A pot experiment with summer cover crops and soil amendments was conducted in two consecutive years to elucidate the effects of these cover crops and soil amendments on `Clemson Spineless 80' okra (Abelmoschus esculentus) yields and biomass production, and the uptake and distribution of soil nutrients and trace elements. The cover crops were sunn hemp (Crotalaria juncea), cowpea (Vigna unguiculata), velvetbean (Mucuna deeringiana), and sorghum sudangrass (Sorghum bicolor × S. bicolor var. sudanense) with fallow as the control. The organic soil amendments were biosolids (sediment from wastewater plants), N-Viro Soil (a mixture of biosolids and coal ash, coal ash (a combustion by-product from power plants), co-compost (a mixture of 3 biosolids: 7 yard waste), and yard waste compost (mainly from leaves and branches of trees and shrubs, and grass clippings) with a soil-incorporated cover crop as the control. As a subsequent vegetable crop, okra was grown after the cover crops, alone or together with the organic soil amendments, had been incorporated. All of the cover crops, except sorghum sudangrass in 2002-03, significantly improved okra fruit yields and the total biomass production (i.e., fruit yields were enhanced by 53% to 62% in 2002-03 and by 28% to 70% in 2003-04). Soil amendments enhanced okra fruit yields from 38.3 to 81.0 g/pot vs. 27.4 g/pot in the control in 2002-03, and from 59.9 to 124.3 g/pot vs. 52.3 g/pot in the control in 2003-04. Both cover crops and soil amendments can substantially improve nutrient uptake and distribution. Among cover crop treatments, sunn hemp showed promising improvement in concentrations of calcium (Ca), zinc (Zn), copper (Cu), iron (Fe), boron (B), and molybdenum (Mo) in fruit; magnesium (Mg), Zn, Cu, and Mo in shoots; and Mo in roots of okra. Among soil amendments, biosolids had a significant influence on most nutrients by increasing the concentrations of Zn, Cu, Fe, and Mo in the fruit; Mg, Zn, Cu, and Mo in the shoot; and Mg, Zn, and Mo in the root. Concentrations of the trace metal cadmium (Cd) were not increased significantly in either okra fruit, shoot, or root by application of these cover crops or soil amendments, but the lead (Pb) concentration was increased in the fruit by application of a high rate (205 g/pot) of biosolids. These results suggest that cover crops and appropriate amounts of soil amendments can be used to improve soil fertility and okra yield without adverse environmental effects or risk of contamination of the fruit. Further field studies will be required to confirm these findings.
Qingren Wang, Yuncong Li and Waldemar Klassen
William B. Evans and Mark A. Bennett
A significant portion of the Great Lakes region's processing tomato crop is used to make whole fruit and diced products, where fruit color and textural uniformity are important. Soil and fertilizer studies were undertaken to better understand the role of soil fertility and potassium application on the color disorder known as internal white tissue (IWT) under this region's conditions and in area soils. During 2 years of replicated potassium rate trials in Ohio, tomato yield was not significantly altered by broadcast potassium applications. Potassium application rate was inversely correlated with frequency and severity of IWT in each season, and positively correlated with titratable acidity. The ability of split applications to influence IWT severity was not significantly different than that of preplant applications. IWT symptom frequency and severity was correlated with elemental concentrations in the fruit, leaves, and soil. In 1998, severity of IWT symptoms was positively correlated with shoulder tissue calcium and sodium concentrations, and negatively correlated with concentrations of phosphorus, magnesium, and nitrogen. Correlations for other nutrients, including potassium, were less clear. A companion study of six grower fields during the second year, using grid sampling techniques and the IWT-susceptible Peto 696 cultivar, found significant variability of IWT symptoms within and among fields. Variability within fields was correlated with soil nutrient concentrations. These data indicate researchers may be able to develop recommendations for field mapping and precision management strategies that can reduce the levels of IWT for area growers.
Mongi Zekri and Robert C.J. Koo
Controlled-release sources of N and K were compared with soluble sources on young `Valencia' orange trees (Citrus sinensis [L.] Osb.). The effects of these fertilizers on leaf mineral concentration, soil chemical analysis, and tree growth were evaluated for 3 years. Soluble fertilizers were generally more readily available but had shorter residual effects on leaves and soil than controlled-release fertilizers. In the top 30 cm of soil, the plots treated with controlled-release N had 23% more total N than those treated with soluble N sources, while the plots fertilized with controlled-release K contained 56% more extractable K than those that received soluble K. Different effects on leaf and soil N between the two controlled-release N sources, sulfur-coated urea (SCU) and methylene urea (MU), were also found. With the use of controlled-release fertilizers, application frequency was reduced from a total of 15 to six applications with no adverse effects on tree growth, leaf mineral composition, or soil fertility during the first 3 years. Combining soluble and controlled-release fertilizers in a plant nutrition program offers an economical and effective strategy for citrus growers.
