19 results
The Broadbalk long-term experiment at Rothamsted: what has it told us about weeds?
- Stephen R. Moss, Jonathan Storkey, John W. Cussans, Sarah A. M. Perryman, Michael V. Hewitt
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- Journal:
- Weed Science / Volume 52 / Issue 5 / October 2004
- Published online by Cambridge University Press:
- 20 January 2017, pp. 864-873
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The Broadbalk experiment was started in 1843 to investigate the relative importance of different plant nutrients (N, P, K, Na, Mg) on grain yield of winter wheat. Weeds were controlled initially by hand hoeing and fallowing, but since 1964, herbicides have been applied to the whole experiment with the exception of the 18 plots on Section 8. Approximately 130 weed species have been recorded on Broadbalk and about 30 of these are currently recorded annually on Section 8. Detailed weed surveys, conducted from 1930 to 1979, provide a unique 50-yr record, but the relatively small number of frequency categories used (six) poses a limitation on the interpretation of these data for ecological studies. Weed surveys were restarted in 1991 on Section 8. The current assessment method records the presence of individual weed species in 25 random 0.1-m2 quadrats per plot, which is more appropriate for detecting long-term trends in weed frequencies and population differences between plots. A principal components analysis of the 1991–2002 survey data for 15 species showed clearly the influence of inorganic N fertilizer levels on the frequency of individual species. The frequency of one species (common chickweed) was greatly favored by increasing amounts of nitrogen fertilizer from 0 to 288 kg N ha−1, others were strongly disadvantaged (e.g., black medic and field horsetail), some were slightly disadvantaged (e.g., common vetch and parsley-piert), and some showed little response to differing N rates (e.g., blackgrass and corn poppy). Other weed investigations include studies on the effects of fallowing on the weed seed bank, seed dormancy and persistence, agroecology, and population dynamics of individual weed species. Recently, molecular approaches have been used to study the genetic diversity of weeds found on Section 8, which is one of the few arable sites in the country where herbicides have never been applied. This site also provides an invaluable reserve for seven nationally rare or uncommon species. Broadbalk continues to act as a valuable resource for weed investigations 160 yr after it was established.
Contributors
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- By Rose Teteki Abbey, K. C. Abraham, David Tuesday Adamo, LeRoy H. Aden, Efrain Agosto, Victor Aguilan, Gillian T. W. Ahlgren, Charanjit Kaur AjitSingh, Dorothy B E A Akoto, Giuseppe Alberigo, Daniel E. Albrecht, Ruth Albrecht, Daniel O. Aleshire, Urs Altermatt, Anand Amaladass, Michael Amaladoss, James N. Amanze, Lesley G. Anderson, Thomas C. Anderson, Victor Anderson, Hope S. Antone, María Pilar Aquino, Paula Arai, Victorio Araya Guillén, S. Wesley Ariarajah, Ellen T. Armour, Brett Gregory Armstrong, Atsuhiro Asano, Naim Stifan Ateek, Mahmoud Ayoub, John Alembillah Azumah, Mercedes L. García Bachmann, Irena Backus, J. Wayne Baker, Mieke Bal, Lewis V. Baldwin, William Barbieri, António Barbosa da Silva, David Basinger, Bolaji Olukemi Bateye, Oswald Bayer, Daniel H. Bays, Rosalie Beck, Nancy Elizabeth Bedford, Guy-Thomas Bedouelle, Chorbishop Seely Beggiani, Wolfgang Behringer, Christopher M. Bellitto, Byard Bennett, Harold V. Bennett, Teresa Berger, Miguel A. Bernad, Henley Bernard, Alan E. Bernstein, Jon L. Berquist, Johannes Beutler, Ana María Bidegain, Matthew P. Binkewicz, Jennifer Bird, Joseph Blenkinsopp, Dmytro Bondarenko, Paulo Bonfatti, Riet en Pim Bons-Storm, Jessica A. Boon, Marcus J. Borg, Mark Bosco, Peter C. Bouteneff, François Bovon, William D. Bowman, Paul S. Boyer, David Brakke, Richard E. Brantley, Marcus Braybrooke, Ian Breward, Ênio José da Costa Brito, Jewel Spears Brooker, Johannes Brosseder, Nicholas Canfield Read Brown, Robert F. Brown, Pamela K. Brubaker, Walter Brueggemann, Bishop Colin O. Buchanan, Stanley M. Burgess, Amy Nelson Burnett, J. Patout Burns, David B. Burrell, David Buttrick, James P. Byrd, Lavinia Byrne, Gerado Caetano, Marcos Caldas, Alkiviadis Calivas, William J. Callahan, Salvatore Calomino, Euan K. Cameron, William S. Campbell, Marcelo Ayres Camurça, Daniel F. Caner, Paul E. Capetz, Carlos F. Cardoza-Orlandi, Patrick W. Carey, Barbara Carvill, Hal Cauthron, Subhadra Mitra Channa, Mark D. Chapman, James H. Charlesworth, Kenneth R. Chase, Chen Zemin, Luciano Chianeque, Philip Chia Phin Yin, Francisca H. Chimhanda, Daniel Chiquete, John T. Chirban, Soobin Choi, Robert Choquette, Mita Choudhury, Gerald Christianson, John Chryssavgis, Sejong Chun, Esther Chung-Kim, Charles M. A. Clark, Elizabeth A. Clark, Sathianathan Clarke, Fred Cloud, John B. Cobb, W. Owen Cole, John A Coleman, John J. Collins, Sylvia Collins-Mayo, Paul K. Conkin, Beth A. Conklin, Sean Connolly, Demetrios J. Constantelos, Michael A. Conway, Paula M. Cooey, Austin Cooper, Michael L. Cooper-White, Pamela Cooper-White, L. William Countryman, Sérgio Coutinho, Pamela Couture, Shannon Craigo-Snell, James L. Crenshaw, David Crowner, Humberto Horacio Cucchetti, Lawrence S. Cunningham, Elizabeth Mason Currier, Emmanuel Cutrone, Mary L. Daniel, David D. Daniels, Robert Darden, Rolf Darge, Isaiah Dau, Jeffry C. Davis, Jane Dawson, Valentin Dedji, John W. de Gruchy, Paul DeHart, Wendy J. Deichmann Edwards, Miguel A. De La Torre, George E. Demacopoulos, Thomas de Mayo, Leah DeVun, Beatriz de Vasconcellos Dias, Dennis C. Dickerson, John M. Dillon, Luis Miguel Donatello, Igor Dorfmann-Lazarev, Susanna Drake, Jonathan A. Draper, N. Dreher Martin, Otto Dreydoppel, Angelyn Dries, A. J. Droge, Francis X. D'Sa, Marilyn Dunn, Nicole Wilkinson Duran, Rifaat Ebied, Mark J. Edwards, William H. Edwards, Leonard H. Ehrlich, Nancy L. Eiesland, Martin