Leachate Electrical Conductivity Research Articles

Salt Tolerance of Phragmites australis and Effect of Combing It with Topsoil Filters on Biofiltration of CaCl2 Contaminated Soil

De-icing salt used for safe winter driving can have negative impacts on local water quality, vegetation, and soils. This study aimed to evaluate the salt tolerance of reeds (Phragmites australis) against calcium chloride (CaCl2) and the biofiltration effect of combining it with topsoil biofilters for desalination in roadside ditches. Two experiments were conducted in a controlled environmental greenhouse over a period of 150 days. For the first experiment, the salt tolerance of P. australis was examined after treating reeds with five different concentrations of de-icing salt: 0, 1, 2, 5, and 10 g·L−1. In a second experiment, the effect of combining two topsoil filters (expanded clay and activated carbon), each planted with and without reeds, was investigated under a high CaCl2 concentration of 10 g·L−1. As the CaCl2 concentration increased, the electrical conductivity (EC) of soil leachate and the level of salt exchangeable cations (K+, Ca2+, Na+, and Mg2+) significantly increased whereas the acidity (pH) significantly decreased (all p ≤ 0.05). No statistical difference was observed in leaf length or width, while plant height, number of leaves, and both fresh and dry weights were significantly increased with increasing CaCl2 concentrations (p ≤ 0.05). Treatments using topsoil filters, particularly those with activated carbon and reeds, showed the greatest reduction in leachate EC and total exchange cations values. These results suggest that combining P. australis with topsoil filters can assist biofiltration effectively, demonstrating its applicability even in roadside soils subject to extreme levels of de-icing salts.

Thermally-treated asbestos-cement wastes as supplementary precursor for geopolymeric binders: CO2 emission and properties

This article explores the impact of thermally treated asbestos-cement waste (ACWT) on metakaolin-based geopolymers, using liquid sodium silicate (LSS) and liquid potassium silicate (LKS) as alkali activators. Through statistical mixture design, various formulations were tested for rheological parameters, mineralogical composition, efflorescence mass, electrical conductivity, compressive strength, and CO2 emissions. Formulations with sodium silicate exhibited higher yield stress compared to those with potassium silicate, while flash setting occurred in LKS-activated mixtures with high ACWT content. Alkali activator content significantly affected mechanical strength and leachate electrical conductivity. CO2 emissions were higher for LKS-activated formulations but lower for those with more ACWT. Finally, by incorporating ACWT, it was possible to optimize the formulations, resulting in high compressive strength, reduced free ions, and reduced negative environmental impact.

Pyrolysis of different organic feedstock combinations as soil amendments enhances the reclamation of saline-sodic soil

Utilizing agricultural wastes (e.g., straw, bagasse, manure) as amendments to remediate saline-sodic soils can be beneficial for improving soil quality and better waste management. In this study, we investigated the impact of raw and pyrolyzed feedstocks on salt leaching potential and physical and chemical properties in a saline-sodic silt loam soil. Utilizing a column experiment within a completely randomized design, we evaluated five feedstock combinations (i.e., rice husk, pine wood, cow manure, sugarcane bagasse) as amendments (69 Mg ha–1), including variations of raw feedstock and feedstock pyrolyzed at 300 and 500 °C, alongside a control (CT). For both the amended soil and the leachate, we measured electrical conductivity (EC), sodium adsorption ratio (SAR), pH and cations. Soil saturated hydraulic conductivity (KS) and bulk density (BD) were also measured. The BWR treatment (i.e., sugarcane bagasse, pine wood, and rice husk) exhibited notable improvements in soil physical quality (i.e., decreased BD and enhanced KS). Raw feedstock significantly (p < 0.01) increased soil leachate EC SAR, except for WM (i.e., pine wood and cow manure). The BWR treatments expedited the reduction of soil salinity and sodicity, evident in lower SAR/SARmax and EC/ECmax ratios, indicative of increased leaching potential. The amendments consistently demonstrated a trend of reducing soil SAR compared to the control, with raw feedstock exhibiting a more pronounced effect. Soil ECe decreased after amending with feedstock pyrolyzed at 500 °C compared to raw feedstock and pyrolyzed at 300 °C. Feedstock pyrolyzed at 300 °C did not significantly alter soil pH after leaching, and there was a decrease in the soil Na+/K+ ratio, especially with pyrolyzed feedstock. After leaching, the pyrolyzed feedstock treatments showed better soil aggregate stability (Mg2+/Ca2+<1) compared to raw feedstock. Based on the aggregated amelioration score for each amendment combination, BWR treatments consistently outperformed other combinations, with BWR300 being the most favorable option due to its lower production cost compared to BWR500. This study highlights BWR pyrolyzed at 300 °C as a suitable amendment for improving soil conditions, reducing salinity and sodicity, and increasing leaching potential.

