Residue management for reducing evaporation in relation to soil type and evaporativity1

Abstract. Usual residue-management options are to remove the residue, use it as mulch with or without undercutting or to incorporate it into the soil. While the role of surface mulch in evaporation has been widely studied, the information on the effect on evaporation of mulch with undercutting or residue incorporated into soil, particularly in relation to soil type and evaporativity (E_o) is lacking. We studied the effect of wheat straw used in various ways on the course of evaporation loss from soil columns with three soils at Ludhiana, India and one soil at Bushland, Texas, USA, under two E_o's Energy-limited evaporation rates under mulch (E_om) followed the soil-specific relation E_om/E_o= a e^(bRes+cEo), where Res is residue rate t/ha and a, b and c are constants; E_o, is expressed in mm/d. In an effort to model the total evaporation (CE) during the energy-limited stage ‘U’ was obtained from appropriate CE versus time curves and (CE-U) was regressed over (t - ti)^0.5 to obtain the slope ‘α’ (Ritchie 1972) for the soil-limited evaporation stage. The observed ‘U’ was independent of mulch rate and E_o but was strongly affected by soil type, Values of ‘α’ decreased with increase in mulch rate and decrease in E_o and coarseness of soil. The otherwise short lived benefit of evaporation reduction with mulch per se, which peaked after a few days was maintained when residue was mixed with soil at the stage when evaporation reduction reached a maximum; this benefit continued for several weeks. Cumulative evaporation values computed from ‘U’ and ‘α’ agreed closely with the observed values under straw mulch for loamy sand and clay loam soils and for ‘undercut’ and ‘residue mixed’ treatments on all soils regardless of E_o, and for all situations under small E_o. However, for sandy loam and silt loam soils under E_o of 10 mm/d, the modified square root of the time function of Jalota et al. (1988) gave a better fit.     

Epidural Morphine in Goats after Hindlimb Orthopedic Surgery

Morphine (0.1 mg/kg) diluted with 0.9% saline to a volume of 0.13 mL/kg was administered into the epidural space at the lumbosacral junction in 10 halothane-anesthetized goats immediately before discontinuation of halothane. The same volume of 0.9% saline was given to control group of eight anesthetized goats. Both groups had undergone an orthopedic procedure that replaced the anterior cruciate ligament with a patellar tendon autograft. The appearance and unprovoked behavior of goats in the morphine group were significantly different (p < .05) from the saline groups. The goats in the morphine group were more sedate and struggled less during recovery. Epidural morphine did not produce respiratory depression or bloat during a 9 hour observation period. Heart rate, respiratory rate, and blood pressure (mean, systolic, and diastolic) of the morphine group did not differ from those of the control group.     

Parenteral Anticholinergics in Dogs With Normal and Elevated Intraocular Pressure

Dogs given parenteral anticholinergic drugs have been thought to be at risk for development or exacerbation of elevated intraocular pressure (IOP). In a randomized, blinded, placebo-controlled study, we evaluated the effect of intramuscular glycopyrrolate (0.01 mg/kg) on pupil diameter and IOP in unanesthetized normal dogs. Treatment with glycopyrrolate did not change pupil diameter or IOP from baseline, nor were there differences between glycopyrrolate and saline-treated (control) dogs. In addition, the authors retrospectively reviewed the medical records of 2,828 dogs undergoing general anesthesia between April 1987 and September 1990 to determine if there was an association between parenteral anticholinergic medication and postanesthetic elevation in IOP. The authors also determined the frequency of bradycardia requiring anticholinergic therapy during anesthesia in dogs with glaucoma. Of the 2,828 cases reviewed, the records of 46 dogs coded for glaucoma were examined in detail. The 46 dogs underwent 62 episodes of anesthesia, with 23 episodes including exposure to an anticholinergic drug. An increase in IOP from preanesthetic to postanesthetic measurement occurred in three dogs. One of these dogs received anticholinergic medication for bradycardia during anesthesia. The postanesthetic elevation in IOP in this dog was probably not drug related. Preanesthetic anticholinergic administration did not affect the incidence of anticholinergic administration for bradycardia during the anesthetic episode. Anticholinergic therapy during anesthesia was more frequent when the preanesthetic medication included an opiate drug. These studies do not indicate an association between parenteral anticholinergic administration and elevations in IOP.     

