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Abstract

Mature trees of ‘Fantasia’ nectarine (Prunus persica L. Batsch. ‘Fantasia’) were treated with the chemical growth regulator paclobutrazol (PP333) in the spring of 1983. Net photosynthetic gas exchange measurements were conducted on treated and control trees in the field at monthly intervals from May through September. Growth responses were measured at the end of the growing season. The paclobutrazol treatment resulted in a 67.9% decrease in annual extension shoot growth compared to controls and no apparent decrease in fruit yield or leaf photosynthetic rate. Total tree leaf area was reduced at the end of the season by an estimated 54.5% (so total tree photosynthesis may have been reduced). There were no apparent effects of either the presence of fruit or stage of fruit maturity on leaf CO2 assimilation rate. Newly produced extension shoots on treated trees had shorter internodes, larger diameters, more flower buds per unit length, higher specific shoot dry weights but fewer buds per unit shoot dry weight, than on untreated trees.

Open Access

Abstract

The original ‘Brooks’ cherry (Prunus avium L.) seedling was evaluated at the Wolfskill Ranch of the University of California, Davis from 1970 to 1985. Clones of the original seedling have been evaluated for fruit quality in Contra Costa County since 1978 and in Fresno County at the University's Kearney Agricultural Center since 1981. ‘Brooks’ registered its most outstanding performance at the Kearney Field Station.

Open Access

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.

Free access

During the initial season of implementation, four tomato production systems differing in soil management, pest control practices, and level of inputs, such as labor, materials, and management intensity were evaluated. These systems were CON, a low input (no mulch, no trellising, overhead irrigation, preplant fertilization, scheduled pest control), conventional agrichemical system; BLD, a high input [straw mulch, trellising, trickle irrigation, compost fertility amendment, integrated pest management (IPM)], ecologically-oriented system that emphasized the building up of soil organic matter levels and used no agrichemicals to supply fertility or for pest control; BLD+, a system similar to BLD, except that agrichemical pesticides were used; and ICM, a high input system (black polyethylene mulch, trellising, trickle irrigation, fertigation, IPM pest control) that used agrichemicals to supply fertility and for pest control. Soil characteristics and fertility levels in the BLD and BLD+ systems were modified with extensive amendments of spent mushroom compost and well-rotted cattle manure. Levels of agrichemical NPK calculated to meet current crop needs were supplied to the CON and ICM systems, with 75% of fertility in the ICM system supplied through the trickle irrigation lines (fertigation). The BLD system had a greater soil water holding capacity and sharply reduced irrigation requirements. During a wet period, fruit cracking and evidence of water-mold root rot were significantly higher in the ICM system than the BLD and CON systems. Defoliation by Alternaria solani was greatest in the BLD system and least in the ICM system. The BLD and ICM systems resulted in a 1 week earlier peak yield compared to the CON system. The yield of No. 1 fruit was 55% to 60% greater in the BLD+ system than the other three systems, which were comparable in yield. Net return was highest in the BLD+ system, although the benefit/cost ratio was greatest in the CON system. This multidisciplinary study has identified important differences in the performance of diverse production systems during the unique transitional season.

Free access