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David M. Hunter and John T.A. Proctor

A system was developed to evaluate the response of grapes (Vitis spp. `Seyval') to soil-applied paclobutrazol. The youngest fully expanded leaf, and its axillary bud, on single shoots 6 to 9 nodes long developing on rooted softwood cuttings, were retained for use in a bioassay. The shoot that developed from the axillary bud exhibited a dosage-dependent growth inhibition following soil applications of paclobutrazol at 4 dosages between 1 and 1000 μg·g-1 soil. Other aerial components showed no response to paclobutrazol. This test plant system has potential for use in physiological studies with soil-applied plant growth regulators. Chemical name used: β -[(4-chlorophenyl)methyl]- α -(1,1-dimethylethyl)1H-1,2,4-triazole-1-ethanol (paclobutrazol).

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G. Steven Sibbett

Pecan [Carya illinoinensis (Wangenh. K. Koch)] soils in the arid western United States are characteristically high in pH, calcareous, and often saline or sodic. Economic production, when trees are grown in such soils, requires that growers pay particular attention to managing soil chemistry to avoid nutrient deficiencies, toxicities, or water deficits due to soil structural deterioration. Soil-applied acidulents, calcium-containing compounds, and water management are used by growers to manage high pH problems, sodic soil conditions, and salinity.

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R. Scott Johnson, Rich Rosecrance, Steve Weinbaum, Harry Andris, and Jinzheng Wang

The suspected contributory role of soil fertilization to nitrate pollution of groundwater has encouraged exploration of novel fertilizer management strategies. Foliar-applied urea has long been used to supplement soil N applications, but there have been no apparent attempts to replace soil N applications completely in deciduous orchard culture. Two experiments were conducted to study the effect of foliar-applied low biuret urea on productivity and fruit growth of the early maturing peach [Prunus persica L. Batsch (Peach Group)] cultivar, Early Maycrest. In a 3-year experiment, a total foliar urea regime was compared to an equivalent amount of N applied to the soil. The foliar treatment supplied adequate amounts of N to the various organs of the tree including the roots, shoots, and fruit buds, but mean fruit weights were lower than in the soil-fertilized treatment. In a 2-year experiment, a 50%-50% combination treatment of soil-applied N in late summer with foliar-applied N in October, maintained yields and fruit weight equal to the soil-fertilized control. Some soil-applied N appears necessary for optimum fruit growth. Soil N application may be needed to support root proliferation and associated processes, but we did not determine a threshold amount of soil-applied N needed. The combination treatment also reduced excessive vegetative growth which is characteristic of early maturing peach cultivars. Therefore, this combination treatment offers promise as a viable commercial practice for maintaining tree productivity and controlling excessive vegetative growth in peach trees.

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David B. Headley, Nina Bassuk, and Robert G. Mower

Two experiments were conducted to determine the relative resistance of 33 selected cultivars of English ivy (Hedera helix L.) to soil- and shoot-applied NaCl. In the soil-applied NaCl experiment, ramets of the 33 cultivars were irrigated with a fertilizer + 0.25-N NaCl solution for 55 days. `Harrison', `Hibernica', `Thorndale', Wilson', and Woerner' exhibited the least amount of visible shoot damage. Dry weights of all cultivars were much lower in the salt treatment. In the shoot-applied NaCl experiment, plants were sprayed daily with a 0.25-n NaCl solution for 48 days. The young leaves and stems of all cultivars were severely injured by the salt spray, while the mature leaves and stems and the dormant buds were only slightly injured. Reduction in dry weight varied between cultivars. Two subsequent experiments focused on resistance to soil-applied NaCl. Ramets of the NaCl-resistant `Harrison', `Hibernica', and `Thorndale', and the NaCl-sensitive `Baltica', `Cathedral Wall', and Wingertsberg' were irrigated with a fertilizer + 0.25-N NaCl solution for 48 days. Whole-plant Cl content for all six cultivars was in the range of 30,000 ppm. Ramets of `Thorndale' and `Cathedral Wall' were irrigated with a fertilizer + 0.25-N NaCl solution for 30 days with replicate plants harvested at S-day intervals. `Cathedral Wall' accumulated more Cl at a faster rate than `Thorndale'. Mean whole-plant Cl concentration peaked at 97,000 ppm for `Cathedral Wall' and 40,000 ppm for `Thorndale'. Salt resistance may be partly based on slower uptake of Cl.

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S.M. Southwick, W. Olson, and J. Yeager

Soil applied potassium (K) may not alleviate K deficiency in fine textured California soils when high numbers of prunes per tree are produced leading to leaf necrosis and limb death. Because K demand is increased by fruit, K nitrate (KN) sprays appear to be a corrective option for growers in this situation. Our objectives were to determine best seasonal KN spray liming strategies to minimize K deficiency, quantify K uptake into leaves after spray and to evaluate spray effects on productivity. Results indicated that regardless of spray timing leaf K was increased by approximately 0.3% and three weeks later decreased 0.2%. Average leaf K in sprayed trees was 0.7% higher than untreated trees at harvest. Fruit fresh to dry weight ratios were lower (better) from summer sprayed trees than spring. Summer KN sprayed trees had yield efficiencies equal to those having soil applied K. Fruit size was similar regardless of K application method. Foliar KN sprays may be a viable K augmentation to soil application in heavy crop years on fine textured soils.

