Estimation of soil strength properties for critical rooting conditions

Methods to aid in the large-scale testing and characterization of Coastal Plain soils based on their susceptibility to root-limiting strength problems were developed and analyzed. They were basically regression equations modeled after a Taylor series expansion. The equations relate changes of soil strength, bulk density and soil water content between field and “critical rooting conditions”. Once equations wered eveloped from a data set of 426 laboratory samples, critical rooting bulk density was predicted for a separate set of laboratory and field samples. All laboratory samples and appropriate field samples were equilibrated at — 100 kPa soil-water potential. Soils used were sandy Ultisols, which may limit the scope of equations.

In many cases, changes in the water contents were not a significant factor in the prediction of soil strength. This may be a reflection of the limited capabilities of the equations, the uniform equilibration of soil-water potential of the soils, or the fact that the slope of the strength vs. bulk density curve is independent of water content over the range of samples considered. Nevertheless, it does simplify the equations and may suggest that a series of several equations for different soil types would be better than a single equation that requires soil-water content.     

Cotton management in a compacted subsurface microirrigated coastal plain soil of the southeastern US

A loamy sand Acrisol (Aquic Hapludult) that had been microirrigated for 6 years became so severely compacted that it had root limiting values of soil cone index in the Ap horizon and a genetic hardpan below it. Deep and surface tillage systems were evaluated for their ability to alleviate compaction. Deep tillage included subsoiling or none. Both deep tillage treatments were also surface tilled by disking, chiseling, or not tilling. Subsoiling was located in row or between rows to avoid microirrigation tubes (laterals) that were buried under every other mid row or every row. Cotton (Gossypium hirsutum) was planted in 0.96-m wide rows. Cotton yield was improved by irrigation from 485 to 1022 kg ha⁻¹ because both 2001 and 2002 were dry years. Tillage loosened the soil by an average of 0.5–1.3 MPa; but compacted zones remained outside tilled areas. Subsoiling improved yield by 131 kg ha⁻¹ when performed in row where laterals were placed in the mid rows; but subsoiling did not improve yield when it was performed in mid rows. For subsurface irrigation management in these soils, the treatment with laterals buried under every other mid row was able to accommodate in-row subsoiling which improved yield; and this treatment was just as productive as and had been shown to be less expensive to install than burying laterals under every row.     

The effect of texture on strength of southeastern coastal plain soils

The effect of texture on soil strength was analyzed for 17 soils, mainly from the Southeastern Coastal Plains. All samples were tested with a 5-mm, flat-tipped probe after equilibration at 100 kPa of soil-water tension. Both mechanical compression and water consolidation (compaction by wetting and drying) were used to compact the soils. Probe resistance of water-consolidated samples was significantly affected by texture. In fact, bulk density or probe resistance of soils compacted by methods of constant compactive force or constant methodology correlated well with texture for Coastal Plain soils.

A secondary effect of texture involved a significant, positive correlation of silt with probe resistance for sandy soils low in organic matter. Bulk densities at root-restricting conditions (2 MPa) compared well with bulk density values obtained by water consolidation and the Random Packing Model of Gupta and Larson, all of which were significantly correlated to texture.     

A prospective comparison between stabilized glutaraldehyde and chlorhexidine gluconate for preoperative skin antisepsis in dogs

