THE BULK DENSITY AND EXCHANGE CAPACITY OF PEAT AND THE EFFECT OF GROWTH RETARDANTS ON PLANTS GROWN IN PEAT
There are certain problems connected with the use of growth retardants in connection with peat culture. Firstly, it has been shown that the effect of growth retardants in peat is slighter than in sand and in ordinary garden soil (2). According to Cathey's studies (1) about 50% more retardant is needed in peat than in sand to bring about the same restriction of stem elongation. Secondly, the same amount of treatment may bring about different results at different times (3), which means that some very unpleasant surprises may occur in practical culture. One of the aims of the research at the Institute of Horticulture, University of Helsinki, has been to find out where this variation in treatment results might come from.
My findings presented at the previous "Peat in Horticulture" symposium in Helsinki (3) showed firstly that the effect of Cycocel1) in peat is good but that of Phosfon2) and B-nine3) weak, and secondly that especially the effect of Phosfon was dependent on the growth temperature. These observations were not sufficient, however, to explain the differences noted in the effect of Phosfon in cases where the growth temperature was identical. This gave reason to suspect that differences in the properties of the peat might be the reason for the differences in treatment results since, as is known, the physical properties of peat can vary to a very great extent. The research I report on here was an attempt to find out the significance of the bulk density and exchange capacity of peat in the use of growth retardants.