M. Fidanza, P. Colbaugh, H. Couch, M. Elliott and S. Davis
Fairy ring has become a troublesome and persistent disease on golf course putting greens and other turf areas in most regions of the United States. Many basidiomycete fungi are associated with this destructive disease in turfgrass. Recent widespread epidemics of fairy ring have led investigators to examine possible management and control options. Curative approaches include topical flutolanil fungicide applications in conjunction with soil surfactants, the application of flutolanil under high-pressure injection, and the use of nitrogen fertility programs. These curative programs were effective at suppressing visual symptoms and turfgrass injury. A preventive approach evaluated repeat applications of flutolanil plus a soil surfactant prior to disease development. This preventive program was effective at eliminating visual disease symptoms on bermudagrass putting greens. Information presented will review results from field research studies conducted over the past 3 years in Florida, North Carolina, Ohio, Texas, and Virginia.
Won Bae Kim, Kwan Soon Choi, Young Hyun Om and Hak Tae Lim
In an attempt to obtain the basic data for the development of Hanabusaya asiatica as horticultural plants, studies were conducted on the habitat environment, ecological characteristics, various treatments for breaking seed dormancy, and morphological and flowering characteristics of H. asiatica at different growth stages. Hanabusaya asiatica was distributed around areas of 850–1400 m above sea level with an inclination of 5–43°. The vegetation structure of H. asiatica was represented in groups as Quercus mongolica and H. asiatica. In a subgroup, Symplocos chinensis v. leucocarpa for. pilosa, Magnolia sieboldii, and Acer mono were included. Indication species of Quercus mongolica and H. asiatica were Quercus mongolica (B1 layer), Tilia amurensis (B2 layer), Rhododendron schlippenbachii (S layer), Ainsliaea acerifolia v. subapoda, Athyrium nipponicum, Spuriopimpinella brachycarpa, and Carex siderostica (K layer). Soil pH was about 5.4, and soil fertility was relatively in a good condition. The optimum conditions for seed germination was at 25Y.
Mahdi Abdal and Majda Sulieman
Agricultural development in Kuwait faces many problems and obstacles, such as limitation of water resources for irrigation, soils conditions, climatic extreme (particularly during the summer periods), and trained labor. With these extreme conditions for agricultural development in Kuwait, there is a strong demand from the public and the government for agricultural activities, particularly in urban landscape and greenery. World travel has enhanced the public's desire for the beautification of the urban areas and has emphasized the importance of the urban landscape. Planning urban landscape and greenery for Kuwait depends on various variables and efficient management of limited resources. Irrigation water is limited in Kuwait, and the quality of water is deteriorating from over-pumping of underground water and increased soil salinity by over irrigation and lack of drainage. Efficient irrigation-water management can be improved in Kuwait with enhanced irrigation research and implementation of the recommendations of this research. Research topics can also include water evaporation, which is high in Kuwait, and the introduction of mulching materials to improve water irrigation efficiency. Most of the soils in Kuwait are sandy with limited organic materials and plant nutrients. Research in soil fertility and plant uptake of nutrients is essential for any agricultural activities. Introducing ornamental plants tolerant to drought, salinity, and heat is a continuous research component of urban landscape and greenery in Kuwait. Training local staff in basic agricultural activities and research development should improve resource management and enhance the greenery of Kuwait.
Teresa Olczyk, Yuncong Li, Waldemar Klassen and Qingren Wang
Summer cover crops can improve soil fertility by adding organic matter, supplying nutrients through mineralization, reducing nutrient leaching, and improving soil water and nutrient holding capacity. Other benefits include weed suppression and reduction of soil parasitic nematodes. A series of field experiments have been conducted at the UF IFAS Tropical Research and Education Center in Homestead, Florida to evaluate several summer cover crops for use in vegetable production in South Florida followed by field demonstrations conducted in the growers' fields. Best performing cover crops were legumes: velvet bean (Macuna deeringiana) and sunn hemp (Crotalaria juncea L. `Tropic Sun') providing 13 and 11 Mt of dry matter/ha, respectively. Sunn hemp supplied 330 kg N/ha followed by velvet been with 310 kg N/ha. Traditional summer cover crop sorghum-Sudan produced 4 Mt of dry matter/ha and retained only 36 kg N/ha. In addition Sunn hemp significantly reduced soil parasitic nematodes for successive crops. Limitations in use of Sunn hemp by more vegetable growers in South Florida include cost and availability of seeds.
