The influence of long-term inputs of catch crops and cereal straw on yield, protein composition and technological quality of a spring and a winter wheat

Under conditions of restricted nitrogen (N) input such as in organic farming systems, crop N uptake must rely on N mineralised from applied animal manure, crop residues and native soil organic matter. Scarcity of N may impede the production of quality grain for bread production, and input and retention of N in soil are therefore important parameters for soil fertility. Toretain N in the crop-soilsystem, catch crops may be grown in breaks between main crops where they provide a significant sink for N mineralised in late summer and autumn (Thomsen, 2005). In corporation of straw may likewise retain mineralised N by microbial immobilisation (Christensen, 1986) and will also directly add to the N mineralisation potential when the N supplied in the straw accumulates (Thomsen & Christensen, 2004). Under northern European conditions, winter wheat may generally be of lower quality than spring wheat, but winter wheat has a higher yield potential. When the N uptake is mainly based on N mineralised from either applied or indigenous soil organic matter, however, this may even out the quality difference between winter and spring wheat as the longer growing season of winter wheat may boost its N utilisation. Growing conditions are highly important for protein quantity whereas main lygenetic factors influence protein composition (Amesetal., 1999; Luoetal., 2000). Wheat grain proteins have been classified as albumins, globulins, gliadins and glutenins on the basis of their solubility (Osborne, 1907). Reverse-phase (RP) high performance liquid chromatography (HPLC) allows the quantitative determination of these different flour protein groups together with single proteins (α5-, α1,2-, α-, γc-type gliadins, x- and γ-type high (HMW) and low (LMW) molecular weights subunits of glutenin) (Wieser & Seilmeier, 1998). The proteins can also be divided into polymers (glutenins) or monomers (gliadins, albumins, globulins) based on their aggregating properties. The polymeric proteins are critical for governing wheat flour processing properties, and their quantity and size distribution reliably measured by size-exclusion (SE) HPLC techniques have been shown to be important indicators of baking quality (Dachkevitch & Autran, 1989; Bateyetal., 1991). The aim of this study was to examine whether wheat yield and baking quality determined by chromatographic techniques together with rheological and chemical quality measurements could be improved by combining agronomic strategies consisting of wheat cultivars and long-term organic matter inputs. The variables tested were (A) a winter wheat and a spring wheat cultivar, (B) three catch crop strategies and (C) four straw incorporation rates

Electronic and phononic Raman scattering in detwinned YBa2_2Cu3_3O6.95_{6.95} and Y0.85_{0.85}Ca0.15_{0.15}Ba2_2Cu3_3O6.95_{6.95}: s-wave admixture to the dx2−y2d_{x^2-y^2}-wave order parameter

Inelastic light (Raman) scattering has been used to study electronic excitations and phonon anomalies in detwinned, slightly overdoped YBa$_2$Cu$_3$O$_{6.95}$ and moderately overdoped Y$_{0.85}$Ca$_{0.15}$Ba$_2$Cu$_3$O$_{6.95}$ single crystals. In both samples modifications of the electronic pair-breaking peaks when interchanging the a- and b-axis were observed. The lineshapes of several phonon modes involving plane and apical oxygen vibrations exhibit pronounced anisotropies with respect to the incident and scattered light field configurations. Based on a theoretical model that takes both electronic and phononic contributions to the Raman spectra into account, we attribute the anisotropy of the superconductivity-induced changes in the phonon lineshapes to a small s-wave admixture to the $d_{x^2-y^2}$ pair wave-function. Our theory allows us to disentangle the electronic Raman signal from the phononic part and to identify corresponding interference terms. We argue that the Raman spectra are consistent with an s-wave admixture with an upper limit of 20 percent.Comment: accepted in Phys. Rev. B, 11 page