ingresos totales

The effect of the irrigation strategies on pruning weight, canopy growth and yield were evaluated in the experimental sites 1 and 2, from 2008 to 2010.

During 2008, leaf area and canopy density parameters were significantly increased by PRD in „Cannonau‟, while pruning weight was significantly lower in FI 100 as compared to DI 50 and

Ana Fernandes de Oliveira - Deficit Irrigation Strategies in Grapevine (Vitis vinifera L). Ecophysiologic Responses,

Growth-Yield Balance, Canopy and Cluster Microclimate for Improving Quality under Mediterranean Climate Page 140 of 234 PRD. DI 25 pruning weight was not significantly different from the other treatments. In 2009, no significant differences were found between treatments regarding pruning weight, and in both years vines vigour was quite low, as indicated by pruning mass which average 200 – 270 g/vine in 2008 and 260 – 300 g/vine in 2009.

Both canopy surface area and yield per vine were higher in PRD plants as compared to FI and DI treatments, although not statistically significant. The same trend was observed in 2009, but in a smaller proportion and with no statistic significance (Tab. 11). Since PRD usually leads to a reduction in vigour and shoot growth (Bindon et al. 2008; Gouveia et al., 2011), the higher vigour and vegetative growth observed in PRD lead us to consider that deep soil water was available to root‟s extraction.

As far as yield components are concerned no significant differences were found between treatments. Nevertheless, PRD presented the highest yield per vine, both in 2008 and 2009, due to higher cluster number per vine, while no significant differences were found in cluster weight and, during the season, the less irrigated treatment DI 25 and also PRD presented lower berry weight. Again, a possible explanation for our yield results is the fact that the PRD plants had access to higher supplementary water resources, as stated before.

During the rainiest year (2008) the water table may have been restocked, leading to a higher watering contribution to roots absorption. During 2009, a drier year, less refilling of the subterranean water source may have slightly reduced its contribution to plant water supply, thus vigour and canopy growth became less stimulated, with less canopy surface area and also yield in all the treatments, as compared to the previous year (2.00 m2_{/vine of canopy surface area and a yield} of 9.19 kg/vine in PRD in 2008 against 0.91 m2_{/vine and 3.62 kg/vine in 2009). Again, the yield} differences between treatments were not statistic significant (Tab. 11). Also in Bowen et al. (2011) study crop yield was unaffected by irrigation in any year of the trials, both in Merlot and in Cabernet Sauvignon and the stress caused by the irrigation reductions had few and inconsistent effects on vine vigor.

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Growth-Yield Balance, Canopy and Cluster Microclimate for Improving Quality under Mediterranean Climate Page 141 of 234

Table 11 – Canopy growth and yield in 2008 and 2009 growing seasons in the site 1 – „Cannonau‟. Canopy Surface data regards harvest. Mean values (4 replicates/block) and ANOVA. * - significant

for P<0.05; ns - not significant.

Date Treatment Pruning Weight (kg/vine) Canopy Surface Area (m2_/vine) LLN Cluster Exposure (%) Canopy Porosity (%) Yield (kg/vine)

2008 FI 100 0.20a 1.00 2.60a 32.9ac 1.67 7.10

DI 50 0.24ab 1.15 1.73b 56.6b 1.25 8.26

PRD 0.27b 2.00 3.05c 25.4c 0 9.19

DI 25 0.23ab 1.01 2.35a 38.7a 2.08 7.59

Sig. * ns * * ns ns

Yield

(kg/vine) clusters/vine N° Cluster weight (kg)

2009 DI 50 0.30 0.62a - - - 3.10 13 0.23

PRD 0.25 0.91b - - - 3.62 16 0.23

DI 25 0.26 0.89b - - - 3.19 15 0.22

Sig. ns * - - - ns ns ns

During 2009, the „Vermentino‟ plants of the second site did not show significant differences in terms of pruning weight, ranging from 580 to 660 g/vine and in 2010, DI 40 presented significantly higher pruning mass than DI 80, though not statistically different from the two PRD treatments. In 2010 vintage, plants presented higher pruning mass and yield but lower canopy surface area as compared to the previous year.

The PRD treatments presented a higher yield in both years, and a significantly higher canopy surface area, only in 2009. Again, these results are in accordance with the existence of deep water table, which was might have been well supplied under PRD plants, during an active shoot grown period, as shown before (Fig. 20, soil water content at 100 cm depth).

