Concentrations In Ryegrass Research Articles

Investigating the Mechanism of Cadmium-Tolerant Bacterium Cellulosimicrobium and Ryegrass Combined Remediation of Cadmium-Contaminated Soil.

Cadmium (Cd) pollution has been rapidly increasing due to the global rise in industries. Cd not only harms the ecological environment but also endangers human health through the food chain and drinking water. Therefore, the remediation of Cd-polluted soil is an imminent issue. In this work, ryegrass and a strain of Cd-tolerant bacterium were used to investigate the impact of inoculated bacteria on the physiology and biochemistry of ryegrass and the Cd enrichment of ryegrass in soil contaminated with different concentrations of Cd (4 and 20 mg/kg). The results showed that chlorophyll content increased by 24.7% and 41.0%, while peroxidase activity decreased by 56.7% and 3.9%. In addition, ascorbic acid content increased by 16.7% and 6.3%, whereas glutathione content decreased by 54.2% and 6.9%. The total Cd concentration in ryegrass increased by 21.5% and 10.3%, and the soil's residual Cd decreased by 86.0% and 44.1%. Thus, the inoculation of Cd-tolerant bacteria can improve the antioxidant stress ability of ryegrass in Cd-contaminated soil and change the soil's Cd form. As a result, the Cd enrichment in under-ground and above-ground parts of ryegrass, as well as the biomass of ryegrass, is increased, and the ability of ryegrass to remediate Cd-contaminated soil is significantly improved.

Enhanced cadmium phytoextraction efficiency of ryegrass (Lolium perenne L.) by porous media immobilized Enterobacter sp. TY-1

Although studies on immobilized microorganisms have been conducted, their performance remains unclear for enhancing plants to remediate cadmium (Cd)-contaminated soil. In this study, a Cd-resistant strain TY-1 with good plant growth promotion traits was immobilized by biochar (BC) or oyster shell (OS) power to strengthen ryegrass to remediate Cd-contaminated soil. SEM-EDS combined with FTIR showed that TY-1 could tolerate Cd toxicity by surface precipitation, and functional groups such as hydroxyl and carbonyl groups might be involved. In the biocomposite treatments, soil pH increased, and the activity of fertility-related enzymes such as dehydrogenase increased by 109.01%–128.01%. The relative abundance of genus Saccharimonadales decreased from 7.97% to 3.35% in BS-TY and 2.61% in OS-TY, respectively. Thus, a suitable environment for ryegrass growth was created. The fresh weight, dry weight, plant height and Cd accumulation of ryegrass in TY treatment increased by 122.92%, 114.81%, 42.08% and 8.05%, respectively, compared to the control. Cd concentration in ryegrass was further increased in BC-TY and OS-TY by 24.14% and 40.23%, respectively. The improvement in soil microcosm and plant biomass forms an ongoing virtuous cycle, demonstrating that using carrier materials to improve the efficiency of microbial-assisted phytoremediation is realistic and feasible.

Synergistic effect of Si and K in improving the growth, ion distribution and partitioning of Lolium perenne L. under saline-alkali stress

The application of Si or K has proven to be beneficial for the growth of plants under saline-alkali stress. However, the synergistic effect of Si and K in improving the growth, ion distribution, and partitioning in Lolium perenne L. under saline-alkali stress remains unclear. In this study, the growth characteristics and ion-selective absorption of ryegrass (Lolium perenne L.) exposed to different levels of saline-alkali stress were evaluated. The growth parameters of ryegrass were significantly improved when Si was applied by itself or coupled with K under low saline-alkali stress. Under a high saline-alkali level, only simultaneous application of Si and K could significantly improve the growth of ryegrass. When Si and K were applied together, the K+/Na+ and Ca2+/Na+ ratios in root, stem, and leaf of ryegrass were maximally improved as compared to the individual treatments and control. The K+ and Ca2+ concentrations in the vacuole, cell wall, and organelle of leaf were increased dramatically. This improvement was due to the ability of applied ions to compete with Na+, allowing the plant to maintain osmotic potential and leaf water content. The concentration of Na+ was significantly reduced when Si and K were applied and mainly concentrated in the soluble fraction and cell wall. The Si concentration in ryegrass increased markedly by the combined application of Si and K, and most of it was accumulated in the cell wall and soluble fraction, which could help in chlorophyll synthesis, reduce membrane injury, and increase water absorption under saline-alkali stress. This study emphasized the advantage of Si and/or K on the growth of plants under different saline-alkaline levels and provided a guide for the production of Si-K fertilizer and its application in saline-alkali soil.

