Nursery Techniques - Afforestation, Reforestation and Forest Restoration in Arid and Semi-arid Tropics - page 36

Table 2.7 Standard tests for quality check of polypots
Sr.
no.

Property to
test

How determined Desired value or

result

Quick field testing
method

1 Strength Tensile strength in

longitudinal and lateral
directions is measured
in laboratory

Longitudinal tensile
strength T

When filled with sand
and dropped on
hard ground from
waist height, it
should not rupture

≥ 55

N/m

2 Leakproofness Filled with water, kept

hanging for 24 h

No leakage should
develop

Fill with water and see
that it does not leak;
blow with mouth,
should balloon out

3 Durability Check for virgin material:

hold it against light and
examine carefully

Clear, transparent,
and free from any
streak, spot,
pinhole, creases,
blister, nicks, and
cuts

Same as in column
'How determined'

4 Ease in

opening

Check if the two films of
a bag are stuck
together, rub the bags
up and down between
hands

Should not stick;
should separate
easily on rubbing
between hands
along its length

Same as in column
'How determined'

5 Consistence

in borders,
size, and
gauge

On taking a random
sample of 50 bags,
measure the sealed
width, length, and
gauge

Standard deviation
should not exceed
5mmin
dimensions, 2 mm
in sealed borders,
and 20 % in gauge
variation

Examine visually,
compare a few bags
by overlaying one
on top of another.
Specified total
length also includes
sealed portion

6 Unit weight Weigh 100 or 500 bags in

a precision balance to
an accuracy of 1 g,
then calculate number
of bags in 1 kg

Number of bags
calculated per
kilogram should
be within 5 % of
value shown in
column 4 of
Table 2.6

Same as in column
'How determined'

of naturally growing plants of the species to be raised in the nursery. The inoculum
is then cultured, that is multiplied, by ploughing it into soil in a plot of land and
growing a cover crop, such as maize or sorghum, on it. The spores of the fungi feed
on roots of the crop and multiply by propagating all over. The cover crop is harvested
on maturity and the soil in the root zone is dug up. The roots are chopped into fine
pieces and mixed with the soil. This homogeneous inoculum is then added to the
potting mix in a proportion of 10-20 % (Fig. 2.10 ).
The polypots should be punched with a sharp punching tool to create sufficient
holes to enable drainage of excess irrigation water. By using a pincer-like punch,
groups of 20s or 30s can be punched together. A scoop can be used for filling the
potting mix into the polypots. After first fill, the pot should be struck on ground to let