Medium Moisture Level Research Articles

Effect of internal moisture content (IMC) on the CO2 sequestration efficiency of hollow natural fiber (HNF)-reinforced reactive magnesia cement (RMC) composites

The incorporation of minor hollow natural fibers (HNF) can significantly accelerate the CO2 diffusion in reactive magnesia cement (RMC). The CO2 diffusivity in HNF is highly related to its internal moisture content (IMC), which subsequently affects the carbonation process of HNF-RMC, but this is outside the scope of the existing studies. Therefore, this work investigates the effect of IMC on carbonation, strength, and microstructure of HNF-RMC composites. HNF-RMC mortar specimens are dried to different levels of nominal IMC (0–100%), and cured under high CO2 concentration for carbonation. Following the curing, the matrix composition was characterized with varying techniques (QXRD, TGA, FTIR, and acid digestion) for quantifying the CO2 sequestration; the compressive strength at different depths was determined with uniaxial compressive test; the microstructure was examined with SEM/ESEM. The results show that the carbonation depth is increased by three to four times by reducing the IMC to 0%. The effects of varying IMC on local carbonation and strength are distinct in the shallow (0–20 mm) and middle/deep region (20–100 mm). In the shallow region, inadequate CO2 dissolution is the limiting factor, these performances decreased with the increasing desiccation. In the deeper regions, moisture absorption by HNF decreased the CO2 diffusivity, hence the CO2 availability is the limiting factor, and these performances increased with the desiccation. These observations suggest that the understanding that carbonation maximizes at a medium moisture level is not valid in HNF-RMC–controlling the moisture can be important for improving the CO2 sequestration and consequent mechanical strength.

Drought accentuates the role of mycorrhiza in phosphorus uptake

Arbuscular mycorrhizal fungi (AMF) greatly facilitate uptake of phosphorus (P) by most plant species. Whether or how this changes if water becomes limiting remained little explored. Medicago truncatula plants were grown in previously sterilized cultivation substrate and inoculated or not with AMF isolate Rhizophagus irregularis ‘PH5’ (M or NM, respectively) in two-compartment rhizoboxes. The compartments were separated or not with root-excluding meshes. A 15-step soil moisture gradient (maintained over 5 weeks) spanned generous water supply through strong water deficiency. Two radioisotopes (33P and 32P) were injected into the plant and distant compartments, respectively, to distinguish cumulative and immediate-term plant P uptake from either of the compartments at each moisture level. M plants were larger than NM plants at high and medium moisture levels and accumulated markedly more P throughout the whole gradient. The immediate-term P uptake did not differ between M and NM plants at high moisture, but at medium and low moistures, M plants acquired significantly more 33P than NM plants, even after accounting for differences in root biomass. Increased immediate-term P uptake by M plants grown under medium and low substrate moistures was probably due to complementary effect of direct hyphal uptake and indirect alterations of substrate hydraulic properties by AMF. This research illustrates that AMF remain functional part of plants even under severe drought stress and thus they should be considered when plant functioning under water deficiency is to be fully understood.

Effects of freeze-thaw and soil moisture on content and spectral structure properties of dissolved organic matter in forest soil leachates.

