Formation of wine pyranoanthocyanins in model wine was monitored by HPLC-DAD-ESI-MS/MS, using red grape skin extracts and wine fermentation metabolites (acetaldehyde, pyruvic and acetoacetic acids, and diacetyl) and also hydroxycinnamic acids (p-coumaric, caffeic, ferulic, and sinapic acids). Pyruvic acid and acetaldehyde reacted fast, the first reaching high product yield and the second inducing mainly pigment polymerization. In contrast, acetoacetic acid and diacetyl reacted slowly with poor product yields. Hydroxycinnamic acids progressively reacted without apparent formation of polymeric pigments, the reaction rate and yield increasing as the number of hydroxy/methoxy groups did. Substituent at C-10 strongly affected the visible maximum absorbance wavelength, whereas B-ring substitution pattern or sugar acylation exerted little effect. The 10-methylpyranoanthocyanins formed from acetoacetic acid were also found as side products in the formation of 10-carboxypyranoanthocyanins. Finally, we report for the first time on UV-vis and MS spectral data of 10-acetylpyranoanthocyanins formed from diacetyl, and their occurrence in commercial red wines is suggested.

Efficient N fertilizer management is critical for the economic production of wheat and the long‐term protection of environmental quality. A 3‐yr field experiment on a rainfed Vertisol was designed to study the effects of N fertilizer timing on the efficiency of N in durum wheat (Triticum turgidum L. var. durum Desf.). A single rate of 150 kg N ha−1 was used with different fractions being applied at planting, tillering, and stem elongation. A 15N experiment was also conducted within the main experiment area, with microplots, to quantify N uptake from fertilizer and soil. Mean wheat recovery of N fertilizer ranged from 12.7% when applied at sowing to 41.6% when applied as a topdressing at the beginning of stem elongation. The mean annual contribution of soil residual N and mineralization was 167 kg N ha−1, representing a considerable proportion of total wheat N uptake—ranging from 80.4% when N fertilizer was applied in the fall to 56.3% when it was applied at stem elongation. This would account for the poor and inconsistent response of grain yield and N efficiency indices, and for the importance of soil N in Vertisols for predicting wheat N fertilizer requirements, due to the carryover effect. It is recommended that N fertilizer be applied mainly as a topdressing in durum wheat, between tillering and stem elongation, to enhance crop N use efficiency (NUE) and reduce losses through leaching and runoff.

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of which depends on rainfall and its distribution during the growing season (Cooper et al., 1987).The combined long-term effects of tillage method, crop rotation, One of the more important rainfed Mediterranean and N fertilizer rates on grain yield have not been studied in rainfed regions, the so-called ''Campiñ a'', is located in Andasystems under Mediterranean climates. As part of a long-term experiment started in 1986, a field study was conducted between 1994 and lusia (southern Spain). This region, characterized by 1998 to determine the effects of tillage (TILL), crop rotation (ROT), Vertisols, produces mostly wheat at yield levels greater and N fertilization on wheat (Triticum aestivum L.) growth and yield than the Mediterranean area average (2-2.5 Mg ha Ϫ1 ). in a rainfed Mediterranean region. Tillage treatments included no Farmers in the region use high levels of inputs, particutillage (NT) and conventional tillage (CT). Crop rotations were wheatlarly N fertilizer. Typically, wheat is rotated with sunsunflower (Helianthus annuus L.) (WS), wheat-chickpea (Cicer arieflower, and to a lesser extent faba bean and chickpea. tinum L.) (WCP), wheat-faba bean (Vicia faba L.) (WFB), wheat-Bare fallow is seldom used on these soils, which are fallow (WF), and continuous wheat (CW). Nitrogen fertilizer rates fertile and possess soil texture favorable for water retenwere 0, 50, 100, and 150 kg N ha Ϫ1 on a Vertisol (Typic Haploxerert). tion. Fallow is only encountered as a result of set-aside A split-split plot design with four replications was used. Heavy rainfall measures of the European's Community Agricultural during this research negatively impacted vegetative growth and grain yield of the wheat due to waterlogging. Wheat yield in the wet years Policy Reform. Conventional tillage with moldboard was lower under NT than under CT. Yield decreased in the following plowing is commonly used but conservation tillage praccrop rotation sequence: WFB WF Ͼ WS Ͼ WCP CW. Wheat

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UK wheat (Triticum aestivum L.) has a low selenium (Se) concentration and agronomic biofortification with Se is a proposed solution. A possible limitation is that UK wheat is routinely fertilised with sulphur (S), which may affect uptake of Se by the crop. The response of wheat to Se and S fertilisation and residual effects of Se were determined in field trials over 2 consecutive years. Selenium fertilisation Plant Soil (2010) 332:31-40 at 20 g ha −1 as sodium selenate increased grain Se by four to seven fold, up to 374 µg Se kg −1 . Sulphur fertilisation produced contrasting effects in 2 years; in year 1 when the crop was not deficient in S, grain Se concentration was significantly enhanced by S, whereas in year 2 when crop yield responded significantly to S fertilisation, grain Se concentration was decreased significantly in the S-fertilised plots. An incubation experiment showed that addition of sulphate enhanced the recovery of selenate added to soils, probably through a suppression of selenate transformation to other unavailable forms in soils. Our results demonstrate complex interactions between S and Se involving both soil and plant physiological processes; S can enhance Se availability in soil but inhibit selenate uptake by plants. Furthermore, no residual effect of Se fertiliser applied in year 1 was found on the following crop.

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