INFLUENCE OF SOIL MAINTENANCE SYSTEMS AND FRUIT LOAD ON GRAPES QUALITY UNDER DROUGHT CONDITIONS

In order to diminish the disturbing effect of climatic changes in viticulture there were studied two agrotechnical factors which have an important impact on water regime in soil and on vine growth, respectively the soil maintenance system and fruit load. In comparison with black furrow (considered as control) there were experimented the total mulching with straws, the partial mulching (between the rows) with marc compost and minimum tillage. To reduce the negative impact of drought conditions in case of each soil maintenance systems a reduction of normal fruit load with 20 and 40% was also experimented. The experimental data obtained reveled that soil maintenance systems by mulching had a positive effect especially on the technological features of the grapes, assuring higher values for grain composition index and for efficiency index, that is a higher must content in grapes and a higher winemaking efficiency. The chemical properties of the grapes (sugar content, acidity, glucoacidimetric index) were not influenced in an obvious manner. Opposite, the reduction of fruit load determined in case of all soil maintenance systems an increase of sugar content in grapes, parallel with an evident decrease of must acidity, determining high values of the glucoacidimetric index, unfavorable for obtaining qualitative and typical wines. The changes induced in grapes quality by the two experimental factors have been reflected also in the wines quality (alchoolic degree, total acidity, unreducing extract). Ranking the wines obtained from all the experimental variants (combinations between the two experimental factors) by using the synthetic index of wines quality (Ntaj) one could notice that the soil maintenance systems by mulching and the fruit load of 15-18 buds/m2 had a positive effect on wines quality under drought conditions.