Do cover crops change the lability of phosphorus in a clayey subtropical soil under different phosphate fertilizers?          下载免费PDF全文

A. P. B. Teles  M. Rodrigues  W. F. Bejarano Herrera  A. Soltangheisi  L. R. Sartor  P. J. A. Withers  P. S. Pavinato 《Soil Use and Management》2017,33(1):34-44

Plants have developed different mechanisms to absorb and solubilize phosphorus (P) in the soil, especially in environments with low P availability. This study evaluated the effects of different winter cover crops on soil P availability in a clayey subtropical (Hapludox) soil receiving soluble P fertilizer and a rock phosphate applied to the summer crop, under no‐tillage. The experiment was carried out over 3 yrs (2009–2011) with five different cover crop species: common vetch, fodder radish, ryegrass, black oat, white clover and fallow as control. The soil was sampled after the third year of cover crop cultivation and analysed for inorganic and organic P forms according to the well‐established Hedley fractionation procedure. Phosphate fertilizers promoted accumulation of both labile and nonlabile P pools in soil in the near surface layer, especially under rock phosphate. Fertilizer applications were not able to change P fractions in deeper layers, emphasizing that the Brazilian clayey soils are a sink of P from fertilizer and its mobility is almost nil. Although the cover crops recycled a great amount of P in tissue, in a short‐term evaluation (3 yrs) they only changed the content of moderately labile P in soil, indicating that long‐term studies are needed for more conclusive results.  相似文献   

A case history of psittacosis in the dog   总被引：2，自引：0，他引：2  

G Fraser  J Norval  A R Withers  W W Gregor 《The Veterinary record》1969,85(3):54-58

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Angus Cunningham     

GN Withers 《Australian veterinary journal》2014,92(8):276-276

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Formation of a Reservoir of Sperm in the Oviduct   总被引：2，自引：0，他引：2  

SS Suarez 《Reproduction in domestic animals》2002,37(3):140-143

A reservoir of sperm in the initial segment of the oviduct has been found in several species of domestic and laboratory mammals. Evidently, the reservoir serves to ensure successful fertilization by providing the appropriate number of sperm in the appropriate physiological state for fertilizing oocytes soon after they enter the oviduct. Recent evidence indicates that sperm are trapped in the reservoir by binding to specific carbohydrate moieties on the surface of the mucosal epithelium of the oviduct. A bovine seminal plasma protein has been identified that associates with sperm and confers on them the capacity to bind to the carbohydrate moiety.  相似文献   

Incidental phosphorus losses – are they significant and can they be predicted?     

Paul J. A. Withers  Barbro Uln  Christian Stamm  Marianne Bechmann 《植物养料与土壤学杂志》2003,166(4):459-468

Fresh applications of phosphorus (P) may cause ‘incidental’ losses of dissolved and particulate P forms in land runoff when rainfall interacts directly with fertilizers and manures which are spread, or excreted, onto the soil surface. Research indicates that when incidental P losses (IPL) occur, they often make the dominant (50–98 %) contribution to measured P loads in surface and sub‐surface runoff from field plots, with increased risk of eutrophication where P‐enriched runoff is routed directly to the watercourse. Rates of P loss are temporally and spatially very variable (< 1 to 25 % of total P applied) depending on the amount of P applied; the P release properties of the materials applied (% P extractable in water), the timing of storm events after application and the amounts of runoff generated. Large P applications left on the surface of wet, frozen, compacted, and intensively underdrained soils in high rainfall areas are particularly vulnerable to IPL. Concentrations of P in runoff are often greatest during the first storm event following P application, but can remain high for several weeks, or even months after application. Catchment scale impacts are more difficult to quantify due to the effects of dilution with runoff from fields without IPL, and the contributions of P from other sources. Approaches to predicting IPL are discussed and need to be improved in order to assess the contribution of IPL to catchment P loads in river basin management planning. Strategies to control IPL should focus on adoption of more sensitive management practices in fields with a high risk of rapid runoff or preferential flow, and are likely to very effective.  相似文献   

Neutron scattering. The case for neutron sources     

Keimer B  Sackmann E  Withers PJ 《Science (New York, N.Y.)》2002,298(5593):543

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Structural basis for the activation of glycogen phosphorylase b by adenosine monophosphate   总被引：12，自引：0，他引：12  

S R Sprang  S G Withers  E J Goldsmith  R J Fletterick  N B Madsen 《Science (New York, N.Y.)》1991,254(5036):1367-1371

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Rise of the Andes     

Garzione CN  Hoke GD  Libarkin JC  Withers S  MacFadden B  Eiler J  Ghosh P  Mulch A 《Science (New York, N.Y.)》2008,320(5881):1304-1307

The surface uplift of mountain belts is generally assumed to reflect progressive shortening and crustal thickening, leading to their gradual rise. Recent studies of the Andes indicate that their elevation remained relatively stable for long periods (tens of millions of years), separated by rapid (1 to 4 million years) changes of 1.5 kilometers or more. Periodic punctuated surface uplift of mountain belts probably reflects the rapid removal of unstable, dense lower lithosphere after long-term thickening of the crust and lithospheric mantle.  相似文献   

Linking phosphorus sources to impacts in different types of water body   总被引：4，自引：0，他引：4  

A. C. Edwards  & P. J. A. Withers 《Soil Use and Management》2007,23(S1):133-143

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Agriculture, phosphorus and eutrophication: a European perspective   总被引：3，自引：0，他引：3  

P. J. A. Withers  & P. M. Haygarth 《Soil Use and Management》2007,23(S1):1-4

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