Wet gluten of wheat varieties cultivated under extenso and PER conditions

The users of the Swiss wheat harvest noted a decrease in the wet gluten content over the past years. To assure a good level of wet gluten, the branch organization swiss granum introduced thresholds for each wheat quality class. These thresholds are for the Top class 31 %, for the class I 29 % and for the class II 27 %. A correction factor will be applied to compensate in years with low or high levels of wet gluten. A ringtest by several private and public laboratories has been carried out to determine the level of wet gluten of the same varieties, cultivated at the same site, produced under extenso or PER conditions. The main difference is 30 units less nitrogen fertilizer used under extenso conditions. Correlations between the results obtained by the various laboratories were very high. The same varieties cultivated under extenso conditions showed a lower level of wet gluten than those cultivated under PER, at all trial sites. The average level of wet gluten was higher in 2010 than in 2009. The difference of wet gluten level between PER and extenso was on average 3,6 % in 2009 and 2,7 % in 2010. For the determination of the wet gluten thresholds it proved to be difficult to include a correction factor taking into account the results of the extenso trials without carrying out detailed analyses each year. For this reason, it was decided to take into account only the results of the two years PER trials to determine if a variety reached the threshold for its quality class.