Seed-Sowing Machines

SEED-SOWING MACHINES The two ancient methods of sowing seed are broadcasting and dibbling. The former method, employed for example with cereal crops, results in the haphazard deposit of seed at varying depths and distances : the latter method employed for setting larger seeds, is laborious. In modern farming practice an endeavour is made as far as possible to substitute a mechanical device. The require ments of the various crops differ, and the character of the soil and climate leads necessarily to different practices in sowing the seed. It is essential that the seed should be placed at a sufficient depth in the seed-bed to enable it to obtain the water necessary for germination and growth. Hence seed is sown deeper in dry soil and in a dry climate than in a moist soil and in a moist climate. In some cases mechanical devices may be unsatisfactory in prac tice because of the injury which may be done to the seed as, for example, in the case of potatoes.

The broadcaster or seeder in its simplest form consists of a knapsack for carrying the seed with a hand-operated centrifugal device for scattering the seed, or a long seed-box carried on a wheel-barrow frame with an agitator to throw out the seed. These simple machines are used mainly for grass and clover seeds. For broadcasting cereals it is more usual to use a cultivator or disk harrow fitted with a seed-box and broadcasting device. Broadcasting does not, however, ensure the seed being covered to a uniform depth, and modern practice favours the employment of the more complicated drill, which not only sows the seed in the ground in rows at a suitable depth but also covers it. The most important requirement of a drill is even and continuous distribu tion in each spout. The distribution must be adjustable to deal with different seeds and rates of sowing but unaffected by varia tions in the speed of the machine, the slope of the land or travelling shocks.

Drills.

Drills can be classified according to the type of feed adopted, namely, cup feed or force feed, either external or nal, or the type of furrow opener or coulter used, as shoe, hoe or disk. To ensure a uniform supply of seed to each distributing unit in the cup-feed drill, the seed-box must be divided into ments and must be kept level. In a separate chamber behind the seed-box there is a horizontal geared shaft carrying a number of flat disks with cups on each side for lifting the seed from small hoppers or feed-runs into funnels connecting with the coulters. The seed passes from the seed-box to the feed-runs through apertures which may be fitted with slides for regulating the supply of grain at this point. Cups may be made with two seed faces so that by reversing the shaft different kinds of seed can be sown. The shaft is driven by a pinion from one of the travelling wheels and the rate of sowing can be altered by using pinions of different sizes. A number of variations of the cup-feed system are employed, e.g., the "melichar" drill, all having for their object increased accuracy of sowing. In the force-feed drill, the seed-box has only one compartment and over each spout there is a small hopper or feed-run in which the feed device works. In the ternal type a wheel with fluted edges is used and is placed side the hopper so that the rim enters the hopper and brings out the seed when the wheel rotates. The rate of sowing is regulated by altering the speed of the ing shaft and special gearing has been devised for the purpose. It is claimed that this type can sow damp seed better than any other drill. In the internal type a fluted roller is usually employed and the rate of sowing is varied either by moving the fluted roller along the driving shafts or by altering the speed of the shaft. The under plate of the feed-run may also be sprung to avoid crushing the seed. The shoe and hoe furrow-openers require pressure, applied by weights or springs, to keep them at the requisite depth and act like ploughshares in opening the furrows which close again immediately the drill passes. The disk furrow-opener, which may be either single or double, operates in the same way as the disk plough. It will cut through rubbish and cover the seed well under adverse conditions. In dry districts drills with special wheeled pressers are used in order to consolidate the seed bed and conserve the moisture.

For sowing roots (turnips, swedes, mangels, sugar beet) on the flat an ordinary cup or force-feed drill can be used, but for sowing on the ridge a special drill is necessary. This is usually a two-furrow implement with a cup-feed. The coulters are pre ceded by concave rollers and may be followed by a flat roller.

Special machines have been developed for planting maize ("corn") which is sown in clusters or "hills." Modern machines deal with two rows at a time and have furrow-openers similar to those of a drill. A special feed device has been evolved for pick ing up the grains or kernels separately or in small quantities and placing them in a compartment which has a valve or shutter for dropping them at intervals at the heel of the furrow-opener. In dry districts maize is sown by an attachment to a kind of double mouldboard plough designed to open a narrow furrow, into which the grains are dropped after a subsoiling device has prepared a seed-bed in the furrow bottom. These machines are called lister planters. The simplest types are based on the ordinary walking plough though elaborate two-row machines are in more general use. Listing is done to enable the plant to withstand drought and winds.

Machines for planting potatoes have also been devised but have not been adopted at all widely in ordinary farming practice. The difficulty is to get even spacing without missing, and potatoes which have been sprouted are liable to damage by a mechanical planter.

Modern farming practice favours the use of combined ferti lizer and seed-sowing machines wherever possible. The various components do not, however, differ in principle from those described above.