Effect of tillage and furrow irrigation timing on efficiency of preplant irrigation

Summary A field study to determine the efficiency of preplant irrigating with furrow irrigation and the effects of tillage and fall or spring application of preplant irrigation on this efficiency was conducted during 1983, 1984, and 1985 at the Texas Agricultural Experiment Station, North Plains Research Field at Etter, Texas on a Sherm, silty clay loam soil. Sorghum residue from the previous crop was shredded, gravimetric soil samples were taken, and five tillage treatments were imposed in the fall. The tillage treatments consisted of various combinations of disking, chiselling, moldboard plowing, and disk bedding. A preplant irrigation was applied in the fall to half of each tillage plot and in the spring to the other half of each plot. Soil samples were taken from each plot one month after the spring preplant irrigation. Sorghum (Sorghum bicolor L. cv. NC 178) was planted and irrigated similarly on all plots during the growing season. On the average, 237 mm of water were required to irrigate the tillage treatments during fall preplant irrigation and 466 mm were required during spring preplant irrigation. The additional water requirement in the spring was associated with increased water uptake by non-wheel-track furrows. Treatments with chiselling required larger water application during spring preplant irrigation. All treatments had similar soil water contents at planting time. Neither timing of preplant irrigation nor type of tillage had any effect on sorghum grain yield. Therefore, fall preplant irrigation was considerably more efficient than spring preplant irrigation. Averaged over the three years do study and five tillage treatments storage efficiency was 26% for fall application and 17% for springtime.Contribution of the Texas Agricultural Experiment Station, Paper No. 21724     

Prediction of phytotoxicity and uptake of metals by models in proposed USEPA 40 CFR part 503 sludge regulations: Comparison with field data for corn and wheat

The United States Environmental Protection Agency (USEPA) has recently (February 6, 1989) proposed the 40 CFR Part 503 regulations which govern sludge use and disposal. The numerical limits on cumulative soil metal loading rates in these regulations were generated through risk assessment analysis based on modeling metal flux through several terrestrial pathways. Field data from a 6300 ha dedicated land application site operated by the Metropolitan Water Reclamation District of Greater Chicago (District) since 1972 indicate that these pathway models do a poor job of predicting bioaccumulation of Cd, Cu, and Zn in corn leaf and grain and wheat grain tissue. The USEPA pathway model does not take soil pH into account and predicts that plant tissue concentration will be linearly related to metal loading rates in soil. District field data indicate that crop tissue metal concentrations are dependent on soil pH and increase at low metal loadings but then become independent of total metal loading rate. No phytotoxicity was observed in corn or wheat despite soil loading rates for Cr, Cu, Ni, and Zn that were 13, 28, 3, and 16 times higher than their respective phytotoxic thresholds predicted by the USEPA pathway model.

     

Husbandry and husbandry-related diseases of ornamental fish.

With the continued popularity of fish as pets, a market can be established for veterinarians with experience with aquatic animals. Fish owners often form a strong and significant emotional, as well as economic, bond with their aquariums or ponds. With proper husbandry, common mistakes made by fish owners can be treated, if not avoided. Diagnosis and treatment of a majority of common fish problems can be facilitated through an understanding of proper saltwater and freshwater fish husbandry.     

Dacryocystomaxillorhinostomy for chronic dacryocystitis in a dog

A 10-year-old female spayed Vizsla had intermittent mucoid ocular discharge from the right eye for 7 years. History, clinical findings, imaging studies, and culture and histopathology results confirmed chronic dacryocystitis with granuloma. A dacryocystomaxillorhinostomy was performed to preserve the functional portions of the nasolacrimal system remaining in this patient, as well as to promote healing of the lacrimal sac granuloma and secondary infection. Complete resolution of the clinical abnormalities was achieved, and the dog remains healthy 3 years postoperatively.     

Detection of Leptospira interrogans DNA and antigen in fixed equine eyes affected with end-stage equine recurrent uveitis.

Equine recurrent uveitis (ERU) is the most frequent cause of blindness in horses worldwide. Leptospira has been implicated as an etiologic agent in some cases of ERU and has been detected in fresh ocular tissues of affected horses. The objective of this study was to determine the presence of Leptospira antigen and DNA in fixed equine ocular tissues affected with end-stage ERU. Sections of eyes from 30 horses were obtained. Controls included 1) 10 normal equine eyes and 2) 10 equine eyes with a nonrecurrent form of uveitis. The experimental group consisted of 10 eyes diagnosed with ERU based on clinical signs and histologic lesions. Sections were subjected to immunohistochemical staining with an array of rabbit anti-Leptospira polyclonal antibodies. DNA extractions were performed by using a commercial kit designed for fixed tissue. Real-time PCR analysis was completed on extracted DNA. The target sequence for PCR was designed from alignments of available Leptospira 16S rDNA partial sequences obtained from GenBank. Two of 10 test samples were positive for Leptospira antigen by immunohistochemical assay. Zero of 20 controls were positive for Leptospira antigen. All test samples and controls were negative for Leptospira DNA by real-time PCR analysis. Leptospira was detected at a lower frequency than that previously reported for fresh ERU-affected aqueous humor and vitreous samples. Leptospira is not frequently detectable in fixed ocular tissues of horses affected with ERU when using traditional immunohistochemical and real-time PCR techniques.     

Uveal schwannoma in a brown‐eyed dog

An eleven‐year‐old, female spayed Boxer dog was diagnosed with a uveal schwannoma (formerly known as the spindle cell tumor of the blue‐eyed dog or SCTBED) despite having a uniformly brown iris. The patient presented to emergency for ocular discomfort, and the right globe was subsequently enucleated due to glaucoma and submitted for histopathology. Upon histopathologic evaluation, a uveal schwannoma was diagnosed and confirmed with immunohistochemical staining. Complete metastatic evaluation 1 and 6 months after initial presentation did not reveal evidence of metastasis, and the dog remains systemically healthy. This case represents a unique variant of uveal schwannoma and is relevant because although the vast majority of these tumors occur in blue‐eyed dogs, clinicians should not completely rule out this tumor as a differential based on the iris color.