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Tim C. Knowles, Billy W. Hipp, and Mary Ann Hegemann

We examined responses of Salvia farinacea Benth. (mealy blue sage, a water- and nutrient-efficient native landscape plant for the southern United States) to slow-release (8- to 9-month), resin-coated urea (39N-0P4K) preplant-incorporated at 0.5, 1, 2, or 3 kg N/m3 in 2 perlite: 1 vermiculite (PV) or 2 pine bark: 1 fine sand (BS) (both by volume). This slow-release fertilization was compared to weekly fertigation at 100 mg N/liter from ammonium nitrate (34N-0P4K). After 21 weeks of greenhouse culture in 3.8-liter containers, shoot dry weight was higher in BS than PV when these media received fertigation or contained slow-release fertilizer at 21 kg N/m3. Shoot dry weight and shoot quality were not increased by exceeding 1 kg N/m3 in PV or 2 kg N/m3 in BS. Fertigation resulted in shoot dry weight and shoot quality equal to the highest values achieved with slow-release fertilizer. Cate-Nelson analysis showed that shoot N concentration should be ≥ 4.0% for this element not to limit plant growth.

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Douglas D. Archbold and Charles T MacKown

Three gel polymers, Hydrosource, REAP, and Agri-gel, wetted with solutions of 15N-ammonium nitrate, were evaluated for controlled release of fertilizer nitrogen (N) to strawberry (Fragaria × ananassa Duch.) in the greenhouse and field. Container-grown plants of `Earliglow' and `Allstar' were harvested every 2 weeks for 8 weeks. Field-grown plants of the same cultivars were collected from matted rows after harvest, and fruit were collected during harvest. Plant and fruit tissues were analyzed for total % N and atom % & 15N, and total fertilizer N recovery was calculated. For the container-grown plants, total % N differed by cultivar, `Earliglow' > `Allstar', and harvest date, declining during 8 weeks. Treatment effects on total % N were observed only in the field study, with Agri-gel showing the highest value. In the greenhouse study, Hydrosource and Agri-gel gave the highest tissue enrichments from fertilizer N. In the field study, REAP and Agri-gel gave the highest enrichments. In spite of the greater tissue enrichments, however, no gel polymer significantly increased total fertilizer N recovery in either study.

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Laura Paine, Astrid Newenhouse, and Helen Harrison

Seedlings of Syn 4-56 hybrid asparagus were planted in May, 1990 on loamy sand in the irrigated Central Sands region of Wisconsin. Treatments were unsuppressed living mulches of perennial ryegrass, Dutch white clover, a mixture of ryegrass and clover and cultivated bare ground. Ammonium nitrate was banded at rates of 90, 45, and 0 kg/ha across all treatments. Measurements of weed populations, asparagus growth, and soil and tissue nitrogen levels were made in 1990 and 1991. Soil nitrate and ammonium levels were measured in 30 cm increments to a depth of 90cm. In 1990, asparagus fern growth was greater in the bare ground controls than in any of the mulch treatment plots. In 1991, asparagus growth in the clover-based mulches was greater than that in the ryegrass mulch, although also still less than that of the bare ground control. Total accumulated nitrogen in clover-based mulch plots at the end of each season was more than twice the level of that of either the grass mulch or the cultivated plots. Percent nitrogen in asparagus tissue varied with mulch treatment: in 1991, the %N was higher in the asparagus tissue grown with clover than either that grown with the grass or on bare ground. Weed control in all mulch plots was good; in clover plots it was nearly 100%.