Elbel, J. Harold Ellens, Stephen Ellingson, Marvin M. Ellison, Robert Ellsberg, Jean Bethke Elshtain, Eldon Jay Epp, Peter C. Erb, Tassilo Erhardt, Maria Erling, Noel Leo Erskine, Gillian R. Evans, Virginia Fabella, Michael A. Fahey, Edward Farley, Margaret A. Farley, Wendy Farley, Robert Fastiggi, Seena Fazel, Duncan S. Ferguson, Helwar Figueroa, Paul Corby Finney, Kyriaki Karidoyanes FitzGerald, Thomas E. FitzGerald, John R. Fitzmier, Marie Therese Flanagan, Sabina Flanagan, Claude Flipo, Ronald B. Flowers, Carole Fontaine, David Ford, Mary Ford, Stephanie A. Ford, Jim Forest, William Franke, Robert M. Franklin, Ruth Franzén, Edward H. Friedman, Samuel Frouisou, Lorelei F. Fuchs, Jojo M. Fung, Inger Furseth, Richard R. Gaillardetz, Brandon Gallaher, China Galland, Mark Galli, Ismael García, Tharscisse Gatwa, Jean-Marie Gaudeul, Luis María Gavilanes del Castillo, Pavel L. Gavrilyuk, Volney P. Gay, Metropolitan Athanasios Geevargis, Kondothra M. George, Mary Gerhart, Simon Gikandi, Maurice Gilbert, Michael J. Gillgannon, Verónica Giménez Beliveau, Terryl Givens, Beth Glazier-McDonald, Philip Gleason, Menghun Goh, Brian Golding, Bishop Hilario M. Gomez, Michelle A. Gonzalez, Donald K. Gorrell, Roy Gottfried, Tamara Grdzelidze, Joel B. Green, Niels Henrik Gregersen, Cristina Grenholm, Herbert Griffiths, Eric W. Gritsch, Erich S. Gruen, Christoffer H. Grundmann, Paul H. Gundani, Jon P. Gunnemann, Petre Guran, Vidar L. Haanes, Jeremiah M. Hackett, Getatchew Haile, Douglas John Hall, Nicholas Hammond, Daphne Hampson, Jehu J. Hanciles, Barry Hankins, Jennifer Haraguchi, Stanley S. Harakas, Anthony John Harding, Conrad L. Harkins, J. William Harmless, Marjory Harper, Amir Harrak, Joel F. Harrington, Mark W. Harris, Susan Ashbrook Harvey, Van A. Harvey, R. Chris Hassel, Jione Havea, Daniel Hawk, Diana L. Hayes, Leslie Hayes, Priscilla Hayner, S. Mark Heim, Simo Heininen, Richard P. Heitzenrater, Eila Helander, David Hempton, Scott H. Hendrix, Jan-Olav Henriksen, Gina Hens-Piazza, Carter Heyward, Nicholas J. Higham, David Hilliard, Norman A. Hjelm, Peter C. Hodgson, Arthur Holder, M. Jan Holton, Dwight N. Hopkins, Ronnie Po-chia Hsia, Po-Ho Huang, James Hudnut-Beumler, Jennifer S. Hughes, Leonard M. Hummel, Mary E. Hunt, Laennec Hurbon, Mark Hutchinson, Susan E. Hylen, Mary Beth Ingham, H. Larry Ingle, Dale T. Irvin, Jon Isaak, Paul John Isaak, Ada María Isasi-Díaz, Hans Raun Iversen, Margaret C. Jacob, Arthur James, Maria Jansdotter-Samuelsson, David Jasper, Werner G. Jeanrond, Renée Jeffery, David Lyle Jeffrey, Theodore W. Jennings, David H. Jensen, Robin Margaret Jensen, David Jobling, Dale A. Johnson, Elizabeth A. Johnson, Maxwell E. Johnson, Sarah Johnson, Mark D. Johnston, F. Stanley Jones, James William Jones, John R. Jones, Alissa Jones Nelson, Inge Jonsson, Jan Joosten, Elizabeth Judd, Mulambya Peggy Kabonde, Robert Kaggwa, Sylvester Kahakwa, Isaac Kalimi, Ogbu U. Kalu, Eunice Kamaara, Wayne C. Kannaday, Musimbi Kanyoro, Veli-Matti Kärkkäinen, Frank Kaufmann, Léon Nguapitshi Kayongo, Richard Kearney, Alice A. Keefe, Ralph Keen, Catherine Keller, Anthony J. Kelly, Karen Kennelly, Kathi Lynn Kern, Fergus Kerr, Edward Kessler, George Kilcourse, Heup Young Kim, Kim Sung-Hae, Kim Yong-Bock, Kim Yung Suk, Richard King, Thomas M. King, Robert M. Kingdon, Ross Kinsler, Hans G. Kippenberg, Cheryl A. Kirk-Duggan, Clifton Kirkpatrick, Leonid Kishkovsky, Nadieszda Kizenko, Jeffrey Klaiber, Hans-Josef Klauck, Sidney Knight, Samuel Kobia, Robert Kolb, Karla Ann Koll, Heikki Kotila, Donald Kraybill, Philip D. W. Krey, Yves Krumenacker, Jeffrey Kah-Jin Kuan, Simanga R. Kumalo, Peter Kuzmic, Simon Shui-Man Kwan, Kwok Pui-lan, André LaCocque, Stephen E. Lahey, John Tsz Pang Lai, Emiel Lamberts, Armando Lampe, Craig Lampe, Beverly J. Lanzetta, Eve LaPlante, Lizette Larson-Miller, Ariel Bybee Laughton, Leonard Lawlor, Bentley Layton, Robin A. Leaver, Karen Lebacqz, Archie Chi Chung Lee, Marilyn J. Legge, Hervé LeGrand, D. L. LeMahieu, Raymond Lemieux, Bill J. Leonard, Ellen M. Leonard, Outi Leppä, Jean Lesaulnier, Nantawan Boonprasat Lewis, Henrietta Leyser, Alexei Lidov, Bernard Lightman, Paul Chang-Ha Lim, Carter Lindberg, Mark R. Lindsay, James R. Linville, James C. Livingston, Ann Loades, David Loades, Jean-Claude Loba-Mkole, Lo Lung Kwong, Wati Longchar, Eleazar López, David W. Lotz, Andrew Louth, Robin W. Lovin, William Luis, Frank D. Macchia, Diarmaid N. J. MacCulloch, Kirk R. MacGregor, Marjory A. MacLean, Donald MacLeod, Tomas S. Maddela, Inge Mager, Laurenti Magesa, David G. Maillu, Fortunato Mallimaci, Philip Mamalakis, Kä Mana, Ukachukwu Chris Manus, Herbert Robinson Marbury, Reuel Norman Marigza, Jacqueline Mariña, Antti Marjanen, Luiz C. L. Marques, Madipoane Masenya (ngwan'a Mphahlele), Caleb J. D. Maskell, Steve Mason, Thomas Massaro, Fernando Matamoros Ponce, András Máté-Tóth, Odair Pedroso Mateus, Dinis Matsolo, Fumitaka Matsuoka, John D'Arcy May, Yelena Mazour-Matusevich, Theodore Mbazumutima, John S. McClure, Christian McConnell, Lee Martin McDonald, Gary B. McGee, Thomas McGowan, Alister E. McGrath, Richard J. McGregor, John A. McGuckin, Maud Burnett McInerney, Elsie Anne McKee, Mary B. McKinley, James F. McMillan, Ernan McMullin, Kathleen E. McVey, M. Douglas Meeks, Monica Jyotsna Melanchthon, Ilie Melniciuc-Puica, Everett Mendoza, Raymond A. Mentzer, William W. Menzies, Ina Merdjanova, Franziska Metzger, Constant J. Mews, Marvin Meyer, Carol Meyers, Vasile Mihoc, Gunner Bjerg Mikkelsen, Maria Inêz de Castro Millen, Clyde Lee Miller, Bonnie J. Miller-McLemore, Alexander Mirkovic, Paul Misner, Nozomu Miyahira, R. W. L. Moberly, Gerald Moede, Aloo Osotsi Mojola, Sunanda Mongia, Rebeca Montemayor, James Moore, Roger E. Moore, Craig E. Morrison O.Carm, Jeffry H. Morrison, Keith Morrison, Wilson J. Moses, Tefetso Henry Mothibe, Mokgethi Motlhabi, Fulata Moyo, Henry Mugabe, Jesse Ndwiga Kanyua Mugambi, Peggy Mulambya-Kabonde, Robert Bruce Mullin, Pamela Mullins Reaves, Saskia Murk Jansen, Heleen L. Murre-Van den