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Bernadine C. Strik and Helen K. Cahn

`Meeker' red raspberry (Rubus idaeus L.) cane densities of 5, 10, or 15 canes/hill in a hill system, with canes topped at 2 m or the entire cane length retained and looped, were compared with a 15- or 30-cm-wide hedgerow with canes topped at 2 m from 1995 to 1997. Cane density among all treatments ranged from 2.2 to 9.9 canes/m2 during the study. Plots were harvested by machine every 2 days. Within the hill system, total yield increased with cane density in all years. Looped treatments produced a higher yield/plot than did topped ones in all years except 1996, when the yield difference was insignificant because looped canes had greater winter injury. Weight per fruit ranged from 5.4% to 9.7% less on looped than on topped canes. Hedgerow systems had a lower yield than hill systems in 1996, but a higher yield in 1997. Losses due to machine harvest were not affected by pruning (cane density or topping) or production system (hill system or hedgerow) and averaged 16.2% of total yield in 1997. Thirty-five percent of the loss due to machine harvest occurred between harvests.

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Roberto Nunez-Elisea*, Helen Cahn, Lilia Caldeira, and Clark Seavert

A `Regina'/Gisela 6 sweet cherry orchard was planted in April 2001 to evaluate a row cover (RC) made of black, woven polypropylene fabric, in water conservation. Trees were trained to a central leader and planted at 3 m x 5.4 m. Soil water content and tree growth variables were compared for trees growing with or without a 2.4 m-wide RC. Irrigation of all trees replenished approximately 80% of weekly evaporation rate. Trees with RC maintained consistently higher (30% to 40%) soil moisture content at 30 cm depth than non-RC trees. In Spring 2003, trees in RC had significantly larger trunk cross sectional area (34%), height (7%), total wood length (65%), total number of branches (20%) and number of 1-year-old-shoots (45%) compared to trees with no row cover. Length of 1-year-old wood for trees in RC was two-fold that of non-covered trees. In Summer 2003, RC had no clear effect on bloom time, intensity or duration. Fruit yields were light and not affected by RC, but fruit size was slightly larger for trees in RC. Although trees were not fertilized, foliar nitrogen content was significantly higher and leaf green color was notably darker green for trees with RC. During Spring and Summer 2003, soil temperatures under RC at 5-cm and-10 cm depths were generally 1 °C to 2 °C warmer than in non-covered ground. The RC did not affect air temperature at 10 cm and 30 cm above ground. It is speculated that RC promoted tree growth by a combined increased available soil moisture and warmer root temperatures, which favor root development and nutrient uptake, particularly in the absence of competing weeds. Increased branching in trees with RC is unclear. It is possible that light quality above RC triggers developmental changes resulting in increased vegetative budbreak.

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Roberto Nunez-Elisea, Helen Cahn, Lilia Caldeira, and Clark F. Seavert

Black, woven polypropylene row covers were compared to chemical sprays as methods to manage ground vegetation in a `Regina'/Gisela 6 orchard planted in 2001. Row covers were installed within 1 month of planting. Exposed row cover width was 2.4 m, with edges (30 cm on each side) buried in the ground. Only a 30-cm band along the edge of row covers was sprayed with herbicide to facilitate mowing. Weed management of control trees consisted of chemical herbicide sprays. Trees were not fertilized since planting in 2001. Irrigation of all trees was applied with low volume (20 L·h-1) microsprinklers and scheduled according to soil water content. Row covers significantly increased trunk cross-sectional area (TCSA) by about 30% annually. By Summer 2004, trees with ground covers had filled their allotted space within rows, while control canopies were ≈50 cm apart. Trees in row covers produced a 130% higher average yield than controls (7.4 kg/tree vs. 3.2 kg/tree). Row covers produced larger and firmer fruit, which matured 2–3 days later than controls. Groundcovers slightly increased soil temperature from April to September by ≈2 °C at 5- and 10-cm depths. Roots under ground covers were denser and more spread out than in controls and water use efficiency was higher for trees growing in ground covers. Amount and labor for herbicide application was reduced to less than half with row covers. Although ground covers are expensive at ≈$2000 per acre, their cost could be offset by earlier and higher production and by long-term savings in labor, water use, and herbicides. Durability of row covers is expected to exceed 15 years.

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Xinhua Yin, Clark F. Seavert, Janet Turner, Roberto Núñez-Elisea, and Helen Cahn

The impacts of synthetic polypropylene groundcover in the row area of young sweet cherry (Prunus avium L.) trees (Regina on Gisela 6) on soil nutrient availability, tree mineral nutrition and productivity, and cash costs and returns were investigated on a Van Horn fine sandy loam soil at Hood River, Ore., from 2001 to 2005. Treatments included 2.44-m wide synthetic fabric groundcover made of black, woven polypropylene over the row area of cherry trees and no groundcover but with herbicide applications in the row area with the same width as the polypropylene groundcover. Soil-available NO3 , P, K, Ca, Mg, S, B, Zn, Mn, and Cu contents in 0 to 30 cm in August did not differ significantly between the cover and no cover treatments in any year except 2005, when soil N and K levels were lower with polypropylene cover. Leaf N concentration in August was enhanced by 11% to 19% each year in the polypropylene cover treatment. However, leaf P concentration was lowered by 19% to 37% with polypropylene cover each year; and leaf Ca and Mg concentrations were reduced by 9% to 13% and 6% to 24%, respectively, as a result of polypropylene cover in 3 of 5 years. Reduced leaf P, Ca, and Mg concentrations in the cover treatment were attributed to the diluting effects of enhanced tree growth and fruit yield. Cumulative cash costs for the orchard within the first 4 years before fruit production were $5246/ha higher with polypropylene cover relative to no cover. However, these costs were offset quickly by increased returns from enhanced fruit yields. In the long-term, more fertilizers may need to be applied on polypropylene groundcovered trees to compensate for the enhanced tree growth and fruit production.

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Xinhua Yin, Janet Turner, Clark Seavert, Roberto Nunez-Elisea, and Helen Cahn

Theinfluences of a synthetic fabric cover in the row area of sweet cherry trees on soil fertility and plant nutrition are largely unknown. A field trial has been conducted on young `Regina' sweet cherry on a sandy loam soil at the Mid-Columbia Agricultural Research and Extension Center, Hood River, Ore., since 2001. The difference in soil NO - 3, P, K, Ca, Mg, S, B, Zn, Mn, Cu, pH, or organic matter was nonsignificant between the covered and non-covered treatments in any year. Leaf N content was 11% to 16% greater with the covered treatment compared with the non-covered treatment in 2002 and 2003, but leaf N was similar for the two treatments in 2001. Leaf P content was similar for the two treatments in 2001, but was about 36% less with the covered treatment than the non-covered treatment in 2002 and 2003. Leaf Ca content was decreased by 11% to 17% due to a synthetic fabric cover in 2002 and 2003. Leaf Mg content was 13% to 24% less with the covered treatment than the non-covered treatment in 2002 and 2003. However, the decreased leaf P, Ca, and Mg contents with the covered trees were due to the dilute effects of increased tree growth. The effects of a fabric cover on leaf K, S, B, Zn, Mn, and Cu contents were primarily nonsignificant. Our results suggest that although nutrient availability in the soil is not reduced by a wide synthetic fabric cover, higher rates of fertilizers may be needed for the covered sweet cherry trees due to the elevated tree growth and fruit production from a long-term perspective.