Harvesting Grain, Grasses and Roots

Slicing inexorably through the ripe golden wheat, dwarfing its attendant tractors, the big combine harvester is an impressive symbol of modern mechanised agriculture.

In a few hot, dusty hours it achieves a task which, a century ago, occupied the people of a whole village for days.

The advantage to the farmer of the big combine harvester is immense. The harvest can be brought in rapidly and at short notice when conditions are right, and with the crop safely off the field and under cover, autumn cultivations can begin without delay, enabling winter cereals to be established before the weather breaks.

The speed at which such machinery works is one of its principal attractions. It is bought, however, at the expense of flexibility. Twenty men may harvest anything, be it grain, roots, vegetables or even mushrooms. The 19th century farmer was free to grow any crop which the market suggested, provided the land was suitable. In contrast, the mechanised farmer of today is constrained by the limitations of his equipment. Each harvesting machine is designed to gather a particular type of crop with speed, precision and economy, a specification which in many cases demands great mechanical complexity. In consequence the harvester is often the most expensive machine on the farm, and the farmer is well advised to tailor his cropping policy to suit it. To do otherwise means incurring the expense of a contractor, or even manual labour, while a major capital investment lies idle.

The combine harvester

For many arable farmers the basis of cropping strategy is the combine harvester. The name refers to its function as a combined harvesting and threshing machine, designed for use on crops grown for their ripe seeds or grain. Before its general adoption in the 1940s and 1950s, these crops (mainly cereals) were cut when half-ripe with a reaper-binder and stacked in the field to ripen. Cut early in this way the crop was less fragile, and less likely to shatter and spill grain back on the field. After a week or so in the sheaf, it could be fed into a threshing machine, which employed a toothed revolving drum to break up the seed-head, and a series of sieves and fans to separate the grain from the chaff. The modern combine harvester incorporates just such a machine, mounted on the back of what is basically a reversed tractor fitted with a cutter bar.

The grain must be ripe for effective threshing, so the old technique of cutting early is out of the question. Nonetheless, most farmers try to bring in the crop while the moisture content is still fairly high to avoid knocking the grain out of the ear on impact. The result is a heap of damp grain which has to be put through an electric drier before it is fit to store.

British arable farming is dominated by cereals, principally barley and wheat, and nearly every farm uses a combine harvester. It is possible with the aid of modern pesticides to grow cereals continuously on the same land, but in practice few farmers do so. Instead they employ variations on the old idea of crop rotation. For a cereals specialist this means giving the soil a rest by planting a crop with different requirements once every few years, which can be harvested with the combine. This is known as a combinable break crop. It may be any seed which will withstand the threshing process, from mustard or oilseed rape to dry, ripe peas or beans: the combine harvester can deal with them all, if properly adjusted. In this way the management of whole agricultural landscapes may be dictated by one particular havesting machine.

Forage crops

The other main crop category found on the average farm is the forage crop. This is grown for its foliage which is fed, fresh or preserved, to livestock.

The stockman enjoys an advantage over the purely arable farmer in that his animals may do their own harvesting. Indeed, it is possible to do without harvesting machinery of any kind and rely on the animals’ own feet to take them from one crop to the next. If that crop is merely permanent grass, as is the case on some hill farms, cultivation equipment may be dispensed with altogether; this is known as `dog and stick farming’. In practice farmers need supplementary rations for the winter so the production (or purchase) of harvestable crops is imperative for all but the hardiest of stock. Cereals and pulses are important, but the bulk of the ration is made up of forage crops.

Of these the most important is grass, traditionally harvested as hay. Haymaking requires simple but specialised equipment, a fair amount of time and energy, and luck with the weather. Many farmers have abandoned it in favour of more dependable alternatives, but as part of the dairy cow’s diet its value is undeniable: the fibre stimulates the production of butterfat and improves the quality of the milk. Thus many dairymen, while not relying on hay, continue to make it.