Berg, Augustine Musopole, Isaac M. T. Mwase, Philomena Mwaura, Cecilia Nahnfeldt, Anne Nasimiyu Wasike, Carmiña Navia Velasco, Thulani Ndlazi, Alexander Negrov, James B. Nelson, David G. Newcombe, Carol Newsom, Helen J. Nicholson, George W. E. Nickelsburg, Tatyana Nikolskaya, Damayanthi M. A. Niles, Bertil Nilsson, Nyambura Njoroge, Fidelis Nkomazana, Mary Beth Norton, Christian Nottmeier, Sonene Nyawo, Anthère Nzabatsinda, Edward T. Oakes, Gerald O'Collins, Daniel O'Connell, David W. Odell-Scott, Mercy Amba Oduyoye, Kathleen O'Grady, Oyeronke Olajubu, Thomas O'Loughlin, Dennis T. Olson, J. Steven O'Malley, Cephas N. Omenyo, Muriel Orevillo-Montenegro, César Augusto Ornellas Ramos, Agbonkhianmeghe E. Orobator, Kenan B. Osborne, Carolyn Osiek, Javier Otaola Montagne, Douglas F. Ottati, Anna May Say Pa, Irina Paert, Jerry G. Pankhurst, Aristotle Papanikolaou, Samuele F. Pardini, Stefano Parenti, Peter Paris, Sung Bae Park, Cristián G. Parker, Raquel Pastor, Joseph Pathrapankal, Daniel Patte, W. Brown Patterson, Clive Pearson, Keith F. Pecklers, Nancy Cardoso Pereira, David Horace Perkins, Pheme Perkins, Edward N. Peters, Rebecca Todd Peters, Bishop Yeznik Petrossian, Raymond Pfister, Peter C. Phan, Isabel Apawo Phiri, William S. F. Pickering, Derrick G. Pitard, William Elvis Plata, Zlatko Plese, John Plummer, James Newton Poling, Ronald Popivchak, Andrew Porter, Ute Possekel, James M. Powell, Enos Das Pradhan, Devadasan Premnath, Jaime Adrían Prieto Valladares, Anne Primavesi, Randall Prior, María Alicia Puente Lutteroth, Eduardo Guzmão Quadros, Albert Rabil, Laurent William Ramambason, Apolonio M. Ranche, Vololona Randriamanantena Andriamitandrina, Lawrence R. Rast, Paul L. Redditt, Adele Reinhartz, Rolf Rendtorff, Pål Repstad, James N. Rhodes, John K. Riches, Joerg Rieger, Sharon H. Ringe, Sandra Rios, Tyler Roberts, David M. Robinson, James M. Robinson, Joanne Maguire Robinson, Richard A. H. Robinson, Roy R. Robson, Jack B. Rogers, Maria Roginska, Sidney Rooy, Rev. Garnett Roper, Maria José Fontelas Rosado-Nunes, Andrew C. Ross, Stefan Rossbach, François Rossier, John D. Roth, John K. Roth, Phillip Rothwell, Richard E. Rubenstein, Rosemary Radford Ruether, Markku Ruotsila, John E. Rybolt, Risto Saarinen, John Saillant, Juan Sanchez, Wagner Lopes Sanchez, Hugo N. Santos, Gerhard Sauter, Gloria L. Schaab, Sandra M. Schneiders, Quentin J. Schultze, Fernando F. Segovia, Turid Karlsen Seim, Carsten Selch Jensen, Alan P. F. Sell, Frank C. Senn, Kent Davis Sensenig, Damían Setton, Bal Krishna Sharma, Carolyn J. Sharp, Thomas Sheehan, N. Gerald Shenk, Christian Sheppard, Charles Sherlock, Tabona Shoko, Walter B. Shurden, Marguerite Shuster, B. Mark Sietsema, Batara Sihombing, Neil Silberman, Clodomiro Siller, Samuel Silva-Gotay, Heikki Silvet, John K. Simmons, Hagith Sivan, James C. Skedros, Abraham Smith, Ashley A. Smith, Ted A. Smith, Daud Soesilo, Pia Søltoft, Choan-Seng (C. S.) Song, Kathryn Spink, Bryan Spinks, Eric O. Springsted, Nicolas Standaert, Brian Stanley, Glen H. Stassen, Karel Steenbrink, Stephen J. Stein, Andrea Sterk, Gregory E. Sterling, Columba Stewart, Jacques Stewart, Robert B. 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Van Bavel, Steven Vanderputten, Peter Van der Veer, Huub Van de Sandt, Louis Van Tongeren, Luke A. Veronis, Noel Villalba, Ramón Vinke, Tim Vivian, David Voas, Elena Volkova, Katharina von Kellenbach, Elina Vuola, Timothy Wadkins, Elaine M. Wainwright, Randi Jones Walker, Dewey D. Wallace, Jerry Walls, Michael J. Walsh, Philip Walters, Janet Walton, Jonathan L. Walton, Wang Xiaochao, Patricia A. Ward, David Harrington Watt, Herold D. Weiss, Laurence L. Welborn, Sharon D. Welch, Timothy Wengert, Traci C. West, Merold Westphal, David Wetherell, Barbara Wheeler, Carolinne White, Jean-Paul Wiest, Frans Wijsen, Terry L. Wilder, Felix Wilfred, Rebecca Wilkin, Daniel H. Williams, D. Newell Williams, Michael A. Williams, Vincent L. Wimbush, Gabriele Winkler, Anders Winroth, Lauri Emílio Wirth, James A. Wiseman, Ebba Witt-Brattström, Teofil Wojciechowski, John Wolffe, Kenman L. Wong, Wong Wai Ching, Linda Woodhead, Wendy M. Wright, Rose Wu, Keith E. Yandell, Gale A. Yee, Viktor Yelensky, Yeo Khiok-Khng, Gustav K. K. Yeung, Angela Yiu, Amos Yong, Yong Ting Jin, You Bin, Youhanna Nessim Youssef, Eliana Yunes, Robert Michael Zaller, Valarie H. Ziegler, Barbara Brown Zikmund, Joyce Ann Zimmerman, Aurora Zlotnik, Zhuo Xinping
- Edited by Daniel Patte, Vanderbilt University, Tennessee
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- The Cambridge Dictionary of Christianity
- Published online:
- 05 August 2012
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- 20 September 2010, pp xi-xliv
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Effects of soil and fertilizer P on yields of potatoes, sugar beet, barley and winter wheat on a sandy clay loam soil at Saxmundham, Suffolk
- A. E. Johnston, P. W. Lane, G. E. G. Mattingly, P. R. Poulton, M. V. Hewitt
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- Journal:
- The Journal of Agricultural Science / Volume 106 / Issue 1 / February 1986
- Published online by Cambridge University Press:
- 27 March 2009, pp. 155-167
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During 1899–1964 various levels of 0·5 M sodium bicarbonate-soluble P had been established in an experiment on a sandy clay loam (pH 6·5–7·0) at Saxmundham, Suffolk. Modification made between 1965 and 1968 widened the range of soluble P values to 3–67 mg/kg. Relationships between these soluble P values and yields of potatoes and sugar beet in 1969–74 and cereals in 1970–7 were assessed. Responses by potatoes and sugar beet to freshly applied superphosphate were also determined at each level of soluble P. Residual effects of these dressings and responses to fresh superphosphate between 1974 and 1976 were measured by barley. Two amounts of N were tested on spring barley in 1976–7 and two cultivars of winter wheat were grown in 1977 and yields related to soluble P.
