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Jin Wook Lee*, Kenneth W. Mudge, Wansang Lim and Joseph Lardner

Woods cultivation of North American ginseng (Panax quinquefolium L.) can generate income for forest land owners and decrease collection pressure on wild populations of this increasingly scarce forest herb. For woods cultivation, supplemental calcium by soil application of gypsum (CaSO4 2H2 O) is often recommended, but the effects of this practice on soil characteristics, plant growth and quality of American ginseng are not well characterized. In a greenhouse pot culture experiment, 3-year-old seedlings were treated with 0, 1, 2, 3, or 4 Mt/ha gypsum and grown for 12 weeks. Gypsum application decreased soil pH slightly and elevated soil electrical conductivity and available soil calcium. Tissue levels of calcium were not affected by gypsum treatment but a significant increase in both shoot and root dry weight occurred. Total ginsenosides, which are the pharmacologically active components of ginseng, were increased slightly in roots but not in shoots of plants treated with 4 Mt/ha gypsum. Rb1, the most abundant ginsenoside in roots, was elevated in roots of plants treated with 3 Mt/ha gypsum. Ginsenoside Rg1 was elevated in shoots of plants treated with 2 Mt/ha gypsum. Regardless of gypsum treatment, qualitative differences (relative concentrations of different ginsenosides) between roots and shoots were observed.

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R.F. Korcak

The beneficial influences of gypsum on soil improvement and plant growth have been well-documented, Among these benefits are reclamation of sodic soils, alleviation of subsoil acidity problems, and contribution of Ca and S as nutrients. There are three industrial byproducts that contain significant amounts of gypsum. Phosphogypsum is probably the best-known byproduct gypsum source; the others are clean-air technology coal combustion byproducts, namely fluidized bed combustion and flue gas desulfurization residues. This review summarizes the beneficial chemical and physical effects of gypsum on soil properties and the resultant benefits on plant growth. Where applicable, emphasis is placed on potential uses and limitations of byproduct gypsum sources on horticultural crops. The potential for incorporating these materials in artificial mixtures with organic materials is discussed.

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Jin Wook Lee and Kenneth W. Mudge

In the Northeast, wild American ginseng (Panax quinquefolium L.) is typically found growing in the dense shade provided by deciduous hardwood tree species such as a sugar maple, in slightly acidic soils with relatively high calcium content. Woods cultivated ginseng is often grown in forest farming agroforestry systems under similar conditions. Supplemental calcium by soil incorporation of gypsum (CaSO4·2H2O) is often recommended for woods cultivated ginseng. The objective of this study was to investigate the effects of this practice on soil chemical properties, plant growth and quality of American ginseng. In a greenhouse pot culture experiment, 2-year-old seedlings were treated with 0, 2, 4, 8, or 16 Mt·ha–1 gypsum and grown for 12 weeks. Gypsum application decreased soil pH slightly, elevated soil electrical conductivity and increased available soil Ca and sulfate concentrations. Tissue calcium concentration was increased with by gypsum treatment, but shoot and root growth was reduced. HPLC analysis of root ginsenosides revealed that Re, Rb1, Rc, and Rb2, PT ginsenoside (sum of ginsenoside Rb1, Rc, Rb2, and Rd) and total ginsenoside concentration increased by gypsum soil amendment.

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S.J. Locascio and G.J. Hochmuth

Watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai] were grown with three rates each of lime, gypsum, and K during two seasons to evaluate their effects on fruit production and mineral concentration. The first experimental site was a recently cleared Sparr fine sand with an initial water pH of 5.0 and Mehlich I extractable K of 8 mg·kg-1 (very low) and 20 mg·kg-1 Ca (very low). The second site was a virgin Pomona fine sand with a water pH of 4.8, 28 mg·kg-1 K (low), and 612 mg·kg-1 Ca (high). `Crimson Sweet' fruit yields were reduced 10% with an increase in lime rate from 0 to 4.48 t·ha-1 in the first season. In the second season, lime rate had no effect on yield. In both seasons, fruit yields were reduced 14% with an increase in Ca from gypsum from 0 to 1.12 t·ha-1. On the soil testing very low in K, yield increased with an increase in K rate from 90 to 224 kg·ha-1 with no lime or gypsum. On the soil testing low in K, greatest yields were obtained with 90 kg·ha-1 K with no lime and gypsum. Application of lime and gypsum increased Ca and decreased K in seedlings but not consistently in older leaf and fruit tissues. An increase in K application increased leaf K in the first season but not in the second. Fruit firmness and soluble solids content were not consistently affected by treatment during the two seasons. Thus, on soils low in toxic elements (Mn and Al) such as used in this study, watermelon will grow well and tolerate a wide range of soil pH values without additional Ca from lime or gypsum.

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John R. Yeo, Jerry E. Weiland, Dan M. Sullivan and David R. Bryla

that gypsum may be useful for reducing phytophthora root rot in northern highbush blueberry ( Yeo, 2014 ). Gypsum provides more soluble Ca 2+ than carbonate sources such as lime and does not increase soil pH appreciably ( Shainberg et al., 1989 ). High

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E. Niyonsaba, E. G. Rhoden, P. K. Biswas and G.W. Carver

A study was conducted to assess the effects of gypsum on the early growth and storage root yield of sweet potato (Ipomoea batatas) cvs `Jewel', `Goergia Jet' and `TI-155'. Three rates of gypsum were applied (1.03, 2.06 and 3.09 tons/acre). These represented half, recommended and 1.5 recommended levels. The experiment was a randomized complete block design with a split plot arrangement of treatment. Leaf area, total dry matter, leaf dry matter and stat-age root weight were recorded at 30-day intervals. Plants receiving half the recommended levels of gypsum produced the highest total storage root dry matter (0.306 t/a) and the highest leaf dry matter (0.116 t/a). Although a positive relationship exists between leaf dry matter and storage root yield between 90 and 120 days, there was no such relationship between those parameters either at 30 and 60 days or 60 and 90 days after transplanting.

