Sweet cherries from the end of the world: options and constraints for fruit production systems in South Patagonia, Argentina

In South Patagonia, development of the fruit production sector has been almost exclusively based on the production of sweet cherry, with an area increase from 176 ha in 1997 to 578 ha at the end of 2006. These orchards are designed as intensive systems and oriented to export markets. Even though sweet cherry seems currently the most profitable crop in the region, other crops may be interesting to increase the use efficiency of the resources, to complement income and to spread risk. The general objective of this thesis was to assess constraints and opportunities for fruit production systems in Chubut and Santa Cruz Provinces, with emphasis on sweet cherry. In the context of cherry production for export, it is important to define fruit quality and how this can be affected. Although quality has different meanings for different stakeholders, consumer acceptance seems to be the most important factor to be considered, but independent of consumer liking, firmness is a key aspect for marketing cherries overseas. To estimate the optimal combination of yield and fruit quality, a “target-tree” approach to maximize gross value of product (GVP) at farm gate was developed and applied to cherry orchards, integrating eco-physiological information, model estimates and expert knowledge. Minimum fruit quality thresholds define the suitable market for the fruit, with their associated price ranges. In addition, on both domestic and export markets, price depends mainly on fruit size. The fruit number to leaf area ratio determines fruit quality (and indirectly fruit price), but in combination with mean fruit weight and leaf area index, also yield. GVP is calculated as the product of yield and fruit price. Quantification of frost damage risk is important in planning the development of new orchards and to decide on design and installation of frost control systems. Therefore, a comprehensive method to quantify frost damage risk was developed and the potential impact of frost control systems on risk reduction was estimated. Frost damage for any specific day of the season was assumed to occur when the minimum temperature on that day was below the specific lethal temperature for the phenological stage predicted at that moment. Frost damage probability was estimated for each production location of the region as the frequency of years in which at least one damaging frost occurs, at any time during the growing season until harvest. Frost damage risk was compared among cultivars and locations, and also the effect of active frost control methods on frost damage risk reduction was analyzed. Due to the long lifespan of orchard systems, an explorative modelling study was performed. OPTIFROP is a dynamic farm model, developed as an Interactive Multiple Goal Linear Program, capable of allocating, throughout the time horizon of the run, production activities to different land units, while optimizing different (conflicting) objectives, subject to several constraints. For deriving land use options and quantifying the TCs, a software called FRUPAT was developed. This allows combining crop-tree species, edaphic environment, training, irrigation and frost control system, and moment of installation of the frost control system. Feasible land use options were completely characterised by their inputs and outputs at each orchard age until their maximum lifespan. The aim of OPTIFROP was to support strategic decision-making, such as ‘when to plant’, ‘what to plant’, ‘with which technology’, and ‘how much area of each activity’. Thus, the model allowed identification of the options for development plans for Patagonian farms (‘window of opportunities’). The model allowed quantifying the trade-off between conflicting objectives. The different methods developed in this thesis contribute significantly to the fruit industry in South Patagonia by supporting growers, extensionists and researchers in developing structured thinking for analyzing and processing available (fragmented) information.