Growth and yield of red raspberries cultivated under open field condition vs. high tunnel or rain shelter in the northern canadian climate
|Advisor:||Desjardins, Yves; Gosselin, André|
|Abstract:||Protected culture such as high tunnels is a new technology to improve red raspberry crop production under Northern climates as found in Quebec, Canada. The main objective of this Ph.D. research was to assess the performance of high tunnels vs. Voen shelters, a novel umbrella-shaped cover structure, in comparison to open field cultivation, in terms of microclimate, photosynthetic performance, plant growth, and fruit yield for both floricane- and primocane-fruiting types of red raspberries (Rubus idaeus, L.). As cultural management practices need to be tailored to the different modified growing environments, relevant practices like summer pruning (for floricane-fruiting cultivar), cane density optimization (for primocane-fruiting cultivar) and reflective mulch (for both fruiting types) were tested under high tunnel and Voen shelter vs. open field. Plants grown under high tunnel produced on average 1.2 and 1.5 times more marketable fruit yield than under Voen shelter for floricane-fruiting cv. ‘Jeanne d’Orléans’ and primocane-fruiting cv. ‘Polka’, respectively. Compared to plants grown in open field, the fruit yield of high tunnel-grown plants was more than double for cv. ‘Jeanne d’Orléans’ and almost three times higher for cv. ‘Polka’. The use of reflective mulch had a significant positive effect on fruit yield, namely 12% for cv. ‘Jeanne d’Orléans’ and 17% for cv. ‘Polka’. Pruning the first or second flush of stems from the rhizome significantly improved fruit yield of cv. ‘Jeanne d’Orléans’ by 26% on average compared to unpruned plants. As cane density increased, the fruit yield of cv. ‘Polka’ increased significantly, namely by 43% and 71% for a cane density of 4 and 6 canes per pot, respectively, as compared to the standard lower cane density of 2 canes per pot. During the fruiting period of cv. ‘Jeanne d’Orléans’, reflective ground cover significantly increased the photosynthetic photon flux density (PPFD) reflected to the lower canopy by 80% in open field and 60% under high tunnel, compared to only 14% under Voen shelter. During the fruiting season of cv. ‘Polka’, a positive reflective mulch effect on the reflected light (up to 42%) was only found in open field. In all cases, ground cover had no significant effect on the total leaf PPFD and photosynthesis under any growing conditions. For cv. ‘Jeanne d’Orléans’, the leaf PPFD was attenuated by approx. 46% under both types of protective covering compared to open field. Correspondingly, photosynthesis was on average reduced by 43% under high tunnel and by 17% under Voen shelter. Cultivar ‘Polka’ plants shared a similar growing condition effects on leaf PPFD and photosynthesis. Despite the fact that lower individual leaf photosynthetic rates were consistently measured in tunnel-grown plants, once leaf-level photosynthesis was scaled up to the whole canopy, the photosynthetic production of tunnel-grown plants was found to be 51% higher than that observed in open field for cv. ‘Jeanne d’Orléans’, and 46% higher for cv. ‘Polka’. This was explained by the greater (nearly twice) leaf area of tunnel-grown plants, which compensated for their lower photosynthetic rate per unit leaf area, the latter being caused by the supra-optimal leaf temperatures found under high tunnel (6.6°C higher on average than in open field) as well as the attenuation of the leaf PPFD (approx. 43%) by the tunnel coverings. Whole-canopy photosynthesis was positively correlated with fruit yield for both fruiting types of red raspberry, whether cultivated under high tunnel or in open field.|
|Document Type:||Thèse de doctorat|
|Open Access Date:||24 April 2018|
|Collection:||Thèses et mémoires|
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