The contents and stability of soil dissolved organic matter (DOM) can affect key processes of soil carbon and nitrogen cycle. The responses of DOM content and its spectral structure pro-perties in forest soils to climate change remain unclear. We collected soil samples from two temperate forests, i.e., the broadleaf and Korean pine mixed forest (BKPF) and adjacent secondary white birch forest (WBF), in Changbai Mountains, northeastern China. Using a combination of three-dimensional fluorescence spectrum and parallel factor analysis, a simulated freeze-thaw experiment was conducted in the laboratory. We examined the effects of freeze-thaw intensity, freeze-thaw cycle and their interaction on the content, components and spectral properties of DOM leached from the two forest surface soils with different moisture levels. The results showed that DOM content and components of soil leachates varied with forest types, soil moisture, freeze-thaw intensity and freeze-thaw cycle. The DOM content in the leachates was lowest at medium moisture level and was significantly affected by the high freeze-thaw intensity. In addition, the DOM content increased first and then decreased with the increases of freeze-thaw cycles. Three fluorescence components of DOM in the forest soil leachates were identified as humic acid-like DOM, fulvic acid-like DOM and protein-like DOM. The DOM components of BKPF soil leachates were mainly consisted of fulvic acid-like substances with a high humification index. However, the DOM from WBF soil leachates was dominated by humic acid-like substances with low stability, and the three fluorescence components were significantly affected by the freeze-thaw intensity. Results from the redundancy analysis showed that under the experimental conditions, forest type played a leading role in changing DOM properties. The DOM content and its three fluorescence intensities of WBF soil leachates were higher than those of BKPF. Soil moisture significantly affected the aromaticity of DOM in the forest soil leachates, and the DOM aromaticity of soil leachates from the two forest stands ranked as medium moisture > high moisture > low moisture. With the increases of freeze-thaw intensity, the DOM aromaticity of BKPF soil leachates significantly decreased. Furthermore, the increases of freeze-thaw cycles significantly increased the humification degree of DOM in the forest soil leachates. Therefore, upon different freeze-thaw disturbance, the DOM content and bioavailability of soil leachates with low moisture tended to increase, particularly in the WBF soil leachates, which may result in an increased lea-ching of DOM in temperate forest soils during spring freeze-thaw periods. The results provide a refe-rence for further investigating DOM turnover in temperate forest soils during spring freeze-thaw periods.

Interaction of Insecticide and Media Moisture on Ambrosia Beetle (Coleoptera: Curculionidae) Attacks on Selected Ornamental Trees.

Exotic ambrosia beetles, particularly Xylosandrus crassiusculus (Motschulsky) (Coleoptera: Curculionidae: Scolytinae) and Xylosandrus germanus (Blandford) (Coleoptera: Curculionidae: Scolytinae), are among the most damaging pests of ornamental trees in nurseries. Growers have had few tactics besides insecticide applications to reduce ambrosia beetle attacks but recent research has shown that attacks may be reduced by maintaining media moisture below a 50% threshold thereby reducing flood stress. We compared the efficacy of managing media moisture and insecticide applications for reducing ambrosia beetle attacks on three ornamental tree species in North Carolina. During trials in spring 2013 and 2015, flooded Cornus florida and Cornus kousa were heavily attacked despite sprays with permethrin, but nonflooded C. kousa or C. florida were not attacked. In spring 2015 trials, both nonflooded and flooded Styrax japonicus were heavily attacked regardless of permethrin applications. Although ethanol emissions were not measured, the apparently healthy nonflooded S. japonicus trees may have been exposed to an unknown physiological stress, such as low temperature injury, the previous winter, which predisposed them to beetle attack. However, ethanol levels within host tissues were not measured as part of the current study. X. crassiusculus (75%), Xyloborinus saxesenii Ratzburg (13%), and X. germanus (9%) were the most abundant species collected in ethanol baited traps deployed in 2015, while X. crassiusculus (63%) and X. germanus (36%) were the predominant species reared from attacked trees. Results indicate that managing media moisture levels at or below 50%, and maximizing tree health overall, may provide significant protection against Xylosandrus spp. attacks in flood intolerant tree species.

Developing a Media Moisture Threshold for Nurseries to Reduce Tree Stress and Ambrosia Beetle Attacks.

