Nitrous oxide emissions from a bermudagrass pasture: Interseeded winter rye and poultry litter

Adequate use of manure in grasslands may constitute an economical means of manure disposal and an abundant source of nutrients for plants; however, excessive nitrogen (N) additions to these soils could create new environmental risks such as increasing nitrous oxide (N₂O) emissions. These potentially adverse effects in grasslands may be mitigated by improved management practices. In pasture systems, the combined effects of poultry litter applications and interseeded rye (Secale cereale L.) on N₂O emissions are still not well established. This study was conducted to estimate the magnitude of soil surface N₂O fluxes as affected by interseeded winter rye forage, annually spring-applied composted turkey litter as well as by weather and soil parameters. Fluxes were measured by vented chambers during 2 yr in a bermudagrass (Cynodon dactylon [L.] Pers.) pasture in moderately well-drained Tonti gravelly silt loam (fine-loamy, active, mesic Typic Fragiudault) located in northwestern Arkansas, USA. During the 60 d following turkey litter applications, N₂O fluxes were frequently well correlated with soil nitrate (NO₃⁻; r: up to 0.82, P's < 0.05) implying substrate stimulation on soil N₂O production. Likewise, rainfall patterns strongly influenced N₂O fluxes. Large rainfalls of 91 and 32 mm occurred within 6 d prior to the maximum N₂O flux means (263 and 290 μg N m⁻² h⁻¹, respectively). Treatment effects on N₂O emissions were significant only in spring periods following manure addition, particularly in the second year of our study. In the spring of 2000, additions of composted turkey litter resulted in 1.5-fold increase in seasonal cumulative N₂O emissions (P = 0.04) which was directly associated to a numerically greater soil NO₃⁻. In the spring of 2001, soils planted to rye exhibited a pronounced significant effect on mitigating N₂O emissions (30 vs. 112 mg N m⁻²; P = 0.04). During the winter and early spring, rye growth also decreased quantities of both soil NO₃⁻ and water-filled pore space (WFPS) partly accounting for the lower N₂O emissions in these fields. These results suggest that because poultry litter additions increased and interseeded rye diminished N₂O emissions, the combined implementation of both management practices can produce environmental benefits while sustaining productivity in temperate pasture systems.     

Variability of light interception and radiation use efficiency in maize and soybean

Variability of light interception and its derivatives are poorly understood at the field-scale in maize (Zea mays L.) and soybean [Glyine max (L.) Merr.]. Quantifying variability can provide reliable estimates of field-scale processes and reliable methodology. A field study was conducted during the 2005 growing season in a 31 ha maize and 23 ha soybean field rotated annually near Ames, IA to measure variability of cumulatively intercepted photosynthetically active radiation (CI-PAR) and radiation use efficiency (RUE) by deploying eight line quantum sensors in each field. Cumulative mean PAR interception for soybean was 575 MJ m⁻² ending on day of the year (DOY) 249 compared with 687 MJ m⁻² in maize ending on DOY 244. Soybean standard error (s_X) for a single sensor was 4.48% and with six sensors was 1.83% of the final CI-PAR. Maize s_X for a single sensor was 5.29% and with eight sensors was 1.87% of the final CI-PAR. Crop biomass was quantified weekly by collecting four 1 m² samples. Soybean RUE using all sensors was 1.44 ± 0.06 g MJ PAR⁻¹. The highest CI-PAR from a single sensor had RUE of 1.32 and the lowest was 1.55 g MJ PAR⁻¹. Maize RUE using all sensors was 3.35 ± 0.09. The highest CI-PAR from a single sensor had RUE of 2.87 and the lowest was 3.70 g MJ PAR⁻¹. Reliable transmitted PAR and RUE estimates are obtainable at the field-scale in maize and soybean with four and three sensors, respectively, assuming that crop biomass is accurately measured.     

