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J.A. Cline

The effect of aminoethoxyvinylglycine (AVG), commercially available as ReTain, and three organo-silicone surfactants were evaluated in a series of four experiments over a 2-year period in two commercial peach orchards. Four rates of AVG (0, 66, 132, and 264 mg·L–1 AVG; all applied with 0.05% Sylgard 309) and three surfactants (0.05% Sylgard 309; 0.05% Regulaid; and 0.50% LI-700; all applied with 132 mg·L–1 AVG) were applied to `Venture' and `Babygold 7' peach trees 10 days before first harvest. Fruit were harvested according to commercial standard maturation criteria of background color, suture filling, and fruit size. Treatments were assessed in relation to fruit maturity, delay in harvest, fruit size and yield, fruit quality (flesh firmness and brix), as well as fruit quality following 2 weeks of cold storage. Based on sequential harvest data, the maturation of the AVG treated trees was delayed by about 3 to 4 days. Fruit from AVG treated trees were firmer at harvest and 2 weeks following cold storage at 2°C. However, no additional increase in fruit size or yield was detected. In addition, the addition of a surfactant was not necessary for AVG to be efficacious for delaying maturity and enhancing firmness when applied at 132 mg·L–1 AVG. However, when the three surfactants were compared, Regulaid and Li 700 advanced color development in one experiment and Li-700 resulted in firmer fruit in another. Aminoethoxyvinylglycine applications to the clingstone cultivars `Venture' and `Babygold 7' can be used successfully to manage harvest activities by delaying the onset of picking and improving fruit firmness.

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John A. Cline and Eric J. Hanson

Individual fruit of `Delicious' apple (Malus domestica Borkh.) were exposed to low, high, or ambient relative humidity (RH) levels during different stages of fruit development to study the importance of transpiration and the xylem system in supplying Ca to fruit. The Ca content of fruit exposed to low RH was the same or higher than that of fruit exposed to high RH. Treatments imposed early or late in the season usually affected fruit Ca levels similarly. Fruit weight was not consistently affected by RH treatments. The xylem may be a significant source of fruit Ca throughout the season.

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Eugene J. Hogue, John A. Cline, Gerry Neilsen, and Denise Neilsen

Fertigated ‘Gala’ apple trees on M.9 (Malus domestica Borkh.) rootstock, planted in 1998, were grown on a coarse soil for 6 years (1998 to 2003) and exposed to eight orchard floor vegetation management treatments within the tree row. These consisted of a glyphosate control; three waste paper mulch treatments [spray-on mulch paper mulch (SM), SM incorporated with dichlobenil, SM applied over uniformly spread shredded office paper (SOP)]; and four living cover crop mulch treatments [dwarf white clover (WC), sweet clover (SC), hairy vetch (HV), and annual rye]. There were no significant treatment effects on leaf nitrogen (N) and phosphorus (P) status; however, leaf potassium (K) levels were negatively affected by the living mulch treatments in 2 of 5 years. Tree vigor was diminished by several of the orchard floor vegetation management systems in 5 of 6 years. Trees receiving an SM treatment grew more rapidly than trees receiving the ground cover treatments and trees receiving a glyphosate treatment had relatively poor but comparable growth to several of the cover crop treatments. Growth response in trees receiving SM were observed in all production years. After 6 years, cumulative yields were highest from trees receiving any of the three SM or glyphosate treatments and significantly less for any of the ground cover treatments. Weed growth within the rye cover crop was significantly reduced in comparison with the other living mulches; however, it remained sufficiently competitive to contribute to diminished overall yield and tree growth in comparison with the SM and gylphosate control treatments. Overall, response of leaf K concentration to mulch treatments was insufficient to prevent low K levels after 5 years. The addition of K through the organic mulches or recycling of K by cover crops was insufficient to avoid the development of low leaf K levels. Annual fertigation of K, in addition to N and P, appears necessary to maintain adequate vigor and yield when using mulches or cover crops in intensive, drip-irrigated apple orchards grown on coarse soils.

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H.J. Hruska, G.R. Cline, A.F. Silvernail, and K. Kaul

Research began in 1999 to examine sustainable production of bell peppers (Capsicum annuum L.) using conservation tillage and legume winter cover crops. Tillage treatments included conventional tillage, strip-tillage, and no-tillage, and winter covers consisted of hairy vetch (Vicia villosa Roth), winter rye (Secale cereale L.), and a vetch/rye biculture. Pepper yields following the rye winter cover crop were significantly reduced if inorganic N fertilizer was not supplied. However, following vetch, yields of peppers receiving no additional N were similar to yields obtained in treatments receiving the recommended rate of inorganic N fertilizer. Thus, vetch supplied sufficient N to peppers in terms of yields. Pepper yields following the biculture cover crop were intermediate between those obtained following vetch and rye. When weeds were controlled manually, pepper yields following biculture cover crops were similar among the three tillage treatments, indicating that no-tillage and strip-tillage could be used successfully if weeds were controlled. With no-tillage, yields were reduced without weed control but the reduction was less if twice the amount of residual cover crop surface mulch was used. Without manual weed control, pepper yields obtained using strip-tillage were reduced regardless of metolachlor herbicide application. It was concluded that a vetch winter cover crop could satisfy N requirements of peppers and that effective chemical or mechanical weed control methods need to be developed in order to grow peppers successfully using no-tillage or strip-tillage.

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S.S. Miller, R.W. McNew, B.H. Barritt, L. Berkett, S.K. Brown, J.A. Cline, J.M. Clements, W.P. Cowgill, R.M. Crassweller, M.E. Garcia, D.W. Greene, G.M. Greene, C.R. Hampson, I. Merwin, D.D. Miller, R.E. Moran, C.R. Rom, T.R. Roper, J.R. Schupp, and E. Stover

Cultivar and planting site are two factors that often receive minimal attention, but can have a significant impact on the quality of apple (Malus ×domestica) produced. A regional project, NE-183 The Multidisciplinary Evaluation of New Apple Cultivars, was initiated in 1995 to systematically evaluate 20 newer apple cultivars on Malling.9 (M.9) rootstock across 19 sites in North America. This paper describes the effect of cultivar and site on fruit quality and sensory attributes at a number of the planting sites for the 1998 through 2000 growing seasons. Fruit quality attributes measured included fruit weight, length: diameter ratio, soluble solids concentration (SSC), titratable acidity (TA), flesh firmness, red overcolor, and russet. Fruit sensory characteristics rated included crispness, sweetness, and juiciness, based on a unipolar intensity scale (where 1 = least and 5 = most), and acidity, flavor, attractiveness, and desirability based on a bipolar hedonic scale (where 1 = dislike and 5 = like extremely). All fruit quality and sensory variables measured were affected by cultivar. The two-way interaction of cultivar and planting site was significant for all response variables except SSC, TA, russet, crispness, and sweetness ratings. The SSC: TA ratio was strongly correlated with sweetness and acidity sensory rating, but was weakly correlated with flavor rating. The results demonstrate that no one cultivar is ideally suited for all planting sites and no planting site is ideal for maximizing the quality of all apple cultivars.