Relationships between yields and soluble P were described by an asymptotic regression equation. This model represented the measured yields well for all crops except barley, in one 4-year-period, when there were insufficient data at low soil P values and a linear regression model was fitted. The asymptotic model was used to estimate plateau yields each year and soluble P values at which yields were less than plateau values by one standard error. Average plateau yields, and associated soluble P values were: potatoes, 43 t/ha and 25 mg P/kg; sugar (from sugar beet) 6·8 t/ha and 20 mg P/kg; spring barley, given 63 kg N/ha, 4·7 t/ha and 25 mg P/kg; barley given 94 kg N/ha, 5·3 t/ha and 33 mg P/kg; winter wheat, 6·5 t/ha and 20 mg P/kg.
The model was further used to estimate responses to dressings of superphosphate at three levels of soluble P (9, 15 and 25 mg/kg) in the soils. Yield responses to 55 kg P/ha were 3·9, 2·1 and 1·8 t tubers/ha and 1·1, 0·3 and 0·0 t sugar/ha, for potatoes and sugar beet respectively, at the three levels of soluble P.
On impoverished soils (soluble P < 10 mg/kg) even the largest fresh applications of broadcast superphosphate did not raise yields to those achieved on enriched soils (soluble P > 25 mg P/kg) in the absence of fresh phosphate.
Soluble P in the soils accounted for much of the within-year variation of yields and estimated reliably and quantitatively the value of phosphate residues derived from both superphosphate and farmyard manure which had been applied in varying amounts and at different times between 1899 and 1976.
Effects of field beans, fallow, lupins, oats, oilseed rape, peas, ryegrass, sunflowers and wheat on nitrogen residues in the soil and on the growth of a subsequent wheat crop
- J. McEwen, R. J. Darby, M. V. Hewitt, D. P. Yeoman
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- The Journal of Agricultural Science / Volume 115 / Issue 2 / October 1990
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- 27 March 2009, pp. 209-219
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The effects on a winter wheat test crop of a preliminary year of winter or spring field beans (Vicia faba), winter oats, winter oilseed rape, winter or spring peas (Pisum sativum), winter wheat, spring lupins (Lupinus albus), spring sunflowers (Helianthus annuus) or a cultivated fallow were compared in three 2-year experiments on clay-with-flints soil at Rothamsted from 1986 to 1989. In one experiment, autumn-sown ryegrass (Lolium perenne) and an uncultivated fallow, given weedkiller, were also included in the first year. Plots of test-crop wheat were divided to compare no N fertilizer with an optimal amount estimated from a predictive model.
Amounts of take-all (Gaeumannomyces graminis) in the test crop of wheat following wheat were very slight in the first experiment, but large in the second and third. All the break crops reduced takeall to none or very slight amounts.
Amounts of NO3-N in the soil in autumn after the first-year crops ranged from 7 to 95 kg N/ha. On average, they were least after oats, and most after cultivated fallow. In autumn 1988they were least after autumn-sown ryegrass. In early spring, amounts of NO3-N were generally less, ranging from 7 to 55 kg N/ha, depending on preceding crops, sowing date of the wheat and the weather. Amounts of NH4-N in soil were little affected by preceding crops or weather and were generally smaller in spring.
The estimated average N fertilizer requirement of test-crop wheat following winter wheat was 230kg N/ha. This was increased by 10 kg N/ha following winter oats, decreased by 40 kg N/ha after spring peas and by 30 kg N/ha after winter rape, winter peas, spring beans and cultivated fallow. Other preliminary crops not represented every year had effects within this range.
Grain yields of test-crop wheat given optimal N averaged 7·2 t/ha after winter wheat, c.1·5 t/ha less than the average after most of the break crops. The yield after oats was limited by self-sown ‘volunteers’ and that after ryegrass by limited soil N after ploughing.
Of the break crops tested, winter and spring beans, winter oats, winter rape and spring peas all gave satisfactory yields. A farmer should choose between these on the basis of local farm circumstances and current economics of the break crops. Differences between effects on take-all and savings on fertilizer N were too small to influence this decision.
Results from an experiment on permanent grass evaluating the cumulative effects of aqueous urea, injected alone or with a nitrification inhibitor, with those of ‘Nitro-Chalk’
- J. Ashworth, F. V. Widdowson, A. Penny, A. J. Gibbs, R. A. Hodgkinson, M. V. Hewitt
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- The Journal of Agricultural Science / Volume 98 / Issue 1 / February 1982
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- 27 March 2009, pp. 141-155
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In an experiment on permanent grass at Rothamsted during 1975–9 fertilizer-N was applied each year either by injecting an aqueous solution of urea (supplying 250, 375 or 500 kg N/ha) in spring, or by broadcasting ‘Nitro-Chalk’ granules (supplying 100, 200, 300, 400 or 500 kg N/ha) in six equal dressings for each of six cuts.
Dry-matter production was largest on plots injected with urea through knives 30 cm apart, and more N was recovered from the injected than from the broadcast applications. Aqueous urea injected at the 60 cm knife spacing nitrified more slowly and persisted in the soil longer than urea injected at 30 cm spacing; this persistence caused grass to grow more uniformly throughout the season, but yields were less. Injecting the nitrification inhibitor sodium trithiocarbonate (STC) with the aqueous urea postponed N uptake much less than doubling knife spacing, but the inhibitor substantially diminished percentage N03-N in harvested grass.
In spring 1977 individual plots were split to measure N residues. Half-plots thus received N at the specified rates, either in 4 successive years (1975–8) or in two pairs of successive years (1975 and 1976; 1978 and 1979). In 1977 urea injected in the 2 previous years gave large residual effects, which were increased by STC and also by injecting in bands 60 instead of 30 cm apart. Broadcast ‘Nitro-Chalk’ had much smaller residual effects. In 1979 residual effects of N applied in the 4 previous years were apparently small, regardless of the method of application, because clover became abundant on plots not given N.
