Abstract
Comparison of mowing by a rotary cutter mounted to a tractor and by a walking type hammer knife mower was carried out in three tree forms that were the hedgerow and the Y form, both forms aimed for easy tractor operation, and the vase form, a common practice.
The tractor ran parallel to tree rows in the hedgerow and the Y form, making turns on head lands adjacent to tree rows.
In the vase form, it ran back and forth between tree rows, making turns within the orchard. It also backed to mow grass as close as possible to pillars, stay wires and tree trunks.
The walking type hammer knife mower ran parallel to tree rows in all the tree forms; In case of the hedgerow and the Y form, it made turns on the head land, while in the vase form, it made turns within the orchard and weaved to dodge the tree trunks.
When mowing was done by a rotary cutter mounted to a tractor, operation hours in the hedgerow and the Y form were respectively 41% and 33% of that in the vase form.
On the other hand, when mowing was done by a walking type hammer knife mower, operation hours in the hedgerow and the Y form were somewhat shorter than in the vase form. but the difference was small.
This was due to the small difference in time required for the straight drive which accounted to about 90% in all three tree forms.
When mowed by a rotary cutter mounted to a tractor, land left unmowed was about double of that mowed by a walking type hammer knife mower, owing to 1) the difficulty for the rotary cutter to mow close to tree trunks, pillars and stay wires of the trellis, and to 2) the unnecessarily wide overlapping of mowing path between tree rows.
Land left unmowed can be reduced by 1) closer operation of the cutter to trees through proper management of shoots in the hedgerow and pulling up the trellis by wires in the Y form, 2) reduction of overlapping of mowing path to the minimum required.
Operation hours can be reduced by using herbicides near tree trunks, pillars and stay wires.
In the vase form, mowing by a hammer knife mower was more labour saving than mowing by a rotary cutter mounted to a tractor. In the Y form and the hedgerow (the new tree forms), mowing by a rotary cutter mounted to a tractor was more labour saving than mowing by a hammer knife mower.
It is apparant that labor efficiency is about 1.5-1.8 times better when a rotary cutter mounted to a tractor is used in the new tree forms compared to when a hammer knife mower is used in the vase form.
