Vine performance and wine composition of ‘Chardonnay’ in relation to organic soil amendment in Mediterranean environment

Abstract

Preservation and improvement of soil organic matter content in vineyards are key goals of agroecosystem resilience against climate change and its negative effects on grapevine water status and vine physiology. There is still a lack of information on the effects of organic amendments on grapevine functions and yield performance. The following research was carried out during the 2016 season in a commercial 'Chardonnay' vineyard located in Apulia region according to a randomized block design, where one factor of fertilization (commercial composted municipal solid organic wastes) was tested. Treatments were: no fertilized control vines (NFC), moderate fertilized vines (D1) at rate of 1 kg vine-1 of organic amendment (4.3 t ha(-1), at the rate of 86 kg N ha(-1)), high fertilized vines (D2) at rate of 1.5 kg vine-1 (6.6 t ha(-1), 132 kg N ha(-1)). The leaf gas exchange during growing season did not show significant differences in terms of net CO(2) assimilation, stomatal conductance, transpiration and water use efficiency. However, lower leaf temperature on D1 and D2 vines was measured. Vines fertilized with organic amendment showed a better water status during the warmest summer days since organic compounds improve the soil-water holding capacity. Monthly field measurements of the greenness of the leaves (SPAD index) revealed the highest green color intensity of leaves by D2 treatments (+11%) to be related to the highest nitrogen amount. Compared to unfertilized vines, D2 vines (high amendment dose) determined a significant increase in yield per vine (+21%) in relation to the highest cluster weight. At harvest, grapes had the same chemical composition with no differences in term of sugar content and pH, while an increment of titratable acidity on D1 and D2 vines was noted. Wines of different treatments have shown similar chemical parameters (alcohol content, titratable acidity and pH). Our preliminary results indicated that application of a high level of soil organic amendment on 'Chardonnay' vines increased grapevines yield while improving soil properties (soil organic content and water retention), contrasting summer drought effect on vines in a Mediterranean environment.