Denitrification in soil: Effects of herbicides     

J.C. Yeomans  J.M. Bremner 《Soil biology & biochemistry》1985,17(4):447-452

The effects of 20 herbicides on denitrification of nitrate in three soils were studied by determining the effects of 10 and 50μgg^?1 soil of each herbicide on the amounts of nitrate lost and the amounts of nitrite, N₂O and N₂ produced when soil samples were incubated anaerobically after treatment with nitrate. The herbicides used were butylate, EPTC, chlorpropham, propham, diuron, linuron, monuron, siduron, alachlor, trifluralin, 2,4-D amine, 2,4-D ester, atrazine, cyanazine, metribuzin, simazine, dalapon, chloramben, dicamba and dinoseb.None of the herbicides studied significantly affected denitrification of nitrate when applied at the rate of 10 μg g^?1 soil, but dinoseb increased the ratio of N₂ to N₂O in the gaseous products of denitrification when applied at this rate. Butylate, EPTC, diuron, simazine and dalapon had no significant effect on denitrification when applied at the rate of 50μgg^?1 soil, whereas metribuzin and dinoseb enhanced denitrification when applied at this rate. The influence of the other herbicides on denitrification when applied at the rate of 50μgg^?1soil depended on the soil, but all enhanced or inhibited denitrification in at least one soil.  相似文献   

Denitrification in soil: Effects of insecticides and fungicides     

J.C. Yeomans  J.M. Bremner 《Soil biology & biochemistry》1985,17(4):453-456

The effects of seven insecticides and six fungicides on denitrification of nitrate in soils were studied by determining the effects of 10 and 50μgg^?1 soil of each pesticide on the amounts of nitrate lost and the amounts of nitrite, N₂O and N₂ produced when soil samples were incubated anaerobically after treatment with nitrate. The insecticides used were lindane, fenitrothion, fonofos, malathion, phorate, terbufos and carbofuran. The fungicides used were mancozeb, maneb, thiram, benomyl, captan and terrazole.None of the insecticides studied had a significant effect on denitrification when applied at the rate of 10 μgg^?1 soil. When applied at the rate of 50μgg^?1 soil, lindane, fonofos and malathion enhanced denitrification in the three soils studied, whereas fenitrothion, phorate, terbufos and carbofuran either had no appreciable effect on denitrification in these soils, or enhanced denitrification in at least one of the soils.None of the fungicides studied had an appreciable effect on denitrification when applied at the rate of 10μgg^?1 soil, but thiram increased the ratio of N₂ to N₂O in the gaseous products of denitrification. Captan inhibited denitrification in two of three soils studied when applied at the rate of 50μgg^?1 soil. The other five fungicides either had no significant effect on denitrification, or enhanced denitrification, when applied at this rate. Reports that maneb, thiram and terrazole inhibit denitrification in soil were not confirmed.  相似文献   

Modelling the Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) site index from site factors in Portugal   总被引：1，自引：0，他引：1  

Fontes  Luis; Tome  Margarida; Thompson  Frank; Yeomans  Alistair; Luis  Jaime Sales; Savill  Peter 《Forestry》2003,76(5):491-507

  相似文献   

Integrated pest management and weed management in the United States and Canada          下载免费PDF全文

Micheal DK Owen  Hugh J Beckie  Julia Y Leeson  Jason K Norsworthy  Larry E Steckel 《Pest management science》2015,71(3):357-376

