The effect of benzolinon on potato tuber formation

Biological efficacy of a preparation Rastim 30 DKV was studied. It is an au xinoid, a plant growth regulator containing benzolinon: 3-[benzyloxycarbony lmethyl]-benzothiazoline-2-on as an active ingredient. Biological efficacy consists in changes in tuber number under the hill, in tuber size and weigh t and it controls qualitative characteristics - contents of dry matter, sta rch and nitrates. Experimental treatments of two potato varieties (Karin, S vatava - both varieties were bred in the Czech Republic) involved three way s of regulator application (dipping of seed tubers for 3 s in benzolinon so lution two days before planting, foliar application and combination of both treatments), four concentrations (0.0003; 0.0015; 0.0045; 0.003%) and four doses (30; 100; 150; 300 mi in 444 liters per ha) that resulted in applica tions of 10 mi of solution to every hill. Another objective of these experi ments was to determine the best application date in the growing season (two weeks after emergence and/or at the stage of flower buds). An experimental spacing was 75 x 30 cm. The effects on the number of table tubers (4 to 7 cm in size) were positive (Figs 1, 2, Tab. I). There were significant to hi ghly significant differences in the weight of all harvested tubers under th e hill, but the preparation itself did not show any significant positive ef fects (Tab. II). Benzolinon effects on tuber weight were positive mainly in tubers of 4 to 7 cm size category in both varieties in the three experimen tal years (Tab. III). Applications to the crop were best in comparison with combined treatment (seed tuber dipping and applications to the crop) and w ith seed tuber dipping (Figs 3, 4, Tab. III). The active ingredient Rastim 30 DKV (benzolinon) did not have any significant effects on tuber quality. Starch content, as well as dry matter percentage, were insignificantly high er in control in the three experimental years (Fig. 5). Nitrate content was higher in some treatments than in control, but the difference was statisti cally insignificant. Similar results were also obtained in other crops, but the effects on tuber quality were not confirmed (Zahradnicek et al., 1993) like it was the case in sugar beet roots, tomatoes, hot and sweet peppers, spring barley and corn (H e n s e l o v a, P o h a n k o v a, 1992; H e n s e l o v a, K o n e c n y, 1994).