A potential method using magnetically modified wheat straw biochars for soil Cd extraction

Every year, hundreds of millions of tons of straw are produced by wheat planting all over the world. In this work, a potential method using wheat straw to produce magnetic sorbents for soil Cd extraction was studied. Wheat straw chips were pyrolyzed at 300 and 700 °C and then mixed with Fe3+/Fe2+ solution for magnetization. The obtained magnetically modified biochars (MMBs) were applied to two Cd-contaminated paddy soils. During a 30-day experiment, MMB recovery from soils by a magnetic rod decreased over time, ranging from 62% to 100% for MMB300 and from 36% to 65% for MMB700. At the end, extraction efficiency of Cd from soils by the MMBs ranged from 21.5% to 31.5%, which was related to sorption capacity of Cd by MMB, recovery percentage of MMB from soils and distribution of Cd fractions in soils. Cd in the exchangeable fraction was more easily extracted by the MMBs (46–78%) than the other Cd fractions. Furthermore, extracting Cd from soils by the MMBs reduced Cd concentration in ryegrass by about 70%, which was largely related to the decrease of soil exchangeable fraction. These findings demonstrate the efficient remediation of Cd-contaminated soils by MMB extraction and meanwhile provide some guidance for further optimization of MMB properties.

Removal of lead from two polluted soils by magnetic wheat straw biochars

Due to high sorption capacity for heavy metals, magnetic biochar (MBC) has the potential to adsorb heavy metals in soils, which are then removed together with MBC from soils by a magnetic field. In this study, two magnetic biochars (MBC300 and MBC700) were derived from the magnetization of wheat straw biochars pyrolyzed at 300 and 700 °C. Strong binding of Pb with iron oxide particles deposited on biochar was observed. After the MBCs (7.5%, w/w) were applied to two naturally Pb-polluted soils (named as He-soil and Hu-soil) for 720 h, the removal efficiency of Pb from the soil by MBC300 (26.8–40.1%) was similar (p > 0.05) to that by MBC700 (25.1–42.1%). This is because MBC300 has lower sorption capacity for Pb but higher recovery percentage from soils as a result of lower saturation magnetization. The removal efficiencies of Pb by the two MBCs were 13–17% higher for He-soil than for Hu-soil, which was due to higher proportion of mobile forms of Pb in He-soil (82.3%) than in Hu-soil (51.5%). Spectroscopic analysis indicated that Pb in soils tended to bind onto the surface of MBC in more stable forms. Moreover, removing Pb from soils by MBC could decrease Pb concentration in ryegrass by about 30%. Therefore, it might be a potential method to remedy Pb-polluted soils.

Heavy metal phytoavailability in a contaminated soil of northeastern Oklahoma as affected by biochar amendment.

High concentrations of heavy metals (HM) in soils have negative impacts on plants, human health, and the environmental quality. The purpose of this study was to evaluate the effects of biochars on the bioaccessibility of Zn, Pb, and Cd in a contaminated soil in the Tar Creek area of NE Oklahoma, as well as on the growth and uptake of these elements by perennial ryegrass (Lolium perenne). Biochars were produced from switchgrass (SGB) and poultry litter (PLB) feedstocks at 700 °C and applied to the soil at 0.0, 0.5, 1.0, 2.0, and 4.0% (w/w), with three replications. Regardless of the feedstock, both soil organic carbon (SOC or OC) and pH increased as the rates of biochars increased, which significantly decreased the HM bioaccessibility (p < 0.01). The Zn and Cd extracted by DTPA were highly correlated (p < 0.0001) with their concentration in ryegrass shoots and roots. Except for some significant positive correlations (p < 0.05), HM concentrations in ryegrass shoots and roots were not correlated with their biomass (p > 0.05). Both bioconcentration factor (BCF) and transfer factor decreased as the rates of biochars applied increased, especially for Pb and Cd (p < 0.01). Our results suggest it is beneficial to use biochars at Tar Creek as a soil amendment to reduce HM bioaccessibility and metal uptake by ryegrass.

