map for larger version
cause of problem: wind blown seed from an adjacent
field to the north, followed by 4 months winter grazing
of sheep (enforced by F & M restrictions).
the trial showed how the ‘RIP’ method can be efficient
when applied to problems in grassland. Before work started,
the field was tram-lined, using the wheel markings of
a light van. These made visible divisions for each operator
to work in, and they were spaced about two metres apart.
Sometimes, when one strip had a far greater number of
plants, the whole team would all help to clear that area.
The work was carried out by four members of the available
farm workforce (including a 14 year old), and broken into
four separate visits to the field. The 3 hrs allowed for
‘follow-up work’ in June, were probably less than recorded.
All Spear thistle plants had been removed by the time
Hay was taken from the field in July,
more conclusions and comparative costs of other solutions,
below. J.Trevelyan BSc. Aberdeen.2002.
to drawing, page 3
conditions : Young plants in moist ground (rosettes
between 3" & 8" across),.
plants in seriously infested area ‘A’ ( 3.0 acres)
Density = 16 plants per 25 sq.m.]
plants in lightly infested area ‘B’ ( 8.5 acres)
Density = 1.20 plants per 25 sq.m]
(weeds removed per man-hour) overall = 439
rosettes per hr.
in seriously infested area ‘A’ = 576 rosettes
in lightly infested area ‘B’ = 232 rosettes per
number of seedling & rosette weeds extracted : 8016
of work : 4 visits during 4 days.
man-hours worked : 18.23.
Clearance Costs : @£7 per hour = £126.
costs : £21. (3 man-hours).
Workforce costs : £146. [ £12.69p. per acre / £31.3p
Costs of Boom / Spot Spray / Weed-wiper solutions.
chemical costs to kill Scotch thistle in pasture are about
£2 per acre.
selective chemicals are more expensive.
costs vary with total area sprayed in the contract. These
could be as little as £3 per acre for 50 acres (or £7
per hectare), or doubled on smaller areas.
from contractor base, and ease / cost of water access
quote from R.Strickland & Son (contractors 3.5 miles
distant to the trial site), came to more than £110,
because of special rates for a relatively small acreage
& a ‘least damage to clovers’ mix of chemical. That’s
£9.56 per acre or £23.62p. per hect.
work-rates are very similar to those of ‘RIP’ (number
of plants dealt with per hr.). Added to those costs, are
the price of chemicals and the time it takes to mix and
refill the knapsack. These would bring the total cost
of spot treating 11.50 acres to at least £200.
There are many other restrictions & disadvantages,
which cost money. These are listed in a L-D document titled
The Removal of Individual Plants’ (see website).
height of weeds has to be greater than the crop, so the
field must be well grazed. The land must be reasonably
level. Contractors should, but do not always take into
account all costs:
Costs of machinery
Costs of obtaining & mixing chemical, fuel, &
of both spot & boom spraying, & damage to soil
fungus, bacteria & clover.
waiting for correct weather conditions (phone- calls,
for removal & replacing of stock ?
for collection & delivery of chemicals (& transport
for filling in records / safety clothing etc.
spraying, paricularly in areas of ‘low weed density (eg.
Zone A in our trial) is absurdly costly ( and damaging).
of High Cross Trial.
large number of rosettes were pulled efficiently, and
the field was cleared.
indicate that the ‘RIP’ method was applied correctly.
Comparisons with chemical solution costs are remarkable.
Why was RIP so successful and why was the work rate so
high ? There are four main reasons:
rosettes were often no bigger than 2" or 8"
across, which meant that they could be dug out easily,
and piled onto the end of the grubbing noses, with little
need to kick them off individually (they accumulated
& tumbled off).
land was still winter-moist to full depth of bigger
task was broken up into 4 separate visits, which meant
that the workforce never became tired.
The workforce was available, and had learnt the knack
of using the tools.