Greater Use of Agricultural Lime in South Canterbury

New Zealand Journal of Agriculture, Volume 81, Issue 4, 16 October 1950, Page 333

Greater Use of Agricultural Lime in South Canterbury

By

J. D. WRAIGHT,

Fields

Instructor, Department of Agriculture, Timaru.

THE growth of “lime consciousness” among farmers in South Canterbury is shown by the greatly increased quantities of lime now being used. The district, which on the whole responds excellently to applications of lime, has numerous outcrops of limestone, and the wider usage has resulted from new developments in production, which are discussed in this article. TOURING the last 10 years three developments in the production of agricultural lime in South Canterbury have substantially affected the amount of lime produced in that area. These developments have been: — 1. The extraction of limestone from the quarry by “rooting” instead of by quarrying in the usual way. 2. The setting up of a number of home-owned plants by farmers who have lime deposits on or near their farms. 3. A “travelling” lime-crushing plant which will produce agricultural lime in areas remote from rail and where limestone outcrops occur. Rooting Lime The first innovation, that of rooting the lime instead of blasting and spalling the stone to reduce it small enough to go through the crushing machinery, was evolved by the Public . Works Department in 1939, when a track-laying tractor and an earthrooter were used experimentally in the Hanging Rock district of South Canterbury. This experiment was undertaken as the result of requests by farmers, who suggested that Public Works Department machinery might be used for the production of lime in . areas remote from rail. It was found that where the limestone was not too hard this machinery could root it up in flakes sufficiently small to be fed into crushing machines and that the process of bulldozing the material into the chute feeding the crusher rendered it still finer, so that it required less crushing than spalled rock. The outcrop on which this experiment was conducted is typical of most of the limestones of South Canterbury in that it is not a very hard stone. The degree of hardness can be tested by scratching a sample with a pocket knife; if it is possible to carve into the stone with the knife, it is usually possible to extract it by the rooting method. It is usually necessary to make some adjustment to the ordinary type of earth-rooter before it can operate successfully on limestone, and this adjustment pertains

mainly to the angle or pitch of . the points of the rooter. In rooting limestone only a very gradual angle is required, as the machine does not rely on digging into the stone for its efficiency; rather, it chips the limestone off in flakes not much more than 6in. deep. Once it was thus established that certain limestones could be rooted successfully one large manufacturer put this method into operation m his quarry. At first a small rooter was used which was designed for scarifymg pavements and roads and which could be drawn by a 40 h.p. tractor; Later, however, the manufacturer installed a large rooter similar to the . one used in. the Public Works Departm«ent experiment and which is drawn by a 100 h.p. tractor. This larger unit actually produces 400 to 500 tons of rooted material during an 8-hour working day. Instead of many men being engaged in shooting, spalling, and loading limestone, the whole output of the quarry is now produced by two menone man operating the rooter and the other bulldozing the material oyer the edge of the. outcrop, whence it is taken by a drag-line scoop into the crushing plant. This modern method of extracting lime in large commercial quarries is gradually becoming more widely used wherever the stone is not too hard, Manufacturers are abandoning the old

costly methods and are accepting the new, which requires a minimum of manpower and which is capable of producing daily tonnages not obtained before. Home Production According to official figures South Canterbury farmers received by rail during each year between 1936-37 and 1945-46 quantities of lime varying between about 12,000 and about 22,000 tons. In the 3 years after 1945-46 the tonnages railed were 34,307, 42,167, and 49,922 respectively. Apart from the farmers whose lime requirements were covered by these figures and who were within reasonable cartage distance from rail, there were many others who were in districts remote from rail, where their soils required heavy dressings of lime - and where there were limestone outcrops. It was among these energetic and longsighted farmers that the second inlportant innovation in the production of agricultural lime, that is, the home production of lime by a small plant, was first developed. The first e-owned plant in South Canterbury was installed by - a farmer whose property was situated 15 miles from the nearest railway station. This farmer was contemplating a full liming programme over 800 acres, but. the cartage cost would . have been too great. He therefore installed his own

small lime-grinding plant. In this case the only specialised machinery found necessary was a pulveriser of a capacity of about 5 tons per hour, which was driven by a belt from a farm tractor. The stone was spalled and fed down to the pulveriser through a covered storage bin capable of holding spalls sufficient for a day’s crushing. This small plant has produced' approximately 2000 tons since its installation, and has enabled the owner to apply about 2 tons of lime per acre over his whole property. The increased production from this pro-, perty has already more than covered the total expenditure on the limecrushing plant. Another plant was installed by two farmers in co-operation in the Kakahu district. In this unit the stone was quarried by the usual blasting method, after which the material was passed through a primary . jaw-crusher mounted directly above a hammer mill or pulveriser. This plant has done very good service, having made it possible to lime both properties adequately. It must be remembered that there are no facilities for drying the limestone artificially, but in the quarrying process large heaps of spalls are set up, covered, and allowed to dry out naturally. The ground product has caused no difficulties in spreading, as most modern lime sowers are of the forced-feed type, and can readily handle this material. The most recently installed plant is one operated by two farmers at Upper Waitohi. This unit differs in its layout in that the lime is not quarried, but is rooted by a heavy scarifying machine. The rooted material is then gathered up by a

AGRICULTURAL LIME IN SOUTH CANTERBURY

rotary scoop and taken to the edge of the limestone outcrop. From there it is pushed down over the edge into a large chute by a home-made “dozer” constructed from an old grader blade attached to the drawbar of a tractor. From this chute it is fed into the pulveriser, which is capable of handling about 15 tons of finely crushed lime per hour. The rooted material is mainly “fines”, with some pieces up to 6in. in size, so there is no necessity for a primary crusher when employing this method.

An interesting feature of this Upper Waitohi plant is the method of transport. There are three 3-ton dualwheeled trailers and a 3-ton farm lorry, each of which is fitted to take a lime spreader. The production is such that a 3-ton trailer can be loaded in about 11 minutes, and the best day’s crushing so far has produced 90 tons of lime. . Travelling Plant The third significant innovation in the lime trade in South Canterbury is a travelling plant which moves from one outcrop to another, extracting and crushing the lime, and delivering and spreading the finished product unbagged on nearby farms. Associated with this plant are three trucks and one lime-spreading vehicle. Two of the trucks usually work together, supplying the lime spreader. The third truck both carts and spreads, using an ordinary detachable box-type spreader, on the flatter areas. Evaluating Limestone Samples .As a result of these developments there is now no need for a farmer in South Canterbury to go short of lime ' because of rail or road transport difficulties. The Department of Agriculture offers assistance to farmers proposing to work limestone deposits; it has in its various offices the equipment necessary to evaluate any limestone sample at short notice. A limestone showing 70 per cent, or more of calcium carbonate is suitable for crushing and applying to the land.