Exotic ambrosia beetles are among the most damaging pests of trees grown in nurseries. The primary pests Xylosandrus crassiusculus Motschulsky and Xylosandrus germanus Blandford use ethanol to locate vulnerable trees. Research, primarily with X. germanus, has shown that flood-stressed trees emit ethanol and are preferentially attacked by ambrosia beetles. Our goal was to develop a media (also called potting soil) moisture threshold as an integrated pest management (IPM) tactic and assess grower practices that lead to ambrosia beetle attacks. Flooded Cornus florida L., Cornus kousa Burg., and Magnolia grandiflora L. trees incurred more attacks than unflooded trees that were not attacked. To determine optimal media moisture levels, we grew flood-tolerant Acer rubrum L. and flood-intolerant C. florida in containers with 10, 30, 50, 70, or 90% media moisture. No flooded or unflooded A. rubrum were attacked. However, C. florida grown in 70 or 90% moisture were attacked and died, whereas trees at 30 and 50% moisture were not attacked. Thus, we suggest an upper moisture threshold of 50% when growing C. florida and other flood-intolerant trees. However, during peak ambrosia beetle flight activity in spring 2013 and 2014, we found that media moisture levels in commercial nurseries were often between 50 and 90%. Implementing a media moisture threshold, as a new IPM tool, could reduce ambrosia beetle attacks and the need for insecticide applications, which is currently the only available management tactic. Future research should focus on how changes in substrates, irrigation, and other practices could help growers meet this threshold.

Influence of Moisture on Cold Hardiness of Six Container-Grown Herbaceous Perennials

Overwintering container-grown plants is often necessary during production. Plants maintained in pots at growing medium moisture levels above (‘wet’) and below (‘dry’) 10% volumetric water content were exposed to −2, −5, −8, −11, and −14 C (28, 23, 18, 12, 7 F) in January, then returned to a greenhouse kept at 3 to 5 C (37 to 41 F). In June, plants were assessed using a visual rating scale (1 = dead, 3 to 5 = increasing quality) and shoot dry weight of new foliage growth. Quality rating and shoot dry weight of Coreopsis L. ‘Tequila Sunrise’ and Carex morrowii Boott. ‘Ice Dance’ were not affected by moisture level. Quality ratings were higher for Geranium × cantabrigiense L. ‘Cambridge’ ‘wet’ plants than for ‘dry’ plants and for Heuchera L. ‘Plum Pudding’ ‘dry’ plants than for ‘wet’ plants. Shoot dry weight was higher for ‘dry’ plants of Carex laxiculmis Schwein. ‘Hobb’ (Bunny Blue™) and Carex oshimensis L. ‘Evergold’ exposed to most temperatures. Of the cultivars studied, effects of moisture level on overwintering container-grown plant growth and quality are cultivar-specific and a universal effect could not be established.

Aerobic Stability and Effects of Yeasts during Deterioration of Non-fermented and Fermented Total Mixed Ration with Different Moisture Levels.

The present experiment evaluated the influence of moisture level and anaerobic fermentation on aerobic stability of total mixed ration (TMR). The dynamic changes in chemical composition and microbial population that occur after air exposure were examined, and the species of yeast associated with the deterioration process were also identified in both non-fermented and fermented TMR to deepen the understanding of aerobic deterioration. The moisture levels of TMR in this experiment were adjusted to 400 g/kg (low moisture level, LML), 450 g/kg (medium moisture level, MML), and 500 g/kg (high moisture level, HML), and both non-fermented and 56-d-fermented TMR were subjected to air exposure to determine aerobic stability. Aerobic deterioration resulted in high losses of nutritional components and largely reduced dry matter digestibility. Non-fermented TMR deteriorated during 48 h of air exposure and the HML treatment was more aerobically unstable. On dry matter (DM) basis, yeast populations significantly increased from 107 to 1010 cfu/g during air exposure, and Candida ethanolica was the predominant species during deterioration in non-fermented TMR. Fermented TMR exhibited considerable resistance to aerobic deterioration. Spoilage was only observed in the HML treatment and its yeast population increased dramatically to 109 cfu/g DM when air exposure progressed to 30 d. Zygosaccharomyces bailii was the sole yeast species isolated when spoilage occurred. These results confirmed that non-fermented and fermented TMR with a HML are more prone to spoilage, and fermented TMR has considerable resistance to aerobic deterioration. Yeasts can trigger aerobic deterioration in both non-fermented and fermented TMR. C. ethanolica may be involved in the spoilage of non-fermented TMR and the vigorous growth of Z. bailii can initiate aerobic deterioration in fermented TMR.