At the end of 2010 season there were no significant differences in canopy surface area but PRD treatments presented higher cluster exposure and yield and less pruning weight and LLN as compared to DI 80. Furthermore, pruning weight and LLN of the two PRD treatments were not statistically different from those of DI 40, nor were yield differences. At a glance, it would seem that 2009 and 2010 had contrasting results but caution must be taken when analysing it. In fact, in 2010 the canopy parameters were only measured later in the season (in September 22nd_{), and}

Ana Fernandes de Oliveira - Deficit Irrigation Strategies in Grapevine (Vitis vinifera L). Ecophysiologic Responses,

Growth-Yield Balance, Canopy and Cluster Microclimate for Improving Quality under Mediterranean Climate Page 142 of 234 therefore they do not clearly indicate higher vigour in DI plants, but a denser canopy, only at the end of the season (Tab. 12).

Table 12 – Canopy growth and yield in 2009 and 2010 seasons in site 2 – „Vermentino‟. Canopy Surface data regards harvest. Mean values (4 replicates/block) and ANOVA. * - significant for

P<0.05; ns - not significant.

Date Treatment Pruning

Weight (kg/vine) Canopy Surface Area (m2_/vine) LLN Cluster Exposure (%) Canopy Porosity (%) Yield (kg/vine) 2009 DI 80 0.60 1.96ab - - - 2.43 a DI 40 0.58 1.67a - - - 2.26 b PRD 80 0.58 2.12b - - - 2.44 ac PRD 40 0.66 2.50c - - - 2.57 c Sig. ns * *

2010 DI 80 0.86 a 1.14 3.2a 25.0a 0.0a 3.96

DI 40 0.71 b 1.32 2.6b 30.4a 3.8a 3.54

PRD 80 0.82 ab 1.14 2.4b 48.3b 9.8b 4.44

PRD 40 0.84 ab 1.13 2.2b 55.6b 10.6b 4.76

Sig. * ns * * * ns

When deficit irrigation was based on -0.8 MPa Ψstem re-watering threshold, significant differences on yield components were detected (Tab. 13). In fact, during the third trial, IC significantly increased yield as compared to the other treatments but at harvest, IC yield was not statistically higher than in ED. Cluster number per vine was independent of the water treatment and so the higher yield obtain in IC plants was due to higher cluster weight. In NC plants was registered the lowest cluster weight but it not statistically different from ED and LD.

The significant loss in weight of NC clusters can be explained by lower values of soil water content during all the growing season and higher temperatures on berry cell elongation period, leading to a reduction in cell division in pericarp tissue (McCarthy, 1999) and to a shrinkage of berries during advanced stages of ripening (Crippen and Morrison, 1986). Nevertheless, ED plants, which were exposed to the same level of mild water stress imposed in NC before veraison, and also LD plants, which endured mild water stress conditions from veraison until harvest, had higher but not statistically significant cluster weight, as compared to NC plants. Thus, we conclude that

Ana Fernandes de Oliveira - Deficit Irrigation Strategies in Grapevine (Vitis vinifera L). Ecophysiologic Responses,

Growth-Yield Balance, Canopy and Cluster Microclimate for Improving Quality under Mediterranean Climate Page 143 of 234 the imposed stress conditions, alternatively pre and post veraison, did not induce significant reduction in berry weight, since an eventual reduction in berry cell division pre-veraison was compensated with less shrinkage during ripening and vice-versa.

Moreover, the differences between seasons, in terms of vigour, canopy density and yield were more impressive than those caused by differences in the irrigation treatments, both in „Cannonau‟ and „Vermentino‟ trials. In a five-year deficit irrigation experiment on cv. Cabernet Sauvignon, Keller et al. (2008) also observed that the variation in growth and other aspects of vine performance, such as yield, cluster initiation and differentiation as well as cane maturation and cold hardiness, were far more affected by seasonal effects (i.e., effects of variation in climate, especially temperature) than that to irrigation treatments and crop adjustments, even supplying as little as 30% of ETc from fruit set to harvest. These authors also observed that seasonal reduction on yield were partly due to poor fruit set, caused by water deficit during bloom.

Table 13 – Yield components in 2011 growing season in experimental site 3 – „Vermentino‟. Canopy Surface data regards harvest. Mean values (4 replicates/block) and ANOVA. * - significant

for P<0.05; ns - not significant.

Date Treatment N°

clusters/vine Cluster weight (kg) (kg/vine) Yield

2011 ED 11 234.27a 2.52ab

LD 10 224.68a 2.33a

IC 11 293.01b 3.25b

NC 11 196.72a 2.14a

Sig. ns * *