Petiole N,P, K Concentrations and Yield of the Potato Cultivar Molli from Certified Organic Amendments and Fertilizer Formulations

This study evaluated the petiole uptake of nitrogen, phosphorus, potassium, and sulfur (N, P, K, and S) by the potato from two seed meals, mint compost, and five commercially available organic fertilizers under an irrigated certified organic production system. Available soil nitrate (NO₃-N) and ammonium (NH₄-N) from each amendment averaged 115 kg N ha^?1 at application and 25 kg N ha^?1 30 d after planting through harvest, with minor differences between fertilizers. Petiole N declined from an average of 25,000 mg N kg^?1, 4 wk after emergence to 3,000 mg N kg^?1 prior to harvest. Petiole P and K concentrations were maintained above 4,000 mg P kg^?1, 10,000 mg K kg^?1, and 2,000 mg S kg^?1 tissue, respectively, throughout the growing season in all treatments. Tuber yields were not different between fertilized treatments averaging 53 Mg ha^?1. This study provides organic potato growers baseline information on the performance of a diverse array of organic fertilizers and amendments.     

Effects of Biochar and Biosolid on Adsorption of Nitrogen,Phosphorus, and Potassium in Two Soils

Increasing the retention of nutrients by agricultural soils is of great interest to minimize losses of nutrients by leaching and/or surface runoff. Soil amendments play a role in nutrient retention by increasing the surface area and/or other chemical processes. Biochar (BC) is high carbon-containing by-product of pyrolysis of carbon-rich feedstocks to produce bioenergy. Biosolid is a by-product of wastewater treatment plant. Use of these by-products as amendments to agricultural soils is beneficial to improve soil properties, soil quality, and nutrient retention and enhance carbon sequestration. In this study, the adsorption of NH₄-N, P, and K by a sandy soil (Quincy fine sand (QFS)) and a silty clay loam soil (Warden silty loam (WSL)) with BC (0, 22.4, and 44.8 mg ha^?1) and biosolid (0 and 22.4 mg ha^?1) amendments were investigated. Adsorption of NH₄-N by the QFS soil increased with BC application at lower NH₄-N concentrations in equilibrium solution. For the WSL soil, NH₄-N adsorption peaked at 22.4 mg ha^?1 BC rate. Biosolid application increased NH₄-N adsorption by the WSL soil while decreased that in the QFS soil. Adsorption of P was greater by the WSL soil as compared to that by the QFS soil. Biosolid amendment significantly increased P adsorption capacity in both soils, while BC amendment had no significant effects. BC and biosolid amendments decreased K adsorption capacity by the WSL soil but had no effects on that by the QFS soil. Ca release with increasing addition of K was greater by the WSL soil as compared to that by the QFS soil. In both the soils, Ca release was not influenced by BC amendment while it increased with addition of biosolid. The fit of adsorption data for NH₄-N, P, and K across all treatments and in two soils was better with the Freundlich model than that with the Langmuir model. The nutrients retained by BC or biosolid amended soils are easily released, therefore are readily available for the root uptake in cropped soils.     

Evaluation of fipronil spot-on in the treatment of flea allergic dermatitis in dogs

The purpose of this study was to evaluate the effectiveness of treatment with 10 per cent fipronil solution for controlling signs of flea allergic dermatitis in dogs under field conditions. Thirty-one client-owned dogs with flea allergic dermatitis were treated with three monthly applications of 10 per cent fipronil solution. Flea counts and pruritus were significantly reduced at all post-treatment visits. At the final visit, on day 90, flea counts were reduced by 98 per cent, and pruritus was reduced or eliminated in 84 per cent of the study dogs. Dermatological lesion scores for erythema, crusts, scales and papules were also significantly improved by the final visit. The overall assessment of efficacy on day 90 was 'excellent' to 'good' for 87 per cent of the study dogs. The results demonstrate that treatment with monthly topical applications of 10 per cent fipronil solution is effective in reducing the prevalence and severity of signs of flea allergic dermatitis in dogs.     