Energy potential of native shrub species in northern Spain

This paper we present an energy review of the waste generated by shrub species in soils of low fertility for use as fuel in a power plant. The residues analysed belong to the species: Rhamus alaternus, Ulex europaeus, Prunus spinosa, Smilax aspera, Erica sp., Rubus ulmifolius, and Pteridium aquilinum. Gross calorific value (GCV), net calorific value (NCV), density, elementary chemical analysis, moisture content, percentage of ash, productivity, energy density and FVI (fuel value index) have been measured. These parameters have been determined for three levels of moisture (maximum, medium and minimum). At medium moisture level, the residues of U. europaeus are those that reach the greatest FVI, 20,000. In the other extreme is the P. aquilinum with an FVI of 403. The average productivity of waste, in t ha−1, of each species has been determined in order to know how much energy is stored per hectare. U. europaeus and P. spinosa are the species which accumulate more energy per hectare, with similar values of around 81 MJ ha−1 yr−1 and installed power of 2.59 W ha−1. The energy recovery of the waste in a thermal power plant would generate an annual revenue of 14.6 M€, taking into account that 40% of the forest land covered by shrub in Cantabria is used for this purpose.

Evaluation of Wood Chip-Based Biofilters to Reduce Odor, Hydrogen Sulfide, and Ammonia from Swine Barn Ventilation Air

A pilot-scale biofilter was developed in which two types of wood chips (western cedar [WC] and 2-in. hardwood [HW]) were examined to treat odor emissions from a deep-pit swine finishing facility in central Iowa. The biofilters were operated continuously for 13 weeks at different airflow rates resulting in variable empty bed residence times (EBRTs) from 1.6 to 7.3 sec. The effects of three media moisture levels were also evaluated. A dynamic forced-choice olfactometer was used to evaluate odor concentrations from both the control (inlet) plenum and biofilter treatments (outlet). Hydrogen sulfide (H2S) and ammonia (NH3) concentrations were also measured from these olfactometry samples. Solid-phase microextraction (SPME) polydimethylsiloxane (PDMS)/divinylbenzene (DVB) 65-µm fibers were used to extract volatile organic compounds from both the control plenum and biofilter treatments. Analyses of separated odors were carried out using a gas chromatography-mass spectrometry-olfactometry (GC-MS-O) system. Static sample results indicated that both types of chips achieved significant reductions in odor (average 70.1 and 82.3% for HW and WC, respectively), H2S (average 81.8 and 88.6% for HW and WC, respectively) and NH3 (average 43.4 and 74% for HW and WC, respectively) concentrations. GC-MS-O aromagram results showed both treatments reached high odor reduction efficiency (average 99.4 and 99.8% for HW and WC, respectively). The results also showed that maintaining proper moisture content and a minimum EBRT are critical to the success of wood chip-based biofilters.

(388) Media Type and Moisture Influence Growth and Development of Ginger (Zingiber officinalis) Propagules

Ginger(Zingiber officinalis) is a spice crop with a variety of medicinal uses. Potentially, it may be suitable for ethnic production following necessary studies to determine optimum cultural conditions. The propagation of ginger from rhizomes was investigated using three growth media, three media moisture levels, and two types of propagules. The media were poultry compost amended with peat and perlite in a volume ratio of 2:1:1, municipal yard waste compost, and the commercial mix Promix. The moisture levels of each medium were: no applied water, moderately watered (between wilting point and field capacity), and field capacity, which represented moisture tension levels of >–1.5, –0.08, and –0.03 MPa, respectively. Growth from single-node rhizome propagules and large pieces of 5.6 to 7.6 cm long with one or more nodes was determined over 90 days. The large propagules and the field capacity moisture regime produced the tallest shoots, and largest number of shoots and leaves per propagule, as well as the highest percentages of secondary rhizomes, root, and shoots per propagule. The yard waste and Promix were superior to poultry compost in the development of the propagules for all the traits measured. The large propagules produced earlier shoot emergence at field capacity than at the moderate moisture levels. Single-node propagules generally failed to emerge without applied moisture or when in poultry compost.

