Designing a “Target-Tree” for Maximizing Gross Value of Product in Patagonian Sweet Cherry Orchards

Abstract

A “target-tree” approach to maximize gross value of product (GVP; US$/ha) at the farm gate was developed and applied to sweet cherry orchards, integrating eco-physiological information, model estimates, and expert knowledge. During the 2003/04 growing season, the effect of the ratio of Fruit Number to Leaf Area (FNLAR; fruit/m2 LA) on Mean Fruit Weight (MFW; g/fruit) was analyzed at both the spur and whole-tree level, for different combinations “training system-cultivar” (Experiment 1). During the 2004/05 season, the effect of FNLAR on MFW, soluble solids content (SSC), titratable acidity (TA), and firmness (F), was evaluated at whole-tree level in a ‘Bing’/‘Mahaleb’ orchard (Experiment 2). In Experiment 1, there were no significant interactions between training system and cultivar for the effect of FNLAR on MFW at spur and whole-tree level. No significant differences were observed between vase and Tatura-trellis training systems. The R²-values for the relationships per cultivar were higher at whole-tree level than at spur level. At both the spur and whole-tree level, ‘Lapins’ had the highest Y-intercept and ‘Van’ the lowest. At spur level, no differences among cultivars were detected in their sensitivity to increments in FNLAR, but at whole-tree level ‘Van’ showed less sensitivity than ‘Lapins’ and ‘Bing’. In Experiment 2, MFW, TA and SSC decreased linearly with increasing FNLAR (P < 0.05). Firmness showed the same tendency, but the relationship was not significant (P = 0.082). Minimum fruit quality thresholds define the suitable market for the fruit (export, domestic, or industry), with their associated price ranges. In addition, in both the domestic and export markets, price depends mainly on fruit size. FNLAR determines fruit quality (and indirectly fruit price), and yield, in combination with MFW and leaf area index (LAI). GVP is calculated as the product of yield and fruit price. The combination ‘Bing’/‘Mahaleb’ on vase was used to illustrate parameter estimation (LAI and FNLAR) for a “target-tree” in Patagonian orchards, using the results of Experiment 2. Under these conditions, a LAI of 3.07 is required to intercept 75% of PAR at harvest. With these parameters, and considering “price-fruit quality” relationships based on expert knowledge, maximum GVP was obtained with 80 fruit/m2 LA and a yield of 18.25 t-ha⁻¹. Although this example is limited to a single combination of cultivar and training system in a specific location, the methodology can be applied to other situations, provided reliable relevant eco-physiological information is available.

Key Words:

• Ideotype
• LAI
• fruit number to leaf area ratio
• fruit size
• fruit quality
• fruit price
• Prunus avium