Rhizobacterial treatments of tall fescue and bermudagrass increases tolerance to damage from white grubs.

BACKGROUND: Inoculation of hybrid bermudagrass with plant growth-promoting rhizobacteria (PGPR) can increase plant growth and influence relationships with above-ground herbivores like fall armyworms. However, few experiments have evaluated PGPR applications relative to root herbivory. Root-feeding white grubs cause severe damage to grasses, especially in tall fescue pastures, golf courses, and lawns. Since bacterial inoculants enhance root growth, the goal of this study was to determine if the inoculation of hybrid bermudagrass by rhizobacteria can increase the tolerance of tall fescue and hybrid bermudagrass to damage from white grub feeding, and if PGPR are compatible with neonicotinoid insecticides commonly used for white grub control. RESULTS: In trials with tall fescue and hybrid bermudagrass, grasses were treated with the PGPR strain mixture Blend 20 or nitrogen or left non-treated and were then infested with Japanese beetle grubs. Grasses treated with PGPR and nitrogen fertilizer produced significantly more top growth than the non-treated grub-infested controls. Tall fescue and hybrid bermudagrass treated with Blend 20 produced root mass similar to or greater than nitrogen fertilized grasses. Both grasses treated with Blend 20 had greater root mass than non-treated infested grass. No treatment negatively impacted grub survival, and weight gains of grubs were similar for all treatments. Bacterial strains were typically compatible with insecticides used to control white grubs. CONCLUSION: PGPR and nitrogen fertilization stimulate root growth resulting in tolerance of tall fescue and hybrid bermudagrass to white grub infestation. PGPR, acting as biostimulants to increase root biomass on grasses, may have utility for IPM of root herbivores. © 2019 Society of Chemical Industry.

Differential uptake of silver, copper and zinc suggests complementary species-specific phytoextraction potential.

The aim of our study, conducted as a pot experiment, was to assess the potential of willow (Salix miyabeana), alfalfa (Medicago sativa), tall fescue (Festuca arundinacea), and Indian mustard (Brassica juncea) to remediate two brownfield soils differentially contaminated with Ag, Cu and Zn (up to 113.60, 47.50, and 117.00 mg kg(-1) respectively). While aboveground Ag accumulation was highest in B. juncea (4.60 ± 2.58 mg kg(-1)), lower levels were also measured in M. sativa and F. arundinacea. Cu accumulation was observed in all species, but only in underground parts, and was highest in F. arundinacea (269.20 ± 74.75 mg kg(-1)), with a bioconcentration factor of 13.85. Salix miyabeana was found to have the highest Zn aerial tissue concentration (119.96 ± 20.04 mg kg(-1)). Because of its high Ag uptake, the remediation potential of B. juncea should be evaluated more extensively on the site from which we excavated the soil for this study. Given the multiple forms of contamination on the site and the differential specie-related uptake evident in our findings, we hypothesize that an optimal plantation allowing expression of complementary remediation functions would include B. juncea for extraction of Ag, in combination with F. arundinacea for stabilization of Cu and S. miyabeana for extraction of Zn.

Angelicin as the principal allelochemical in Heracleum sosnowskyi fruit.

Distribution patterns of furocoumarins in fruits of the invasive species Heracleum sosnowskyi Manden. (Sosnowskyi's hogweed) during a cold stratification period were investigated. Angelicin, bergapten, methoxalen and imperatorin were mainly localized in the fruit coats and their content varied depending on the fruit source. Cold stratification treatment (90 days, 2-3 degrees C) reduced the content of furocoumarins in the fruit coats by more than two times, compared with those before stratification. The specific activity of the detected furocoumarins and total activity of crude extracts were evaluated using Lactuca sativa, as acceptor plant. Crude extracts obtained from fruit coats and seeds of H. sosnowskyi suppressed 50% of radicle and hypocotyl growth of lettuce seedlings at the concentration range of 1.0-1.7 mg/mL. The inhibitory activity of angelicin was proved to be the highest compared with the other tested furocoumarins, and the inhibitory activity of crude extracts could be explained mainly by the presence of angelicin. Both, monocots (Lolium multiflorum, Phleum pratensis, Festuca pratesis, Lolium perenne) and dicots (Tripholium repens, Trifolium pretense) were found to be sensitive to the exudates of whole H. sosnowskyi fruits. Thus, we assume, that high inhibitory potential of furocoumarins, especially angelicin, at high seed productivity of H. sosnowskyi might have an ecological significance in plant-plant interaction.