Seedcoat Structure and Oxygen-enhanced Environments Affect Germination of Triploid Watermelon

Triploid or seedless watermelon [Citrullus lanatus (Thunb.) Matsum & Nakai] cultivars often have erratic germination and low seedling vigor. The morphology of the seedcoat on two triploid cultivars—Tri X 313 and Tri X Sunrise—was examined by scanning electron microscopy (SEM) to identify structural differences compared to diploid seeds. Triploid seeds incubated with oxygen-enhanced treatments that included nicking, 1% hydrogen peroxide (H2O2), and 40% oxygen were investigated at low and high medium moisture levels. Triploid seed has a thicker seedcoat with a dense endotesta layer and a larger and highly variable air space surrounding the embryonic axis as compared with diploid seed. All cultivars rapidly imbibed water (≈50% of the original weight) during the first hour of imbibition, with a faster increase for triploids than for diploids. High moisture affected germination to a lesser extent in diploid than triploid seeds. Triploid germination under low medium moisture ranged from 96% to 76%, but was severely reduced to <27% under high medium moisture. Triploid seed germination was significantly improved at high moisture by H2O2 and by 40% oxygen. Triploid watermelon seed is very sensitive to submerged conditions, possibly due to a combination of physiological and morphological defects. The rapid imbibition and excess water collected in the seedcoat and air space surrounding the embryo, could reduce oxygen diffusion and impair metabolic pathways leading to normal germination and seedling development.

Interference and Water Use of Biotypes Differing in Sensitivity to MSMA

Biotypes of common cocklebur were identified, which were assumed to differ only with respect to sensitivity to MSMA. Water use of these biotypes when grown as isolated plants in a growth chamber was determined with stem flow gauges. The MSMA-tolerant biotype exhibited less whole-plant sap flow at media moisture levels above 17%. Furthermore, only in the tolerant biotype did sap flow differ between the upper and lower canopy; the upper canopy had greater sap flow. Field experiments were conducted to compare growth parameters, water use and competitive ability toward cotton of the MSMA-sensitive and -tolerant biotypes. Sensitive biotype plants were taller and had greater leaf area than those of the tolerant biotype; dry weight was equivalent. The tolerant biotype used less water and reduced seed cotton yield more than the sensitive biotype.

Production and Postproduction Performance of Two New Guinea Impatiens Cultivars Grown with Controlled-release Fertilizer and No Leaching

The objectives of this study were to determine 1) the minimum controlled-release fertilizer (CRF) rate and the lowest constant medium moisture required to produce the highest quality plants and 2) if this production system affected quality of these plants under two postproduction light levels. Two New Guinea impatiens (Impatiens sp. hybrids) `Illusion' and `Blazon' (Lasting Impressions Series) differing in salt tolerance were grown for 42 days with a CRF at three rates (3.3, 6.6, or 9.9 g/pot) and two medium moisture levels (low or high) without leaching. The high moisture level (tension setpoints of 1 to 3 kPa) and 6.6 g of CRF/pot produced optimum biomass. Low medium moisture (tension setpoints of 4 to 6 kPa) reduced leaf area, leaf number, leaf N content, root, stem, and leaf dry masses as CRF rate increased from low to high for `Illusion'. Similar results in `Blazon' were observed as CRF rates increased from 3.3 to 6.6 g. Biomass decreased no further at the high rate of 9.9 g/pot. Biomass increased in both cultivars under high medium moisture when CRF rates increased from 3.3 to 6.6 g. Biomass of `Illusion' decreased at 9.9 g/pot, although no symptoms of salt sensitivity were observed (i.e., leaf tip burn). `Blazon' maintained a similar biomass when amended with 9.9 or 6.6 g CRF/pot, although electrical conductivity (EC) in the medium was 5.9 dS·m-1 in the upper half and 4.1 dS·m-1 in the lower half of the medium at the end of production. Growth of `Illusion' responded more favorably to postproduction light levels that were similar to those of production regardless of treatment imposed during production. Similar biomass responses occurred for `Blazon' regardless of the postproduction light level.

