DTA

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Tesi etd-03302021-135050

Type of thesis
Dottorato
Author
WARREN RAFFA, DYLAN
URN
etd-03302021-135050
Title
Exploring the effects of vineyard soil management on spontaneous vegetation, soil health, vine growth and grape quality
Scientific disciplinary sector
AGR/02
Course
SCIENZE AGRARIE E BIOTECNOLOGIE - AGROBIODIVERSITY
Committee
relatore Prof. BARBERI, PAOLO
Keywords
  • Nessuna parola chiave trovata
Exam session start date
21/05/2021;
Availability
parziale
Abstract
Soil is an essential element of the terroir’s concept and a critical natural resource, which mediates essential Ecosystem Services (ES). In Mediterranean areas vineyards have been historically planted on marginal, poor-developed soil, prone to degradation. The intensive tillage practices normally applied in modern viticulture has further escalated soil degradation and, to date, vineyard is among the land uses with the highest soil loss rate in Mediterranean Europe. Cover crops (CC) can improve soil health and biodiversity but to be acceptable by farmers should not compromise grape yields and musts’ quality. <br>This PhD work takes on the challenge of exploring the trade-offs across soil health and productive objectives testing five different soil management practices in two organic farms in Chianti Classico (Italy), namely Fattoria San Giusto a Rentennao (SG) and Montevertine (MT). We compared five treatments: conventional tillage (CT), spontaneous vegetation (S), soil-incorporated pigeon bean (Vicia faba var. minor) CC (PBI), a mixture of barley (Hordeum vulgare) and clover (Trifolium squarrosum) CC, either mulched (BCM) or incorporated (BCI). We aim at providing a holistic assessment of those practices by analysing their effects on soil, weeds and grapevine in order to discuss with farmer’s innovative and sustainable soil management schemes. <br>Chapter one focuses on the short-term effects of groundcovers on the chemical (Soil Organic Matter-SOM, N, P2O5 and K), physical (soil structure stability index; soil resistance to penetration) and biological soil health (soil biological quality index). We also used gamma-ray and apparent electrical conductivity to study the fine-scale soil variability of the sites. To the best of our knowledge this is the first time in viticulture research that fine-scale soil variability is taken into account when assessing the effects of given agronomic practices. We found that mulched groundcovers were associated with higher SOM as compared to tillage, already after two years. An increased N availability was found under groundcovers, irrespectively of CC type and management. The effect of soil management practices on P2O5 was not fully clear while it was no statistically significant on K availability. S positively influenced the soil structure index and soil penetration resistance. S also improved soil biological health, although with a variable effect between farms. Results show that mulched groundcovers can improve soil health already in the short term, thereby potentially increasing the sustainability of the wine sector. <br>In chapter two we studied the effects of soil management practices on the competitive potential of groundcovers and their biodiversity value. This work was based on extensive biomass per species samplings which, to the best of our knowledge, has never been carried out in vineyards. We, particularly, monitored biomass of groundcovers (CC+ spontaneous vegetation) both in autumn and spring over three years. We studied the effects of soil management practices on species composition, species richness, diversity indexes (Shannon diversity - H’; Pielou evenness - J) and three functional traits typically related to the competitive potential of groundcovers (Specific Leaf Area -SLA, plant height and Grime strategy). Soil management strongly affected weed biomass, diversity and functional traits. CT decreased weed biomass and selected more homogenous communities with higher SLA, compared to S. In spring, CC showed higher biomass than CT, with PBI being the most productive and selecting the most homogenous plant communities. Mulched annual CC selected for the least competitive (CSR-strategist, sensu Grime) weed assemblages in autumn; however, autumn sowing of CC may increase the risk for sediment losses. S ensured a permanent soil cover but also selected more stable and competitive weed assemblages. Alternating sown and spontaneous mulched groundcovers might be an effective strategy to guarantee soil protection and select for more diverse and less competitive weed assemblages, compared with tillage and CC incorporation. These results suggest that mulched groundcovers can potentially provide ecosystem services without compromising grapevine yield.<br>Chapter three focuses on the effects of soil management practices on vine stress (SPAD; stem water potential- Ψstem), grape production (yield per plant; number of cluster per plant; cluster weight; berries weight) and must quality (titrable acidity –TA; malic acid; pH; sugar concentration; yeast assimilable N –YAN; potential anthocyanin and total polyphenol indicator- TPI). Soil management affected SPAD and Ψstem with a variable effect between farms and years. Mulched-CC showed lower SPAD values than treatments receiving tillage at both farms and especially in 2019 and 2020. S effects on SPAD varied considerably across farms showing low values and no difference compared to tillage at SG and MT, respectively. CT also decreased water stress compared with S especially at MT in 2020. Mulched-CC did not highlight significant differences in Ψstem, compared with tillage at SG. Significant higher yields were found under PBI and S compared with the other treatments. We found that the higher production was mainly driven by the weight of the clusters. The most productive treatments also showed higher pH and malic acid concentration but lower anthocyanin and IPT as compared with the other treatments. CT increased YAN in 2019 while S recorded the lowest values. These results indicated that the stress triggered by groundcovers differently affected production and quality. While barley and trifolium mixture significantly affected grape production irrespectively of the termination type, S and PBI maintained grape yields. Moreover soil management is a valuable strategy to modulate musts’ quality according to specific oenological objectives.<br>Overall, this study demonstrated that soil management significantly affected soil health, weeds communities, grape yield and musts’ quality. Among the different treatments, S may be more appealing for growers as significantly improved soil health already in the short-term without compromising yields. Still farmers should consider that this type of management can decrease YAN and increase competitive weeds species (Grime sensu) in the long run. Finally this study does not aim at providing prescriptive recommendation on soil management practices. Rather this work provides valuable information, which will be discussed with viticulturists, to fine tune soil management practices according with their environmental and productive objectives. <br>
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