Functional co-expression of a fungal ferulic acid esterase and a ß-1,4 endoxylanase in Festuca arundinacea (tall fescue) modifies post-harvest cell wall deconstruction.

MAIN CONCLUSION: Improved post-harvest cell wall deconstruction of tall fescue leaves has been demonstrated by in-planta co-expression of a constitutively expressed ferulic acid esterase together with a senescence-induced ß-1,4 endoxylanase. Tall fescue plants (Festuca arundinacea) constitutively expressing vacuole- or apoplast-targeted ferulic acid esterase from Aspergillus niger were retransformed with a senescence-induced and apoplast-targeted ß-1,4 endo-xylanase from Trichoderma reesei. Enzyme activities in co-expressing plants stabilized after repeated vegetative propagation, with xylanase activity in senescent leaves increasing and ferulic acid esterase activity decreasing after tillering. Plants co-expressing both enzymes in the apoplast, with the lowest levels of ferulate monomers and dimers and the lowest levels of cell wall arabinoxylans, released ten times more cell wall hydroxycinnamic acids and five times more arabinoxylan from the cell wall on autodigestion compared to expression of ferulic acid esterase or xylanase alone. These plants also showed a 31 % increase in cellulase-mediated release of reducing sugars, a 5 % point increase in in vitro dry matter digestibility and a 23 % increase in acetyl bromide-soluble lignin. However, plant growth was adversely affected by expressing FAE in the apoplast, giving plants with narrower shorted leaves, and a 71 % decrease in biomass.

Allelopathic Potential of Invasive Plantago virginica on Four Lawn Species.

Plantago virginica L. has invaded many lawn ecosystems in the Eastern part of China. The invasion has incurred an economic cost to remove them. In order to prevent the invasion, it is critical to understand the invasive mechanisms of this species. However, few studies have been conducted on the allelopathic mechanisms of its invasion. In this study, we examined allelopathic effects of P. virginica on germination of seeds and growth of seedlings of four widely used lawn species. We found extensive allelopathic potential of P. virginica on other lawn species, which varied with species and developmental stage. While most effects of the extracts of P. virginica were inhibitory, some variables in some species were promoted by the addition of the extracts. The extracts of P. virginica significantly inhibited seed germination of Agrostis matsumurae. While the overall differences in seed germination rate of Poa annua were significant among treatments, difference between control and any of the treatments was not significant. The height of seedlings of A. matsumurae and Cynodon dactylon was significantly lower under the treatments of adding extracts of P. virginica. In contrast, growth of seedlings of Festuca elata and P. annua did not show significant differences among treatments. The root length of A. matsumurae, C. dactylon and P. annua was suppressed by the extracts of P. virginica whereas root length of F. elata was not affected. Aboveground biomass of A. matsumurae and F. elata was significantly higher than control, except for F. elata at the concentration of 50mg/mL, whereas aboveground biomass of C. dactylon and P. annua was reduced at higher concentrations of the extracts. Except for A. matsumurae, root biomass of the other three lawn species declined under the treatments with the extracts of P. virginica. Our results revealed that P. virginica had allelopathic potential on four lawn species and supported the theory of "novel weapons hypothesis". Invasion by P. virginica in lawn can be moderated by selecting those species that are not affected or promotionally affected by it.

The effect of glyphosate on the growth and competitive effect of perennial grass species in semi-natural grasslands.

Biodiversity within European semi-natural biotopes in agro-ecosystem is declining, and herbicide drift from neighbouring fields is considered as an important factor for the decline. The aim of the present study was to investigate whether the growth and competitive interactions in a model system of two perennial grass species, Festuca ovina and Agrostis capillaris, are affected by sub-lethal doses of glyphosate in field margins. In a glasshouse experiment with ample nitrogen, the interspecific competitive interactions were found to be significantly affected by glyphosate; the competitive effect of F. ovina on A. capillaris increased and the competitive effect of A. capillaris on F. ovina decreased with increasing doses of glyphosate. Furthermore, the importance of interspecific competition increased with the glyphosate dose. The results of the study of competitive interactions are in agreement with the observed plant community dynamics at the field site where F. ovina was found to be more dominant in plots treated with a relatively high dose of glyphosate. Importantly, the effects of glyphosate on the plant community dynamics critically depended on the effect of glyphosate on the plant competitive interactions. The study concludes that the current practice in the environmental risk assessment of non-target effects of herbicides, where single species are tested in the greenhouse, may be inadequate for assessing the effect of herbicides in semi-natural plant communities. The presented methods can be used for assessing the importance of competitive interactions for the sensitivity of non-target plants to herbicides in risk assessment.