Influence of combustion temperature on the performance of sewage sludge ash as a supplementary material in manufacturing bricks

The influence of combustion temperature on the properties of sewage sludge ash (SSA) as a substitute material for the production of fired clay bricks was studied. The experiments were performed with sewage sludge (SS) from wastewater treatment plants (WWTP) in Zagreb (ZG) and Karlovac (KA). SS samples were fired at temperatures of 800, 900 and 1000 °C, and the properties of the resulting SSA were determined and compared with clay and SS. Bricks with 5 wt% SSA as clay substitute were prepared and compared with clay bricks (control). SSA bricks produced at higher temperatures are of higher strengths and lower water absorption, which are both desirable properties. Compressive strength tests showed that SSA obtained at a firing temperature of 900 °C is the most suitable for use in bricks. For the first time, the influence of SSA on the content of soluble salts in bricks was tested. The content of soluble salts, expressed by the electrical conductivity of leachate, in SSA bricks showed increased values compared to the control bricks, which were 2.8 and 4.6 times higher in bricks with SSA produced at 800 °C. Still, bricks with SSA prepared at higher temperatures had lower content of soluble salts and also SSA from KA had lower soluble salts content than SSA from ZG. The total amount of Na+, K+, Mg2+ in all bricks made with SSA was below the limits for category S2 according to EN 771-1.

Mechanically-Incorporated Controlled-Release Fertilizer Results in Greater Nitrogen and Salt Leaching Losses from Soilless Substrate in Containers

Uniform incorporation of controlled-release fertilizer (CRF) is a recommended best management practice to reduce nitrogen leaching losses from container-plant production. The potential for damage to CRF prill coating when mechanically incorporated into a soilless substrate was tested. Osmocote Plus 15-9-12 was uniformly incorporated mechanically or manually at the same rate into a soilless substrate and leachate was collected over 76 days. Two experiments were conducted, with or without lavender plants planted into the soilless substrate. Leachate volume, electrical conductivity (EC), and pH were recorded and aliquots were later analyzed for inorganic nitrogen content. Electrical conductivity and leachate volume were used to calculate total salt content. Greater total salts, ammonium, and nitrate were leached from planted or unplanted mechanically incorporated soilless substrate compared to manually incorporated. Plants grown in soilless substrate with mechanically incorporated CRF did not have decreased plant shoot biomass even though leachate EC was consistently greater throughout the experiment. Mechanically incorporating CRF in soilless substrate results in greater leaching losses and is likely a result of CRF prill coating damage during incorporation. Researchers should report incorporation method when publishing results on CRF in container-plant production. Container-plant producers should ensure that their mechanical-incorporation equipment does not cause unintended damage to their CRF of choice.

Increased Leaching Requirements Allow the Use of Source Water High in Salts for Plant Growth