There is interest in more diverse weed management tactics because of evolved herbicide resistance in important weeds in many US and Canadian crop systems. While herbicide resistance in weeds is not new, the issue has become critical because of the adoption of simple, convenient and inexpensive crop systems based on genetically engineered glyphosate‐tolerant crop cultivars. Importantly, genetic engineering has not been a factor in rice and wheat, two globally important food crops. There are many tactics that help to mitigate herbicide resistance in weeds and should be widely adopted. Evolved herbicide resistance in key weeds has influenced a limited number of growers to include a more diverse suite of tactics to supplement existing herbicidal tactics. Most growers still emphasize herbicides, often to the exclusion of alternative tactics. Application of integrated pest management for weeds is better characterized as integrated weed management, and more typically integrated herbicide management. However, adoption of diverse weed management tactics is limited. Modifying herbicide use will not solve herbicide resistance in weeds, and the relief provided by different herbicide use practices is generally short‐lived at best. More diversity of tactics for weed management must be incorporated in crop systems. © 2014 Society of Chemical Industry  相似文献   

Benchmark study on glyphosate‐resistant cropping systems in the United States. Part 7: Effects of weed management strategy (grower practices versus academic recommendations) on the weed soil seedbank over 6 years          下载免费PDF全文

David J Gibson  Bryan G Young  Micheal DK Owen  Karla L Gage  Joseph L Matthews  David L Jordan  David R Shaw  Stephen C Weller  Robert G Wilson 《Pest management science》2016,72(4):692-700

  相似文献   

Larval fish assemblages and mesoscale oceanographic structure along the Mesoamerican Barrier Reef System     

Barbara A. Muhling  Ryan H. Smith  Lourdes Vásquez–Yeomans  John T. Lamkin  Elizabeth M. Johns  Laura Carrillo  Eloy Sosa‐Cordero  Estrella Malca 《Fisheries Oceanography》2013,22(5):409-428

The Mesoamerican Barrier Reef System (MBRS) is of high ecological and economic importance to the western Caribbean region, and contains spawning sites for a number of reef fish species. Despite this, little is known of the distribution and transport of pelagic fish larvae in the area, and basic in situ information on larval fish assemblages is lacking. Here we describe the results of two biological oceanography research cruises conducted in winter‐spring of 2006 and 2007, focusing on larval fish assemblages. We use multivariate assemblage analyses to examine vertical and horizontal distribution characteristics of larval fish assemblages, to highlight key distinguishing taxa, and to relate these to the observed oceanographic structure. Our results showed a general separation between the Gulf of Honduras region, which was characterized by weaker currents and high abundances of inshore and estuarine taxa (Eleotridae, Priacanthidae), and the northern MBRS, which was subject to strong northward flow and contained a mixture of mesopelagic and reef‐associated taxa (Myctophidae, Sparidae). Although distinct patterns of vertical distribution were observed among taxa, both shallow and deep living larvae were broadly distributed throughout the study area. Analysis of historical drifter tracks highlighted the strong northward flow and low retention conditions typically present along the northern MBRS, as well as potential connectivity between the western Caribbean Sea, the Gulf of Mexico and the Atlantic Ocean.  相似文献   

Radio science results during the NEAR-shoemaker spacecraft rendezvous with eros   总被引：1，自引：0，他引：1  

Yeomans DK  Antreasian PG  Barriot J  Chesley SR  Dunham DW  Farquhar RW  Giorgini JD  Helfrich CE  Konopliv AS  McAdams JV  Miller JK  Owen WM  Scheeres DJ  Thomas PC  Veverka J  Williams BG 《Science (New York, N.Y.)》2000,289(5487):2085-2088

We determined the mass of asteroid 433 Eros, its lower order gravitational harmonics, and rotation state, using ground-based Doppler and range tracking of the Near Earth Asteroid Rendezvous (NEAR)-Shoemaker spacecraft and images of the asteroid's surface landmarks. The mass of Eros is (6.687 +/- 0.003) x 10(18) grams, which, coupled with our volume estimate, implies a bulk density of 2. 67 +/- 0.03 grams per cubic centimeter. The asteroid appears to have a uniform density distribution. The right ascension and declination of the rotation pole are 11.37 +/- 0.05 and 17.22 +/- 0.05 degrees, respectively, and at least over the short term, the rotation state of Eros is stable with no measurable free precession of the spin pole. Escape velocities on the surface vary from 3.1 to 17.2 meters per second. The dynamical environment of Eros suggests that it is covered with regolith and that one might expect material transport toward the deepest potential wells in the saddle and 5.5-kilometer crater regions.  相似文献   