Species-specific responses to community density in an unproductive perennial plant community.

Most studies of density dependent regulation in plants consider a single target species, but regulation may also occur at the level of the entire community. Knowing whether a community is at carrying capacity is essential for understanding its behaviour because low density plant communities may behave quite differently than their high density counterparts. Also, because the intensity of density dependence may differ considerably between species and physical environments, generalizations about its effects on community structure requires comparisons under a range of conditions. We tested if: (1) density dependent regulation occurs at the level of an entire plant community as well as within individual species; (2) the intensity (effect of increasing community density on mean plant mass) and importance (the effect of increasing density, relative to other factors, on mean plant mass) of competition increases, decreases or remains unchanged with increasing fertilization; (3) there are species-specific responses to changes in community density and productivity. In 63 1 m2 plots, we manipulated the abundance of the nine most common species by transplanting or removing them to create a series of Initial Community Densities above and below the average natural field density, such that the relative proportion of species was consistent for all densities. Plots were randomly assigned to one of three fertilizer levels. At the community level, negative density dependence of mean plant size was observed for each of the 4 years of the study and both the intensity and importance of competition increased each year. At the species level, most species' mean plant mass were negatively density dependent. Fertilizer had a significant effect only in the final year when it had a negative effect on mean plant mass. Our data demonstrate a yield-density response at the entire community-level using perennial plant species in a multi-year experiment.

Scanning electron microscopic investigations of root structural modifications arising from growth in crude oil-contaminated sand.

The choice of plant for phytoremediation success requires knowledge of how plants respond to contaminant exposure, especially their roots which are instrumental in supporting rhizosphere activity. In this study, we investigated the responses of plants with different architectures represented by beetroot (Beta vulgaris), a eudicot with a central taproot and many narrower lateral roots, and tall fescue (Festuca arundinacea), a monocot possessing a mass of threadlike fibrous roots to grow in crude oil-treated sand. In this paper, scanning electron microscopy was used to investigate modifications to plant root structure caused by growth in crude oil-contaminated sand. Root structural disorders were evident and included enhanced thickening in the endodermis, increased width of the root cortical zone and smaller diameter of xylem vessels. Inhibition in the rate of root elongation correlated with the increase in cell wall thickening and was dramatically pronounced in beetroot compared to the roots of treated fescue. The latter possessed significantly fewer (p < 0.001) and significantly shorter (p < 0.001) root hairs compared to control plants. Possibly, root hairs that absorb the hydrophobic contaminants may prevent contaminant absorption into the main root and concomitant axile root thickening by being sloughed off from roots. Tall fescue exhibited greater root morphological adaptability to growth in crude oil-treated sand than beetroot and, thus, a potential for long-term phytoremediation.

[Effects of Festuca arundinacea on the microbial community in crude oil-contaminated saline-alkaline soil].

By using the routine soil physical and chemical analysis methods and the Biolog technique, this paper studied the effects of Festuca arundinacea growth on the pH value, total salt content, and microbial community in the rhizosphere of crude dil-contaminated saline-alkaline soil in Songnen Plain of Northeast China. Crude oil contamination resulted in the increases of average well color development (AWCD), Shannon index (H), and carbon source utilization richness index (S), and altered the utilization patterns of carbon sources by the microbes. F. arundinacea had greater potential to remediate crude oil-contaminated soil. This plant could decrease the soil pH and soil total petroleum hydrocarbon (TPH) content, and increase the soil water content. The AWCD and S in F. arundinacea rhizosphere soil were obviously higher than those in the soil of naked land, providing a suitable environment for the growth and development of rhizosphere soil microbes.