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Patrick E. McCullough, Haibo Liu, Lambert B. McCarty, and Joe E. Toler

Dwarf-type bermudagrass (Cynodon dactylon Pers. × C. transvaalensis Burtt-Davy) putting greens tolerate long-term mowing heights of 3.2 mm but require heavy nitrogen (N) fertilizations that increase ball roll resistance. Applying a plant growth regulator, such as trinexapac-ethyl (TE), could reduce uneven shoot growth from high N fertility and improve putting green ball roll distances. Field experiments were conducted from April to August 2003 and 2004 in Clemson, SC to investigate effects of ammonium nitrate applied at 6, 12, 18, or 24 kg N/ha per week with TE applied at 0 or 0.05 kg a.i. per ha every 3 weeks on `TifEagle' bermudagrass ball roll distances (BRD). BRD were measured weekly with a 38-cm stimpmeter in the morning (900 to 1100 hr) and evening (>1700 hr) beginning 1 wk after initial TE treatments. Interactions were not detected among N, TE, or time of day. TE increased BRD about 15% from non-TE treated. BRD was reduced with increased N rate and from am to pm; however, bermudagrass treated with TE averaged 10% longer PM BRD than am distances of non-TE treated. Overall, increased N fertility and diurnal shoot growth may reduce BRD but TE will be an effective tool for mitigating these effects on bermudagrass putting greens. Chemical name used: [4-(cyclopropyl-[α]-hydroxymethylene)-3,5-dioxo-cyclohexane carboxylic acid ethyl ester] (trinexapac-ethyl).

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Mark D. Hamilton, Frank J. Cruz, and James McConnell

The performance and leaching behavior of six nitrogen fertilizers on bermuda grass were studied under humid tropical conditions. The grass was established in 20 × 36 cm pots filled with 8 cm pea gravel and 28 cm of silica sand. Ammonium nitrate was applied to the turf at monthly rates between 0.25 and 6 lb/1000ft2. Performance was gauged by clipping dry weights, image analysis for greeness, and visual ratings. Leachates were checked for nitrate levels. A rate of 2 lbs/1000ft2 produced quality turf while yielding a minimum of nitrate leaching. Rates of 6 and 4 lb./1000ft2/mo. resulted in the highest readings without an increase in quality. Rates less than 2lb/1000ft2 had leachate nitrate less than 9 ppm but produced turf of unacceptable quality.

Nutralene, Nitroform, sulfur coated urea, IBDU, and AN were applied at a rate of 2 lb./1000ft/mo. The slow-release forms were applied as a 3 month dose. Performance was determined as above and nitrate leaching was monitored by weekly collections. Nutralene, SCU and Nitroform had peak nitrate levels 2 weeks after application, IBDU had peak nitrate levels after 4 weeks. Turf quality diminished at 6 weeks.

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Curt R. Rom, R.A. Allen, K. Kupperman, and J. Naraguma

Three studies were established to compare spring (S) vs. autumn (F) N fertilizer applications on apple tree performance. The studies used newly planted trees, 4-yr-old trees, and 8-yr-old trees, fertilized with either ammonium nitrate or urea at 2 weeks after harvest (F) or at bud break (S). In the first 3 years growth in a newly planted orchard, time of fertilizer did not significantly affect tree height or TCSA. In the first cropping year, F fertilized trees had the greatest flower cluster number and bloom density but similar % set and yield compared to S fertilized trees. F fertilized trees in mature orchards studies tended to be shorter and have smaller TCSA increment after 3 yrs. Treatments did not affect bloom density, % set or total yield although spring fertilized trees had a greater % drop. Although spur leaves of F fertilized trees had greater N content at bloom, shoot leaves typically had lower N and Mn, and higher P, K, and Ca at 90 days after bloom compared to S treatment trees.

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Theresa Bosma, John Dole, and Niels Maness

Marigold flower pigments can be extracted and used as a natural source of food colorants in the poultry and dairy industry. These pigments impart an orange color to egg yolks and a yellowish color to dairy products. We examined four African marigold cultivars for their ability to be commercially grown and harvested mechanically. `E-1236' yielded the highest quantity of lutein (22 kg/ha), a carotenoid pigment, using a spectrophotometer for quantification. `E-1236' and `A-975' were the earliest flowering cultivars, 11 June 1998 for transplants and 9 July 1998 for direct-seeded, at 8 weeks after sowing regardless of field establishment method. `E-1236' produced the greatest number of flowers in a production season, both as transplants (68 flowers/plant) and direct-seeded (57 flowers/plant) at 363,290 plants/ha. Transplants resulted in two more harvests in a single season than direct-seeded plants. Subsequently, more flowers and petal material were produced for pigment extraction than with direct-seeded plants. A one-time application of ammonium nitrate (28.02 kg/ha) at mid-season did not significantly effect flower number, flower weight, or pigment yield. Experiment was repeated in 1999 with four cultivars, two field establishment methods, seven harvest dates, and five nitrogen applications.