Performance Comparisons of Conventional and Laboratory‐Scale Alfalfa Hay Bales in Isolated Environments

AbstractNegative quality changes, including Maillard reaction damage, in alfalfa (Medicago sativa L.) hay frequently are associated with spontaneous heating resulting from packaging and storing forage at moisture levels in excess of 200 g kg−1. Forage at three moisture levels (268, 229, and 185 g kg−1) was packaged in laboratory‐scale bales at 1.0, 1.3, 1.7, and 2.0 times the density of parent, conventional bales and subsequently incubated in two different isolated environments such that all measured heat accumulation was the result of self‐generated heat. Laboratory scale hay packages generated measurable heat and exhibited quality changes when incubated (i) between straw bales stacked in an open‐air pole shed and (ii) in insulated incubator boxes in a storeroom where the minimum ambient storage temperature was set at at 25°C. Heat development and negative quality changes were greater in the box‐incubation system, indicating a need to control ambient storage temperature. At the high and medium moisture levels, acid‐detergent insoluble N (ADIN) fractions for high‐density, box‐incubated laboratory bales were at least similar (P = 0.05) to those of parent, conventional bales, despite large disadvantages in measures of accumulated heat. These responses in laboratory bales were consistent with those reported in previous haystack‐incubated studies and suggest that the environmental heat component created by adjacent conventional bales in those studies may have had a limited direct effect on ADIN content. Increasing density of laboratory bales probably rendered alfalfa proteins more susceptible to Maillard reaction damage and/or allowed the reaction to proceed more efficiently with respect to self‐generated heat than it did in conventional bales.

Propagation Medium Moisture Level Influences Adventitious Rooting of Woody Stem Cuttings

Stem cuttings of Blue Rug juniper (Juniperus horizontalis Moench `Wiltonii'), `Hino-Crimson' azalea [Rhododendron (Lindl.) P1anch `Hino-Crimson'], and `Helleri' holly (Ilex crenata Thunb. `Helleri') were propagated in 1 peat: 1 perlite (v/v) at one of five moisture levels based on medium dry weight (125%, 250%, 375%, 500%, or 625%). Cutting survival and percentage of rooted cuttings were highest at the highest medium moisture level in all three species. Incidence of cutting basal rot was not directly related to medium moisture level, but more to the growth stage of the stock plant. Midday xylem water potential (ψ) of cuttings for each species was highest in the wettest propagation medium and lowest in the driest medium. During propagation, stem cutting ψ below - 2.0 MPa occurred even in the wettest medium tested, and frequently reached - 4.0 MPa in cuttings in the driest treatment (125%). Basal water uptake by cuttings was highest in the wettest medium moisture level. Water uptake was highest during the first few days after insertion, and thereafter decreased until root emergence.

