BS EN 16086-2-2011 pdf download.Soil improvers and growing media Determination of plant response
Part 2: Petri dish test using cress.
7.1 General preparation
Pass the sample through a 10 mm sieve (see 6.8). Any foreign material such as plastic, metal or glass retained on the sieve shall be removed, the percentage shall be noted. Any other material retained on the sieve which is an intrinsic part of the sample shall be physically reduced to parts of similar size as few times as are necessary to permit the entire sample to pass through the sieve. Fibrous materials i.e. coir fibres and straw shall be cut to a length ≤ 10 mm by using scissors. Thoroughly mix the laboratory sample with the broken particles retained on (lie sieve taking care to minimise physical damage to the sample as a whole. Transportation and possible storage of the samples shall be done in accordance with EN 13040, using food grade polyethylene bags.
NOTE In cases wtiere the proportion of the retained material is above 30 % weight. the extract method is more appropriate.
7.2 Sample storage and preparation
If necessary, samples can be stored according to EN 13040. The material to be tested shall be moistened to the approximate optimum moisture content according to the fist test (see Annex B).
The electrical conductivity of the moistened test sample shall be determined according to EN 13038. If the EC of the sample is> 80 mS m1, the sample shall be diluted with a sufficient amount of sphagnum peat (see 6,3) until the EC does not exceed 80 mS rn’1. The pH according to EN 13037 is ideally within the range between 5,5 and 6.5. If it is below, the pH shall be adjusted by adding limestone (see 6.10). After adding limestone, the sample shall be equilibrated for 24 h.
NOTE Usually, 29 to 3 g of limestone per litre should be sufficient.
If required (for example to fulfil certain quality certification requirements or legislation), materials can be tested without checking the EC.
7.3 Procedure
Fill the petri dish completely and level the surface (fOr example with a spatula) without heavy compression. Where the seed is being placed, remove any particles > 5 mm. Sow 10 cress seeds per dish evenly spaced on the test material 10 mm to 20 mm from the top and press the seed gently into the surface of the test material. It is important that there is good contact with the test material. To ensure this, a drop of water shall be added to each seed using a pipette. Perform the procedure in at least three replicates.
NOTE 1 A higher number of replicates can be used. The number of replicates should be taken into account for the calculation or the results.
As a control sample, perform the same procedure with limed and fertilized sphagnum peat (see 6.4), in three replicates.
NOTE 2 As a ‘positive reference, the procedure can be performed using fertilized Sphagnum peat (see 6.4) wetted with a solution of acetic acid resulting in a final concentration of approximate’y 350 mg acetic acid per tre of sphagnum peat. This should give a reduction of the germination rate andior the root length of about 50 %.
Close the dishes with their covers and incubate with the Petri dish placed 70°to 80° to the horizontal with the end where the seeds are placed uppermost and with the substrate on the lower surface in the dark at (25 ± 5) °C (see Figure 1). Incubate as described for 72 h. Determine the percentage germination (germination rate) root development (root score) by measuring the length in mm. If the average germination rate (see 7.4) in the reference material is below 85 %, the test is invalid.
NOTE 3 The covers can be fixed by using a rubber band or wrapping them in aluminium foil. If the Petn dish is completely covered by the foil, it can be incubated without additional darkening.
NOTE 4 A digital photograph can be taken and an image analysis can be prepared using an image analysis programme. This will give root length and root diameter and the results can be reported as percentage of control.BS EN 16086-2-2011 pdf download.