Hubble space telescope observations of comet p/shoemaker-levy 9 (1993e)     

Weaver HA  Feldman PD  A'hearn MF  Arpigny C  Brown RA  Helin EF  Levy DH  Marsden BG  Meech KJ  Larson SM  Noll KS  Scotti JV  Sekanina Z  Shoemaker CS  Shoemaker EM  Smith TE  Storrs AD  Yeomans DK  Zellner B 《Science (New York, N.Y.)》1994,263(5148):787-791

The Hubble Space Telescope observed the fragmented comet P/Shoemaker-Levy 9 (1993e) (P indicates that it is a periodic comet) on 1 July 1993. Approximately 20 individual nuclei and their comae were observed in images taken with the Planetary Camera. After subtraction of the comae light, the 11 brightest nuclei have magnitudes between approximately 23.7 and 24.8. Assuming that the geometric albedo is 0.04, these magnitudes imply that the nuclear diameters are in the range approximately 2.5 to 4.3 kilometers. If the density of each nucleus is 1 gram per cubic centimeter, the total energy deposited by the impact of these 11 nuclei into Jupiter's atmosphere next July will be approximately 4 x 10(30) ergs ( approximately 10(8) megatons of TNT). This latter number should be regarded as an upper limit because the nuclear magnitudes probably contain a small residual coma contribution. The Faint Object Spectrograph was used to search for fluorescence from OH, which is usually an excellent indicator of cometary activity. No OH emission was detected, and this can be translated into an upper limit on the water production rate of approximately 2 x 10(27) molecules per second.  相似文献   

Radar Image of Asteroid 1989 PB     

Ostro SJ  Chandler JF  Hine AA  Rosema KD  Shapiro II  Yeomans DK 《Science (New York, N.Y.)》1990,248(4962):1523-1528

Radar observations of the near-Earth asteroid 1989 PB, made shortly after its optical discovery, yield a sequence of delay-Doppler images that reveal it to consist of two distinct lobes that appear to be in contact. It seems likely that the two lobes once were separate and that they collided to produce the current "contact-binary" configuration.  相似文献   

Seasonal Variations in Seminal Plasma Proteins of Buffalo     

L Sharma  V Pandey  R Nigam  P Singh  A Saxena  DK Swain 《Reproduction in domestic animals》2014,49(3):387-391

The study was designed to evaluate the influence of season on semen characteristics and seminal plasma protein profile of buffalo bull semen. Thirty‐six ejaculates were collected in three seasons (winter, summer and rainy) from six adult Bhadawari bulls, and semen characteristics were evaluated immediately after collection. The seminal plasma was harvested by centrifugation and protein profiling, and percentage protein fractions were analysed by SDS‐PAGE. The significant effect of season was observed on ejaculate volume, sperm concentration, progressive motility, percentage live spermatozoa, hypo‐osmotic swelling test (HOST) and acrosomal integrity. The electrophoretogram of seminal plasma proteins revealed 20 protein bands in winter, 23 bands in rainy and 25 bands in summer seasons, illustrating the significant effect of seasons on seminal plasma proteins. Among these protein bands, 18 bands were observed common in semen samples of all three seasons while protein bands of 46, 55, 58, 144 and 160 kDa were found in rainy and summer seasons. The protein bands of 48 and 60 kDa were observed only in winter season, whereas 184 and 200 kDa were reported in summer season only. The protein fractions (protein%) of common protein bands observed in three seasons revealed a significant effect of season on protein bands of 24.5, 66, 70, 72, 84 and 86 kDa. From the study, it was pertinent that bull seminal plasma contains specific proteins in particular season, which may be associated with some of the semen characteristics, and these proteins could be used as markers of the semen quality of buffalo bulls.  相似文献