YIELD, QUALITY AND PRESERVATION OF MOIST HAY SUBJECTED TO RAIN-FREE AND WEATHERED CONDITIONS

The effects of moisture level and a neutralized propionate preservative on yield, quality and preservation of rain-free and weathered alfalfa (Medicago sativa L.) hay were studied in separate trials. Moisture levels of 252, 185 and 138 g kg−1 in rain-free hay and 297, 211 and 180 g kg−1 in weathered hay were designated as High, Medium and Low, respectively. The weathered hay received 66 mm of rain at about 600 g kg−1 moisture and another 15 mm prior to baling at the Low moisture level. The preservative (680 g kg−1 propionic acid equivalent) was applied at 1.25 and 1.50% (wt wt−1) for rain-free and weathered hay, respectively. The High and Medium moisture level treatments had similar harvested dry matter (DM) yields in both rain-free and weathered hay. Rain-free hay DM yield at harvest was 6–9% higher for the High and Medium treatments than the Low moisture level, while for the weathered hay the Medium level was 3.0% higher (P < 0.05) than the Low moisture level. Poststorage forage qualities of the Low and Medium moisture level treatments were similar and higher than the High moisture treatment (P < 0.05) in rain-free hays, while the Medium level treatment was highest (P < 0.05) for forage quality in weathered hay. The Medium moisture level compared with Low moisture level resulted in 10.4, 10.6 and 15.8% higher yields of DM, in vitro digestible organic matter (IVDOM) and crude protein, respectively, in rain-free hay and 3.1, 6.3 and 5.7% higher, respectively, in weathered hay. The propionate was inconsistent in preventing DM loss during storage, but reduced temperature and mould count in both hay types. Application of 1.25 and 1.50% (wt wt−1) of propionate improved poststorage IVDOM by 2.0 and 3.6%; increased crude protein yield by 3.0 and 5.7% and IVDOM yield by 3.3 and 5.7%; reduced neutral detergent fiber by 5.4 and 7.6%; reduced acid detergent fiber by 5.4 and 7.1%; and reduced acid detergent insoluble nitrogen by 9 and 18% in rain-free and weathered hay, respectively. It is recommended that large round bales be harvested at moisture levels somewhat above 170 g kg−1 for both rain-free and weathered hay with or without a neutralized propionic acid preservative. Serious losses may occur above 250 g kg−1 moisture with or without the use of a preservative. Key words: Alfalfa, moist hay, neutralized propionate, large round bales, weathering, preservation

Dissipation of s-triazines and thiocarbamates from soil as related to soil moisture content

Half-lives ( t 1 2 ) of two soil incorporated s-triazine (atrazine and prometon) and two thiocarbamate (EPTC and triallate) herbicides were determined in relation to soil moisture content in two California soils. Treated soils were incubated at three moisture levels in aerated glass vials at 25 ± 1°C and were analyzed at 0, 7, 16, 28, 56 and 112 day intervals. Loss of herbicides in all treatments followed first-order kinetics. The t 1 2 - values of all herbicides decreased with increasing soil moisture and followed an empirical equation, t 1 2 = aM −b (where t 1 2 is half-life; M the moisture content; and a and b are constants). Soil moisture had a greater effect on carbamates than on s-triazines. Prometon exhibited the longest half-life in both soils, whereas EPTC was least persistent in one soil and atrazine in another. The t 1 2 - values for atrazine, prometon, EPTC, and triallate with medium moisture levels and 10 μg/g concentration were 34·6, 43·2, 25·4 and 38·1 days in sandy loam and 26·5, 44·4, 44·1 and 25·9 days in loamy sand, respectively. Disappearance of 50% of the applied concentrations of most of the herbicide-soil combinations (except EPTC and triallate in one soil) took longer for lower initial concentrations (1 μg/g) than for higher concentrations (10 μg/g).

Effect of the chemical and physical condition of the soil on Verticillium wilt of antirrhinum

In vitro study showed thatVerticillium dahliae Kleb. grew well in a wide range of acid and alkaline media (viz. pH 3.5 to 10.5). The best growth of the fungus was observed in pH 5.5. Soil pH 3.5 was toxic for growing antirrhinum seedlings. Development of Verticillium wilt of antirrhinum was affected by soil pH. The severity of the disease was greater in alkaline soil conditions compared with acid conditions. Soil of pH 3.5 gave very good control of the symptom expression by the infected plants. Rhizosphere analysis results showed that fungal population with the exception ofPenicillium spp., was drastically reduced in the rhizosphere of the plants grown in acid soil. Although the overall population of fungi was reduced in theV. dahliae infected antirrhinum rhizosphere in acid soil, the population ofPenicillium spp. markedly increased. The antagonistic activity of thePenicillium spp. in the rhizosphere might also have reduced the disease severity. Since the seedlings did not grow properly in very dry and very wet soil, rhizosphere analysis of these soils was not possible. Disease severity was much less in wet soil compared with plants grown in medium moisture level and dry soil, but the plant growth was very poor.