In 1978 dry-matter production was smaller where N had been given each year during 1975–8 than where N was withheld in 1977. Analysis showed this was caused by a shortage of potassium. This effect was most pronounced where 375 or 500 kg N/ha had been injected in bands 60 cm apart.
The results showed that a single, injected application of aqueous urea increased yields of dry grass as effectively as equivalent repeated dressings of ‘Nitro-Chalk’.
The relationship of soil mineral NO3-N with stem NO3-N concentration, and of fertilizer-N with the amount of nitrogen taken up by winter wheat, in experiments testing nitrogen fertilizer in combination with aphicide and fungicides, from 1980 to 1982
- R. J. Darby, F. V. Widdowson, E. Bird, M. V. Hewitt
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- Journal:
- The Journal of Agricultural Science / Volume 106 / Issue 3 / June 1986
- Published online by Cambridge University Press:
- 27 March 2009, pp. 497-507
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Experiments on winter wheat were made from 1980 to 1982 to test fungicide and aphicide sprays in factorial combination with four amounts of nitrogen fertilizer, applied in either one or two dressings in spring. The wheat was grown on three farms with contrasting calcareous clay soils from three soil series; each year it followed a 2-year break on one farm, a cereal rotation on the second and continuous wheat on the third. Soils were sampled to a depth of 0·9 m at seedling emergence in autumn, and again in February and April, to determine the NO3-N and NH4-N in each 0·3 m horizon. Crops were sampled for growth analysis at monthly intervals from March onwards and analysed for nitrogen content. Measurements of stem sap NO3-N concentration were also made at 2-weekly intervals from February or March to late June.
Measurements of soil mineral N were used to calculate the fertilizer nitrogen dressings used in the experiments. The concentration of NO3-N in the stem sap was related to NO3-N in soil; concentiations remained high until most of the soil NO3-N had been removed by the crop. The time at which stem sap NO3-N concentration declined therefore acted as an index of soil N supply, and the data showed that fertilizer-N was needed when the NO3-N concentration fell below a 200 μg/ml threshold. Yields benefited from N applied in February or March only when stem sap NO3-N concentration fell below the threshold at this time.
Apparent fertilizer nitrogen efficiency exceeded 70 % where yields were very large, but ranged between 53 and 64% where yields were smaller because either soil physical problems or disease restraints were present.
A severe attack by take-all (Gaeumannomyces cerealis) caused premature senescence at one centre in 1980; this apparently prevented previously assimilated nitrogen from moving into the grain.
Tests of nitrification and of urease inhibitors, when applied with either solid or aqueous urea, on grass grown on a light sandy soil
- G. A. Rodgers, A. Penny, F. V. Widdowson, M. V. Hewitt
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- Journal:
- The Journal of Agricultural Science / Volume 108 / Issue 1 / February 1987
- Published online by Cambridge University Press:
- 27 March 2009, pp. 109-117
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In 1984 and 1985 a field experiment on a grass ley on a light sandy soil at Woburn Experimental Farm, Bedfordshire, tested injected aqueous urea and broadcast prilled urea, applied alone or with a nitrification or urease inhibitor. Aqueous urea, prilled urea and ‘Nitro-Chalk’ were applied as a single 375 kg N/ha dressing, and prilled urea and ‘Nitro-Chalk’ also as three 125 kg N/ha dressings. The nitrification inhibitor nitrapyrin or a mixture of sodium trithiocarbonate (STC) plus potassium ethyl xanthate (KEtX) was injected with aqueous urea. The nitrification inhibitor dicyandiamide (DCD) or the urease inhibitor phenyl-phosphorodiamidate (PPDA) was broadcast with prilled urea.
The nitrification inhibitors significantly retarded nitrification of both aqueous and prilled urea. PPDA reduced ammonia volatilization from 375 kg N/ha broadcast as urea, and hence losses to the atmosphere, which otherwise ranged from 13 to 33 kg N/ha.
Nitrapyrin or STC and KEtX increased yield and nitrogen uptake in both years when urea was injected in January. Nitrapyrin also increased yield and nitrogen uptake in 1985, but not in 1984, when urea was injected in March, whereas the STC and KEtX mixture was then either detrimental or ineffective. DCD increased yield and nitrogen uptake from a single dressing of broadoast urea only in 1985. PPDA increased yield and nitrogen uptake from a single broadcast dressing of urea in both years, but had little effect when applied with divided dressings.
In 1984 a divided broadcast dressing of ‘Nitro-Chalk’ gave the largest yield and nitrogen uptake, but in 1985 aqueous urea injected with nitrapyrin in January or without or with a nitrification inhibitor in Maroh and prilled urea broadcast as a divided dressing all gave a larger yield. Similarly, a single application was generally more effective as ‘Nitro-Chalk’ in 1984, but as urea in 1985.
A comparison of the effects of prilled urea, used alone or with a nitrification or urease inhibitor, with those of ‘Nitro-Chalk’
- G. A. Rodgers, A. Penny, M. V. Hewitt
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- Journal:
- The Journal of Agricultural Science / Volume 106 / Issue 3 / June 1986
- Published online by Cambridge University Press:
- 27 March 2009, pp. 515-526
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Prilled urea, with or without a nitrification inhibitor (dicyandiamide, DCD) or urease inhibitor (hydroquinone), was compared with ‘Nitro-Chalk’ as a nitrogen fertilizer for winter oil-seed rape in field experiments on a clay loam soil at Rothamsted in 1984 and 1985. Each was tested when supplying 50 kg N/ha to the seed bed; each was also broadcast in early spring to supply 150 kg N/ha as either a single dressing or two equal dressings, the form of nitrogen being the same as that applied in the seed bed.
Seed-bed nitrogen increased plant growth during autumn and winter in both years but increased yield only in 1985.
Scorching of plant leaves was severe in spring after application of urea or urea plus DCD given as a single dressing, but was much less with urea plus hydroquinone or when the dressings were divided. DCD inhibited nitrification of fertilizer nitrogen but had little effect on yield compared with urea alone. Ammonia volatilization losses were reduced by urea plus hydroquinone but, irrespective of the type of fertilizer applied, loss was always less than 3% of the nitrogen applied. Soil pH rose rapidly after urea application and thereafter fell slowly, whereas pH fell immediately after application of ‘Nitro-Chalk’. Neither dicyandiamide nor hydroquinone affected the pH changes after urea application. Overall, grain yields from urea were 90%, whereas those from urea plus hydroquinone were 97%, of those obtained from ‘Nitro-Chalk’. Dividing the spring dressings of urea-nitrogen increased yield in 1985 compared with a single dressing, but not in 1984. Yields from divided and single dressings of ‘Nitro-Chalk’ were similar. Oil and protein yields generally showed the same patterns of response to the fertilizer treatments as were shown by grain yields.
Effects of several nitrification inhibitors, when injected with aqueous urea, on yields and nitrogen recoveries of ryegrass leys
- G. A. Rodgers, F. V. Widdowson, A. Penny, M. V. Hewitt
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- Journal:
- The Journal of Agricultural Science / Volume 101 / Issue 3 / December 1983
- Published online by Cambridge University Press:
- 27 March 2009, pp. 637-656
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Several nitrification inhibitors were compared with nitrapyrin, which was taken as the standard, when injected with aqueous urea into ryegrass leys at Rothamsted during 1977–81 and at Liscombe Experimental Husbandry Farm, Dulverton, Somerset, during 1977–9. Injection was done in either autumn or winter or spring.
