disease were not
particularly evident. An interaction between BNYVV and V. dahliae may have been present and interfered with establishing
differences in yield parameters. Based on Spearman's rank correlation coefficient, the means values for leaf symptoms did
not correlate with those for root yield, sugar, or estimated recoverable sugar (P = 0.9443, 0.7497, and 0.9548, respectively).
Good resistance to V. dahliae exists in some commercial cultivars based on the reduction in foliar symptoms
Influence of host resistance and insecticide seed treatments on curly top in sugar beets
Get PDFCurly top on sugar beets (Beta vulgaris) caused by Beet severe curly top virus or closely related
species is a considerable problem in arid growing regions of the western United States. Two
insecticide seed treatments, Poncho Beta (60 g a.i. clothianidin + 8 g a.i. beta-cyfluthrin/100,000
seed) and Gaucho (45 g a.i. imidacloprid/100,000 seed), and four sugar beet hybrids varying in
curly top resistance were evaluated for their influence on the control of curly top in comparison
with untreated checks. Plots were established at two locations in southern Idaho in 2005 and
evaluated for curly top. Moderate to severe curly top due to natural inoculum and leafhopper
infestations occurred at both locations. Untreated, the four hybrids performed as expected with
the fewest curly top symptoms on PM21 and the most on Monohikari. Both insecticide treatments
lowered curly top ratings compared with the untreated check, but Poncho Beta reduced
symptoms more than Gaucho as the season progressed. Poncho Beta led to increased yield and
estimated recoverable sugar across all hybrids at harvest, particularly on the more susceptible
hybrids. When considering the yield parameters for only the most resistant hybrids individually,
Poncho Beta did not always outperform Gaucho. Poncho Beta provided a level of control that
would justify its application as a supplement to host resistance under Idaho conditions
Use of time domain reflectometry for continuous monitoring of nitrate-nitrogen in soil and water
Get PDFNitrate-Nitrogen (NO3 -N) losses to ground and surface water are an environmental and agronomic concern in
modern crop production systems in the Central Great Plains. Monitoring techniques for nitrogen use in agricultural
production are needed to increase crop yield, optimize nitrogen use, and reduce NO 3 -N leaching. Time domain reflectometry
(TDR) could potentially be calibrated to continuously measure NO3 -N in soil and water. The objectives of this study were to:
(1) evaluate the effect of different factors affecting the response of the bulk electrical conductivity (ECb) sensed by TDR, (2)
compare the sensitivity and differences between vertically-installed and horizontally-installed probes for measuring NO3 -N
leaching in the soil profile, and (3) evaluate the feasibility of using TDR to measure changes in NO 3 -N concentration in an
irrigated agricultural soil. Studies were conducted in the laboratory and in the field at the University of Nebraska West
Central Research and Extension Center in North Platte, Nebraska. Temperature of the medium (Ts), solute concentration,
TDR cable length, and volumetric soil water content (O p) all influenced and were linearly related to the bulk electrical
conductivity (ECb) sensed by the TDR probes. In the field, measured soil NO3 -N correlated well with values estimated using
TDR measurements of ECb, corrected for changes in CC and Ts. These results indicated that TDR, if properly calibrated for
a particular soil, could be used to continuously monitor NO3-N in soil, and should also be well-suited for monitoring NO3-N
in groundwater and surface water. It is, however, important to perform the calibration over a long enough period of time to
include the expected range of 0v, Ts, and NO3-N values to obtain adequate accuracy
Sediment and phosphorus transport in irrigation furrows
Get PDFSediment and phosphorus (P) in agricultural runoff can impair
water quality in streams, lakes, and rivers. We studied the factors
affecting P transfer and transport in irrigated furrows in six freshly
tilled fallow fields, 110 to 180 m long with 0.007 to 0.012 m m' slopes
without the interference of raindrops or sheet flow that occur during
natural or simulated rain. The soil on all fields was Portneuf silt loam
(coarse-silty, mixed, superactive, mesic Durinodic Xeric Haplocalcids).
Flow rate, sediment concentration, and P concentrations were monitored
at four, equally spaced locations in each furrow. Flow rate decreased
with distance down the furrow as water infiltrated. Sediment
concentration varied with distance and time with no set pattern. Total
P concentrations related directly to sediment concentrations (r2 =
0.75) because typically >90% of the transported P was particulate P,
emphasizing the need to control erosion to reduce P loss. Dissolved
reactive phosphorus (DRP) concentrations decreased with time at a
specific furrow site but increased with distance down the furrow as
contact time with soil and suspended sediment increased. The DRP
concentration correlated better with sediment concentration than extractable
furrow soil P concentration. However, suspended sediment
concentration tended to not affect DRP concentration later in the irrigation
(>2 h). These results indicate that the effects of soil P can be
overshadowed by differences in flow hydraulics, suspended sediment
loads, and non-equilibrium conditions
Daily carbohydrate accumulation in eight tall fescue cultivars
Get PDFEight cultivars of tall fescue (Loliumarundinaceum Schreb., S.J. Darbyshire = Festuca arundinacea Schreb.), Barcel, Kenhy, Kentucky-31, Missouri-96, Mozark, Stargrazer, C-1 (an experimental selection), and HiMag, were sampled at 2-h intervals during daylight on four cutting dates. Cultivars varied in concentrations of carbohydrate fractions but accumulation rates were not different. Daily mean total non-structural carbohydrate (TNC) concentrations for cutting dates in May, July, August and September declined from 239 to 231, 143 and 120 g TNC kg−1 adjusted dry weight (ADW) respectively. Concentrations of fructans were highest in July but sucrose, glucose and starch concentrations were highest in May. Sucrose was the largest contributor proportionately to TNC daily means across accessions in May (0·33), August (0·30) and September (0·38). Glucose composed an equivalent proportion of TNC in the August harvest. Starch concentration was highest in May at 53 g kg−1 ADW and lowest in August at 23 g kg−1 ADW. The TNC concentration increased by 22·4 (May), 16·8 (July), 21·0 (August) and 30·8 g kg−1 ADW (September) from dawn to dusk. Forage samples taken to estimate preference by ruminants or for TNC analyses should be cut and preserved within 1 h to control the diurnal variation of TNC proportionately within 0·05. Tall fescue should generally be cut between noon and sunset for TNC concentrations to be greater than the daily mean