Germination trial

The photographs below show the results of a germination test of various compost mixes. Pots 2-4 and 7 were mixed at 4:1 by volume. Pot 6 was originally soil from the garden, no seeds germinated.

All pots were planted with 6 Radish seeds (Scarlet Globe) at the same time. The pots were placed on a heated bench (18C) under a double fluorescent fitting with 2 x 55w tubes on 12 hours per day. This is my standard germination bench. The seeds were planted on 15 Jan 2004. The photographs were taken on 12 Mar 2004.

germ_01 germ_02 germ_03
Plain compost Compost + sharp sand Compost + rock dust from Johnstons (Basalt)
germ_04 germ_05 germ_07
+ rock dust from Pinetum Products
commercial compost
+ rock dust from the seer centre (Basalt)

From the appearance of the top growth, the results speak for themselves. The plain compost and compost and sharp sand worked but pots 3 and 7 show better growth. This shows that the rock dust did add something. The best top growth is pot 5, the ‘Danu’ commercial compost perhaps showing that it was higher in nitrogen.

The radishes were harvested and the results are shown below.

Sample Number
of plants
root (gms)
weight per root (gms)

Plain compost
4 62 40 64.52% 10.00
+ sharp sand
3 62 46 74.19% 15.33
+ rock dust from Johnstons (Basalt)
5 69 43 62.32% 8.6

Compost + rock dust from Pinetum Products (unknown constituents)
2 43 35 81.39% 17.50

‘Danu’, commercial compost
6 66 31 46.96% 5.16
+ rock dust from the seer centre (Basalt)
4 77 55 71.42% 13.75

The aim of the trial was to see if seeds would germinate in a compost/rock dust mix. They certainly did. The results in terms of yield are mixed. Some of the rock dust mixes did very well and others not so well. The number of seeds germinating was also variable but showed good results for the Johnstons rock dust mix which out performed the ‘Danu’ commercial compost. It should be noted that the rock dust from Pinetum Products has other, unknown constituents. The two other rock dusts were plain ‘Basalt fines’ straight from the quarry.

A single test like this cannot give conclusive results as to the superiority of one mix over another. What is important is the viability of the compost/rock dust as a seed germination medium. This has been further proved in trials on the growing beds where early carrots and parsnips have germinated very evenly. They were sown in March under a plastic cover and are doing well.

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