All the inhibitors slowed down the rate of nitrate formation from the injected urea. Sodium trithioearbonate (STC) was less effective than nitrapyrin and potassium ethyl xanthate (KEtX) less effective than STC. A mixture of nitrapyrin and carbon disulphide was better than nitrapyrin alone, and a mixture of STO and KEtX was better than STC alone.
At Rothamsted, injecting inhibitors in autumn or winter improved yields and N uptakes, probably because they prevented loss of nitrate N by leaching and perhaps by denitrification. STC, STC-KEtX mixture and etridiazole were as good as, and nitrapyrin–CS2 mixture better than, nitrapyrin alone. Injecting inhibitors in spring frequently decreased yields, perhaps because NH4:NO3 ratios were too large, and increased them only when more than 150 mm of rain fell afterwards.
At Liscombe, where rainfall was higher, but soil temperatures were similar to those at Rothamsted, the benefits from using inhibitors in autumn were larger, but there were none from using them in spring.
Comparison of the effects of aqueous and of prilled urea, used alone or with urease or nitrification inhibitors, with those of ‘Nitro-Chalk’ on ryegrass leys
- G. A. Rodgers, F. V. Widdowson, A. Penny, M. V. Hewitt
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- Journal:
- The Journal of Agricultural Science / Volume 103 / Issue 3 / December 1984
- Published online by Cambridge University Press:
- 27 March 2009, pp. 671-685
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Field experiments on ryegrass leys at Rothamsted in 1981, 1982 and 1983 examined the eifects of injected aqueous urea and of broadcast prilled urea applied alone or with one of several nitrification or urease inhibitors, on yields and N, K, Ca and Mg uptakes. Aqueous urea, prilled urea or ‘Nitro-Chalk’ were applied as single 375 kg N/ha dressings, and prilled urea or ‘Nitro-Chalk’ as three 125 kg N/ha dressings. The nitrification inhibitors etridiazole or nitrapyrin were injected with aqueous urea, but dicyandiamide (DCD) was broadcast with prilled urea. Neither the urease inhibitor hydroquinone nor the nitrification inhibitors slowed the rate of urea hydrolysis. Neither hydroquinone nor DCD diminished volatilization losses of ammonia from broadcast urea which ranged from 8 to 25 kg N/ha; they were less than 4 kg N/ha from injected urea or broadcast ‘Nitro-Chalk’. Nitrapyrin, etridiazole and DCD effectively inhibited nitrification. DCD, and to a lesser extent hydroquinone, increased yields and nitrogen uptakes from a single broadcast application of prilled urea given either in winter or in spring. However, these yields were still smaller than those given by injected urea or by divided dressings of urea, whether or not an inhibitor was used. The inhibitors did not increase yields with divided broadcast dressings of urea, which were slightly smaller than those with equivalent dressings of ‘Nitro-Chalk’. Inhibitors did not consistently increase yield when injected with aqueous urea. Inhibitors applied with injected or broadcast urea slightly increased K uptakes, and slightly decreased Ca and Mg uptakes.
Effects of one to six year old ryegrass-clover leys on soil nitrogen and on the subsequent yields and fertilizer nitrogen requirements of the arable sequence winter wheat, potatoes, winter wheat, winter beans (Vicia faba) grown on a sandy loam soil
- A. E. Johnston, J. McEwen, P. W. Lane, M. V. Hewitt, P. R. Poulton, D. P. Yeoman
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- The Journal of Agricultural Science / Volume 122 / Issue 1 / February 1994
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- 27 March 2009, pp. 73-89
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The largest yields of wheat and potatoes came from the combination of longer ley plus optimum fertilizer N but yields of winter beans were decreased where N had been given to the previous crops. Without fertilizer N, two year old leys significantly increased yields compared to one year leys and the effect of longer leys was small except for the first wheat, when grain yields were large and plateaued after the three year ley.
Exponential response curves were fitted to the wheat yields and an exponential plus linear trend to the potato yields after each of the leys. Maximum yields and maximum economic yields and their associated N dressings were then estimated. Maximum economic yields of wheat in 1987 ranged from 811 to 914 t/ha grain and the fertilizer N needed declined from 174 kg/ha after the one year ley to 48 kg/ha after the six year ley. For potatoes in 1988, yields ranged from 63 to 71 t/ha tubers but the N required (137–150 kg/ha) varied little with ley age. For winter wheat, in 1989 yields ranged from only 5·51 to 6·99 t/ha grain, because of drought but, as with the potatoes, the N required (203–218 kg/ha) varied little. For each crop the six individual N response curves could be shifted to bring them into coincidence, and the benefits of the ley estimated in terms of a quantity of fertilizer N applied in spring (horizontal shift) and effects other than spring N (vertical shift). The spring N effects relative to the one year ley varied with ley age; for the first wheat the range was from 6 to 126 kg N/ha for the two to six year leys respectively. Spring N effects were negligible, however, for potatoes (average 6 kg/ha) and also for wheat in the third year (6 kg/ha). Benefits other than those which could be ascribed to spring N increased yield of the first wheat, on average, by 0·94 t/ha grain for the two to five year leys; for potatoes they ranged from 3·5 to 8·1 t/ha tubers for the three to six year leys; for the third crop wheat they ranged from 0·86 to 1·49 t/ha grain for the three to six year leys.
On average, the first wheat recovered only 34% of the applied fertilizer N whilst potatoes and the following wheat recovered 55 and 56% respectively. There was a benefit from the longer leys which affected the efficiency with which fertilizer N was used.
Increasing ley age up to five years increased total soil carbon by a maximum of 0·17%C; 18% of the carbon content of the soil in the one year ley plots. This small increase in soil organic matter provided up to 230 kg/ha mineral N in the first autumn after ploughing. Between 17 October 1986 and 27 April 1987 the average loss of NO3-N from soils following three to six year leys was equivalent to 202 kg N/ha, whilst the average uptake of N by 11 May in the above-ground wheat was only 88 kg/ha; the net loss was 114 kg N/ha. A computer simulation, which included mineralization of organic N during this period together with N uptake and nitrate leaching losses, computed a loss of 250 kg N/ha following the six year ley, and this would have given 400 mg NO3/1 in the 275 mm through drainage that winter.
Comparisons between the establishment, growth and yield of winter wheat on three clay soils, in experiments testing nitrogen fertilizer in combination with aphicide and fungicides, from 1980 to 1982
- R. J. Darby, F. V. Widdowson, M. V. Hewitt
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- Journal:
- The Journal of Agricultural Science / Volume 103 / Issue 3 / December 1984
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- 27 March 2009, pp. 595-611
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From 1980 to 1982 fungicide and aphioide sprays were tested in factorial combination with four amounts of nitrogen fertilizer, applied in one or two dressings to winter wheat, on three contrasting clay soils. These experiments were at Hexton (Burwell series) in Hertfordshire, at Billington (Evesham series) and at Maulden (Hanslope series) in Bedfordshire, following a 2–year break, an all-cereal rotation, and continuous wheat respectively. The nitrogen dressings were calculated after taking into account mineral N in the soil. In 1981 and 1982 soil density was measured by penetrometer. This showed compaction in soil at Maulden 28 cm deep which caused waterlogging in spring; this delayed growth which was not made good later.