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L. Gene Albrigo and James P. Syvertsen

In order to evaluate possible reduced nitrate leaching while maintaining yield, `Hamlin' orange and `Flame' grapefruit trees on `Carrizo' or `Swingle Citrumelo' rootstocks were grown from planting using only foliar urea or soil-applied nitrate or ammonium N. An intermediate treatment of foliar and ground N was included also. From the 4th year, yields were recorded for 3 years. As previously reported, canopy growth was greater for the foliar urea treatment for the first 3 years. For 2 of the next 3 bearing years, the grapefruit trees in the foliar urea N treatment produced significantly less yield than the soil-applied treatment and the intermediate treatment was intermediate. The orange trees in the foliar urea treatment produced significantly less fruit than the soil N treatment in only 1 of 3 years, but the yields were numerically less every year. Results for fruit quality and nitrate leaching will be reported also. Foliar urea application alone was more costly and less productive than a soil N program.

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Geoffrey M. May and Marvin P. Pritts

The main effects and interactions of soil-applied P, B, and Zn on yield and its components were examined in the field at two pH levels with `Earliglow' strawberries (Fragaria × ananassa Duch.). Applied nutrients had significant effects on several yield components, but responses depended on the levels of other nutrients or the soil pH At a soil pH of 5.5, yield responded linearly to B and quadratically to P. At pH 6.5, P interacted with B and Zn. Fruit count per inflorescence was the yield component most strongly associated with yield followed by individual fruit weight. However, these two yield components responded differently to soil-applied nutrients. Foliar nutrient levels generally did not increase with the amount of applied nutrient, but often an applied nutrient had a strong effect on the level of another nutrient. Leaf nutrient levels were often correlated with fruit levels, but foliar and fruit levels at harvest were not related to reproductive performance. Our study identifies some of the problems inherent in using foliar nutrient levels to predict a yield response and demonstrates how plant responses to single nutrients depend on soil chemistry and the presence of other nutrients.

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Jeanine M. Davis, Douglas C. Sanders, Paul V. Nelson, Laura Lengnick, and Wade J. Sperry

Boron deficiency in fresh-market tomatoes (Lycopersicon esculentum Mill.) is a widespread problem that reduces yield and fruit quality but is often not recognized by growers. Tomatoes were grown in field and hydroponic culture to compare the effects of foliar and soil applied B on plant growth, fruit yield, fruit quality, and tissue nutrient levels. Regardless of application method, B was associated with increased tomato growth and the concentration of K, Ca, and B in plant tissue. Boron application was associated with increased N uptake by tomato in field culture, but not under hydroponic culture. In field culture, foliar and/or soil applied B similarly increased fresh-market tomato plant and root dry weight, uptake, and tissue concentrations of N, Ca, K, and B, and improved fruit set, total yields, marketable yields, fruit shelf life, and fruit firmness. The similar growth and yield responses of tomato to foliar and root B application suggests that B is translocated in the phloem in tomatoes. Fruit from plants receiving foliar or root applied B contained more B, and K than fruit from plants not receiving B, indicating that B was translocated from leaves to fruit and is an important factor in the management of K nutrition in tomato.

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W.D. Scott and B.D. McCraw

Three cultivars of watermelon (Citrullus lanatus), `Crimson Sweet', `Charleston Gray' and `Tri-X Seedless' were grown in combination with 4 levels of soil applied calcium (0, 280, 560, 1120 kg Ca/ha). Gypsum was incorporated into 6 m plots on 5 m centers then covered with black plastic mulch. Irrigation requirements were provided through a hi-wall drip system and soil water status monitored with tensiometers. Transplants were spaced 1.2 m apart in-row spacing allowing for 5 plants per plot and replicated 3 times. Melons were harvested at 7, 14, 21 days from anthesis and at full maturity. Rind tissue was analyzed for total and extractable Ca, Mg, K, Mn, Zn and Fe. Leaf samples were taken 6 weeks from transplanting for similar analysis, Yield, vine growth and the incidence of blossom-end rot were recorded. The study was conducted at 2 locations during the 1989 and 1990 growing seasons. Data will be presented at the meeting,

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William E. Roberson, H. Brent Pemberton, and George L. Philley

To determine the efficacy of cyproconazole for control of black spot [Marssonina rosae (Lib.) Lind] when applied as a drench, treatments of 0, 32.5, 65, 97.5 and 130 g a.i./ha were initiated 9 May 1994 on individual Rosa `Peace' plants in a randomized complete-block design. Treatments were applied once per month until 18 Oct. 1994. Data were taken in July, Sept., and Nov. 1994 when separate disease and defoliation ratings were assigned. By July, the controls were heavily infected; the higher treatment rates resulted in significant control. By September, the disease and defoliation ratings exhibited a linear response with cyproconazole rate, with the highest treatment rate giving the best control. The relationship between disease and defoliation ratings and treatment rate remained the same in November, although there was increased disease incidence overall. No phytotoxicity was observed. These results indicate that soil applied treatments of cyproconazole can control black spot effectively on roses.