An Ecological Foodniche Concept as a Proxy for Fish-Pond Stocking Rates in Integrated Aquacultural Farming for Malaysia

The merits of integrated aquaculture farming (IAF) as a strategy for bolstering income for the rural poor have been recognized, but the economic efficiency and sustainability are yet to be determined. The effects of one species on another and the economic benefits, net of government support, have not been critically evaluated. The concept of a foodniche for alternative species in an aquatic environment has not been properly tested in an economic setting. Thus, this report reflects the results of applying the technique of mixed integer linear programming to determine the optimum combination of species within the context of a foodniche. The objective also included maximizing revenues, with minimal external input requirements, for a representative small Malaysian wet-rice farm. It was found that the foodniche concept permitted flexibility in stocking rates, and that farmers could actually stock species at the exact rate that was optimal for profit, instead of standard fixed rates. Also, government subsidies for pond construction were essential for IAF success. The net revenues from IAF were low without interest-free loans for pond construction.     

Developmental biology of T cell receptors

T cell receptors are the antigen-recognizing elements found on the effector cells of the immune system. Two isotypes have been discovered, TCR-gamma delta and TCR-alpha beta, which appear in that order during ontogeny. The maturation of prothymocytes that colonize the thymic rudiment at defined gestational stages occurs principally within the thymus, although some evidence for extrathymic maturation also exists. The maturation process includes the rearrangement and expression of the T cell receptor genes. Determination of these mechanisms, the lineages of the cells, and the subsequent thymic selection that results in self-tolerance is the central problem in developmental immunology and is important for the understanding of autoimmune diseases.     

Reproductive emergencies.

The emergency clinician is frequently called on to manage problems relating to the female reproductive tract. Because owners sel-dom have the medical knowledge needed to differentiate normal from abnormal reproductive behaviors, they frequently look to the emergency veterinarian for guidance and information during and after parturition. For this reason, it is essential that the veterinarian have a good understanding of the normal reproductive cycle as well as the common emergencies that may occur. This article reviews the events surrounding normal parturition in the dog and cat and the reproductive emergencies seen most commonly in practice.     

Effects of Carbon Dioxide Exposure on Intensively Cultured Rainbow Trout Oncorhynchus mykiss: Physiological Responses and Fillet Attributes

Rainbow trout Oncorhynchus mykiss (261.6 × 24.7 g initial weight, mean × SEM) at 13.1 × 0.2 C were exposed for 94 d to one of three CO₂ treatments: control (22.1 × 2.8 mg/L), medium (34.5 × 3.8 mg/L), or high (48.7 × 4.4 mg/L). Trout were checked daily for survival, and fish were sampled at 0, 28, 56, and 84 d for physiological responses, growth, and fillet quality assessments. Trout were also challenged to a 15-min crowding stress at 93 d to assess their ability to initiate a stress response during hypercapnia. Chronically exposed trout showed nearly 100% survival through 84 d exposure (1 of 1,500 fish died). Growth and physiological results showed that increasing elevated CO₂, concentrations result in corresponding decreased growth rates and CO₂specific physiological parameters: The medium and high CO₂ treatments had significantly slower growth and subsequently smaller fish by 84 d. Exposed trout also showed significantly ( P < 0.05) decreased plasma chloride for medium and high CO₂ treatments compared to the control from 28 through 84 d. Decreased growth and smaller fish in the medium and high CO₂ treatments resulted in correspondingly smaller fresh and smoked fillet weights. Chronic CO₂ exposure did not result in notable changes in ultimate muscle pH. Exposure to 15-min crowding stress at 93 d resulted in significant changes in hematocrit, plasma cortisoI, glucose, and chloride for all treatment groups. CO₂-specific changes were detected in hematocrit, plasma cortisoI, and plasma chloride responses following the 15-min crowding stress.