At Hexton a small seed rate was used; plant losses during winter were proportionally larger than elsewhere. At Billington, the maximum number of stems occurred in March and elsewhere in April. Despite these differences in seed rate and number of plants, number of ears varied little, and each year the wheat at Hexton accumulated dry matter most rapidly. The growth rate there ranged from 20·0 to 21·8 g/m2/day during the linear growth phase as compared with 14·4 to 16·6 g/m2/day at the other two sites. Giving N in two dressings rather than in one increased dry-matter yield at all sites in May, but later this benefit remained static and so became a smaller proportion of the total. Fungicides increased post-anthesis dry-matter yield by 0·75 t/ha, most of which was incorporated in the grain.
Mean grain yields from 1980 to 1982 where nitrogen fertilizer was given were 9·86 t/ha at Hexton, 7·88 t/ha at Billington and 6–91 t/ha at Maulden. Additional nitrogen fertilizer always increased grain yield when fungicides and aphicides were given, but not where they were not. Grain yields in excess of 10 t/ha were achieved with numbers of ears ranging between 360 and 435/m2. The components of yield showed that grain yield was related to the number of grains per ear and 1000·grain weight, but not number of ears. Grain weight was increased by 3·1 mg by the fungicides.
The fungicides controlled the diseases eyespot (Pseudocercosporella herpolrichoides), Septoria spp. and yellow and brown rust (Pucdnia striiformis and P. recondita) where they occurred, but even where these diseases were absent or at very low levels the fungicides significantly increased grain yield. At Billington and Maulden take-all (Qaeumannomyces graminis) infected between 44 and 90% of the plants and sharp eyespot (Rhizoctonia cerealis) infected from < 1 to 20% of the stems because the wheat followed cereals. Yields of straw behind the combine-harvester were from 50 to 70% of those obtained from sheaves cut at ground level.
A comparison of the effects of single or multiple spring applications of prilled urea or ‘Nitro-chalk’ to winter oilseed rape (Brassica napus)
- R. J. Darby, M. V. Hewitt
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- Journal:
- The Journal of Agricultural Science / Volume 115 / Issue 3 / December 1990
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- 27 March 2009, pp. 363-368
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An earlier report of leaf scorch and diminished yield when using large amounts of urea on winter oilseed rape (Brassica napus) was investigated by applying 200 kg N/ha as calcium ammonium nitrate (‘Nitro-chalk’) or urea as a single dressing or divided in six ways. The ‘single-low’ variety Mikado (low in erucic acid) was grown in 1986 and was compared with the ‘double-low’ variety Ariana (low in erucic acid and glucosinolates) in 1987 and 1988. No scorch was seen in these experiments. Yield from rape fertilized with prilled urea was, on average, 98% of that from rape fertilized with ammonium nitrate. The timing and distribution of the fertilizer also had little effect on yield, though yield slightly decreased when part of the dressing was withheld during March. The earlier-maturing variety Mikado always outyielded Ariana except when harvest was delayed by bad weather.
When plots were fertilized with urea, the oil content of the seed was a little larger than when fertilized with Nitro-chalk, which compensated for the smaller seed yield, resulting in almost equal oil yield from both forms of N fertilizer. Crude protein content was lower after a large single dose of urea fertilizer but parity with ammonium nitrate was restored by smaller amounts applied on a number of occasions. Neither form nor timing of N fertilizer had any consistent effect on the total glucosinolate content.
The incidence of disease was significantly greater in rape given either form of N fertilizer than where none was given, but when downy mildew (Peronospora parasitica) was prevalent on pods there was significantly less infection in plots fertilized with urea than with ammonium nitrate.
Tests of amounts and times of application of nitrogen and of sequential sprays of aphicide and fungicides on winter wheat, following either beans or wheat, and the effects of take-all (Gaeumannomyces graminis var. tritici), on two varieties at Saxmundham, Suffolk 1980–3
- F. V. Widdowson, A. Penny, R. J. Gutteridge, R. J. Darby, M. V. Hewitt
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- Journal:
- The Journal of Agricultural Science / Volume 105 / Issue 1 / August 1985
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- 27 March 2009, pp. 97-122
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From 1980 to 1983 factorial experiments at Saxmundham were made on winter wheat following beans, so as to minimize losses from foot and root rots and increase potential yields. All tested seed-bed N, and amounts and times of application of N in spring, both with and without sprays intended to limit losses from aphids and from diseases. The tests were made on one semi-dwarf variety in 1980 and on two contrasting varieties from 1981 to 1983. In 1982 and 1983 a comparison was made between wheat following beans and wheat following wheat; all treatments were applied cumulatively to the two successive wheat crops.
In 1980 and in 1981 N given in March greatly increased the number of shoots in April but had little effect on the final number of ears. Yields of grain were greatly increased by N given during April and by sequential sprays with fungicides and aphicide; these two factors interacted so that responses to N were larger with the sprays than without. Yield responses to seed-bed N, although small, were greater than the benefits from applying divided instead of single N dressings in spring. The number of ears was greatly increased by increasing the amount of N given in April, but only slightly by any of the other treatments. The weight of 1000 grains was greatly increased by the sprays of aphicide and fungicides and was decreased by N in 1981, but not in 1980. Largest yields of grain were 10·14 t/ha in 1980 and 10·91 t/ha in 1981 when N was given in spring at 160 and 200 kg/ha respectively, and the crops were sprayed with pesticides.
In 1982 and 1983 N applied in March again greatly increased the number of shoots in April, but not the final number of ears. Yields of grain were larger after beans than after wheat, mainly because the number of ears and the weight of 1000 grains were greater. This may have been because take-all (Gaeumannomyces graminisvar. tritici) was more severe where wheat followed wheat. Previous cropping also interacted with variety; Avalon yielded slightly less than Norman where take-all was slight but much less where take-all was severe. Where N was given the mean loss in yield from growing Avalon rather than Norman in the 2 years was 2·47 t/ha after wheat and 0·37 t/ha after beans. The take-all disease ratings of Norman and Avalon after wheat were 132 and 197 respectively. Yields of grain were greatly increased by N given during April, especially of wheat following wheat and where it was protected with sprays; then the mean yield was only 2·79 t/ha without N but 8·78 with 235 kg N/ha. Where wheat followed beans, yields were 6·89 t/ha without N and 11·07 with 175 kg N/ha. Applying N to the seed bed increased yields slightly, and again by more than by dividing the dressing of N in spring. The number of ears was greatly increased by N in spring and a little by all the other factors that increased grain yield. The weight of 1000 grains was increased greatly by the sprays of aphicide and fungicides, was decreased by N, and was larger for Norman than for Avalon.
In 1980–1, after beans, the mean amounts of N removed by the grain (where aphicide and fungicides were given) ranged from 81 kg/ha without N fertilizer to 167 where most N was given. In 1982–3 comparable values ranged from 86 kg N/ha to 191 where wheat followed beans and from 35 kg N/ha to 168 where wheat followed wheat.
