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Harvesting arable crops

Harvest is usually the busiest time of year for arable farmers and in the UK most crops are harvested in July, August and the early part of September. For much of the past 6,000 years crops have been harvested by hand although the Romans did develop a machine that stripped the ears of the corn from the straw. This appears not to have lasted after the decline of the Roman Empire and it was not until the 19th Century that parts of the harvesting process became mechanised again. The modern combine harvester which integrates the cutting of the crop with the separation of the grain from the ear, became widespread in the agricultural revolutiion after the second world war. Today the same principles apply as have always done and cutting a crop cannot commence until the crop is ready or "fit". The most important aspect of this is moisture content. Crops need to be harvested dry so that they can be stored for long periods without deterioration.

A crop of wheat ready for harvestA crop of wheat ready for harvest. This picture was taken in early August and the crop was cut a few days later. At the top of the crop are the ears which are now bent over and pointing downwards, a sign that the crop is fit for combining. Cereal crops tend to become a golden brown colour towards harvest. This is because the crop is senescing and the resources of the plant are being transferred to the grain in the ear.

Combine harvesterThe combine is crucial for harvesting arable crops and completes several operations at the same time. The plant is first cut about 9 inches above ground before being fed into the heart of the combine where it is spun very fast against a metal grate with holes in it. This is known as "thrashing". In the process the grain is pushed through the holes and separated from the ear and straw. The grain is then further "cleaned" over a series of seives before being moved to a grain tank for unloading.

Collecting the grainAt harvest time the combine will work as many hours as possible and may start cutting as early as 9.00 am and finish after midnight. Dampness in the crop from evening dew will normally make the crop tough to cut and force the combine to stop. Although many aspects of the combine's operation are electronically controlled, the experience of the driver is required to ensure that the machine operates at optimum efficiency.

view from the combineThe view from the combine as grain is unloaded into a grain trailer. The grain trailer is driven alongside the combine while the combine continues to cut grain. Grain is stored in a tank on the combine. This holds about five tonnes of grain and the combine will unload two tanks to fill up the grain trailer. High standards of driving are required by the tractor driver to accurately fill the trailer and prevent loss over the side.

A crop of oil seed rapeA crop of oil seed rape that has been harvested and now fills the trailer awaiting transport to the grain store. Oil seed rape has a very small seed size in contrast to crops like beans and peas. The combine harvester has to deal with these variations and there are many variables that can be adjusted by the driver to ensure that the end crop is clean and free free from the contamination of other seeds and straw.

Sraw baleIt is easy to overlook the importance of straw. Each acre can yield over a tonne of straw, invaluable for winter bedding cattle and pigs as well as being a useful low value feed at times when forage stocks run low. Straw exists in surplus in the eastern arable areas where there are less livestock and through the autumn months it is transported westwards to the main livestock areas. If the straw is not to be baled it is chopped and spread from the combine and then ploughed into the ground to maintain soil organic matter.

Grain storeAfter harvest the grain is stored in purpose build stores that are free from pests and the risk of contamination.

Statistics for Cereals in the UK

Cereals in the UK
Total Cereals - area
(000 hectares)
3348 3014 3245 3059 3133 2919 2864 2881 3274 3075 3013
Production area total cereals
(000 hectares)
3 348 3 014 3 246 3 060 3 133 2 915 2 859 2 884 3 274 3 075 3 013
Production volume cereals
(000 tonnes)
23 989 18 959 22 965 21 511 22 029 21 001 20 838 19 130 24 283 21 618 20 946
Cereal value incl area payments
(£ millions)
2 333 1 982 2 255 2 218 2 417 1 434 1 507 1 949 3 147 2 338 2 306
Total new supply cereals
(000 tonnes)
21 164 19 512 23 243 19 043 21 413 20 364 20 609 19 454 23 415 20 660 18 696
Total domestic use cereals
(000 tonnes)
20 711 21 304 21 171 21 079 20 977 20 672 20 585 20 442 20 505 20 585 21 032
Cereals production as % UK use
113% 97% 99% 113% 103% 103% 101% 98% 104% 105% 112%