Growers have different capabilities to alleviate salt stress in the growing substrate. One method to reduce substrate salt levels is to increase the volume of water applied during irrigation. This increases the leaching fraction (LF) which is the volume of water that drains from the growing substrate divided by the volume applied during irrigation. We can determine the leaching requirement (the minimum LF to maintain a desired substrate salt level) using the formula LF = ECw/5(ECe − ECw), where ECw is the electrical conductivity (EC) of the water and ECe is the desired EC of the substrate. We tested this formula to see if we could maintain an acceptable substrate EC of 4 dS⋅m−1 by modifying the LF for ‘Hope’ philodendron (Philodendron selloum) and ‘Tineke’ ficus (Ficus elastica) irrigated with tap water (EC 0.17 dS⋅m−1) or reclaimed wastewater (RWW) from Davie, FL, USA (EC 1.66 dS⋅m−1) and RWW from Hollywood, FL, USA (EC 2.93 dS⋅m−1). Shoot and root dry weight was greatest for both species with the tap water applied with a 5% LF. Increasing the LF to 15% for Davie RWW and a 55% for Hollywood RWW, produced acceptable growth for ‘Hope’ philodendron and ‘Tineke’ ficus. In our second experiment, we monitored the growth of ‘Looking Glass’ begonia (Begonia fibrous), ‘Freddie’ calathea (Calathea concinna), and ‘Déjà vu’ philodendron (Philodendron selloum) irrigated with tap water (EC 0.15 dS⋅m−1), salt water (EC 3.49 dS⋅m−1), or RWW (EC 3.48 dS⋅m−1) with LFs of 28%, 50%, or 65%. ‘Looking Glass’ begonia and ‘Freddie’ calathea growth was greater with 65% LF than 28% LF, respectively, for all three water sources. Philodendron growth was not different due to LF. However, philodendron, calathea, and begonia growth was greater with tap water and RWW than with saltwater. Although final leachate EC with saltwater and RWW was around 2 dS⋅m−1 using 50% LF, leachate sodium (Na) levels from salt watered plants was higher than for RWW or tap watered plants. We suspect that high Na levels in combination with lower potassium (K) and calcium (Ca) levels in the saltwater solution resulted in poor plant growth. Although the Na levels in leachate from RWW substrates was higher than tap watered substrates, Ca and K levels also were greater. Although we were able to use the salt equation to maintain substrate EC levels ranging from 2 to 4 dS⋅m−1, volumes of solution applied were two to three times higher when using RWW or salt water compared with tap water. We suspect that a balance between Na, Ca, and K supported better plant growth with RWW than salt water. However, additional work needs to be done on the benefits of supplemental Ca and K when using water high in salts or Na. This works suggests that in addition to monitoring EC, it also is important to monitor Na, Ca, and K concentrations.

Evaluation of Compost and Soil Mix Ratios for Perennial Ryegrass Establishment on Topsoil and Subsoil

Soil degradation during construction often results in soil loss through erosion and reduced vegetation establishment. Composted organic materials are used to restore soil health of compromised urban soils when planting trees and shrubs; however, less is known about compost amendments for turfgrass establishment. The objective of this trial was to determine the effects of differing compost incorporation rates in two soil types on perennial ryegrass [PR (Lolium perenne)] establishment. The hypothesis was that as compost incorporation rates increase, turfgrass germination would increase until the compost rate becomes detrimental to turfgrass germination because of increased nitrate content and electrical conductivity (EC) levels. A salt-sensitive PR cultivar and a salt-tolerant PR cultivar were seeded into a loam topsoil and a clay subsoil at soil:compost volume ratios of 100:0, 80:20, 70:30, 60:40, 50:50, 40:60, and 0:100 using a mixed-source mature compost. Percent green cover (PGC) and leachate pH, EC, and nitrate content were measured during the 5-week establishment period. This trial showed that with a suitable topsoil, compost incorporation may be unnecessary to obtain acceptable PGC, but that compost additions (30% to 40%) to a clay subsoil achieve faster establishment while limiting the potential for reduced establishment because of increased nitrate content or EC associated with greater levels of compost incorporation. The EC or pH of soil:compost leachate was not found to predict turfgrass establishment. This trial suggests that soil type should be considered when making compost use rate recommendations; however, further research is needed to link compost physiochemical properties to compost use rates.

