Journal of Applied Horticulture. 2005: 7(2): 142-144

Testing potting mixes with addition of dried blood, blood and bone and bentonite

Kahl, H; Krug, A

School of Horticulture, Christchurch Polytechnic Institute of Technology, P.O. Box 540, Christchurch, New Zealand.

An experiment was conducted to study the effect of dried blood or blood and bone and bentonite, as a slow release fertilizer, on germination rate of lettuce, tomato, and white and red cabbages, plant yield and the attraction of sciarid flies (Sciaridae) and whiteflies (Trialeurodes vaporariorum). The potting mixes comprised: standard mix (60 litres compost + 20 litres sand + 20 litres composted bark + 300 g gypsum + 200 g kelp powder) + 250 g dried blood, 250 g blood and bone, 125 g bentonite (a); standard mix + 250 dried blood, 250 g blood and bone (b); standard mix + 125 g bentonite (c); and standard mix (d). The germination rate for lettuce and tomato was similar for the mixes with and without blood and bone. The germination of red and white cabbages was strongly affected by the presence of blood and bone. Only 13 seeds out of 80 germinated in the samples with blood and bone compared with a total number of 80 germinated seeds out of 80 in the samples without blood and bone. In the mixes with bentonite, 113 seeds out of 160 germinated compared with 107 out of 160 in the mixes without bentonite. Plants in samples without dried blood and blood and bone had significantly higher mean weight than those in the samples with blood and bone and dried blood. The treatments with bentonite have on average a higher fresh and dry weight than the treatments without bentonite. However, bentonite when used with dried blood and blood and bone gave significantly low plant fresh and dry weight. Samples with dried blood, blood and bone and without bentonite had a high dry:fresh weight ratio. The presence of dried blood or blood and bone in a soil also had a strong attracting effect on sciarid flies, but no effect on whitefly attraction.