Phytoremediation and removal mechanisms in Bouteloua curtipendula growing in sterile hydrocarbon spiked cultures.

Tolerance index and phytoremediation factors of side oats grama (Bouteloua curtipendula) with recalcitrant polycyclic aromatic hydrocarbons (PAH) phenanthrene (PHE), pyrene (PYR), and benzo[a]pyrene (BaP) and the resulting impact on phenotypic response, were evaluated in sterile conditions with whole plant growing in test-tube cultures with MS medium with PAH and compared with Tall fescue (Festuca arundinacea), control for this study. PAH mixture of PHE, PYR and BaP (1:1:1 w/w/w) blended with Maya crude oil (1:1 w/w), final concentration of 1500 mg kg(-1) was used. After 40 days, BaP removal, in the presence of Maya crude was superior compared with PHE and PYR removal Although the presence of PAH negatively affects the phenotypic response of the plants; sterile conditions experiments were helpful to evaluate phytoremediation factors to elucidate some important questions regarding phytoremediation mechanisms; in this study, B. curtipendula was able to phytostabilizate BaP associated to a significant hydrocarbon removal (57.4%) with high root accumulation but attenuated transport to stems, here reported as translocation factor. To our knowledge, this is the first time that quantifiable phytoremediation factors were used to evaluate the tolerance and removal capacity of a native semi-arid climate plant which is probably able to phytoremediate hydrocarbon contaminated soils.

Phytoremediation of an aged petroleum contaminated soil using endophyte infected and non-infected grasses.

Phytoremediation is a promising technique for cleaning petroleum contaminated soils. In this study, the effects of two grass species (Festuca arundinacea Schreb. and Festuca pratensis Huds.), infected (E(+)) and non-infected (E(-)) by endophytic fungi (Neotyphodium coenophialum and Neotyphodium uncinatum, respectively) on the degradation of petroleum hydrocarbons in an aged petroleum contaminated soil was investigated. Plants were grown in the soil for 7 months and unplanted soil considered as control. At the end of the experiment, total and oil-degrading bacteria, dehydrogenase activity, water-soluble phenols, total petroleum hydrocarbons (TPH) and polycyclic aromatic hydrocarbons (PAHs) contents were measured in the soil. The results demonstrated that E(+) plants contained more root and shoot biomass than E(-) plants and created higher levels of water-soluble phenols and dehydrogenase activity in the soil, while there was no significant difference in bacterial counts of planted soils. Planting stimulated total and oil-degrading bacterial numbers, dehydrogenase activity and the soil content of water-soluble phenols. Regardless of endophyte infection, PAH and TPH removal in the rhizosphere of plants were 80-84 and 64-72% respectively, whereas the removals in controls were 56 and 31%, respectively. It was revealed that TPHs in retention time range of n-alkanes with C(10)-C(25) chain lengths and TPH were more degraded in the rhizosphere of E(+) plants compared to E(-) ones. Thus, grasses infected with endophytic fungi could be more efficient for removal of TPH from oil-contaminated soils.

Litter decomposition and nitrogen and phosphorus dynamics in peatlands and uplands over 12 years in central Canada.

The large accumulation of organic matter in peatlands has been partially attributed to litter decomposition rates, which are slowed by a high water table. To test this, we examined whether there were significant differences in the decomposition and N and P dynamics of ten foliar litters and wood blocks at three pairs of upland forest and peatland sites in the transitional grassland, high boreal and low subarctic regions of central Canada, using litterbags collected over a 12-year period. At two of the three pairs, the decomposition rate, as determined by proportion of the original mass remaining after 12 years and by the exponential decay coefficient (k), was faster overall at the upland than at the peatland. In the third pair, there was no significant difference, despite the water table being close to the peat surface; warmer soil temperatures in the peatland than the upland may be the cause. In general, there were small losses or gains of N in the litters after 12 years, compared to the original litter, though there were some differences among litter types and sites, net gains in N likely reflecting the higher exogenous N availability. P was lost from most litters at the two northern pairs of sites, but at the transitional grassland pair, there were large net gains in P and greater variation among litters. The N:P ratio in the original litters ranged from 5 to 26 and after 12 years the ratio narrowed, with the site average of the ten litters ranging from 13 to 22, varying with the soil ratio. Decomposition rates and N and P dynamics after 12 years are different between upland and peatland sites: although the water table is a primary control on these differences, other factors such as temperature and soil nutrient status are also important.

