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J.A. Anchondo, M.M. Wall, V.P. Gutschick, and D.W. Smith

Growth and yield responses of `New Mexico 6-4' and `NuMex R Naky' chile pepper [Capsicum annuum L. var. annuum (Longum Group)] to four Fe levels were studied under sand culture. A balanced nutrient solution (total nutrient concentration <2 mmol·L-1) was recirculated continuously to plants potted in acid-washed sand from the seedling stage to red fruit harvest. Plants received 1, 3, 10 or 30 μm Fe as ferric ethylenediamine di-(o-hydroxyphenyl-acetate). Plant growth was determined by leaf area, specific leaf area [(SLA), leaf area per unit dry weight of leaves], instantaneous leaf photosynthetic rates, and dry matter partitioning. Low Fe (1 or 3 μm Fe) in the nutrient solution was associated with lower relative growth rates (RGR), increased SLA, and higher root to shoot ratios (3 μm Fe plants only) at final harvest. High Fe levels (10 or 30 μm Fe) in the nutrient solution were associated with an increased yield of red fruit and total plant dry matter. RGR of low-Fe young chile plants was reduced before any chlorotic symptoms appeared.

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Cale A. Bigelow, Daniel C. Bowman, and D. Keith Cassel

sand-based rootzones are specified for golf course putting greens because they resist compaction and maintain drainage, even under heavy traffic. Although sands provide favorable physical properties, nutrient retention is generally poor and soluble nutrients like nitrogen (N) are prone to leaching. Laboratory experiments were conducted to evaluate several inorganic soil amendments (clinoptilolite zeolite (CZ), diatomaceous earth, and two porous ceramics), which varied in cation exchange capacity (CEC), and sphagnum peat for their ability to limit N leaching. Columns (35 cm tall × 7.6 cm diameter) were filled with 30 cm of sand-amendment mixtures (8:2 v/v) and NH4NO3 was applied in solution at a N rate of 50 kg·ha-1. Leaching was initiated immediately using 2.5 pore volumes of distilled water in a continuous pulse. Leachate was collected in 0.1 pore volume aliquots and analyzed for NH4 +-N and NO3 --N. All amendments significantly decreased NH4 + leaching from 27% to 88% which was directly proportional to the CEC of the amendments. By contrast, NO3 - losses were consistently high, and no amendment effectively decreased loss compared to nonamended sand. Two amendments with the highest CECs, CZ and a porous ceramic, were selected to further study the effects of amendment incorporation rate, depth, and incubation time on N leaching. Ammonium but not NO3 - leaching was decreased with increasing amendment rate of both products. At 10% amendment (v/v) addition, only 17% to 33% of applied NH4 + leached from the amended sands. Depth of amendment incorporation significantly affected NH4 + leaching, with uniform distribution through the entire 30 cm tall column being more effective than placement within the upper 2.5 or 15 cm. Allowing the NH4NO3 to incubate for 12 or 24 hours following application generally did not affect the amount leached. These results suggest NH4 +-N leaching is inversely related to CEC of the root-zone mixture and that uniform distribution of these CEC enhancing amendments in the root-zone mixtures reduced N leaching to a greater extent than nonuniform distribution.

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Charles F. Mancino, Mohammad Barakat, and Alison Maricic

This study examined the numbers of specific soil and thatch microbial populations in a U.S. Golf Association (USGA) specification sand-peat putting green of creeping bentgrass (Agrostis palustris Huds.) over 17 months. Changes caused by adding a water-soluble or bio-organic (water-insoluble, contains microbial inoculum) N source were examined. Thatch was found to contain 40 to 1600 times as many bacteria as the soil, 500 to 600 times as many fungi, and up to 100 times as many actinomycetes. Soil populations of nitrate- and nitrite-reducing anaerobes were similar and ranged from 103 to 105 per gram of dry soil. Adding the bio-organic N source increased soil fungal counts and thatch thickness when compared with the control (no N applied), but not as much as the water-soluble N source. The amendments had no effect on soil respiration, total organic carbon. or total N content.

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W.L. Berndt and J.M. Vargas Jr.