Estrus Synchronization in Sheep and Goats Using Combinations of GnRH,Progestagen and Prostaglandin F2α

The objective of this experiment was to evaluate the effect of GnRH, progestagen and prostaglandin F_2α on estrus synchronization in sheep and goats. Sixty Awassi ewes and 53 Damascus does were used in the study. The experiment started at the beginning of the breeding season (June/July). The same treatments were applied to sheep and goats as follows: no treatment (CON), 14‐day progestagen sponges and 600 IU equine chorionic gonadotropin (S), gonadotropin releasing hormone followed 5 days later by prostaglandin F_2α (GP) and gonadotropin releasing hormone, progestagen sponges for 5 days and prostaglandin F_2α on the day of sponge removal (GSP). None of the ewes in the S group lambed from mating during the induced cycle. A greater lambing rate (p < 0.05) was observed in the GSP group compared with the CON and S groups while the GP group was intermediate. The number of lambs born per lambed ewe was similar among the CON, GP and GSP groups. However, the number of lambs per exposed ewe was greater (p < 0.05) in the GSP than the remaining groups. The induced cycle kidding rate was 77% for all treatments combined. Similar kidding rate were observed among treatments. The numbers of kids born per kidded and exposed doe from mating during the induced estrus were also similar among treatments. Greater numbers of multiple births were observed in the GP and GSP than in the S group. In conclusion, a combination of GnRH, progestagen sponges and PGF_2α can be effective in synchronizing estrus and improving fecundity in sheep and goats. Although the use of GnRH–PGF_2α was effective, the addition of progestagen sponges at the time of GnRH administration appeared to improve reproductive parameters.     

Podzol development with time in sandy beach deposits in southern Norway

The coastal areas of SE Norway provide suitable conditions for studying soil development with time, because unweathered land surfaces have continuously been raised above sea level by glacio‐isostatic uplift since the termination of the last ice age. We investigated Podzol development in a chronosequence of six soils on sandy beach deposits with ages ranging from 2,300 to 9,650 y at the W coast of the Oslofjord. The climate in this area is rather mild with a mean annual temperature of 6°C and an annual precipitation of 975 mm (Sandefjord). The youngest soil showed no evidence of podzolization, while slight lightening of the A horizon of the second soil (3,800 years) indicated initial leaching of organic matter (OM). In the 4,300 y–old soil also Fe and humus accumulation in the B horizon were perceptible, but only the 6,600 y–old and older soils exhibited spodic horizons. Accumulation of OM in the A horizons reached a steady state in <2,300 y, while in the B horizons OM accumulated at increasing rates. pH dropped from 6.6 (H₂O)/5.9 (KCl) in the recent beach sand to 4.5 (H₂O)/3.8 (KCl) within approx. 4,500 y (pH_H2O)/2,500 y (pH_KCl) and stayed constant thereafter, which was attributed to sesquioxide buffering. Base saturation showed an exponential decrease with time. Progressive weathering was reflected by increasing Fe_d and Al_d contents, and proceeding podzolization by increasing amounts of pyrophophate‐ and oxalate‐soluble Fe and Al with soil age. These increases could be best described for most Fe and Al fractions by exponential models. Only the increasing amounts of Fe_p could be better described by a power function and those of Fe_o by a linear model.     

The structure of the upper atmosphere of mars: In situ accelerometer measurements from mars global surveyor

The Mars Global Surveyor (MGS) z-axis accelerometer has obtained over 200 vertical structures of thermospheric density, temperature, and pressure, ranging from 110 to 170 kilometers, compared to only three previous such vertical structures. In November 1997, a regional dust storm in the Southern Hemisphere triggered an unexpectedly large thermospheric response at mid-northern latitudes, increasing the altitude of thermospheric pressure surfaces there by as much as 8 kilometers and indicating a strong global thermospheric response to a regional dust storm. Throughout the MGS mission, thermospheric density bulges have been detected on opposite sides of the planet near 90 degreesE and 90 degreesW, in the vicinity of maximum terrain heights. This wave 2 pattern may be caused by topographically-forced planetary waves propagating up from the lower atmosphere.     