Ground cover impacts on sediment and phosphorus export from manured riparian pasture.

Maintaining pasture ground cover is important in preventing environmental degradation of grasslands and associated riparian areas. The objective of this work was to determine the effect of ground cover on sediment and P export from pastured riparian areas under simulated rainfall events. Plots were established on two sites in the North Carolina Piedmont: a 10% slope with Appling sandy loam soils (fine, kaolinitic, thermic Typic Kanhapludults) and a 20% slope with Wedowee sandy loam soils (fine, kaolinitic, thermic Typic Kanhapludults), both with mixed tall fescue (Festuca arundinacea Schreb.)-dallisgrass (Paspalum dilatatum Poir.) vegetation. Existing forage stands were modified to represent a range of ground cover levels: 0, 45, 70, and 95% (bare ground, low, medium, and high cover, respectively), and amended with beef steer (Bos taurus) feces and urine (about 10 kg P ha(-1)). Mean runoff volume from bare ground was generally twice that observed from low, medium, and high levels of cover, which were similar. For all rainfall events combined, export of dissolved reactive P was greatest (P < 0.1) at bare ground and was reduced 31% at low cover, which did not differ from medium or high cover. Mean total Kjeldahl P export was greater (P < 0.001) from bare ground than from other cover levels. Results indicate that riparian bare areas can contribute substantial sediment (>215 kg ha(-1)) and P (0.7 kg P ha(-1)) to surface waters during heavy rainfall, whereas export may be reduced equally well by low cover (45%) as by high cover.

[Allelopathy of aqueous extract from Ligularia virgaurea, a dominant weed in psychro-grassland, on pasture plants].

Ligularia virgaurea is a noxious weed widely distributed in the alpine grassland of east Qinghai-Tibet Plateau of China. This paper studied the allelopathy of its aqueous extract on the pasture plants Festuca sinensis, Bromus magnus, Elymus nutans, Poa annua, and F. ovina in the region. The mean response index (RI) values of the pasture plants were calculated, and used to quantitatively assess the allelopathic sensitivity of the receptors at three levels, i. e., growth items, development stages, and species. Corresponding values of the weed were also treated in similar way to assess the allelopathic potential of the donor. The results showed that the allelopathic sensitivity was in the order of P. annua > B. magnus > F. sinensis > F. ovina > E. nutans. Both the seed germination and the seedling growth of test pasture plants were inhibited at species level, suggesting that rain eluviation was one of the means by which the weed released allelochemicals. The aqueous extracts from L. virgaurea root and leaf had a significant inhibitory effect at species level, and the effect of root extract was stronger than that of leaf extract, suggesting the competition among species on the underground resources in natural grassland. Allelopathy played an important role in L. virgaurea invasion, and might be responsible to the formation of mono-dominant community and the degeneration of grassland.

Field evaluation of in situ remediation of a heavy metal contaminated soil using lime and red-mud.

We evaluated the effectiveness of lime and red mud (by-product of aluminium manufacturing) to reduce metal availability to Festuca rubra and to allow re-vegetation on a highly contaminated brown-field site. Application of both lime and red mud (at 3 or 5%) increased soil pH and decreased metal availability. Festuca rubra failed to establish in the control plots, but grew to a near complete vegetative cover on the amended plots. The most effective treatment in decreasing grass metal concentrations in the first year was 5% red mud, but by year two all amendments were equally effective. In an additional pot experiment, P application in combination with red mud or lime decreased the Pb concentration, but not total uptake of Pb in Festuca rubra compared to red mud alone. The results show that both red mud and lime can be used to remediate a heavily contaminated acid soil to allow re-vegetation.

Phytoremediation management of selenium-laden drainage sediments in the San Luis Drain: a greenhouse feasibility study.