Y.C. Li, P.J. Stoffella, A.K. Alva, D.V. Calvert and D.A. Graetz
Compost amendment to agricultural soils has been shown to either reduce disease incidence, conserve soil moisture, control weeds or improve soil fertility. Application of compost can range from 5 to 250 Mt·ha–1 (N content up to 4%). Large application of compost with high N and P levels may result in excessive leaching of nitrate, ammonium, and phosphate into groundwater. It could be a serious concern on the east coast of Florida with its high annual rainfall and shallow water table. In this study, five composts (sugarcane filtercake, biosolids, and mixtures of municipal solid wastes and biosolids) were collected from different facilities throughout Florida. Composts were applied on a surface of 15-cm sandy soil columns at the rate of 100 Mt·ha–1 on the surface basis and leached with deionized water by 300 ml·d–1 for 5 days (equivalent to 34 cm rainfall). The concentrations of NO3-N, NH4-N, and PO4-P in leachates reached as high as 246, 29, and 142 mg·L–1, respectively. The amount of N and P leached following 5-day leaching events accounted for 3.3% to 15.8% of total N and 0.2% to 2.8% of total P as inorganic forms.
Kathryn S. Orvis and Irwin L. Goldman
Organosulfur compounds in onion extracts inhibit the aggregation of human blood platelets. Antiplatelet activity is important to human cardiovascular health. We hypothesized that modification of sulfur fertility may increase organosulfur compound concentration and thereby affect platelet inhibitory activity in onion. Four contrasting onion genotypes were grown at four sulfur levels in a hydroponic system in the greenhouse and in contrasting sulfur environments in seven field locations in Wisconsin, Oregon, and New York. The contrasting field sites were comprised of sandy soils with a mean sulfate level of 5.4 ppm and muck soils with a mean sulfate level of 20.3 ppm. Onions grown in field environments with increased soil sulfur concentrations had significantly higher antiplatelet activity (33% higher than sand-grown onions; P < 0.001). The greenhouse experiment was conducted in hydroponics with nutrient solutions containing four sulfur levels ranging from 0.8 mM to 15 mM sulfate. The 10-mM sulfur treatment resulted in onion bulbs with 10% higher antiplatelet activity over those grown in the 0.8-mM sulfur treatment (P < 0.06). These data suggest that sulfur concentration in nutrient solution and in soil may be directly responsible for the increased antiplatelet activity in onion extracts observed in this study.
F. Christine Pettipas*, Rajasekaran R. Lada and Claude D. Caldwell
Carrot (Daucus carota L. var sativus) production in Nova Scotia is challenging as carrots are grown under cool temperatures, rainfed conditions, and in mineral soils usually of low fertility. Growers must rely on fertilizer inputs to optimize yields. Excess application can result in high costs and may lead to soil and environmental problems. There is no up-to-date solidly-based, fertilizer recommendation available for carrot production in Nova Scotia. A greenhouse trial was conducted to identify the critical tissue(s) at various growth stages and optimal tissue nutrient concentrations for yield and quality. This will provide a diagnostic tool for assessing plant nutrient health and the opportunity to correct nutrient deficiencies to prevent yield losses, as well as provide an up-to-date fertilizer recommendation. Dicer carrot seeds, variety Red Core Chatenay were grown in sand culture system that used a gravity-fed drip irrigation system. Nine fertility treatments consisting of a complete 20-20-20 plus micronutrients fertilizer was used to deliver at 0, 50, 100, 150, 200, 250, 300, 350, and 400 ppm equivalent of N, P, and K. Soil and plant tissue samples were taken at 4 and 9 weeks and at final harvest at 13 weeks. Critical tissues varied for each element studied at each of the growth stages. Results suggest 0 and 50 ppm treatments did not provide enough fertilizer to obtain maximum growth while plants receiving above 300 ppm were found to be more susceptible to disease. The treatment with 100 ppm N, P, and K was optimal, being significantly higher in yield and quality than all treatments except 150 ppm.