Linking winter and summer events in a migratory bird by using stable-carbon isotopes

For migratory birds, early arrival and physical condition on the breeding grounds are important determinants of reproductive success and fitness. Differences in arrival times often exceed a month, and later arriving individuals are often in poorer condition. Habitat-specific isotopic signatures indicate that the quality of winter habitats occupied by American redstarts (Setophaga ruticilla) determines their physical condition and spring departure dates, which in turn result in variable arrival schedules and condition on temperate breeding grounds. These findings link events in tropical winter grounds with those in temperate breeding areas for a migratory songbird and provide evidence that winter habitats may be limiting.     

A REVIEW OF HIGH RESOLUTION COMPUTED TOMOGRAPHY AND A PROPOSED TECHNIQUE FOR REGIONAL EXAMINATION OF THE CANINE LUMBOSACRAL SPINE

High resolution computed tomography (CT) is a noninvasive imaging modality that has been used extensively in evaluating diseases of the human lumbosacral spine. Excellent spatial and contrast resolution, combined with multiplanar reformatting capability make high resolution CT scanners well-suited for similar applications in dogs. Consistently good quality images can be obtained when careful attention is given to factors affecting resolution. This paper reviews and illustrates some principles of high resolution CT, and proposes a technique for regional CT examination of the canine lumbosacral spine.     

15N-leucine and 15N-isoleucine isotope dilution techniques versus the 15N-isotope dilution technique for determining the recovery of endogenous protein and amino acids in digesta collected from the distal ileum in pigs.

Twelve gilts, with an average initial BW of 38 kg, were fitted with simple T-cannulas at the distal ileum and two catheters in the external jugular veins. The animals were fed twice daily (0800 and 2000) 700 g of one of four diets containing either soybean meal, canola meal, wheat, or barley as the sole protein source. 15N-leucine was infused continuously for 9 d at a rate of 40 mg/kg of BW daily via one of the jugular catheters. Blood samples were taken during feeding. Ileal digesta samples were collected continuously for 24 h on d 7 and 9 of the infusion period. 15N-enrichment excess in leucine and isoleucine in the trichloroacetic acid (TCA)-soluble fraction of blood and in digesta were measured using single-ion monitoring gas chromatography-mass spectrometry. Assuming that the 15N-enrichment excess in leucine and isoleucine in the TCA-soluble fraction of the blood is similar to that in endogenous protein secreted into the digestive tract and that the amino acid composition of endogenous protein is constant, the contribution of endogenous to total protein in ileal digesta was calculated using the 15N-isotope dilution technique for leucine and isoleucine, respectively. These contributions were much smaller for the 15N-leucine than for the 15N-isoleucine isotope dilution technique: 7.1 to 11.0 vs 21.8 to 24.9 g of protein/kg of DM intake. The values obtained with the 15N-isoleucine isotope dilution technique were close to those obtained with the 15N-isotope dilution technique as described in a previous publication.     

MAGNETIC RESONANCE IMAGING—A GENERAL OVERVIEW OF PRINCIPLES AND EXAMPLES IN VETERINARY NEURODIAGNOSIS

Magnetic resonance imaging (MRI), a noninvasive technique that provides accurate, detailed, anatomic images, has had a major impact in the diagnosis of human disease. This technique is based upon the inherent magnetic properties of certain nuclei. Induction of the nuclei into a low energy state is achieved by placing them in a static magnetic field. The nuclei may then be excited into a high energy state by application of a radio frequency pulse. When the second field is stopped, the nuclei return to ground state and emit the absorbed energy in the form of a radio signal. This signal is received by a coil that generally surrounds the specimen and converted to an anatomic image through a process of computer-assisted reconstruction. Contrast is altered by applying the second pulse in different sequences (saturation recovery, inversion recovery, and spin echo) and using enhancing agents such as gadolinium. In this paper, we present an overview of the general principles of MRI and some clinical examples in dogs and cats with central nervous system disease.