An estimated 100,000m(3) selenium (Se)-laden drainage sediment resides in the San Luis Drain (SLD) of Central California. This greenhouse study was undertaken to evaluate the feasibility of growing salt- and boron-tolerant plant species in sediment for reduction of Se content by plant extraction. Drainage sediment was collected from the SLD and mixed with control soil (i.e., uncontaminated soil) to the following ratios (sediment:control soil) by volume: 0:3 (i.e., control soil only), 1:2 (i.e., 1/3 sediment and 2/3 control soil), 2:1 (i.e., 2/3 sediment and 1/3 control soil), and 3:0 (i.e., sediment only). Salt-tolerant plant species consisted of canola (Brassica napus var. Hyola 420), tall fescue (Festuca arundinacea var. Au Triumph), salado grass (Sporobulus airoides), and cordgrass (Spartina patens var. Flageo). Increased ratios of sediment:soil resulted in decreased dry matter production for all tested plant species; especially at ratios of sediment:soil greater than 1:2. Plant Se concentrations (mgkg(-1) DM) ranged as follows for plant species at all ratios of sediment:soil: canola (51-72), tall fescue (16-36), and cordgrass and salado grass (9-14). Total Se concentrations in the soil were at least 20% lower at postharvest compared to preplant concentrations for all plant species at each ratio of sediment:soil. In contrast, water-extractable Se concentrations in the soil were at least three times higher at postharvest than at preplant for all plant species, irrespective of the ratio of sediment:soil. Leaching of Se occurred in irrigated bare pots from each respective ratio of sediment:soil over a duration of 60 days. Based upon the downward movement of Se in bare pots of sediment:soil, it may be more prudent to leave the drainage sediment in the SLD, incorporate clean soil, and then grow low maintenance salt-tolerant plants (e.g., cordgrass, salado grass) in the concrete-lined canal. By this means, possible contamination of groundwater with soluble Se will be eliminated, while phytoremediation slowly reduces Se content in the drainage sediment.

Stabilization of metals in acidic mine spoil with amendments and red fescue (Festuca rubra L.) growth.

Stabilization of metals with amendments and red fescue (Festuca rubra, cv. Keszthelyi 2) growth was studied on an acidic and phytotoxic mine spoil (pH(KCl) 3.20-3.26; Cd 7.1 mg kg(-1), Cu 120 mg kg(-1), Pb 2154 mg kg(-1) and Zn 605 mg kg(-1)) from Gyöngyösoroszi, Hungary in a pot experiment. Raising the pH above 5.0 by lime (CaCO(3)), and supplementing with 40 mg kg(-1)nitrogen (NH(4)NO(3)) made this material suitable for plant growth. All cultures were limed with 0.5% (m/m) CaCO(3) (treatment 1), which was combined with 5% (m/m) municipal sewage sludge compost (treatment 2), 5% (m/m) peat (treatment 3), 7.5% (m/m) natural zeolite (clinoptilolite) (treatment 4), and 0.5 (m/m) KH(2)PO(4) (treatment 5). Treatments 1-5 were combined with each other (treatment 6). After 60 days of red fescue growth, pH of the limed mine spoil decreased in all cultures units. Application of peat caused the highest pH decrease (1.15), while decrease of pH was less than 0.23 in treatments 2, 5 or 6. Application of lime significantly reduced concentrations of metals in the 'plant available' fraction of mine spoil compared to non-limed mine spoil. Amendments added to limed mine spoil changed variously the ratio of Cd, Cu, Pb and Zn in exchangeable or 'plant available' fractions, differently influencing the phytoavailability of these metals. Most of the metals were captured in the roots of test plants. Treatment 2 caused the appearance of less Cd in shoots (<0.1 microg g(-1)) or roots (3.11 microg g(-1)), while treatment 5 resulted in the highest Cd concentration (2.13 microg g(-1)) in shoots. Treatments did not influence significantly the Cu accumulation in shoots. The Pb accumulation of roots (44.7 microg g(-1)) was most effectively inhibited by combined treatment, while the highest value (136 microg g(-1)) was found in the culture treated with potassium phosphate. Pb concentration in shoots was below the detection limit, except for treatments 5 and 6. Peat application resulted in higher Zn concentration (448 microg g(-1)) in shoots than other amendments, where these values were around 100 microg g(-1). All amendments influenced positively the dry matter yield of red fescue grown in limed mine spoil, however the application of 0.5 phosphate was less favourable. Liming, application of amendments and growth of red fescue can stabilize metals in acidic and phytotoxic mine spoil, and by phytostabilization they can reduce the risk of metal contamination of the food chain.