Amounts of NO3-N and NH4-N in soil, from autumn to spring, under winter wheat and their relationship to soil type, sowing date, previous crop and N uptake at Rothamsted, Woburn and Saxmundham, 1979–85
- F. V. Widdowson, A. Penny, R. J. Darby, E. Bird, M. V. Hewitt
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- Journal:
- The Journal of Agricultural Science / Volume 108 / Issue 1 / February 1987
- Published online by Cambridge University Press:
- 27 March 2009, pp. 73-95
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Soil NO3-N and NH4-N were measured to 90 cm depth in autumn and again in spring, under several sets of winter wheat experiments, on contrasting sites. Crop samples were taken throughout the growing season, both before and after the fertilizer N was applied, to measure N uptake. The amount of NO3-N in soil at the outset of growth in autumn was related to the uptake of N by wheat not given any fertilizer N until April.
The effect of sowing date (September v. October) on both crop and soil N was compared, as also was the effect of soil type (retentive of NO3-N v. readily leached) and previous crop (potatoes v. oats and wheat v. beans).
The amounts of NO3-N in the soils in autumn related well with previous crop and declined gradually during winter on the heavier soils, but rapidly on the sandy soil, in the latter case as a consequence of leaching. On the heavier soils, where little leaching occurred, the decline in soil NO3-N related well with the amount of N taken up by September-sown wheat during autumn and winter, but not with that taken up by October-sown wheat, where NO3-N accumulated in the soil during winter, because uptake was so small. Hence delayed sowing enhanced the likelihood of losses of NO3-N by leaching or by denitrification. On the sandy soil at Woburn, whilst the September-sown wheat removed more N than the October-sown, losses of NO3-N by leaching were severe, so that late winter growth was restricted by shortage of N in soil, and the amount of N taken up was far smaller than at Rothamsted.
The soil measurements distinguished between the NO3-N residues remaining after beans or wheat in the same field and between residues after oats or potatoes on soils of the same soil series, but in different fields on the same farm.
The amount of NO3-N in soil and the N taken up by wheat in February-March were together used to adjust the amount of fertilizer N applied in April, using a balance sheet approach to meet a specific yield objective. Some of the N uptake data from these experiments are presented. This should aid the calculation of N requirement during specific growth periods and thus help improve the prediction of fertilizer N dressings in spring.
Masers as probes of massive star formation in the nuclear disk
- F. Yusef-Zadeh, R. G. Arendt, C. O. Heinke, J. L. Hinz, J. W. Hewitt, P. Pratap, S. V. Ramirez, G. H. Rieke, D. A. Roberts, S. R. Stolovy, M. Wardle, B. A. Whitney
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- Journal:
- Proceedings of the International Astronomical Union / Volume 3 / Issue S242 / March 2007
- Published online by Cambridge University Press:
- 01 March 2007, pp. 366-373
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- March 2007
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OH(1720 MHz) and methanol masers are now recognized to be excellent probes of the interactions of supernova remnants with molecular clouds and tracers of massive star formation, respectively. To better understand the nature of star formation activity in the central region of the Galaxy, we have used these two classes of masers combined with the IRAC and MIPS data to study prominent sites of ongoing star formation in the nuclear disk. The nuclear disk is characterized by massive GMCs with elevated gas temperatures, compared to their dust temperatures. We note an association between methanol masers and a class of mid-infrared “green sources”. These highly embedded YSOs show enhanced 4.5μm emission due to excited molecular lines.
The distribution of methanol masers and supernova remnants suggest a low efficiency of star formation (with the exception of Sgr B2), which we believe is due to an enhanced flux of cosmic ray electrons impacting molecular clouds in the nuclear disk. We also highlight the importance of cosmic rays in their ability to heat molecular clouds, and thus increase the gas temperature.
The contribution of transfusion to HCV infection in England
- K. SOLDAN, M. RAMSAY, A. ROBINSON, H. HARRIS, N. ANDERSON, E. CAFFREY, C. CHAPMAN, A. DIKE, G. GABRA, A. GORMAN, A. HERBORN, P. HEWITT, N. HEWSON, D. A. JONES, C. LLEWELYN, E. LOVE, V. MUDDU, V. MARTLEW, A. TOWNLEY
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- Journal:
- Epidemiology & Infection / Volume 129 / Issue 3 / December 2002
- Published online by Cambridge University Press:
- 10 January 2003, pp. 587-591
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The English HCV lookback programme has identified some individuals with transfusion-transmitted HCV infection. The path from the collection of donations from HCV-infected donors to the identification of infected recipients was constructed. The probability of different outcomes at each branch was derived from data collected during this programme. This path of probabilities was then used to produce a complete estimate of the number of recipients infected by blood transfusions (dead and alive at the end of 1995) by re-entry of blood components that fell out of the lookback at various steps prior to recipient testing, and entry of components from HCV-infected donations that were never identified for lookback. Less than 14 000 recipients were estimated to have been infected with HCV during the decade prior to the start of donation testing. Over 60% of these were expected to have died by the end of 1995. Transfusion has infected a large group of individuals. However, this group constitutes a very small, and declining, proportion of all HCV infections in the population.
A comparison of management regimes for one-year rotational set-aside within a sequence of winter wheat crops, and of growing wheat without interruption. 1. Effects on soil mineral nitrogen, grain yield and quality
- E. T. G. BACON, M. V. HEWITT, C. E. SHEPHERD
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- Journal:
- The Journal of Agricultural Science / Volume 130 / Issue 4 / June 1998
- Published online by Cambridge University Press:
- 01 June 1998, pp. 377-388
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A series of three experiments on loam to sandy loam soil at Woburn, all following winter or spring wheat, tested the effects of six different 1-year set-aside treatments and crops of winter wheat in 1989, 1990 and 1991 on two following winter wheat test crops. Effects of the treatments on overwinter changes in soil mineral nitrogen (SMN) and plant N in the set-aside years and in the first test crops were measured, as were the grain yields of both the first and second test crops.
Differences in net overwinter changes in SMN plus plant N between set-aside treatments were variable and dependent on rainfall. During a wet winter, SMN plus plant N losses were large under fallow and natural regeneration, intermediate under winter wheat and small under Italian ryegrass (Lolium multiflorum). Ryegrass restricted the growth of the following wheat but yields were unaffected where fertilizer N was applied. Ryegrass proved difficult to control in the subsequent wheat test crops. Forage rape (Brassica napus) took up large amounts of N but after topping did not compete well with weeds.
Yields of the first wheat test crops after winter wheat were smaller than after the set-aside treatments, take-all was probably the cause of this yield depression. No consistent yield differences were recorded in the second wheat test crops.
VLBI Observations of the Gravitational Lens System 2016+112
- M. B. Heflin, M. V. Gorenstein, E. E. Falco, I. I. Shapiro, B. F. Burke, J. N. Hewitt, A. E. E. Rogers, C. R. Lawrence
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- Journal:
- Symposium - International Astronomical Union / Volume 129 / 1988
- Published online by Cambridge University Press:
- 03 August 2017, pp. 209-210
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- 1988
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On June 1, 1984 we conducted a seven station 18-cm VLBI observation of the 2016+112 gravitational lens system. Preliminary brightness distributions for A and B have been obtained via model fitting. Weak correlated flux density was detected in the C component region.