Roller
The roller is an agricultural tool used for flattening land or breaking up large clumps of soil, especially after ploughing. Typically, rollers are pulled by tractors or, prior to mechanisation, a team of animals such as horses or oxen.
Flatter land makes subsequent weed control and harvesting easier, and rolling can help to reduce moisture loss from cultivated soil. On grassland, rolling levels the land for mowing and compacts the soil surface.
For many uses a heavy roller is used, and rollers may be weighted in different ways. Heavy rollers may consist of one or more cylinders made of thick steel, a thinner steel cylinder filled with concrete, or a cylinder filled with water. A water-filled roller has the advantage that the water may be drained out for lighter use or for transport. In frost-prone areas a water filled roller must be drained for winter storage to avoid breakage due to the expansion for water as it turns to ice.
Segmented rollers
On tilled soil a one-piece roller has the disadvantage that when turning corners the outer end of the roller has to rotate much faster than the inner end, forcing one or both ends to skid. A one-piece roller turned on soft ground will skid up a heap of soil at the outer radius, leaving heaps, which is counter-productive. Rollers are often made in two or three sections to reduce this problem, and the Cambridge roller overcomes it altogether by mounting many small segments onto one axle so that they can each rotate at local ground-speed.
The surface of rollers may be smooth, or it may be textured to help break up soil or to groove the final surface to reduce scouring from rain. Each segment of a Cambridge roller has a rib around its edge for this purpose.
Rollers may be ganged, or combined with other equipment such as mowers.
Stone picker
A stone picker (or rock picker) is an implement to remove the top layer of soil to separate and collect rocks and soil debris from good topsoil. It is usually tractor-pulled. A stone picker is similar in function to a rock windrower (rock rake); a stone picker generally digs to greater depths to remove stones and rocks.
Stone pickers are used in farming and landscaping, where stones need to be removed from the soil and ground surface to prevent damage to other farm machinery (such as hay balers, combines, and mowers), improve the soil for crop production, or improve the appearance of the ground surface in preparation for a lawn or a golf course. Surface stones and large rocks often left from plowing can damage a hay bailer, the header or reciprocating knives on a combine, and blades on a rotary mower. Land with rock instead of fine soil are often less useful for crops.
A stone picker has digging teeth, a conveyor system, a sieve or screen, and a stone bin. The digging teeth are at the leading edge of the stone picker and removes soil, which is placed on the conveyor system. If the sieve is not combined with the conveyor system, the conveyor system transports the stones and large rocks to a bin or hopper for periodic dumping. Some stone pickers use a large tractor, generally over 100 horsepower, equipped with hydraulics and power take-off driven mechanisms. PTO pump driven equipment can use 60 horsepower tractors. The tractor’s hydraulics control the depth to which the stone picker digs to excavate soil material; whereas, the PTO controls the movement of the conveyor and picking system.
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