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Haibib Khemira, T.L. Righetti, and A.N. Azarenko

Seven-year-old `Royal Ann' cherry trees were given a total of 244 g of actual N as ammonium nitrate depleted in 15N (0.01 atom % 15N) either in March (M), June (J), or both in March and June (Split). The fertilizer was soil-applied to eight single-replicate trees. The following August, leaves from the trees that had the M treatment had 15.3% of their N from the fertilizer compared to 9.6% for the split treatment. Trees that had a J application were not different from the control trees. Even though cherry trees are physiologically active during the late summer months, little N is translocated to the leaves once the crop is fully developed. The percentage of newly acquired N in the fruit is similar to that in the spur leaves. Leaves from the different treatments had similar N contents; therefore, labeled N is the tool of choice to assess the performance of different fertilization practices.

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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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Bielinski M. Santos and Jose Pablo Morales-Payan

Greenhouse experiments were carried out to determine the tolerance of two radish cultivars to soil-applied B, Mo, and Zn. Sources used were boric acid (0, 54, 108, 216, 324, and 432 ppm), molybdic acid (0, 1.4, 2.8, 5.6, 8.5, and 11.3 ppm), and zinc sulfate (0, 40, 80, 160, 240, and 360 ppm) applied at planting in addition to the control. Plants were grown in plastic containers of 1.5 L, filled with a potting medium composed of 50% vermiculite, 30% sphagnum peat, and 20% perlite. Treatments were arranged within a randomized complete block design with six replications. Fresh weight of commercial roots was not affected by Mo or Zn applications in either cultivar. However, B applications decreased root fresh weight as rate increased. These results suggest that these radish cultivars perform well in a relatively wide range of Mo and Zn application rates, whereas tolerance to B appears to be low.

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Juan Pablo Arce, J. Benton Storey, and Calvin G. Lyons

Fall soil treatments of ZnEDTA and ZnSO4 at three increasing rates (32.2, 64.4 and 128.8 g. Zn/tree) and 1, 2 and 3 spring foliar sprays of NZN (0.35 g. Zn/tree/application) were tested to correct Zn deficiency in three year old `Earligrande' peach trees. All Zn carriers increased the Zn leaf content. Peach trees treated with three applications of NZN were equal to the medium or high rates of soil applied ZnEDTA or ZnSO4 respectively, in appearance, chlorophyll content and foliar Zn content. Three applications of NZN at 0.35 g. of Zn/tree (473 ml/378 gal H2O) gave excellent tree response and was cost effective.

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Harry S. Agamalian

Initial weed competition in newly planted grapevines can delay vine development, resulting in reduced first harvest. The experiments were conducted over a three year period on three wine grape varieties: Chardonnay, Semillon, and Napa Gamay.

Dormant rooted plants were winter planted and subjected to soil applied preemergence herbicides. The experiment was conducted on a Greenfield sandy loam under sprinkler irrigation. Major weeds were little mallow (Malva pariflora), hairy nightshade (Solanum sarachoides), lambsquarters (Chenopodium album), and Russian thistle (Sasola iberica).

Vine growth was evaluated on cane weights, cane diameter, and cane length. Weed interference over the three year period resulted in 50% reduction in vine growth the first year. Yield data obtained from the third year resulted in significant differences between the weed free vines compared to the non-weeded treatments.

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Brent K. Harbaugh

Interveinal chlorosis of lower (oldest) leaves followed by development of interveinal necrotic spots, marginal necrosis, downward cupping of leaves, and leaf abscission were symptoms of a disorder commonly observed during production of potted pentas. The disorder was determined to be an Fe toxicity problem associated with accumulation of extremely high levels of foliar Fe (649 to 1124 ppm). Cultivars varied in their response to soil-applied Fe-DTPA chelate solutions: `Starburst', `Mauve' and `Ruby Red' were very susceptible, `Pink Profusion' was intermediate, and `White', `Lavender Delight', and `Pink Rose' were resistant. Potted plant production in a root medium with an initial pH of 6.7 ± 0.1 and a end pH of 6.4 ± 0.2 reduced the accumulation of foliar Fe to levels ranging from 59 to 196 ppm and prevented development of significant visual symptoms for all Cultivars.

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Bielinski M. Santos and Jose P. Morales-Payan

The response of young `Cartagena Ombligua' papaya (Carica papaya) plants to soil-applied copper (Cu), zinc (Zn), iron (Fe), and manganese (Mn) was determined. Nursery experiments were conducted in the Dominican Republic, where Cu (0, 0.023, 0.046, 0.069, and 0.092 g), Mn (0, 0.27, 0.54, 0.81, and 1.08 g), Fe (0, 0.49, 0.98, 1.47, and 1.96 g) and Zn (0, 0.2, 0.4, 0.6, and 0.8 g per plant) were individually applied 20 days after transplanting. There were significant responses to the four elements. Maximum growth was obtained with 0.092 g Cu, 0.4 g Zn, 0.54 g Mn, or 0.98 g Fe per plant.

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Justine E. Vanden Heuvel and Joan R. Davenport

Information on growth and carbon partitioning of cranberry uprights in response to soil N application is lacking. Therefore, two experiments were initiated on `Stevens' uprights to determine the effect of soil-applied N on tissue N, growth, net carbon exchange (NCER), and nonstructural carbohydrate production of uprights of `Stevens' cranberry. Tissue N concentration increased linearly with increasing soil N but was greater in vegetative uprights than in fruiting uprights. Current season growth on vegetative uprights was more responsive to tissue N than on fruiting uprights. Although chlorophyll concentration and NCER increased with increased soil N, upright starch concentration and often total nonstructural carbohydrate concentration decreased with increased soil N at midfruit development and preharvest, especially in vegetative uprights.

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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 M-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 times. Rind tissue from mature watermelon fruit was divided into 4 sections, blossom-end, middle top, grounds spot and stem end. Each section was measured for resistance to shear and puncture by a Model T-1200-G texture and tenderometer system. Thickness was also measured. Lab determinations for total and extractable calcium on the sections was done to determine if there is a relationship between rind resiliency and calcium concentration. Data will be presented et the meeting.

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W. Dennis Scott, Gerald E. Brust, and R.E. Foster

Field and laboratory experiments were conducted to study the effect of soil applied (Carbofuran) Furadan on watermelon and cantaloupe yields. Yields were significantly (p≤ 0.05) greater when Furadan was used than when it was not. The observed yield increases may have been due to factors other than just the insecticidal properties. Other systemic insecticides demonstrated no similar increase in yield. Yield increases were also evident even when plants were grown in sterile soil. Yield increase was due to a significant increase in the first harvest of watermelon and the first three harvests of cantaloupe. Numbers of fruit and average wt/fruit were increased for watermelon at the first harvest. Midwest growers usually receive the highest price per pound of watermelon at the first harvest. This significant increase in early harvest more than pays for the application of the chemical.