Cross‐linked polymers increase nutrient sorption in degraded soils

AbstractCross‐linked polymer hydrogels, polyacrylamide co‐polymer (XPAM) or polyacrylate (XPAA) offer potential solutions for soil degradation, declines in soil resilience, and poor productivity in marginal soils. However, little is known about their long‐term effect on soil nutrient availability. This 9‐yr, irrigated, outdoor, cropped pot study evaluated a single, one‐time addition of XPAM or XPAA at 0.25 or 0.5% dry wt. (5.6 or 11.2 Mg ha–1) in a degraded (artificially eroded) soil. Controls included an unamended degraded soil and an unamended, non‐degraded soil (i.e., topsoil). We measured nutrients in soil and leachate water each year, and in the first 5 yr, crop yields and nutrient uptake. Both hydrogels increased average soil pH and electrical conductivity (EC), soil extractable K, Na, and total organic carbon (TOC), and decreased soil extractable Mg relative to the control. Unlike XPAM, XPAA produced a greater increase in soil extractable K, increased extractable Fe, Zn, Mn, and Cu, increased Olsen P, and decreased total inorganic carbon (TIC). Neither hydrogel affected crop yields but XPAA increased K and Zn and decreased Mg and Na uptake in crops compared to controls. Relative to the control, both hydrogels decreased cumulative Ca, Mg, and S leaching mass losses and increased mean EC of leachate. Unlike XPAM, XPAA increased cumulative leaching mass losses of K, P, NO3–N, and NH4–N relative to the control. The hydrogels’ soil effects persisted for ≥7 yr, differing as a function of the quantity of included counterions and the stability of the gel structure after soil placement.

Performance of Two Seashore Paspalum (Paspalum vaginatum Sw.) Varieties Growing in Shallow Green Roof Substrate Depths and Irrigated with Seawater

The continuing decline in global drinking water reserves necessitates finding alternative water sources for turfgrass irrigation, especially in southern semi-arid Mediterranean countries. The aim of the present study was to evaluate the potential of using seawater for irrigating two varieties of seashore paspalum (Paspalum vaginatum Sw.), “Marina” and “Platinum ΤΕ”, growing in shallow green roof substrates, and to determine their recuperative capacity after the termination of the salt stress period. The greenhouse study comprised of 48 lysimeters equipped with extensive green roof layering. Treatments included: (i) two substrate depths (7.5 cm or 15 cm) and (ii) three seawater irrigation regimes (7 mm, 15 mm, or 45 mm every two days). Measurements included the determination of green turf cover (GTC) as well as the leaching fraction (LF) and leachate electrical conductivity (ECL) draining from the lysimeters. It was found that during the 46-d salt stress period, none of the seawater irrigation regimes managed to maintain acceptable GTC levels for both seashore paspalum varieties. Increasing the green roof substrate depth from 7.5 cm to 15 cm resulted in GTC improvement. During the recovery period, the use of potable water as irrigation source improved GTC levels. After 40 d the recovery was complete since GTC exceeded 90% in all treatments for both varieties. Regression curves correlating GTC response to ECL can be used to estimate the leaching requirements of turfgrasses grown in shallow green roof systems when irrigated with saline water.

Response and Modeling of Hybrid Maize Seed Vigor to Water Deficit at Different Growth Stages

Research is imperative to predict seed vigor of hybrid maize production under water deficit in arid areas. Field experiments were conducted in 2018 and 2019 in arid areas of northwestern China to investigate the effects of different irrigation strategies at various growth stages with drip irrigation under film mulching on grain yield, kernel weight, seed protein content, and seed vigor of hybrid maize (Zea mays L.). Water deficit at vegetative, flowering, and grain-filling stages was considered and a total of 16 irrigation treatments was applied. A total of 12 indices of germination percentage, germination index (GI), shoot length (SL), and root length (RL) under different germination conditions (standard germination and accelerated aging); electrical conductivity (EC) of the leachate; and activities of peroxidase, catalase, and superoxide dismutase in seeds were measured and analyzed using the combinational evaluation method (CEM). Furthermore, five water production functions (Blank, Stewart, Rao, Jensen, and Minhas) were used to predict seed vigor evaluated by CEM under water deficit. The results showed that leachate EC was higher under water deficit than that under sufficient irrigation. The SL, RL, and GI of different germination conditions increased under water deficit at the flowering stage. The Rao model was considered the best fitted model to predict the vigor of hybrid maize seeds under water deficit, and an appropriate water deficit at the flowering stage is recommended to ensure high seed vigor of hybrid maize production with drip irrigation under film mulching. Our findings would be useful for reducing crop water use while ensuring seed vigor for hybrid maize production in arid areas.