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Eric J. Hanson and G. Stanley Howell

Mature `Concord' vines (Vitis labrusca L.) were excavated at 2- to 4-week intervals through the season to study seasonal changes in vine N concentration. Vine N content began increasing 2 weeks after budbreak, increased most rapidly from mid-May to mid-July, and declined between fruit maturation and the beginning of leaf senescence. Vine N content was lowest at budbreak (18 g) and maximum at fruit maturity (75 g). This change represented a net accumulation of 57 g N/vine or 77 kg N/ha. In a separate study, `Seyval blanc' vines were treated with double 15N-labeled ammonium nitrate at either budbreak or bloom. Labeled N was applied as a spray beneath vines to simulate a broadcast vineyard application. Vines were excavated when leaves began to senesce in October, partitioned into various components, and analyzed by mass spectrophotometry to determine fertilizer-derived N content. Vines had recovered statistically similar percentages of fertilizer N applied at budbreak (7.1%) and bloom (10.6%). The low recovery of fertilizer N likely resulted from the method of fertilizer application, the presence of a competitive grass sod between the rows, and relatively high native soil N levels.

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Anthony F. Silvernail and Gary R. Cline

Effects of tillage, winter cover crops, and inorganic N fertilization on watermelon production were examined in a split-plot factorial experiment. Main plots received tillage or no tillage, whereas cover crops consisted of hairy vetch, winter rye, or a mix. Nitrogen treatments consisted of plus or minus addition of ammonium nitrate. Following melons not receiving inorganic N, vetch produced cover crop total N yields of ≈130 kg·ha–1, which were four times greater than those obtained with rye. Melon yields and foliar N concentrations obtained without inorganic N fertilization following vetch were similar to those obtained with N fertilization following rye. Available soil N in vetch treatments remained significantly (P < 0.05) higher than in rye treatments for ≈70 days after melon planting and was greater in tilled treatments. Tillage significantly (P < 0.05) reduced melon yields by 20% and also reduced soil temperatures compared with no-till treatments. We conclude that N fixed by vetch could sustain watermelon production and no tillage may be useful when soil erosion is a problem.

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Christopher C. Gunter, Matthew D. Kleinhenz, and Jiwan P. Palta

Pathogenic bacteria (Erwinia spp.) can have a significant impact on stand establishment and sprout health. These bacteria cause soft rot of the seed piece, which is common in wet spring conditions resulting in great economic loss. Recent studies have demonstrated that the incidence and severity of soft rot can be significantly reduced by increasing tuber calcium. We investigated the influence of seed piece calcium on tuber production. Field growing potato plants were treated with supplemental calcium during tuber bulking (calcium at 168 kg·ha–1 from calcium nitrate or N-Hib) to increase the seed tuber medullary calcium levels. All three cultivars (`Superior', `Atlantic', `Dark Red Norland') responded to supplemental calcium application with increases in mean calcium contents, even though soil tests showed high native calcium levels (1000 kg·ha–1). Seed tubers were sampled for calcium by removing a longitudinal slice from the center of each tuber and planting one of the resulting halves for seed piece decay evaluation and the other for yield evaluation. Calcium nitrate-treated seed tubers produced higher yields compared to ammonium nitrate and N-Hib in `Atlantic' in `Dark Red Norland'. This trend did not hold true for `Superior'. Our results suggest that a) it is possible to increase seed piece tuber calcium levels with supplemental calcium application even in soils testing high in calcium and b) improving the calcium concentration of the seed piece can increase tuber yield in some cultivars.