Gypsum Application Reduces Selenium Uptake by Vegetation on a Coal Ash Landfill

Selenium, a potentially toxic trace element, is present in coal fly ash and is accumulated by plants growing on ash landfills. Application of gypsum (CaSO₄·2H₂O) can reduce Se accumulation. The persistence of this effect and the efficacy of repeated gypsum applications were investigated in forbs and grasses on a soil-capped, fly ash landfill near Lansing, New York. Gypsum was applied as a top-dressing at a rate of 0 or 11.2 t ha-1 in 1990 to three plots, and one-half of each of these plots received an additional top dressing of gypsum at 11.2 t ha-1 in 1991, producing four treatments – no gypsum, gypsum only in 1990, gypsum only in 1991, and gypsum in both years. Vegetation was harvested in July and October of 1991 and in July of 1992 and analyzed for Se, S, and Ca. Application of gypsum: (1) decreased Se accumulation by forbs and grasses harvested later in the season; (2) decreased Se accumulation in a subsequent year; (3) produced no further decrease when reapplied in a second year; and (4) did not decrease Se accumulation two years after a single application. The decrease in Se accumulation was not due to dilution caused by S fertilization. Variation in Se accumulation was not explained by variation in the pH and Se concentration of the soil and ash.     

Influence of microbial inoculation (Pseudomonas sp. strain ADP), the enzyme atrazine chlorohydrolase,and vegetation on the degradation of atrazine and metolachlor in soil

The concentrations of atrazine in the freshly added soils and the soils that had been incubated for 50 days significantly decreased 1 day after the addition of the enzyme atrazine chlorohydrolase or the soil bacterium Pseudomonas sp. strain ADP as compared with those in the uninoculated soils. Atrazine chlorohydrolase or ADP had no effect on the degradation of metolachlor. The half-lives of atrazine in the freshly added soils and in the aged soils after the treatment with atrazine chlorohydrolase or ADP markedly decreased as compared with those in the uninoculated soils. The half-lives of metolachlor in the aged soils were much longer than those of freshly added metolachlor. The percentage atrazine degraded in the freshly treated soils was much higher than that in the aged soils. This indicates that aging significantly decreased the bioavailability of atrazine. Vegetation significantly decreased the concentration of metolachlor. However, vegetation showed no effect on the degradation of atrazine.     

Sorption-desorption of "aged" sulfonylaminocarbonyltriazolinone herbicides in soil

Sorption-desorption interactions of pesticides with soil determine the availability of pesticides in soil for transport, plant uptake, and microbial degradation. These interactions are affected by the physical and chemical properties of the pesticide and soil, and for some pesticides, their residence time in the soil. The objective of this study was to characterize sorption-desorption of two sulfonylaminocarbonyltriazolinone herbicides incubated in soils at different soil moisture potentials. The chemicals were incubated in clay loam and loamy sand soils for up to 12 wks at -33 kPa and at water contents equivalent to 50 and 75% of that at -33 kPa. Chemicals were extracted sequentially with 0.01 N CaCl(2) and aqueous acetonitrile, and sorption coefficients were calculated. Sufficient sulfonylaminocarbonyltriazolinone herbicides remained (>40% of that applied) during incubation to allow calculation of sorption coefficients. Aging significantly increased sorption as indicated by increased sorption coefficients. For instance, for sulfonylaminocarbonyltriazolinone remaining after a 12-wk incubation at -33 kPa, K(d) increased by a factor of 4.5 in the clay loam soils and by 6.6 in the loamy sand as compared to freshly treated soils. There was no effect of moisture potential on sorption K(d) values. These data show the importance of characterization of sorption-desorption in aged herbicide residues in soil, particularly in the case of prediction of herbicide transport in soil. In this case, potential transport of sulfonylaminocarbonyltriazolinone herbicides would be over-predicted if freshly treated soil K(d) values were used to predict transport.     

