AGRONOMIC FACTORS RELATED TO THE QUALITY OF WHEAT FOR THE STARCH INDUSTRY .2. NITROGEN-FERTILIZATION AND OVERALL CONCLUSIONS

In the N.W.-European wheat growing system high levels of nitrogen fertiliser are applied. Especially late nitrogen applications are thought to increase the amount of soluble proteins, leading to extra losses and wastage. On the other hand, protein content is the most important factor determining gluten yield. The effects of fertilisation on processing quality have been investigated using a pilot separator. Samples from fertilisation trials show a high correlation between gluten yield and protein content of the flour. This relation is variety dependent, due to differences in water-soluble proteins. For both varieties the percentage of water-soluble proteins appeared to decrease with increasing N-fertilisation levels. At low protein contents of the flour the coagulation of the gluten is adversely influenced. Using soft bread wheats, this may cause severe difficulties during separation. At high fertilisation levels the amount of solubles in the waste water increased slightly. - A review on research results is made, showing the criteria for wheat for the starch industry.