OBJECTIVE: To compare the efficacy of 0.3% stabilized glutaraldehyde and alcohol (SG+A), 0.3% SG and water (SG+W), and 4% chlorhexidine gluconate tincture (CG+A), as skin disinfectants in dogs undergoing ovariohysterectomy. STUDY DESIGN: Prospective, blinded clinical study. ANIMALS: One hundred and twenty-one dogs. METHODS: Cutaneous bacterial colony forming units (CFU) from the perioperative site after skin preparation, after antisepsis, and after surgery (incisional and paramedian), were quantified. The influence of high initial bacterial counts (> or =150 CFU) and surgical time on antibacterial efficacy was examined and the proportion of dogs from which Staphylococcus intermedius was cultured, determined. Perioperative skin reactions and wound infections were documented. RESULTS: All 3 antiseptic solutions significantly and equally reduced CFU to all post-antisepsis sampling levels irrespective of surgical duration (mean surgical times 151.6, 136.2, and 149.6 minutes for CG+A, SG+A and SG+W, respectively). Median percentage reductions in CFU ranged between 99.3% and 100%. In dogs with initial high counts and disinfected with CG+A and SG+W, the incisional samples had significantly higher counts than the post-antisepsis samples. In the CG+A and SG+W groups, the proportion of post-surgery samples yielding S. intermedius was significantly higher at the incisional than the paramedian sites. Eight mild cutaneous reactions were recorded in equal proportions for the 3 solutions. There were no recorded infections. CONCLUSIONS: All 3 preparations had an equal ability to reduce and maintain low CFU counts, with minimal cutaneous reactions. CLINICAL RELEVANCE: SG solutions are safe and effective preoperative skin antiseptics for elective clean-contaminated surgical procedures.     

What is your diagnosis? Shoulder mass in a dog with lameness

Abstract: An adult castrated male Golden Retriever of unknown age was presented with a history of weight loss and progressive left thoracic limb lameness. On physical examination, a solid mass was palpated on the left scapula that had areas of lysis on radiographs and an area of cortical bone loss on ultrasound. Hepatomegaly, abdominal distension, and numerous intra‐abdominal soft tissue masses were also found. Fine‐needle aspirates of the scapula and several abdominal masses contained numerous free nuclei mixed with fewer individualized, intact cells that were round in shape and rarely formed small sheets. The cells had high nuclear to cytoplasmic ratios, central nuclei, coarsely stippled chromatin, 1–2 prominent nucleoli, and basophilic cytoplasm with indistinct cell borders. The cytopathologic interpretation was neuroendocrine neoplasia, either metastatic or multicentric. The dog was subsequently euthanized and based on gross and histologic findings at necropsy, a diagnosis of pheochromocytoma with multiple metastases was made. The neoplastic cells stained positive with Grimelius stain and were immunoreactive for synaptophysin and chromogranin A. Pheochromocytomas are rare tumors in dogs and uncommonly undergo distant metastasis, especially to bone.     

Field application of PAM as an amendment in deep-tilled US southeastern coastal plain soils

In sandy soils of the southeastern USA coastal plains, crop production is limited by low water holding capacity and compacted soil layers that reduce root growth and productivity. Polyacrylamide (PAM) was added to sandy coastal plain soils to improve physical properties and yield. Soils were amended with linear and cross-linked PAMs. Treatments and controls included the following: (1) spraying a 600 mg kg⁻¹ solution of linear PAM behind a subsoil shank at a rate of 3.93 kg ha⁻¹, (2) spraying a 100 mg kg⁻¹ solution at 0.66 kg ha⁻¹, (3) spraying only water at 13.1 m³ ha⁻¹, (4) dropping a dry PAM powder formulation (3005 KB) behind a subsoil shank at 300 kg ha⁻¹, (5) dropping another dry PAM powder formulation (3005 K2) at 230 kg ha⁻¹, (6) dropping a dry PAM powder formulation 3005 K2 at a lower rate of 55 kg ha⁻¹, (7) applying nothing behind a subsoil shank, and (8) not subsoiling. In each of the 3 years of the experiment, new sets of treatments were set up while the old ones were maintained to look at longevity of the PAM effect. Though treatment effects were dominated by the tillage, the cross-linked PAMs were the only treatments more effective than tillage alone. The cross-linked PAMs may have been more effective because we could add more in dry form than in the spray form. The effect diminished with time similar to or faster than the results seen in tillage only. Though some PAM applications may have reduced cone indices, yields were not affected.     

Severe gastric impaction secondary to a gastric polyp in a horse

A 13-year-old Percheron gelding was presented for refractory gastric impaction. At necropsy a pedunculated 10 cm × 11 cm × 14 cm mass, histologically identified as an inflammatory polyp, was suspected to have been partly obstructing the pylorus. This is the first report of a polyp resulting in gastric outflow obstruction in a horse.