Tutkimuksia kasvua hillitsevien aineiden käytöstä turveviljelyssä

Authors

• Erkki Kaukovirta Helsingin yliopiston puutarhatieteen laitos

DOI: https://doi.org/10.23986/afsci.71747

Abstract

Earlier studies on the use of growth retardants for plants grown in peat showed that the intensity of growth retardation varied from case to case and the effect of Phosfon in peat was low compared to its effect in sand and soil. The purpose of the experiments reported here was to study the cause of these variations. The experiments were carried out at the Institute of Horticulture, partly in experimental greenhouses and partly in growth chambers. B-nine (N-dimethylamino succinamic acid), Cycocel (2-chloroethyl) trimethylammonium chloride) and Phosfon (2,4-dichlorobenzyl-tributulphoshonium chloride) were applied as soil drench for plants grown in different peat media, (see Table 1) in peat and sand mixture, and in sand. In addition, corresponding amounts of growth retardants were mixed in peat and extracted by Carver laboratory press 7 and 14 days after the mixing. Phosfon was extracted also with 1N KNO3-solution. The effect of the extracts on beans grown in sand, and on chrysanthemum grown in peat-sand mixture, were compared with the effects of direct soil drench. The results are reported in Tables 1—5 and in Figure 1. The following conclusions were drawn from the results: One of the reasons for the weak retarding effect on stem growth of Phosfon in peat was that Phosfon was taken up by peat and was not available to the plant at the beginning. Later, more Phosfon was available to the plant. This was shown by the fact that the extract pressed 14 days after adding Phosfon to the peat did restrict stem growth, but the extract pressed 7 days after the application of Phosfon did not. The availability of Phosfon and B-nine to the plant was dependent on the cation exchange capacity and the bulk density of the peat. These compounds retarded significantly stem growth only in peat with a high cation exchange capacity and with a low bulk density. Cycocel was only partly taken up by peat. It restricted stem growth in all peat media, but the intensity of retardation increased with the increase of the cation exchange capacity of the peat medium. In peat-sand mixtures Phosfon and B-nine restricted stem growth more than in peat, but Cycocel was most effective in peat.