不同时期追施肥水对冬小麦根系、根系活性和植株性状的影响

冬前至孕穗期不同生育期追施肥水，对根系的影响不同。追施肥水可提高根系活性，早施，根系活性最大值出现得早，后期根系活性降低得也快。开花、灌浆期的根系活性均以拔节、孕穗肥水为高。根系活性对叶片衰老速度有明显的影响，与上部干重、产量及产量性状存在着密切的关系。     

Spectrophotometric methods to determine carbohydrates in soil

Two common spectrophotometric procedures for determining neutral carbohydrates—the phenol-sulfuric acid and anthrone methods were evaluated for soil analysis. The phenol-sulfuric acid procedure gives results comparable to those obtained by gas-liquid chromatography, and is applicable to a variety of soil types. Prior removal of interfering substances by anion and cation exchange is required. Glucose is recommended as the spectrophotometric reference standard. The anthrone method is not satisfactory under the conditions employed.     

Influence of tillage and plant residue management on respiration of a Florida Everglades Histosol

Subsidence of drained, high organic matter Histosols in the Everglades Agricultural Area (EAA) is a concern for the sustainability of crop production in southern Florida. Histosol subsidence is primarily due to oxidation of organic matter by aerobic microorganisms, but far less is known about the influence of agricultural practices. The use of shallow tillage, as opposed to deep tillage, combined with proper plant residue management, may help to reduce the present rate of subsidence and soil CO₂ emissions. The present study was conducted on a Lauderhill soil (euic, hyperthermic, Lithic Haplosaprist) previously cropped in sugarcane (Saccharum spp.). The objectives were to (1) determine the effects of tillage depth on short-term CO₂ losses in a herbicide-killed weedy residue covered field and another field kept fallow without residue cover, and (2) compare soil respiration measurements made with two different dynamic closed-system portable chamber techniques. Four tillage practices common to the EAA were used to produce soil disturbance ranging in depth from approximately 20 to 300 mm. These practices included switch plowing, disk harrowing, and single and multiple tine cultivation. Twenty-four hours after tillage, cumulative CO₂ loss from the deepest tillage treatment (switch plow; 300 mm deep) was as much as 33 times greater than that from the no-till (control) treatment. Cumulative CO₂ loss following intermediate tillage (disk harrow; 78–145 mm deep) was as much as 2.3-fold greater than the no-till treatment, but shallower tillage (tine cultivation; 20–41 mm deep) was generally not different. Short-term tillage-induced CO₂ loss was primarily related to soil moisture content and soil porosity. Soil respiration measurements made with the two chamber techniques agreed well with each other except for the deepest tillage treatment, where the larger chamber measured CO₂ flux that was approximately 10 times greater than for the smaller chamber. Results indicate that minimum or no-tillage may reduce short-term tillage-induced CO₂ emissions on organic soils, thus minimizing soil subsidence.     

Sphingomonas sp. strain SB5 degrades carbofuran to a new metabolite by hydrolysis at the furanyl ring

Microorganisms capable of degrading carbofuran were isolated from soils and examined for the degradation of this pesticide at ring structure. An isolate that could degrade carbofuran and carbofuran-7-phenol was selected for further studies. The 16S rRNA analysis results showed that the isolate belongs to the genus of Sphingomonas, close to dioxin and dicamba degraders, and is named Sphingomonas sp. SB5. SB5 did not show any similarity of 16S rRNA to known carbofuran degraders. When time-course degradation of carbofuran by SB5 was examined by solvent extraction combined with liquid chromatographic analysis, almost complete disappearance of carbofuran was observed within 12 h, giving several accumulative metabolites. Bacterial cultures incubated with carbofuran-7-phenol suggested that the accumulated metabolites were derived from carbofuran-7-phenol. The control without SB5 and kanamycin-treated SB5 did not show any metabolite, suggesting a biological involvement in the degradation of carbofuran. GC/MS and LC/MS analyses identified 2-hydroxy-3-(3-methylpropan-2-ol) phenol as one of the accumulated metabolites, suggesting that the strain SB5 could degrade carbofuran-7-phenol by hydrolysis at the furanyl ring. This is the first report to identify 2-hydroxy-3-(3-methylpropan-2-ol) phenol as a new product derived biologically from carbofuran-7-phenol.     

The composition of grain and forage from glyphosate tolerant wheat MON 71800 is equivalent to that of conventional wheat (Triticum aestivum L.)

