2.2. Belt feed planters
Belt feed planters space the potatoes less accurately but they can be used at high speed. Intended for unchitted seed, spacing in the row will be improved if the seed is carefully graded for size.
Two-, four-, six-, eight- and twelve-row belt-feed potato planters usually have a hydraulically tipped seed hopper, and some are equipped with a control unit in the tractor cab to regulates tuber spacing and monitor planter performance. The hopper is gradually tipped as the potatoes are deposited on to a wide belt or belts which transfer them on to a series of small belts used to convey the tubers to soil immediately behind furrow openers. The potatoes are covered with ridging bodies or with concave disc which can be adjusted to leave a wide or narrow ridge.
Figure 18.14 The cup feed mechanism on a four-row potato planter with a 2.5 tonne capacity hopper. The belts have a double row of cups which allow high speed planting with an output of up to 10 hectares in a normal day. (Kverneland)
Figure 18.15 A cup-feed machine planting two staggered double rows of potatoes six inches apart in pre-formed beds. (Grimme)
Figure 18.16 This cup-feed planter makes narrow furrows for two separate rows of potatoes which are covered before the rear shaping board forms two even-shaped ridges.
Figure 18.15a Planting four, five or six rows of potatoes in 1.8-2.0 m wide beds instead of individual rows improves soil moisture retention and gives more regular shape and size of potatoes for specialist markets.
Figure 18.17 A two-row trailed belt-feed potato planter working on the flat. As the 1250 kg hopper empties, it is tipped in stages by a pair of hydraulic rams to maintain the flow of potatoes to the feed belts.
3. Fertiliser Attachment
Fertiliser should not touch the potatoes when they are planted because it may damage the young shoots. For this reason it may either be spread and mixed with the soil before planting or placed in continuous bands near the potatoes. Some two- and four-row planters have a fertiliser attachment which consists of a hopper, feed mechanism, flexible tubes and coulters. It is usually mounted in front of the potato hopper (Plate 18.13) and has land-wheel drive to the feed mechanism. Fertiliser is metered into the coulter tubes at a controlled rate and is placed in the soil in a band slightly below and to one side of the potatoes. Some planters have two fertiliser coulters which place fertiliser on both sides of the row.
The hopper on a two-row mounted planter holds from 200-500 kg and a four-row trailed model has a capacity of about 1 tonne of fertiliser.
4. Potato planter adjustments
Row width Row spacings of 400 to 1000 mm are in common use. The furrow openers and coverers can be moved along the toolbar to achieve the required row spacing.
Tuber spacing Belt feed machines give rather irregular spacing if the potatoes are not of an even size. Spacings of 150 to 400 mm can be achieved by changing the planting belt speed.
Spacing is more accurate with cup feed planters. The cup belts are driven through a gearbox and cup belt speed is varied through either a gearbox or a chain drive. Tuber spacing can be changed automatically on planters equipped with an electronic control box in the tractor cab. Depending on the planting method and intended use of the crop, the tuber spacing can be anywhere between 100 and 600 mm or more.
Planting depth This is adjusted with either depth wheels on the planter or the tractor hydraulic system. More sophisticated planters have an automatic depth control system monitored by a sensor wheel running on the field surface. This maintains the pre-set working depth of the ridging bodies or discs used to cover the planted crop. The depth of the discs or covering bodies is adjusted by moving them up and down in their mounting brackets. However, varying the working depth may alter the size and shape of the ridge.
Maintenance of potato planters. Regular lubrication of all moving parts, checks on belt and chain tensions and tyre pressures are the main routine maintenance tasks. Fertiliser hoppers should be cleaned out at the end of each day it may rain next day and fertiliser will corrode metal parts at an alarming rate.
At the end of the season, bright parts should be protected from rust and any parts which have come into contact with fertiliser must be thoroughly cleaned and protected from corrosion.