Penetration Resistance,Root Growth,and Water Content in a Subsoiled Claypan1

Penetration resistance, root length density, and water content of soil with maize (Zea mays L.), soybean (Glycine max [L.] Merr.), or a mixture of alfalfa (Medicago sativa L.) and fescue (Festuca arundinacea Schreb.) were measured during two summers, one of which was dry. Plants grew on a silt loam (Mollic Albaqualfs; fine, mixed, thermic), 0.25 m deep overlying a claypan, 1.75 m thick. Half of the plots were subsoiled before planting in the first year of the study and the other half were not subsoiled. During both years, subsoiling had no measurable effect in lowering the penetration resistance in the claypan. Root length density was greater in the claypan than in the topsoil. Subsoiling did not increase root length density in either year. Water content in plots that had been subsoiled was usually similar to that in plots that had not been subsoiled. In the dry year, roots of maize proliferated more in the claypan than did roots of soybean or alfalfa + fescue.     

Water relations of drought-resistant and drought-sensitive wheat cultivars sprinkled with saline water

Summary Water potential, osmotic potential, turgor potential, and stomatal resistance were measured on leaves of a drought-sensitive (Ponca) and a drought-resistant (KanKing) cultivar of winter wheat (Triticum aestivum L.) treated with foliar applications of NaCl to determine the effect of salt on the water status of two cultivars varying in drought resistance. Plants were grown under controlled conditions in soil, which was watered or allowed to dry. Water potential of the soil was determined. Given an ample water supply, water potential and osmotic potential of leaves of both cultivars with NaCl were lower, and stomatal resistance was higher, than without NaCl. The combination of salt and drought killed both cultivars, but the turgor potential of the drought-sensitive cultivar with the two stresses reached zero before that of the drought-resistant cultivar. Under limited water supply, both cultivars with foliar applications of salt extracted more water from soil than they did with no salt, and the drought-resistant cultivar took up more water than did the drought-sensitive cultivar. The drought-resistant cultivar with foliar NaCl maintained a higher turgor potential and extracted more water from the drying soil than did the drought-sensitive cultivar with foliar NaCl, suggesting that the drought-resistant cultivar was also more salt tolerant.     

Antimicrobial susceptibility patterns of the A and T types of Pasteurella haemolytica

Minimal concentrations of penicillin, ampicillin, cephalothin, chloramphenicol, tetracycline, erythromycin, nitrofurantoin, kanamycin and gentamicin inhibitory to Pasteurella haemolytica biotypes A and T were determined. They were found to be significantly higher for T than for A type strains in the case of all the antimicrobial drugs tested except the two aminoglycosides kanamycin and gentamicin, for which no differences were observed. In the case of penicillin the differences were so marked that they may be useful as a basis for biotyping P haemolytica isolates. The emergence of antibiotic-resistant strains observed in recent years, however, may limit such application.     

Influence of Abrams M1A1 Main Battle Tank Disturbance on Tallgrass Prairie Plant Community Structure

The Department of Defense's Range and Training Land Assessment program provides information and recommendations to range managers regarding the condition of training lands. This information is used to assist in scheduling training areas and in monitoring the effectiveness of rehabilitation projects. Fort Riley Military Installation is a major training reservation located in the Flint Hills of northeastern Kansas, within the tallgrass prairie ecosystem. A randomized complete block design composed of three treatments (M1A1 Abrams tank traffic during wet and dry soil conditions, and a nontrafficked control) with three replications was established in each of two soil types, a silty clay loam and a silt loam soil, on Fort Riley in 2003. Disturbance was created by driving the tank for five circuits in a figure-eight pattern during either during wet or dry soil conditions. Two additional experimental treatments were added during the study: five additional tank passes on one-half of each figure eight in 2004 and burning in 2006. Two areas, a curve and straightaway, within each traffic intensity (and later, burn treatment) subplot were designated for sampling. Aboveground biomass, species composition, and ground cover were measured during each growing season. Recovery of grass and total aboveground biomass in silty clay loam soil was delayed for curve areas and following disturbance in wet soil conditions, respectively. Species composition and ground cover continued to exhibit significant disturbance effects in 2007, with greatest damage observed for repeated traffic under wet soil conditions. Fire effects on vegetation were variable and generally greater for undisturbed control plots than for disturbed areas. The tallgrass prairie typically is considered to be among the most resilient of military training lands, but our research suggests that resiliency is dependent upon soil type and training conditions, and may require longer periods of recovery than previously thought.     