Glyphosate tolerant wheat MON 71800, simply referred to as MON 71800, contains a 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) protein from Agrobacterium sp. strain CP4 (CP4 EPSPS) that has a reduced affinity for glyphosate as compared to the endogenous plant EPSPS enzyme. The purpose of this work was to evaluate the compositional equivalence of MON 71800 to its nontransgenic parent as well as to conventional wheat varieties. The compositional assessment evaluated the levels of proximates, amino acids, fatty acids, minerals, vitamins, secondary metabolites, and antinutrients in wheat forage and grain grown during two field seasons across a total of eight sites in the United States and Canada. These data demonstrated that with respect to these important nutritional components, the forage and grain from MON 71800 were equivalent to those of its nontransgenic parent and commercial wheat varieties. These data, together with the previously established safety of the CP4 EPSPS protein, support the conclusion that glyphosate tolerant wheat MON 71800 is as safe and nutritious as commercial wheat varieties.     

The EPRI state-of-the-art cooling water treatment research project a tailored collaboration program

The EPRI Tailored Collaboration State-of-the-Art Cooling Water Treatment Research Program has been initiated with several electric utility participants. Started in January 1995, the program will provide O&M cost reduction through improved cooling water system reliability and operation. This effort is discussed along with the objectives and goals, the participants and project timetable. The program will provide three (3) main results to the participating utilities: cost effective optimization of cooling water treatment, production of a new Cooling Water Treatment Manual and updating of two (2) EPRI software products — SEQUIL and COOLADD. A review of the specific objectives, project timetable and results to date will be presented.     

Comparison of irrigation strategies for surface-irrigated corn in West Central Nebraska

Many farmers in West Central Nebraska have limited irrigation water supplies, and need to produce crops with less water. This study evaluated the impact of four water management strategies on grain yield of surface-irrigated corn (Zea mays L.) at North Platte, Nebraska. Treatments included: (1) no irrigation (DRYLAND), (2) one irrigation prior to tassel formation (EARLY), (3) one irrigation during the silk stage (LATE), and (4) irrigation following farmer’s practices (FARMER). The study included three wet years (1992, 1993, and 1996) and 2 years with average annual rainfall for the area (1994 and 1995). Significant yield differences among treatments, and a yield response to irrigation, were only observed during the 2 years with average rainfall. During all years, the FARMER treatment was over-irrigated and resulted in considerable water losses by runoff and deep percolation. Grain yield response to irrigation during the three wet years was insignificant among the treatments, but significant during the dry years. The results of this study suggest that inducing stress is not a good strategy for increasing crop water productivity (yield per unit ET_d) for corn and point out the need to minimize irrigation water losses and improve irrigation scheduling.     

A NEW DEVICE FOR STEREOTACTIC CT-GUIDED BIOPSY OF THE CANINE BRAIN: DESIGN, CONSTRUCTION, AND NEEDLE PLACEMENT ACCURACY

An inexpensive device was created for computed tomographic (CT)-guided stereotactic biopsy of the canine brain. The accuracy of the device was tested using 16, formalin-perfused, canine head specimens. For each dog, a 6-inch biopsy needle was guided into pituitary gland and caudate nucleus targets. Needle tracks were measured using the CT computer and infused with tissue staining solution. Hit success and actual needle track lengths were determined from sliced brain specimens. The device enabled accurate orientation and placement of the canine head in the slice plane, such that progressive penetration of the biopsy needle could be monitored. The caudate nucleus was hit 12/16 times (75% accuracy) and the pituitary gland 15.5/16 times (98.6% accuracy). Hit proportions for the two targets did not differ (P < 0.05). A significant difference was found between CT and actual track length for both targets (P < 0.01). This was attributed to incomplete staining of the bevel portion of the needle track.     

First Atmospheric Science Results from the Mars Exploration Rovers Mini-TES

Thermal infrared spectra of the martian atmosphere taken by the Miniature Thermal Emission Spectrometer (Mini-TES) were used to determine the atmospheric temperatures in the planetary boundary layer and the column-integrated optical depth of aerosols. Mini-TES observations show the diurnal variation of the martian boundary layer thermal structure, including a near-surface superadiabatic layer during the afternoon and an inversion layer at night. Upward-looking Mini-TES observations show warm and cool parcels of air moving through the Mini-TES field of view on a time scale of 30 seconds. The retrieved dust optical depth shows a downward trend at both sites.     

An eccentric binary millisecond pulsar in the galactic plane

Binary pulsar systems are superb probes of stellar and binary evolution and the physics of extreme environments. In a survey with the Arecibo telescope, we have found PSR J1903+0327, a radio pulsar with a rotational period of 2.15 milliseconds in a highly eccentric (e = 0.44) 95-day orbit around a solar mass (M(middle dot in circle)) companion. Infrared observations identify a possible main-sequence companion star. Conventional binary stellar evolution models predict neither large orbital eccentricities nor main-sequence companions around millisecond pulsars. Alternative formation scenarios involve recycling a neutron star in a globular cluster, then ejecting it into the Galactic disk, or membership in a hierarchical triple system. A relativistic analysis of timing observations of the pulsar finds its mass to be 1.74 +/- 0.04 M solar symbol, an unusually high value.