Biological production of sulfide (S2-) in soil has been reported to depend on system redox potential and on the concentrations of available sulfate (\batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{SO}_{4}^{2-}\) \end{document}) and organic carbon (OC). The purpose of this laboratory study was to determine whether elemental sulfur (So) could influence redox potential and S2- production in sand used to construct putting greens. Treatment with So depressed redox potential as pe + pH, and stimulated accumulation of both free H2S and acid-soluble S2-. Organic carbon as lactate (C3H5O3Na) intensified the effects of So, primarily by influencing pH. Thus, So application could induce anaerobiosis and subsequently affect turf quality by heightening production of free hydrogen sulfide (H2S). It could also contribute to S2- accumulation possibly expressed as a black layer or blackening of the root zone.

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K.J. Sauter, G.R. Gingera, and D.W. Davis

Pigeonpea, a subtropical legume, was successfully grown in a high-latitude (≈45°N) environment. Four short-season pigeonpea accessions from the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) were subjected to three cycles of pedigree selection. Performance trials (175,000 plants/ha) were conducted on loamy sand with dryland and irrigated sites in 1991 and 1992. Thirty-eight S3-derived lines from ICRISAT ICPL 83004 were used in both years and seven S3-derived lines from ICRISAT P 2125 and ICRISAT ICPL 85010 were added the second year. Differences (P ≤ 0.05) in seed yield (kg·ha–1) were observed among the S3 lines, with a maximum yield of 1468 kg·ha–1. The lines also differed (P ≤ 0.05) for harvest index (HI), calculated as the ratio of seed yield to shoot total dry matter (TDM) with a maximum of 0.48 (line MF-26). Dryland seed yield was strongly correlated with TDM (r 2 = 0.98), HI (r 2 = 0.92), and early bloom (r 2 = 0.76). In a time-of-planting comparison of seven lines in 1992, seed yield was highest (754 kg·ha–1) at the earliest (29 Apr.) planting date and declined progressively to 178 kg·ha–1 at the latest (2 June) planting date, while HI decreased from 0.42 to 0.12. Plants were shorter at maturity in the earliest planting date.

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C.A. Sanchez

The low desert region of Arizona is the major area of lettuce (Lactuca sativa L.) production during the winter. Most lettuce is grown on alluvial valley loam and clay loam soils. There is interest in moving some vegetable production onto sandy soils on the upper terraces (mesa) to partially relieve the intensive production pressure currently being placed on land in the valleys. Water and N management is a major concern in coarse-textured soils. Studies were conducted to evaluate the response of crisphead lettuce to sprinkler-applied water and N fertilizer on a coarse-textured soil (>95% sand). The experiments were irrigated using a modified lateral irrigation system that applied five levels of water and five levels of N in specified combinations. Nitrate-N concentrations were determined in samples collected in ceramic suction cups placed below the crop rooting zone. Leaching fraction was estimated by frequent neutron probe soil moisture measurements. Lettuce yield increased with water and N but rates required for maximum economic yield exceeded rates typically required on finer-textured valley soils. These data show the potential for large N leaching losses on this coarse-textured soil.

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Richard E.C. Layne and Perry Y. Jui

