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  • Author or Editor: R. Beede x
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The effects of four mechanical pruning treatments [hedging, topping, hedging/topping, and hand-pruning (control)] on nut yield, nut quality, alternate bearing, and growth of 14-year-old female `Kerman' pistachio trees on Pistacia atlantica L. rootstocks were assessed. A single pruning was done before an “off,” or low-crop, year followed by retopping of those treatments incorporating topping the first year. Over 7 years, yields of hedged/topped and topped trees were equal to those of control trees, while hedged trees produced significantly less. The incidence of nonsplit shells and blank nuts were not affected by pruning. Nuts weighed more all years for hedged/topped and topped trees than for the others. Alternate-bearing indices within 7 years were lower for pruning treatments incorporating topping. Topping mitigated the fluctuating annual vegetative growth pattern and resulted in 27% of the shoots retaining buds through three successive alternate-bearing cycles after the year of treatment. Hedged/topped and topped trees had significantly less alternation in annual girth growth than control or hedged trees. These results demonstrated that two successive seasons of mechanical topping, started before the off year, produced changes in shoot growth, trunk growth, and bud retention that mitigated alternate bearing through three biennial cycles, without decreasing yield. Thus, severe annual hand-pruning could be used to prevent or minimize alternate bearing of pistachios.

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Current recommendations for fruit thinning of processing clingstone peaches in California suggest that growers delay thinning until an assessment of fruit size is made at reference date (10 days after first indications of pit hardening) and then adjust the crop load according to the fruit size attained. Recent research on modelling peach fruit growth indicates that delaying thinning until reference date (usually mid-May) can substantially limit final fruit size potential and crop yield when initial fruit set is heavy. In 1991 we initialed a field study to lest these model predictions and evaluate the yield response and economic feasibility of fruit thinning within 50 days of bloom to a specific crop load. The experiment was conducted in commercial orchards of the extra-early maturing cling peach cultivars Loadel and Carson. Three thinning treatments involved thinning different sets of trees on April 10, April 30, (∼30 and 50 dafb) and May 23 (reference date). Although costs of thinning at the earlier dates were 140-290% of thinning at reference date the increase in yield resulting from early thinning more than compensated for the higher thinning costs. There were no major effects of thinning treatment on the occurrence of split pits or other quality characteristics. This research has stimulated a re-evaluation of commercial fruit thinning practices used for clingstone peaches in California.

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