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S. J. Locascio and G. J. Hochmuth

Watermelons [Citrullus lanatus (Thunb.) Matsum. & Nakai] were grown with three rates each of lime, gypsum, and K during two seasons to evaluate their effects on fruit production and mineral concentration. The first experimental site was a recently cleared Sparr fine sand with an initial pH of 5.4 and Mehlich I extractable K of 32 ppm (low) and 948 ppm Ca. The second site was a virgin Pomona fine sand with a pH of 4.8, 28 ppm K, and 612 ppm Ca. `Crimson Sweet' fruit yield was reduced 10% with an increase in lime rate from to 4.48 Mt·ha-1 in the first season. In the second season, lime rate had no effect on yield. In both seasons, fruit yields were reduced 14% by an increase in Ca from gypsum from 0 to 1.12 Mt·ha-1. Fruit yields were not influenced by K rates from 90 to 224 kg·ha-1. Application of lime and gypsum increased leaf tissue Ca concentrations and decreased K. An increase in K application significantly increased leaf K and decreased Mg in the first season but not significantly in the second season. Fruit firmness and soluble solid content were not consistently affected by treatment.

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G.A. Picchioni, C.J. Graham and A.L. Ulery

Asimina triloba (L.) Dunal is an underused tree species with demonstrated potential as a new fruit crop and landscape ornamental plant. Best management practices for A. triloba are not adequately defined, particularly for field establishment in high-Na conditions characteristic of numerous southern U.S. production areas. We evaluated the growth and net macroelement uptake of field-grown A. triloba seedlings on soil amended with a single addition of gypsum at 0, 7.5, or 15.0 t·ha-1 and later receiving a regular supply of Na-affected but nonsaline irrigation water [sodium adsorption ratio (SAR) of 15.5 and electrical conductivity (EC) at 0.4 dS·m-1]. Over two growing seasons, the soil saturation extract Ca concentration increased while the soil saturation extract SAR decreased with increasing gypsum rate. Amending the soil with gypsum increased total lateral branch extension per tree by 60% to 73% and trunk cross-sectional area (TCSA) per tree by 68% to 87% above a non-gypsum-amended control treatment. Total dry matter accumulation and the net uptake of N, P, and K per tree were over 100% greater following gypsum application as compared to controls. The growth and mineral uptake-enhancing effects of gypsum were likely related to functions of Ca at the root level and on soil physical properties that should be considered in establishing young A. triloba trees with irrigation water containing high sodicity but relatively low total salinity.

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Edison Miglioranza, Phillip Barak, Kenneth Kmiecik and James Nienhuis

Soils were fertilized with gypsum (CaSO4·2H2O) at rates up to 4 t·ha-1, and Ca2+ concentrations in pods of 12 snap bean (Phaseolus vulgaris L.) cultivars were determined, with the intention of improving snap beans as a source of Ca2+ for human nutrition. The addition of gypsum to the soil did not affect the Ca2+ concentration of pods, even though Ca2+ in the soil solution increased from 4 to 15 mmol·L-1. Calcium concentrations of pods of the various snap bean cultivars ranged from 4.1 to 5.7 mg·g-1 dry mass. `Top Crop', `Astrel', `Tenderlake', and `True Blue' had the highest Ca2+ concentration in the pods and `Labrador' and `Roma II' had the lowest. The results suggest that factors other than Ca2+ supply influenced the Ca2+ concentration of the snap bean pod. Therefore, increased Ca2+ concentration of pods may be better achieved through breeding and selection rather than Ca2+ fertilization when Ca2+ levels in soil are sufficient.

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W. Dennis Scott, B. Dean McCraw, James E. Motes and Michael W. Smith

Field experiments were conducted to quantify the effect of Ca supplied as gypsum in factorial combination with watermelon [Citrullus launatus (Thumb) Matsum and Nakai] cultivars Charleston Gray, Crimson Sweet, and Tri-X Seedless on yield and the elemental concentration of leaf and rind tissue. Also, the effect that ontogenetic changes and sectional differences had on the elemental concentration in rind tissue was investigated. The experiments were conducted at two locations in Oklahoma. Yield was not affected by Ca; however, mean melon weight was reduced at 1120 kg Ca/ha. Leaf Ca concentration increased linearly in response to Ca rate. `Tri-X Seedless' had lower leaf Ca and higher K concentrations than did `Charleston Gray' or `Crimson Sweet'. Fruit ontogeny (days from anthesis) and melon section (blossom or stem-end) interacted to affect elemental concentrations in the rind tissue. There was also a significant genotypic effect on elemental concentration in rind tissue. Increasing rates of Ca applied to soil reduced the incidence of-blossom-end rot (BER) in `Charleston Gray' melons. Calcium treatment did not affect flesh redness or soluble solids concentration (SSC) of watermelon.