Response of three cereal crops in continuous arable or ley-arable rotations to fertilizer nitrogen and soil nitrogen at Rothamsted's Woburn Ley-arable experiment

Rothamsted's Woburn Ley-arable experiment, started in 1938 on a sandy loam soil, provides valuable real-world data on the effects of all-arable and ley-arable rotations. In this study, six rotations were compared from 1973 to 2001. Two had 3-year arable “treatment” crops, two had 3-year leys, and two had 8-year leys; the leys being all-grass given fertilizer nitrogen (Ln3 and Ln8), or grass/clover (Lc3 and Lc8). Here, we present the yields of two test crops, winter wheat (1981–2000) followed by spring barley (1982–1991) or winter rye (1997–2001) in each of the six rotations, and their response to four rates of fertilizer N and soil N. From fitted yield/N response curves, we show that maximum wheat yields were least (7.10 t ha⁻¹) in the AB rotation, slightly higher, but not significantly so (7.65 t ha⁻¹) following Ln leys but significantly higher (8.12 t ha⁻¹) following Lc leys. Significantly less fertilizer N (30 kg ha⁻¹) was needed to achieve the higher yields following Lc leys. Yields of the second cereal following the leys were 0.3–0.8 t ha⁻¹ higher than those in the AB rotation; these increases were not statistically significant. However, significantly less fertilizer N, 26–38 kg N ha⁻¹, was required to achieve those yields. There was no difference found between the type of ley. The initial benefit of the Lc leys was short-lived. If leys are to be introduced into mainly arable farming systems, they may need to be subsidized to make them financially viable.     

Determination of ascorbic acid and carotenoids in food commodities by liquid chromatography with mass spectrometry detection

Two methods, one to determine ascorbic acid and one to determine lycopene and beta-carotene, in vegetables and fruits by liquid chromatography coupled with mass spectrometry (LC-MS) have been established. The chromatographic separation of the studied compounds and their MS parameters were optimized to improve selectivity and sensitivity. In both methods, separation was carried out with two coupled columns, first a C(18) and then a dC(18), using as mobile phase 70% methanol (0.005% acetic acid) and 30% acetic acid 0.05% for ascorbic acid determination and a mixture of methanol, tetrahydrofuran, and acetonitrile (60:30:10 v/v/v) for carotenoid analysis in isocratic mode. The molecular ion was selected for the quantification in selective ion monitoring (SIM) mode. Ascorbic acid was detected with electrospray ionization probe (ESI) in negative mode, while chemical ionization atmospheric pressure (APCI) in positive mode was used for the target carotenoids. The methodology for ascorbic acid analysis is based on an extraction with polytron using methanol and a mixture of methaphosphoric acid and acetic acid. Extraction of the carotenoids was carried out with tetrahydrofuran/methanol (1:1) (v/v). The proposed methods were applied, after their corresponding validations, to the analysis of four varieties of tomatoes, tomato in tin enriched and dried tomato, and to the analysis of mango and kiwi fruits, to compare the content in these compounds. Moreover, the influence of the process of freezing and the effect that the manipulation/preservation has in the content of ascorbic acid in tomato have also been studied.     

Spatial and Temporal Variation in Calcium and Aluminum in Northern Hardwood Forest Floors

Acid rain results in losses of exchangeable base cations from soils, but the mechanism of base cation displacement from the forest floor is not clear, and has been hypothesized to involve mobilization of aluminum from the mineral soil. We attempted to test the hypothesis that losses of calcium from the forest floor were balanced by increases in Al in NewHampshire northern hardwoods. We measured exchangeable (six stands) and acid extractable (13 stands) Ca and Al in horizons of the forest floor over an interval of 15 years. Our sampling scheme was quite intensive, involving 50 or 60 blocks per stand, composited in groups of 10 for chemical analysis. Even at this level of effort, few stands exhibited changes large enough to be significant. Because of high spatial variability, differences would have had to be greater than about 50% to be statistically detectable. Differences in Ca and Al concentrations between Oi, Oe, Oa, and A horizons, however, were readily detected. Acid-extractable Al increased with depth, while Ca concentrations decreased; Ca-to-Al ratios decreased from 8.3 (charge basis) in the Oi to 0.2 in the A horizon. Therefore, a small change in sampling depth, or the inclusion of more or less A horizon material in the forest floor, could cause large differences in measured Ca and Al concentrations. To detect small changes in exchangeable cations over time would require sampling very intensively with careful control for comparability of horizons.     

Nitrogen efficiency in hydroponic chicory

An experiment was conducted to develop a model of vegetative growth based on the nitrate concentrations in nutrient solutions using the nutrient film technique and to determine the best cultivar for each concentration. The chicory cultivars (“Pão de Açúcar,” “Folha Larga,” “Precoce de Trieste” and “Catalonha”) and the subplots corresponded to different nitrate concentrations (6.68, 10.0, 13.32 and 16.64 mmol L^?1). There was an interaction between the evaluated factors, such that there was no similarity in the response of the chicory cultivars to the N concentrations in the nutrient solution. The most productive chicory cultivar was “Pão de Açúcar,” which exhibited 10.5% higher productivity than the average, and the least productive was “Folha Larga,” which showed approximately 8.5% lower productivity than the average.     