Evaluation of winter wheat cultivars for drought resistance

Summary Cultivars of winter wheat (Triticum aestivum L. em. Thell.), considered by wheat breeders to be drought sensitive or drought resistant, were grown under two irrigation regimes (daily or weekly waterings) to determine physiological responses to drought and to evaluate methods to use in screening for drought resistance. Leaf water potential, stomatal resistance, plant resistance to water flow, and soil water potential were measured for three weeks on vernalized plants in a growth chamber. When water was lacking, drought-sensitive plants had a lower leaf water potential than did drought-resistant plants. With both daily and weekly waterings, stomatal resistance was higher in drought-resistant plants than in drought-sensitive plants. Plant resistance to water flow, calculated as the difference between the soil water potential and leaf water potential divided by the amount of water used by the plant, was usually higher in drought-resistant plants than in the drought-sensitive plants. The results showed that, when screening for drought resistance, stomatal resistance was a better method to use than determinations of leaf water potential or plant resistance to water flow.Journal article 3578 of the Agricultural Experiment Station, Oklahoma State University. Work was partially supported by a Grant-in-Aid of Research from Sigma Xi, The Scientific Research Society of North America, to the senior author.     

Water-conserving wheat irrigation schedules based on climatic records

Summary Correlations between spring rainfall and grain yield were determined for four winter wheat cultivars (Triticum aestivum L. em. Thell. Triumph, Wichita, Concho, and Triumph 64), grown between 1950 and 1977 under dryland conditions at Stillwater, in the East Central region of Oklahoma, and at Goodwell, located in the drier, western part of the state.At Stillwater, all but one of the cultivars exhibited maximum positive correlations between rainfall and yield in the fourth week of March, when stem-extension occurs. Smaller positive correlations were observed in mid-April when flowering. Results at Goodwell were similar except that the correlations between rainfall and yield were lower and occurred earlier than at Stillwater and showed a less marked secondary peak at flowering. These results agree with those of experiments in which irrigation has been applied at different growth stages of wheat, and have shown that both stem-extension and flowering are critical stages of water requirement. As the results of this climatic study show that the peak correlations between rainfall and yield occur at these same two stages, it is suggested that long-term climatic data could be used to determine optimum timing for irrigation of wheat.Such an approach should save water and energy by limiting irrigation to those times when analysis of local records demonstrates the maximum positive correlation between rainfall and yield.     

Detection of Follicular Apoptosis in Water Buffalo (Bubalus bubalis) Ovary by Histology and Nick End Labelling Technique

The objective of this experiment was to assess the features and extent of follicular apoptosis in the water buffalo (Bubalus bubalis) ovary using classical histology and nick end labelling technique. Ovaries (n = 40) procured from the slaughterhouse were used for the study. The sections (5 μm) were used for detection of terminal deoxynucleotidyl transferase‐mediated dUTP‐biotin nick end labelling (TUNEL) and classical histology (H&E). Those follicles showing ≥ 5% TUNEL positivity (TUNEL assay) and pyknotic nuclei (histology) in granulosa cells were classified as atretic. Based on histology, the atretic primary and secondary follicles (%) were 93.82 and 95.62 respectively. The histology study reveals that the rates (%) of atresia in <1, 1–3, 3–5 mm and >5 mm were 36.90, 40.50, 62.84 and 74.5 respectively. Further the atretic tertiary follicles (%) were significantly lower than the primary and secondary classes of follicles. TUNEL assay reveals that the atretic rate (%) of tertiary follicles in <1, 1–3, 3–5 and ≥ 5 mm class follicles were 50.88, 53.84, 81.81 and 36.36 respectively. The percentage of atresia in >5 mm diameter follicles were significantly lower in TUNEL than histology. Percentages of granulosa and thecal cells positive for atresia by TUNEL were 30.7 ± 0.53 and 13.82 ± 0.18 respectively per follicle. The initial structural changes in atretic follicles were seen primarily in the granulosa cells. In severely atretic follicles TUNEL positive granulosa cells along with theca cells have to be considered in assessing the rate and extent of atresia.     

The impact of organic and inorganic fertilizers and lime on the species-richness and plant functional characteristics of hay meadow communities

Vegetation responses to fertilizers and lime applied in a seven-year study at paired unimproved and semi-improved mesotrophic hay meadows in Cumbria and Monmouthshire, UK, are described in terms of species-richness and several other plant community variables. Treatments were farmyard manure (FYM) applied at rates of between 6 and 24 tonne ha⁻¹ annually or every third year, inorganic fertilizers giving equivalent amounts of N, P and K, and lime applied either alone or with FYM applied annually or three-yearly. Annual FYM at 24 tonne ha⁻¹ reduced species-richness and the richness of positive indicator species at all sites and increased the proportional cover of nutrient-demanding species, whilst liming in conjunction with 12 tonne ha⁻¹ annual FYM application was equally detrimental at the unimproved site in Wales but not in Cumbria. Inorganic fertilizers were apparently no more detrimental to vegetation quality than equivalent FYM treatments, although medium-term nutrient supply from FYM may have been underestimated. Species-richness was maintained by FYM at ?12 tonne ha⁻¹ year⁻¹ in the semi-natural northern meadow, where such levels had been used in the past, but only by amounts equivalent to ?6 tonne ha⁻¹ year⁻¹ at the Welsh sites which had no recent history of fertilizer use. It is unclear to what extent such differences are attributable to innate differences in plant community type, rather than to site-specific differences in past management. The implications of our findings for defining sustainable fertilizer practices to maintain or enhance the nature conservation value of mesotrophic meadows are discussed.