S13 - Session O4 - Investigations into the effects of a commercial organic fertilizer and of quality compost on the soil and the vines

Authors: Martin Mehofer *, Bernhard Schmuckenschlager, Karel Hanak, Christian Bader, Ingrid Hofstetter

The influences of quality compost and of a commercial organic fertilizer on the humus content, on the nitrogen content in the soil, in the must and in the vine leaves, on pruning wood weight and on yield and maturity were determined with the varieties 'Blauburger', 'Pinot Noir', 'Blaufränkisch' and 'Riesling' over a period of six years. Because of the annual application of 15 t/ha quality compost, humus content in the topsoil increased from 2.9 % to 3.7 % on one site and from 3.4 % to 4.1 % on the second site. The application of the commercial organic fertilizer indicated no change or a slight increase of the humus content depending on the site, respectively. In the subsoil at no site and with no organic fertilization method significant changes of the humus content could be analyzed. At both sites significant differences between the mean values of the mineral nitrogen contents in the soil of all sampling dates and of all years of the three experimental variants could be determined. The mean values were 18.9 kg/ha and 41.7 kg/ha (control), respectively, 30.6 kg/ha and 44.1 kg/ha (quality compost), respectively, and 46.5 kg/ha and 95 kg/ha (commercial organic fertilizer), respectively. Depending on the grape variety and the year, the contents of yeast assimilable nitrogen and of total nitrogen in the musts increased in part significantly because of organic fertilization. On average of all grape varieties and years, nitrogen content in vine leaves of the control variant was 2.35 %, which was significantly lower than in the vine leaves of the variants quality compost and commercial organic fertilizer. With yield, the maturity parameters and pruning wood weight significant differences between the experimental variants could be recognized only in some years and with some varieties.