Influence of Mean Leaf Angles and Irrigation Volumes on Water Capture, Leaching, and Growth of Tropical Tree Seedlings

Research Highlights: The mean leaf angle and crown projection area can be used as criteria for grouping tree seedling species in different irrigation zones in tree nurseries with overhead microsprinkler systems, preventing water and fertilizer waste, and increasing growth. Background and Objectives: There are important gaps in current functional knowledge about how plant architecture, especially the mean leaf angles of tree seedlings, affect water and nutrient solution capture in overhead microsprinkler systems. These gaps contribute to water and fertilizer waste in tree nurseries. This research aimed to ascertain how mean leaf angles affect irrigation water capture, leaching, and the growth of tree seedlings given different volumes of irrigation. Materials and Methods: Nine species of tree seedlings with different mean leaf angles were submitted to four irrigation volumes (8, 10, 12, and 14 mm) applied daily by overhead microsprinklers in a split-plot design completely randomized. The variables leaching fraction, height, stem diameter, shoot, root, and total dry mass, Dickson quality index, crown projection area, root system quality, and leachate electrical conductivity were evaluated. Results: For species with mean leaf angles of −54, 31, 38, 42, 55, 57, and 58°, the 8 mm irrigation volume was sufficient to produce greater growth and less leaching. For species with angles of −56 and −14°, the 14 mm irrigation volume was required to produce greater growth. Conclusions: The tree seedling species with positive mean leaf angles facilitate irrigation water and nutrient solution capture, allowing the application of lower irrigation volume. On the other hand, some tree seedling species with negative mean leaf angles hinder irrigation water and nutrient solution capture, requiring the application of higher irrigation volume. When the tree seedling species have a negative mean leaf angle, but the crown projection area is small, the difficulty of water and nutrient solution reaches directly the substrate is attenuated.

Response of tomato plants to diesel fuel, gasoline and benzene

Oil and gas industry produces wastewater (produced water), which contains hydrocarbons, heavy metals, and other components, such as mineral salts essential for plant nutrition. Hydrocarbons presence on produced water limits its potential use in the agriculture, as its lead to inhibition of plant growth. The present study aimed to investigate the effect of hydrocarbons analogous contained in the produced water on 1) pH and electrical conductivity (EC) of irrigation leachate, 2) plant´s morphological variables, 3) mineral concentration, 4) fruit pH, EC and total dissolved solids (TDS), during flowering and fruiting stages in tomato grown into greenhouse conditions. As source of produced water were used diesel at concentrations of 20 and 25 mg L‑1, gasoline at 40, 50 and 60 mg L-1, and benzene at 75 mg L-1, applied in the substrate by means of a syringe. All plants treated with hydrocarbons reached the fruit setting and ripening stage at the 6-cluster. Depending on their type, concentration, and exposure time, hydrocarbons modif ied the pH and EC of the irrigation leachate, caused signif icant morphological changes with longer exposure time, and restricted the biomass production. Mineral concentration differed signif icantly among plant organs, affecting mainly the sodium uptake in stems and fruits. The variables of fruit quality, EC and TDS were favorably modif ied by most treatments.

Desiccation Tolerance, Germination and Moisture Sorption Isotherm of Garcinia afzelii seeds