Establishment of Sod‐seeded Alfalfa at Various Levels of Soil Moisture and Grass Competition1

AbstractAlfalfa (Medicago sativa L.) establishment in competition with grass sods is not always successful, especially under conditions of soil moisture deficiency. Our objective was to evaluate the effect of soil moisture concentration and grass competition on alfalfa establishment and yield when it was interseeded into perennial grass sods.In a greenhouse experiment, alfalfa was seeded into Kentucky bluegrass (Poa pratensis L.) or smooth bromegrass (Bromus inermis Leyss.) sods which had been sprayed with 0, 0.6, and 2.2 kg/ha glyphosate [N‐(phosphonomethyl)glycine]. Three soil moisture regimes were established by watering to field capacity when soil moisture tensions reached 0.1, 1, and 12 bars. Grass‐shading treatments were also applied.At two field locations alfalfa was seeded into an unimproved Kentucky bluegrass, smooth bromegrass, and quackgrass (Agropyron repens L.) pasture and into a smooth bromegrass pasture. The soil at both locations was a Waukegan silt loam (Typic Hapludoll). Three levels of grass suppression were obtained by spraying with 0, 0.8, and 3.3 kg glyphosate/ha. Soil moisture regimes consisted of watering to field capacity when soil moisture tension reached 1 and 15 bars.Under shaded conditions in the greenhouse and with low grass suppression (no glyphosate) in the field, moisture did not significantly affect alfalfa establishment or dry matter yield. However, when shading was eliminated or grass suppression increased, low soil moisture tensions resulted in increased legume yields.In the greenhouse, alfalfa dry matter yields and root weights were generally greater when it was seeded into Kentucky bluegrass compared to smooth bromegrass. Smooth bromegrass was more tolerant of glyphosate application than Kentucky bluegrass. When seeded into smooth bromegrass, alfalfa yields from low and medium moisture level treatments were not significantly different, but when seeded into Kentucky bluegrass yields from high and medium moisture levels were significantly greater than for the low moisture treatment.Our results show that both adequate soil moisture and reduced grass competition for light are important for successful alfalfa sod‐seeding.

Bioactivity of Systemic Insecticides in Corn: Relationship to Leafhopper Vector Control and Corn Stunt Disease Incidence12

Of seven granular systemic insecticides applied in-furrow at 1 1b per acre to corn, Zea mays L., at planting, carbofuran was the most effective for control of the leafhopper Dalbulus maidis (DeLong & Wolcott), followed in order of efficacy by aldicarb, methomyl, propoxur, phorate, disulfoton, and fenthion. Insect control was reflected in corn stunt disease incidence data which ranged from 16, 62, and 78% in carbofuran, aldicarb, and methomyl treatments, respectively, to 94-97% in the propoxur, disulfoton, phorate, and fenthion treatments, and the untreated control 77 days after planting. The efficacy of aldicarb and carbofuran applied in furrow at 0.5, 1, and 2 lb/acre at planting in a sandy loam soil at a medium moisture level was found to be rate-dependent in greenhouse tests. Carbofuran at 2 1b/acre was effective against D. maidis up to 5 weeks when leafhoppers were allowed a 2-hour feeding period on treated plants; aldicarb at this rate was effective for 3 weeks after planting. Carbofuran and aldicarb at 1 1b/acre were effective for 3 and 2 weeks, respectively, and at 0.5 1b/acre for 2 and 1 weeks, respectively. Carbofuran and disulfoton side-dressed at 1 1b/acre to one side of corn 28 days after planting were absorbed and trans located in sufficient quantities to be toxic to D. maidis between Days 2 and 4 after application when the insects were allowed to feed on the test plants for at least 8 hours. Insecticide activity was greater in leaves on the plant side above placement of the toxic ant than in leaves on the plant side opposite placement of the toxic ant. The side-dress application did not reduce the incidence of corn stunt disease compared to plants not treated with insecticide.