Cereals processing technology

in turn, influence assimilate supply. The rate and timing of nitrogen can have an
important role in both the production and survival of tillers; indeed it is one of
the main tools that the grower has at his disposal to influence ear population at
final harvest. The practical significance of this is that satisfactory yields can be
achieved from a wide range of sowing rates, especially for winter wheat and
barley.
The target population of established plants is between 200 and 300 plants/m 2 .
To achieve this between 100 and 200 kg/ha of seed is sown, depending on seed
size. The higher the individual seed weight, the higher the seed rate required to
achieve the target plant population. Allowance must also be made for seedling
mortality and the loss of established plants to pest and disease attack. The use of
fungicide seed dressings is common practice to control soil and seed borne
pathogens. Seedling losses can be higher in winter compared to spring sown
cereals.
Cereals are relatively insensitive to variations in row width and inter-row
spacing. Similarly sowing depth is less critical than in many of the smaller
seeded arable crops, such as oilseed rape. Sowing at the target depth of 2 to 3 cm
is easily achieved with conventional drills.
2.4 Crop nutrition
Cereal production methods 19
The yield and quality of all cereal crops is strongly dependent on the availability
of an adequate supply of soil mineral nutrients throughout the growing season.
The higher the yield potential the higher the nutrient demand, while the grain
nitrogen content is a major quality determinant in wheat and barley.
The nutrient status of most arable soils in the UK is too low to achieve
satisfactory yields in the absence of applied nutrients. Crop demand is normally
met through the application of inorganic fertilisers, although in organic cereal
systems additional nutrients can only be supplied from manures and other
organic sources. The results of numerous field trials over the last fifty years have
provided a sound basis on which to base the nutrient requirements of cereals.
Compared to many arable crops, cereals have a relatively low demand for
phosphate and potassium. As a rule of thumb phosphate and potassium are
applied at the rate of 10 kg/tonne of expected grain yield to replace the P and K
removed and maintain soil reserves. The amount applied may be reduced
slightly in soils with high P and K reserves. In recent years with the decline in
atmospheric SO2 deposition and the trend away from sulphur-containing
fertilisers some cereal crops grown on light land may benefit from sulphur
application. Recent research has also identified the importance of sulphur to the
breadmaking qualities of wheat.
Cereals do not have a high demand for trace elements, although copper and
manganese deficiencies have been recorded in wheat and barley. Copper
deficiency is frequently associated with high organic matter soils; symptoms of
deficiency are most common when the ears emerge as white heads, producing