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Y.L. Grossman and T.M. DeJong

Plant dry matter production is proportional to light interception, but fruit production does not always increase with increased light interception. Vegetative growth potential, the effect of cropping on vegetative growth, light interception and cropping efficiency of a clingstone peach [Prunus persica (L.) Batsch `Ross' on `Nemaguard' rootstock] were assessed in four production systems differing in tree density and training system. The four systems were a perpendicular V (KAC-V) system, a high-density perpendicular V (HiD KAC-V) system, a cordon system, and an open vase system. Vegetative growth potential, assessed on defruited trees, was higher in the cordon system and lower in the open vase system compared to the V systems. Cropping reduced leaf growth on the V and cordon systems and stem growth on the KAC-V and cordon systems. On a ground area basis, the HiD KAC-V system had the highest crop yields and the open vase system had the lowest. The cordon and HiD KAC-V systems intercepted more light and produced more fruit, stem, and leaf biomass than the open vase system. However, the modified harvest increment, the ratio of fruit dry mass to the sum of fruit, leaf, and stem dry mass, was lower in the cordon system than in the other systems. Thus, on this basis, the cordon system was the least efficient. On a trunk cross-sectional area basis, there were no significant differences in fruit production among any of the four training systems. For current year production, crop production per unit ground area is the best measure of economic efficiency. However, when planning the spacing, training and pruning of orchard trees, the most appropriate goal seems to be a system that increases light interception without increasing vegetative growth potential, such as the HiD KAC-V system.

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T.M. DeJong, W. Tsuji, J.F. Doyle, and Y.L. Grossman

A clingstone peach (Prunus persica L. Batsch `Ross' on `Nemaguard' rootstock) orchard was established at the Univ. of California Kearney Agricultural Center, Parlier, for evaluating the economic efficiency of three high-density planting systems in comparison with the conventional Open Vase system. The orchard contained four replicate plots (0.80 ha/plot), each containing four different planting systems. The four planting/training systems (in-row spacing given first) were: the “KAC-V” (a perpendicular V system spaced 2.0 × 5.5 m, 919 trees/ha); the “HiD KAC V” (spaced 1.8 × 4.6 m, 1196 trees/ha); the “Cordon” (spaced 2.4 × 4.0 m, with perpendicular harvest drives 4.8 m every 22 m and tree height limited to 2.5 m, 919 trees/ha); and the “Open Vase” (spaced 6.1 × 5.5 m, 299 trees/ha). All system-specific costs and crop yields were recorded annually on each subplot for the first 5 years. Although the Cordon system had the highest yields in the second year, the V systems had the highest returns after 5 years. Cumulative costs were: HiD KAC-V system > KAC-V ≥ Cordon > Open Vase. The system that was designed to maintain tree height <2.5 m (Cordon) tended to be less profitable than the V systems because of modest crop yields and high pruning costs that were not offset by increased harvest efficiency. In the last 3 years of the study, pruning, thinning, and harvesting accounted for the majority of the system-specific costs.