Cereals processing technology

populations of leatherjackets (Tipula paludosa) in spring. The incidence of
barley yellow dwarf virus increases, especially in early drilled crops, if the
autumn is warm, due to the increased activity of aphids.
Increasing emphasis is currently being placed on the production of high
quality grain whilst minimising pesticide use. To achieve this objective more
information is needed to identify situations where the use of pesticides cannot be
avoided without serious financial loss. Forecasting pest activity by modelling
their behaviour is one way in which more effective control strategies can be
developed in the future. Threshold levels for individual pests, below which it is
cost effective to apply a pesticide, are already helping to reduce pesticide usage.
There is further scope to encourage beneficial organisms to counteract cereal
pests in the field under the common aim of developing ‘integrated pest
management systems’. This approach places greater reliance on promoting
vigorous crop growth through appropriate cultivations, rotations, and other
agronomic inputs and the encouragement of beneficial organisms. In such a
system selective pesticides could be used precisely timed to have the greatest
impact on the pest, but to leave the ‘beneficials’ to prosper.
2.8 Harvesting and grain storage
Cereal production methods 25
Grain quality is largely determined during the growing season. Once the grain
has been harvested it is difficult to improve its quality, although quality can
easily be destroyed by conditions during harvest and subsequent drying and
storage. Indeed grain quality can start to deteriorate in the field prior to harvest.
Rainfall prior and during the harvest period can encourage ear diseases and
premature sprouting, whilst high grain moisture levels will necessitate increased
drying costs. For example, delaying the wheat harvest can result in grain with
high -amylase content, lower specific weight and protein contents, factors that
will seriously reduce the quality of the grain for breadmaking.
Almost all UK grain will be harvested by large self propelled combine
harvesters which are highly efficient, causing minimal physical damage to the
grain when they are properly set and operated. The condition of the crop at
harvest has a significant influence on combine performance; severely lodged
crops not only produce inferior quality grain, but also reduce combine speed and
efficiency. The presence of weeds also interferes with the harvesting process and
often leads to higher grain moisture levels and contamination with weed seeds
which increase the costs of cleaning. Unless the straw is required for animal
feeding or bedding the combine harvester is extremely effective in chopping and
spreading straw evenly over the soil. This is of considerable help in preparing
the seedbed for the subsequent crop.
In Britain grain is often harvested at moisture contents of around 16 to 20%,
whilst in exceptionally late seasons in northern regions grain may be harvested
at around 25%. At these moisture levels stored grain is extremely susceptible to
fungal contamination and deterioration. For safe storage the grain has to be dried