Surface runoff losses of phosphorus from Virginia soils amended with turkey manure using phytase and high available phosphorus corn diets.

Many states have passed legislation that regulates agricultural P applications based on soil P levels and crop P uptake in an attempt to protect surface waters from nonpoint P inputs. Phytase enzyme and high available phosphorus (HAP) corn supplements to poultry feed are considered potential remedies to this problem because they can reduce total P concentrations in manure. However, less is known about their water solubility of P and potential nonpoint-source P losses when land-applied. This study was conducted to determine the effects of phytase enzyme and HAP corn supplemented diets on runoff P concentrations from pasture soils receiving surface applications of turkey manure. Manure from five poultry diets consisting of various combinations of phytase enzyme, HAP corn, and normal phytic acid (NPA) corn were surface-applied at 60 kg P ha(-1) to runoff boxes containing tall fescue (Festuca arundinacea Schreb.) and placed under a rainfall simulator for runoff collection. The alternative diets caused a decrease in manure total P and water soluble phosphorus (WSP) compared with the standard diet. Runoff dissolved reactive phosphorus (DRP) concentrations were significantly higher from HAP manure-amended soils while DRP losses from other manure treatments were not significantly different from each other. The DRP concentrations in runoff were not directly related to manure WSP. Instead, because the mass of manure applied varied for each treatment causing different amounts of manure particles lost in runoff, the runoff DRP concentrations were influenced by a combination of runoff sediment concentrations and manure WSP.

Laboratory assessment of the allelopathic effects of fine leaf fescues.

Laboratory screening studies were conducted to evaluate the allelopathic potential of fine leaf fescues. Of the seven accessions selected from prior field evaluations for weed-suppressive ability, all inhibited root growth of large crabgrass and curly cress in laboratory assays. Grown in agar as a growth medium and in the presence of living fescue seedlings for 14 or 21 days, test species were sensitive depending on the fescue cultivars. Growth inhibition increased when fescue was grown for increasing periods of time in agar. Seedling fescues produced significant quantities of bioactive root exudates, which were released into the agar medium. Bioactive root exudates were extracted from living fescue roots by using methylene chloride. Shoot tissue was extracted in water and the aqueous extract was partitioned against hexane, ethyl acetate, and methylene chloride. Extracts were tested for inhibitory activity on seedling growth as measured by inhibition of curly cress germination and radicle elongation. Root exudates were more toxic (70% inhibition) than shoot extracts (up 40% inhibition), when formulated at 0.25 mg/ml concentration. Light microscopy and transmission electron microscopy were utilized in an attempt to identify the cellular location of production of secondary products contained in bioactive root exudates. Ultrastructural analysis indicated that the exudate is produced in actively dividing tips of fibrous root cells. The mode of release of these exudates into the environment remains unknown.

Compost and calcium surface treatment effects on subsoil chemistry in acidic minespoil columns.

Surface incorporation of a liming agent in combination with compost or biosolids is a proven way to revegetate acidic minespoils, but little is known about the effect of the surface amendments on subsoil chemistry. We conducted a greenhouse column experiment to investigate how different surface amendments affected plant growth and subsoil chemistry in highly acidic minespoil material. Columns were filled with shale minespoil material (pH approximately 2.5), amended with CaCO3, CaSO4 x 2H2O (gypsum), and two rates of compost, and seeded with birdsfoot trefoil (Lotus corniculatus L.) and 'Kentucky 31' tall fescue (Festuca arundinacea Schreb.). We measured leachate and plant growth over a 170-d period with extensive irrigation. Without CaCO3, plants could only grow at the high compost rate (68.8 g kg(-1)), even though the soil pH in those treatments was below 3.5, indicating the capability of natural organic matter to detoxify Al(3+) by forming Al-organic matter complexes. Compost had no effect on the subsoil. When CaCO3 or gypsum was added to the surface, extractable Ca increased in the subsoil, but there was no relevant increase in subsoil pH. Even in the first 5 cm of subsoil material, extractable Al did not decrease very much, possibly because a jurbanite-like solid phase controlled subsoil Al(3+) activities. During the reclamation of highly acidic minespoil material one should therefore not expect significant effects of the surface treatment on the untreated subsoil. A sufficient root zone would have to be achieved by incorporating the liming agent down to the desired rooting depth.