Ten genetically diverse peach [Prunus persica (L.) Batsch] seedling rootstocks were studied for 10 years on Fox sand using `Redhaven' as the scion. The purpose of the experiment was to assess the performance of three Harrow Research Station (Ont.) hybrid selections (H7338013, H7338016, and H7338019) and two northern China introductions (`Chui Lum Tao' and `Tzim Pee Tao') against five commercial standards, two of which were selected in Canada (`Harrow Blood' and `Siberian C') and three in the United States (`Bailey', `Halford', and `Lovell'). Rootstock performance was assessed indirectly by measuring or subjectively rating various aspects of scion performance including annual trunk cross-sectional area (TCA); final tree height, spread, and TCA; bloom and fruit set intensity; yield and yield efficiency; canker (Leucostoma spp.) severity; defoliation rate; winter injury; cold hardiness of flower buds and shoot xylem; and tree survival. Rootstock effects on the above measurements and ratings were significant in some years and not in others. Year effects were always large and significant, while rootstock × year interactions were usually small and not significant. In the combined analyses over years, the largest rootstock effects were obtained for bloom, fruit set, and defoliation ratings and for TCA measurements. Three cumulative responses, including marketable yields, yield efficiency, and tree survival, were used for comparing the five experimental rootstocks with the five commercial standards and also for ranking the 10 rootstocks with respect to each other to assess their potential commercial value as peach rootstocks. `Chui Lum Tao', H7338013, and `Bailey' had the most commercial potential for southern Ontario because they typically promoted above average cumulative yield, yield efficiency, and tree survival. `Tzim Pee Tao', `Siberian C', and `Harrow Blood' were less valuable, with low cumulative marketable yields. `Halford' and `Lovell' were the least valuable, with the lowest tree survival (17%). Performance of H7338013 exceeded that of both parents (`Bailey' and `Siberian C'), H7338019 exceeded `Siberian C' but not `Bailey', while performance of H7338016 was inferior to both parents. Wider testing of the experimental rootstocks on different soil types and climatic zones is needed.

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B. Todd Bunnell, Lambert B. McCarty, and Hoke S. Hill

Creeping bentgrass (Agrostis palustris Huds.) is used on putting greens for its fine-leaf texture, consistent speed, smooth ball roll, and year-round color. In recent years bentgrass use has extended into the warmer climates of the southern United States. Being a C3 plant, bentgrass is not well adapted to extended hot and humid environmental conditions. Subsurface air movement systems are now commercially available that can transport air through the root zone to alter soil conditions and potentially improve bentgrass survival. This research investigated the effects of subsurface air movement on the composition of soil gases, matric potential, temperature, and growth response of a sand-based creeping bentgrass golf green. Treatments included: air movement direction (evacuate, inject, and no air) and duration of air movement (0400-0600 hr, 1000-1800 hr, and 24 hours). Treatment combinations were imposed for 13 days. Subsurface air movement reduced CO2 at the 9-cm depth to values <0.0033 mol·mol-1 when evacuating or injecting air, depending upon duration. Soil matric potentials at a 9-cm depth were decreased by a maximum of 96% when evacuating air for 24-hour duration compared to no-air plots. Soil temperatures at 9 cm were decreased ≈1 to 1.5 °C when injecting air from 1000 to 1800 hr and 24-hour treatments and increased ≈0.75 °C when evacuating air from 1000 to 1800 hr. Subsurface air movement did not improve creeping bentgrass turf quality or rooting. Although not effective in improving the growth response of creeping bentgrass, subsurface air movement may be a useful tool to improve soil gas composition, reduce excess soil moisture, and potentially reduce soil temperature(s) of heat-stressed creeping bentgrass golf greens.

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Luther C. Carson, Monica Ozores-Hampton, Kelly T. Morgan, and Jerry B. Sartain

, on Basinger fine sand (hyperthermic Spodic Psammaquents) ( Carson et al., 2013 , 2014c ). The CRFs were divided into two independent studies containing an equal number of CRFs ( Table 1 ). The CRF fall mixes (M112, M168, and M224) were CRF and SF

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David N. Sasseville and Rufus Jones

Tomato cv. 'Show Me' were grown in the greenhouse for six weeks in a 50%;50% (v:v) soil:sand mixture and provided weekly with a quarter-strength Hoagland solution with nitrogen provided as 100%:0% 50%;50% 0%:100% nitrate:ammonium ratios at rates of 0, 10, 20, 40, 80 mg N/kg medium with and without 5 mg/kg nitrapyrin. Nitrapyrin induced plant phytotoxic symptoms of stunted growth, curled leaves and deformed terminal buds. These effects were reduced with increasing amount of applied nitrogen and greater percent of nitrate. A second similar experiment using 0, 80, 160, 240, 320 mg N/kg medium and 1 mg/kg nitrapyrin showed no phytotoxic effects and also induced no significant changes in dry weight, tissue nitrogen content or residual medium nitrogen content regardless of nitrogen treatment. N concentration and N form effects were similar to previously reported research with an accumulation of nitrates in tissues with higher nitrate nutrition.