The desiccation tolerance of Garcinia afzelii seeds was determined and sensitive vigour tests for assessing seed deterioration of this species were identified. Matured fruits were harvested in March 2009 from a small plantation at Ho in the Volta Region of Ghana. Depulped seeds were mixed with moistened sawdust and placed in white cotton sacks and quickly transported by air to the Seed Conversation Department of the Royal Botanic Gardens in the United Kingdom where a part of the experiment was carried out. The second season’s seeds was also harvested from the same plantation in April 2010 and used for another part of the studies in Ghana. Seed equilibrium relative humidity and moisture content on receipt in the United Kingdom were 93.3 % and 38.2 % respectively. Seed germination percentage decreased gradually with reduction in seed moisture content until after 25 % moisture content when germination percentage reduced drastically to 43 % at 23 % moisture content. The seeds of Garcinia afzelii are recalcitrant, with ‘critical moisture content’ about 25 %. Seedling dry weight, seed vigour index and speed of germination also decreased as seeds were dried. Electrical conductivity of leachate from seeds increased with desiccation of seeds. Water sorption isotherm curve for the species showed the typical sigmoid shape curve similar to that of orthodox species. Key words: Garcinia afzelii, vigour index, seedling dry weight, electrical conductivity, critical moisture content, moisture sorption isotherm.

Temporal changes in soil properties and physiological characteristics of Atriplex species and Medicago arborea grown in different soil types under saline irrigation

Salinity stress tolerance is a complex polygenic trait composed of numerous sub-traits that operate at very different timescales. This work elucidates the time-dependence and physiological mechanisms conferring differential salinity stress tolerance between Atriplex lntiformis (halophyte) and Medicago arborea (glycophyte) exposed to prolonged NaCl treatments grown in various soil types. Plant (leaf sap Na+, K+ and Cl− concentrations and osmolality, chlorophyll content, stomatal conductance) and soil characteristic (pH, soil and leachate electrical conductivity) were measured at monthly intervals for up to five months of salinity treatments and then correlated with each other. The overall poor performance of salt-grown M. arborea (compared with A. lentiformis) was associated with several factors. This included: (i) its strong reliance on organic osmolytes (hence, associated carbon costs) for osmotic adjustment; (ii) poor K+ retention that compromised stomatal opening; (iii) its inability to prevent Na+ loading into the xylem; and (iv) its poor shoot tissue tolerance, most likely due to inability to provide efficient Na+ sequestration in vacuoles. Also, the salinity of sandy loam soil was only ~50% of the salinity of irrigation water suggesting the possibility of long-term usage of saline irrigation in soils with low clay content.

The effect of anaerobic baffled reactor effluent on nitrogen and phosphorus leaching from four soils in a laboratory column experiment

Leaching of nitrogen and phosphorus from soil columns during application of anaerobic baffled reactor effluent was evaluated. The soils used were from Inanda (Ia), Cartref (Cf), and Sepane (Se) forms, and a silica sand (SS). Each was packed into duplicate columns (103 mm internal diameter; 200 mm length), four each for up-flow and down-flow leaching. Effluent was delivered continuously for 6, 8 and 35 days at high (32 mm·h-1), medium (16 mm·h-1), and low (2 mm·h-1) rates, respectively. At each flow rate, 9 pore volumes were collected. Leachates were analysed for pH, electrical conductivity (EC), nitrate and phosphate. Leachate pH from all soils was lower than the original effluent (6.4). Leachate EC varied between 0.5 and 0.9 dS·m-1 compared to the effluent EC of 0.84 dS· m-1. At high flow rate, the amount of nitrogen leached was similar from all soils. At low and medium rates, more nitrogen was leached from the coarser-textured SS and Cf than the finer-textured Ia and Se, at both flow directions. Flow direction had a greater effect on nitrogen leaching from finer- than coarser-textured soils. Phosphorus concentrations were higher than the original effluent at medium and high flow rates indicating that the soils were a source of phosphorus. At low flow rate, phosphorus concentrations were much lower than the original effluent, indicating soil retention. Phosphorus leaching was greater from coarser- than finer-textured soils in the up-flow columns, but the opposite occurred in the down-flow columns.