The first step is to cut the long grass while it is still green and succulent. At this stage the moisture content is high; the quicker the grass dries the better, so a mower-conditioner is employed to break and bruise the stems and leaves as they are cut, enabling moisture to escape more rapidly. Driven from the power-take-off shaft of the tractor, the mower-conditioner leaves the cut grass in a series of long heaps or swathes, ready for the next operation. This is accomplished by the hay tedder, a pair of contra-rotating rakes mounted on the tractor which fluff up the grass to dry in the sun. This rough treatment is repeated until the increasing fragility of the grass dictates a switch to the swathe turner, a set of rimless wire wheels driven by ground contact which roll the swathe over on to warm, dry land until the haymaking is complete.

The next job is to bale the hay. The standard rectangular bale, designed for manual handling, is popular with haymakers for its portability and the scope it allows for further drying. Drawn down the swathe, the baler picks up the hay and rams it into a chamber where it is automatically strapped with twine. The completed bale is then ejected on to the field, or into a bottomless sledge which accumulates eight bales before dropping them in a group for collection by a tractor equipped with a ‘flat eight’ fore-end-loader.

An alternative to this is the big baler, which simply rolls up the swathe into a big round bale, trusses it with twine and drops it. Designed from the start for mechanical handling, the bale is transported by impaling it on a tractor-mounted spike.

These baling systems are also used to collect straw in the harvest field, either for livestock bedding or, in the case of barley or oat straw, to add to the feed ration. Baled straw is, however, little use to the cereal grower with no livestock, and many farmers either plough it in or burn it. For this it helps if the straw is well scattered, and the combine may be fitted with a device to chop and distribute the waste straw instead of leaving it in a neat swathe for the baler.

Another way of laying in food for winter is to preserve the newly cut green forage in an airtight enclosure as silage. This technique requires more skill than haymaking but it is quicker, involves less work in the field, and is less dependent on good weather. It is practical with a much wider variety of crops, and the end result is similar in dietary value to fresh forage. The forage harvester gathers and chops the green crop, which is then emptied into a silo or, more commonly, a walled enclosure which is called a clamp. As the heap grows, it is compressed by driving a tractor over it, and finally covered with plastic sheeting held down with straw bales or old motor tyres.

Care must be taken that there are no leaks: if air is allowed to circulate, the silage will rot. Normally the crop is cut and allowed to wilt to reduce the moisture content before being harvested. Maize is normally dry enough to be put straight in the clamp, and it is often cut by the forage harvester itself, furnished for the occasion with an alarming display of toothed spikes which penetrate between the rows and sever the thick stems.

Root harvesting

Whereas grain and forage crops are well suited to mechanical harvesting, roots are more awkward. The easiest to deal with are the types with a high water content used for stockfeed — certain varieties of turnip, swede and fodder beet — which can be levered out by inclined discs drawn along the rows. Since much of their great weight is water, however, transporting them off the field costs more than their worth, so many farmers feed them to their animals in situ.

In general the only roots worth the cost of transport are those with a high dry matter content, such as sugar beet and potatoes. Unfortunately they are the most difficult to harvest; they grow low down in the soil and their cash value makes careful handling imperative. Sugar beet can be lifted cleanly and efficiently by a specialised harvester. It is an expensive piece of equipment and only a big grower or contractor can justify the investment. It moves slowly down the rows, slicing off the tops of the plants; the roots are then prised out between inclined discs and elevated into a tank or trailer. Conical varieties are the easiest to extract, and light soil is preferred as it falls away from the root during the harvest. Potatoes are a greater problem, being unpredictable in location and almost indistinguishable from stones and clods. A digger-elevator excavates the potatoes and drops them to be sorted and collected by hired hands. More sophisticated machines can also sort and grade the crop, but in practice the odd stone still gets through, and many growers prefer to invest in a travelling shed occupied by a gang of sorters and packers; a mobile bastion of manual labour in an increasingly mechanised industry.

29. July 2011 by admin
Categories: Crops, Farming | Tags: , , , , | Comments Off on Harvesting Grain, Grasses and Roots


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