Genotype and Environment Variation for Arabinoxylans in Hard Winter and Spring Wheats of the U.S. Pacific Northwest

The development of high‐quality wheat (Triticum aestivum L.) cultivars depends on a thorough understanding of the constituents of grain and their variation due to genetics and environment. Arabinoxylans (pentosans) are key constituents of wheat grain and have broad and far‐reaching influences on milling and baking quality. However, variation in arabinoxylans due to genotype and environment are not fully understood. In this study, 25 hard winter and 25 hard spring wheat commercial cultivars and advanced breeding lines developed from eight public and private breeding programs in the U.S. Pacific Northwest were analyzed for water‐extractable and total arabinoxylan contents (WE‐AX and total AX), and the proportion of total AX that was water‐extractable. Winter and spring genotypes were grown in three environments each. The results indicated that there were significant differences among both sets of hard wheat genotypes for WE‐AX, total AX, and proportion of total AX that was WE‐AX. The WE‐AX and total AX mean content ranges for the winter cultivars were 0.390–0.808 and 3.09–4.04%, respectively; and for the spring cultivars 0.476–0.919 and 3.94–4.70%, respectively. WE‐AX as a percentage of total AX was similar between the two genotype sets, 11.7–23.0%. Arabinoxylan fractions were generally not correlated with grain protein, test weight, and kernel hardness. The two highest correlations for winter wheats were between protein and total AX (r = –0.40) and test weight and percentage of total AX that were water‐extractable (r = 0.37) for winter wheats. Among spring wheats, single‐kernel characterization system hardness was negatively correlated with WE‐AX and proportion of total AX that was WE‐AX (r = –0.46 and –0.51, respectively). Although often significant, arabinoxylan fractions were usually not highly intercorrelated, indicating some independence of traits. Notable genotypes, being especially high or low for one or more arabinoxylan fraction and, thus, candidates for further genetic study and cross‐breeding, included Juniper, Eddy, and ORN980995 winter wheats, and Hollis, Alta Blanca, and WQL9HDALP spring wheats. Although the results indicate that arabinoxylan fractions of wheat grain can be highly influenced by environment, there is clear support for the existence of genetic differences, especially for WE‐AX and the proportion of total AX that is water‐extractable. As such, the manipulation of arabinoxylan content of wheat grain seems to be a reasonable breeding objective.     

Responses of lettuce to salinity. I. Effects of NaCl and Na2SO4 on growth

Two lettuce cultivars (Lactuca sativa L., cv. Calmar and cv. Climax) were selected to compare their tolerance to salt stress. The plants were grown in a hydroponic system using a 0.5 modified Hoagland solution. Treatments of 0, 40, 80, and 120 mol m^–3 NaCl or 0 and 20 mol m^–3 Na₂SO₄ were started when the second leaf above the cotyledons appeared. The plants were harvested 20 days later. Climax showed a greater tolerance to salinity at the 40 mol m^–3 NaCl concentration; the % decrease in both shoot and root fresh weight was significantly less than Calmar. No differences between the cultivars were found in the Na₂SO₄ experiments. Differences in root Cl^– content at the 40 mol m^–3 concentration corresponded to an enhanced water content of the roots. A mechanism for the observed differences in salt tolerance between the two cultivars is discussed.     

Biomass characterization of morphological portions of alamo switchgrass

Comparative studies between the leaf and internode portions of switchgrass, Panicum virgatum L., were performed by compositional analysis and structural determination. GC-MS, ICP, and HPAEC-PAD were employed to analyze the chemical compositions of the fractionated switchgrass samples. Quantitative (13)C NMR and CP/MAS (13)C NMR techniques were employed to determine the structures of lignin and cellulose, respectively. These results indicated that the leaves and internodes differed chemically in the amounts of inorganic elements, hot-water extractives, benzene/ethanol extractives, carbohydrates, and lignin content. However, the ultrastructure of isolated cellulose was comparable between leaves and internodes. Ball-milled lignins isolated from leaves and internodes were found to have H/G/S ratios of 12.4/53.9/33.7 and 8.6/54.8/36.6, respectively.