Seasonal Effects on Leachate Quality from an Ozark Highlands Managed Grassland Using Automated, Equilibrium‐Tension Lysimeters

Core Ideas Lysimeters aid subsurface water quality assessments in long‐term nutrient management plots. Broiler litter rates affected few leachate quality parameters during a continuous 8‐yr period. Leachate water quality was affected by season during a continuous 8‐yr period. In regions with concentrated broiler (Gallus gallus) production, land application is a useful means of managing broiler litter (BL). However, surface and subsurface water quality issues may arise when continued annual BL application to fields occurs for extended periods. The application of manure follows seasonal guidelines for surface water quality protection. The objective of this study was to evaluate the effects of BL rate (0, 5.6, and 11.2 Mg litter ha−1) and season on drainage and leachate water quality over an 8‐yr period (2003–2011) in the Ozark Highlands with karst geology using automated, equilibrium‐tension lysimeters. During the 8‐yr period, seasonal drainage was unaffected by season or BL rate, averaging 118 mm per season. Averaged across BL rates, seasonal leachate pH, electrical conductivity (EC), flow‐weighted mean (FWM) NO3–N, dissolved organic C, S, and Zn concentrations, and NH4–N, Cu, Fe, and Se loads differed (P &lt; 0.05) among seasons. Averaged across seasons, seasonal leachate EC, FWM PO4–P, total P, and S concentrations, and Ni load differed (P &lt; 0.05) among BL rates. With the exception of As and Se, seasonal FWM leachate Cd, Cr, Cu, and NO3–N concentrations were at least five times smaller than their maximum contaminant level for drinking water during any of the four seasons. Since rainfall patterns seasonally change in many regions of concentrated poultry production, seasonal differences in the leachate water quality response to continuous annual application of BL are important to help tailor best management practices to protect soil and water resources in regions underlain by karst geology.

Plant Growth and Leachate Electrical Conductivity and pH as Influenced by Controlled-release Fertilizer Blends and Coating Technologies

Although controlled-release fertilizers (CRFs) have been used in container-grown ornamental plants for decades, new coating technologies and blends of fertilizers coated for specific release rates are being employed to customize fertility for specific environments and crops. A study was conducted in the transitional climate of Kentucky to determine the nutrient release rates of three controlled-release blends of 8- to 9-month release and growth response of ‘Double Play Pink’ japanese spirea (Spiraea japonica) and ‘Smaragd’ arbovitae (Thuja occidentalis). Fertilizer 1 (16N–3.5P–8.3K–1.8Mg + trace elements) and Fertilizer 2 (18N–3.1P–8.3K–1.8Mg + trace elements) were prototype blends with different experimental polymer coatings. Fertilizer 3 was a blend of 18N–2.2P–6.6K–1.1Ca–1.4Mg–5.8S + trace elements, which combined 100% resin-coated prills with a polymer coating. Fertilizer 4 was commercially available 15N–3.9P–10K–1.3Mg–6S + trace elements. Fertilizer 3 released its nutrients earlier in the 12-week study than the other three fertilizers and resulted in lower shoot dry weight in both species. The new polymer coating technologies show promise for delivering a predicted release rate and are appropriate for container production of these woody shrubs in Kentucky. An interesting side note of this experiment was that leachate pH measurements across treatments averaged 1.2 units lower for arbovitae (6.3) than for japanese spirea (7.5) at week 12. It was assumed that chemical and/or biological reactions at the root/substrate interface in arbovitae moderated pH increases over the study.

Effects of Cultivar and Maternal Environment on Seed Quality in Vicia sativa.

Production of high quality seeds is of fundamental importance for successful crop production. However, knowledge of the effects of increased temperature resulting from global warming on seed quality of alpine species is limited. We investigated the effect of maternal environment on seed quality of three cultivars of the leguminous forage species Vicia sativa, giving particular attention to temperature. Plants of each cultivar were grown at 1700 and 3000 m a.s.l., and mass, germination, electrical conductivity (EC) of leakage and longevity were determined for mature seeds. Seeds of all three cultivars produced at the low elevation had a significantly lower mass and longevity but higher EC of leachate than those produced at the high elevation, suggesting that increased temperatures decreased seed quality. However, seed viability did not differ between elevations. The effects of maternal environment on seed germination strongly depended on cultivar and germination temperature. At 10 and 15°C, seeds of “Lanjian 3” produced at high elevation germinated to higher percentages and rates than those produced at low elevation, but the opposite trend was observed at 20°C. However, for seeds of “Lanjian 1” and “Lanjian 2,” no significant effect of elevation was observed in germination percentage. Our results indicate that the best environment for the production of high quality seeds (e.g., high seed mass, low EC, high seed longevity) of V. sativa is one in which temperatures are relatively low during seed development.

