With harvest upon us, and poor weather affecting progress, I thought it pertinent to write something about grain quality, how it is influenced and the effect bad weather and a delayed harvest can have. A late harvest coupled with excessive rainfall means more time for late season mold growth, mycotoxin accumulation, specific weight reduction and sprouting; all of which can result in poor overall grain quality.
Grain quality is affected by myriad factors form the variety, to the soil and climate and crop management practices.
Crop nutrition is vitally important with nitrogen and potassium playing important roles, with the N increasing protein and starch whilst the potassium strengthens the straw reducing the risk of lodging that can have negative impacts on hagberg falling number and specific weight in wheat. Potassium is essential for a good specific weight and well filled grains, and a deficiency can give premature ripening, leading to smaller gains with lower weight. Sulphur, magesium and zinc also play important roles in influencing grain protein and specific weight. Specific weight is heavily influenced by the variety and is a genetic trait, but crop nutrition is also important.
One of the main causes of low Hagberg falling number is pre harvest sprouting and lodging, brought about by wet weather. Even ripening crops can give better HFNs. It should be said that this trait is also heavily influenced by the variety.
Though the three main quality components are very dependent on variety choice, delays to harvest and lodging will have a significant impact. Harvesting as soon as the crop is ripe and at high moisture is the best way to protect quality.
As with wheat, variety has the biggest influence but crop nutrition and lodging also have an impact on grain quality.
Specific weight is predominantly determined by plant variety genetics, and factors affecting length of the grain filling period. Poorly managed crop nutrition and lodging can reduce specific weight. Screenings due to small grains is determined by a combination of plant variety genetics and weather during the growing season. High levels of screenings can reduce milling throughput, and so screening percentages should be considered when selecting varieties for milling end use. Specific weight tends to be higher in the north whilst screenings are lower.
Kernel content is a highly heritable trait but is also influenced by management practices, particularly high N. Protein content is significantly affected by the crop nutrition. Environmental factors and variety also have an impact. Beta-glucan content in oats is mainly determined by environmental factors and variety. Kernel content tends to be higher in the north whilst protein and beta glucan are higher in the south.
Malting markets have specific requirements including variety, germination, grain nitrogen content and size, malt extract levels and physical integrity. Most feed grain buyers require a minimum specific weight
Nitrogen is highly influenced by variety but also by nitrogen availability and uptake during grain filling. High nitrogen levels can also result from drought, lodging or disease all of which will reduce yield and hence N concentration as redistribution remains unaffected. Grain concentrations tend to be lower in the north where most malting barley is used for malt distilling. In the south where grain N tends to be higher, barley is used for brewing. The export market for brewing tends to allow higher N concentrations in the grain.
Specific weight is influenced by variety but also plant population. Large well-filled grains have a high malt extract potential, so screenings need to be minimised. Intermittent wetting and drying of barley grain can cause skinning, the partial of complete loss of the husk. Combine settings and variety will also have an effect.
Malsters like varieties with high malt extract which increases productivity in brewing and distilling. It is influenced by variety choice, grain size and homogeneity, grain N content and enzymes. Large even sized grains mill better whilst low grain N increases starch content.