Effect of topical application of fipronil in cats with flea allergic dermatitis

OBJECTIVE: To determine whether topical application of a 10% fipronil solution would control signs of flea allergic dermatitis in cats housed under natural conditions. DESIGN: Multicenter open clinical trial. ANIMALS: 42 client-owned cats with flea allergic dermatitis. PROCEDURES: Study cats along with all other cats and dogs living in the same houses were treated with 10% fipronil solution topically on days 0, 30, and 60. Flea counts and clinical assessments were performed on study cats on days 0, 14, 30, 60, and 90. RESULTS: Percentage reductions in geometric mean flea counts on days 14, 30, 60, and 90, compared with day-0 geometric mean count, were 75, 73, 85, and 94%, respectively. Pruritus score was significantly improved at each examination after day 0, and pruritus was reduced or eliminated in 31 of 40 (78%) cats at the final examination. Similarly, scores for severity of miliary dermatitis and alopecia were significantly improved at each examination, except for alopecia score on day 14. Overall treatment efficacy, assessed on day 90, was excellent for 28 (70%) cats, good for 6 (15%), moderate for 3 (7.5%), and poor for 3 (7.5%). CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that monthly topical application of fipronil is effective for treatment of flea allergic dermatitis in cats housed under natural conditions.     

Nitrogen uptake and growth of two citrus rootstock seedlings in a sandy soil receiving different controlled-release fertilizer sources

Understanding the fate of different forms of nitrogen (N) fertilizers applied to soils is an important step in enhancing N use efficiency and minimizing N losses. The growth and N uptake of two citrus rootstocks, Swingle citrumelo (SC), and Cleopatra mandarin (CM), seedlings were evaluated in a pot experiment using a Candler fine sand (hyperthermic, uncoated, Typic Quartzipsamments) without N application or with 400 mg N kg^–1 applied as urea or controlled-release fertilizers (CRF; either as Meister, Osmocote, or Poly-S). Meister and Osmocote are polyolefin resin-coated urea with longevity of N release for 270 days (at 25°C). Poly-S is a polymer and sulfur-coated urea with release duration considerably shorter than that of either Meister or Osmocote. The concentrations of 2 M KCl extractable nitrate nitrogen (NO₃ ^–-N) and ammonium nitrogen (NH₄ ⁺-N) in the soil sampled 180 days and 300 days after planting were greater in the soil with SC than with CM rootstock seedlings. In most cases, the extractable NH₄ ⁺ and NO₃ ^– concentrations were greater for the Osmocote treatment compared to the other N sources. For the SC rootstock seedlings, dry weight was greater with Meister or Poly-S compared with either Osmocote or urea. At the end of the experiment, ranking of the various N sources, with respect to total N uptake by the seedlings, was: Meister = Osmocote > Poly-S > Urea > no N for CM rootstock, and Meister = Poly-S = Osmocote > Urea > no N for SC rootstock. The study demonstrated that for a given rate of N application the total N uptake by seedlings was greater for the CRF compared to urea treatment. This suggests that various N losses were lower from the CRF source as compared to those from soluble fertilizers. Received: 11 April 1997     

Efficacy and safety of firocoxib in the management of canine osteoarthritis under field conditions

A total of 249 client-owned dogs with osteoarthritis were treated with firocoxib (5 mg/kg/day) or a positive control, etodolac (10-15 mg/kg/day), for 30 days. Veterinary examinations were performed on approximately days 0 (visit 1), 14 (visit 2), and 29 (visit 3). Based on defined noninferiority criteria, firocoxib and etodolac were comparable. Based on the magnitude of the change from baseline, improvement with firocoxib was significantly greater than with etodolac for lameness at a trot (visits 2 and 3) and for lameness at a walk, pain on manipulation, and range of motion (visit 3) (P < .05). In weekly owner evaluations, firocoxib provided significantly greater improvement than etodolac (P < .05) at each scoring.     

Regulation of an ATG7-beclin 1 program of autophagic cell death by caspase-8

Caspases play a central role in apoptosis, a well-studied pathway of programmed cell death. Other programs of death potentially involving necrosis and autophagy may exist, but their relation to apoptosis and mechanisms of regulation remains unclear. We define a new molecular pathway in which activation of the receptor-interacting protein (a serine-threonine kinase) and Jun amino-terminal kinase induced cell death with the morphology of autophagy. Autophagic death required the genes ATG7 and beclin 1 and was induced by caspase-8 inhibition. Clinical therapies involving caspase inhibitors may arrest apoptosis but also have the unanticipated effect of promoting autophagic cell death.     