Leaching of Cu, Cd, Pb, and phosphorus and their availability in the phosphate-amended contaminated soils under simulated acid rain.

Phosphate amendments have been used to immobilize heavy metal-contaminated soils. However, phosphate amendments contain large amounts of phosphorus, which could leach out to potentially contaminate groundwater and surface water. A laboratory column leaching experiment was designed to study the effects of simulated acid rain (SAR) on the potential release of copper (Cu), lead (Pb), cadmium (Cd), and phosphorus (P), and their availability after immobilizing with hydroxyapatite (HAP) and potassium dihydrogen phosphate (PDP). The application of HAP and PDP enhanced the leachate electrical conductivity, total organic carbon, and pH. Higher P was found in the PDP- (>4.29mgL-1) and HAP-treated (>1.69mgL-1) columns than that in untreated (<0.2mgL-1) columns, and they were both over the class V limit (0.4mgL-1) mandated by the Chinese National Quality Standards for Surface Waters (GB 3838-2002). PDP application decreased the leachate Cu, Pb, and Cd effectively; however, HAP addition increased leachate Cu and Pb. HAP and PDP applications decreased the soil CaCl2-extractable and exchangeable fraction of Cu, Pb, and Cd, and increased resin P. However, eluviations transformed the heavy metals from inactive to active fractions and reduced soil labile P. These findings showed that HAP and PDP had a potential risk of excessive P-induced eutrophication. Meanwhile, more attention should be paid to the leaching loss of multiple metals because phosphate amendments might promote the leaching of some metals while immobilizing others.

Safflower (Carthamus tinctorius L.) seed vigor tests for the prediction of field emergence

It is important to predict how plant seeds may germinate in the field using the lab tests. Accordingly, lab and field experiments were conducted to determine safflower (Carthamus tinctorius L.) seed emergence. The vigor tests including electrical conductivity (EC) of seed leachate, seed germination and seedling growth rate were performed. The research work consisted of multi-stage experiments during seed germination (in the lab), seedling growth (in the growth chamber) and seed germination and yield production (in the field). At the germination stage (in the lab, split plot experiment) seed lot (SL), seed size (SS), and seed age (AA) were used as the experimental treatments to determine EC of leachate and germination percentage (GP) from day 1 to 6 (temperatures of 10 and 20°C). Moreover, total seed germination, rate of germination, mean of germination time and germination index were determined. At the seedling growth stage (in the growth chamber, split plot experiment), seed lots and the groups of emergence (GE) were used as the experimental treatments (temperatures of 10 and 20°C). Seedling related parameters including radicle and plumule length and weight were determined. At the seed germination (in the field, split plot experiment) planting date (PD) and seed lot were used as the experimental treatments. At the seedling growth stage (in the field, split split plot experiment) seed lot and group of emergence were also used as the experimental treatments. Seed vigor tests including seed germination and final emergence (FE), and crop yield and yield components including the number of tray per plant (NTP) and grain per tray (NGP), weight of 1000 grains (W1000), harvest index (HI) and grain yield (GY) were determined. In the lab, the seed related parameters were superior in the controlled seeds than the aged seeds, in the large seeds than the small seeds and in SL1 than the other SL’s. There was a negative and highly significant correlation between SL, SS and AA with the EC of the seed leachate as the highest rate of seed germination was resulted by the treatments, which had the least rate of leachate EC. However, GE’s were the functions of environmental conditions including temperature and moisture. In the lab, although at 20°C, GE1 resulted in the highest percentage of seed germination, under the cold conditions GE2 and GE3 significantly increased seed germination percentage, compared with GE1. PD1 and GE1 increased NTP, NGP, W1000 and GY. The lab tests indicated that among the vigor tests, the EC of the leachate and the rate of seed germination and final emergence in the field were highly and significantly correlated with safflower grain yield under field conditions and can be used for the prediction of safflower grain yield.