Characterization of phytotoxic aluminum in soil solutions from phosphogypsum amended soils

Phosphogypsum (PG), an industrial by-product from phosphoric acid plants, is being used as an ameliorant for acid soil infertility. Phosphogypsum is primarily CaSO₄ and contains F among several impurities. An increase in SO₄ ^2– and F^– ligands in soil solutions following amendment with PG is important for the alleviation of Al toxicity. In soil solutions containing abundant SO₄ ^2– and F^–, a measure of Al that is not complexed with either of the ligands represents phytotoxic Al. Alleviation of Al toxicity by SO₄ ^2– in some instances is due to SO₄ ^2–-induced precipitation and/or sorption of Al. Some studies have demonstrated a decrease in Al toxicity by SO₄ ^2– even though precipitation of Al was not evident.In such cases, formation of the Al-SO₄ ⁺ ion-pair (predicted by speciation models) has been attributed as the reason for alleviation of Al toxicity. Recent evidence has indicated that the proportion of Al complexed with SO₄ ^2– was much greater than that predicted by using speciation models, which suggests that alleviation is not fully attributable to the formation of AlSO₄ ⁺ species. The existing colorimetric Al assay techniques have failed to discriminate Al complexed with SO₄ ^2– and have therefore, proved to be unsuitable for determination of phytotoxic Al in solutions containing SO₄ ^2–. Fractionation of Al complexed with SO₄ ^2– by size exclusion chromatography (SEC) has permitted a more precise characterization of Al complexed with SO₄ ^2– which has been demonstrated as less phytotoxic than the uncomplexed Al. Therefore, size exclusion chromatography is a promising technique for characterization of phytotoxic Al in solutions in the presence of SO₄ ^2–. In solutions containing F^–, alleviation of Al toxicity is due to formation of Al-F complexes which are less phytotoxic. The 8-hydroxyquinoline method with a 15 second reaction time excludes Al-F complexes and, therefore is a measure of phytotoxic Al in solutions containing F^–.     

An evaluation of plant-available soil nitrogen in selected sandy soils by electro-ultrafiltration, KCl, and CaCl2 extraction methods

 Improving the precision in estimating the nitrogen (N) requirement for citrus trees on sandy soils is important for increasing N efficiency by the trees and minimizing potential losses of N in commercial citrus production areas. In this study, representative Florida soils were sampled from major citrus production areas and the electro-ultrafiltration (EUF) technique was used to measure the concentrations of total EUF-extractable nitrogen (EUF-N_t), ammonium-N (EUF-NH₄ ⁺–N) and nitrate-N (EUF-NO₃ ^––N). Available organic N (N_org) was calculated as: EUF-N_t–(NH₄ ⁺–N+NO₃ ^––N). The N concentrations in the EUF extraction were greater than those by the KCl or CaCl₂ method. The N_org fraction, estimated by the EUF method, varied from 4.4 to 40.8 mg kg^–1 soil, equivalent to 10 to 91 kg N ha^–1 (for the top 15 cm depth soil) and was positively correlated with the total soil N determined by the Kjeldahl method. The presence of appreciable amounts of N_org in these soils indicates that these soils contain high proportions of the total soil N in easily mineralizable N_org forms. This study demonstrates that the EUF-extractable organic bound N must be considered in developing N fertilizer recommendations for citrus. Received: 13 January 1999     

Influence of fungal-soil water interactions on phytophthora root rot of alfalfa

Summary Phytophthora root rot of alfalfa (Medicago sativa L.) is a serious problem in wet soils. This disease is caused by Phytophthora megasperma f. sp. medicaginis. The influence of soil-water interactions with P. megasperma f. sp. medicaginis and other factors on the severity of phytophthora root rot of mature alfalfa plants (10–12 weeks) was studied in greenhouse experiments. Severe and reproducible root rot was produced by subsurface (3–4 cm) placement of mycelial suspension. Soil saturation 3 days prior to inoculation followed by alternating 3-day wet (soil saturation) and 4-day dry (surface watering once a day) moisture regimes (for 30–40 days following inoculation) resulted in severe root damage.The severity of root rot was greater when the inoculation was done at an ambient temperature of 20°C than at 15°C. Water quality (tap water or deionized distilled water) had no effect on severity of infection. The isolates PT 78-3 (Minnesota) and TN-2 (Maryland) were equally effective in terms of severity of damage.The impact of excess soil water stress (described above) alone on the shoot and root dry weight as well as on shoot symptoms was similar to that of root rot stress. However, root symptoms showed a marked difference. A close examination of root symptoms is highly recommended to differentiate clearly the plant injury due to root rot from that due to excess soil water stress.