Influence of amendments on metal environmental and toxicological availability in highly contaminated brownfield and agricultural soils.

The immobilizing effects of wood biochar (BW2%) and iron grit (Z1%) applied alone or in combination (BW2% + Z1%) to agricultural (M750) and brownfield (MAZ) soils highly contaminated by metals were assessed in a greenhouse experiment. The results showed that Z1% and BW2% + Z1% were the most efficient amendments to reduce Cd, Cu, Pb, and Zn mobility, environmental availability, and phytoavailability in the M750 soil. The oxidation of Z1% allowed part of the Cu and Zn pools present in exchangeable or carbonate-bound forms (labile fraction) to complex in less mobile forms. In this soil, the metal chemical extractions (0.01 M CaCl2 and 0.05 M EDTA) and the DGT (diffusive gradient in thin films) devices to assess metal in soil solution and soil pore water (SPW) also highlighted the immobilizing characteristic of Z1%. In most cases, the addition of BW2% to Z1% (BW2% + Z1%) did not improve this effect, except for the dissolved Pb and Zn concentrations in the M750 soil solution. It was also observed that Cd, Pb, and Zn passed throughout DGT mimicking the biological cell membrane were reduced by all amendments of the M750 soil corroborating metal concentrations measured in rye grass shoots. In the MAZ soil, metals were less available as shown by their low extractability rate, low capacity of metal resupply from the solid phase to pore water, and low phytoavailability. The poor metal availability could be explained by the high levels of carbonate and organic matter contents in this soil. Nevertheless, a decrease of the Cu environmental availability and the Cu concentrations in rye grass shoots grown on the MAZ soil was also observed in the soil amended with Z1% alone or in combination with BW2%. From a health point of view, the most effective amendment to reduce human exposure through ingestion of soil particles for the M750 and MAZ soils was BW2% for Cd and BW2% + Z1% for Pb. However, the presence of rye grass minimized the amendments' beneficial effects.

Investigate the influence of halloysite and activated carbon mixtures in phytostabilization of Pb-contaminated soil with Lolium perenne L.

Abstract A pot experiment was conducted to investigate the effects of halloysite and activated carbon mixtures on the biomass and distribution of macronutrients (Mg, K, Ca, Na, P) in ryegrass grown in Pb-contaminated soil. The soil was spiked with four different levels of lead contamination, i.e. 0 (control), 200, 400, 800 mg·kg−1 were applied in an analytical grade Pb(NO3)2 solution mixed thoroughly with the soil. Raw halloysite (3%) and activated carbon (1% relative to soil mass) mixtures were used to reduce the effect of soil lead contamination. Ryegrass of the Bokser variety was harvested after 42 days, and soil samples were collected for laboratory tests. The mixture of sorbents applied in the experiment which turned out to be most effective at doses of lead amounting to 400 and 800 mg·kg−1 of soil, with the increase in the yield of ryegrass being the highest. Increasing contamination of soil with lead in the series without the mixture of sorbents increased the contents of phosphorus, sodium, calcium and magnesium in ryegrass. The applied mixture of halloysite and activated carbon changed the macronutrient concentration in ryegrass, with the greatest changes found in that of potassium and sodium.

Silicon-Mediated Alleviation of Aluminum Toxicity by Modulation of Al/Si Uptake and Antioxidant Performance in Ryegrass Plants.

Silicon (Si) has been well documented to alleviate aluminum (Al) toxicity in vascular plants. However, the mechanisms underlying these responses remain poorly understood. Here, we assessed the effect of Si on the modulation of Si/Al uptake and the antioxidant performance of ryegrass plants hydroponically cultivated with Al (0 and 0.2 mM) in combination with Si (0, 0.5, and 2.0 mM). Exposure to Al significantly increased Al concentration, mainly in the roots, with a consequent reduction in root growth. However, Si applied to the culture media steadily diminished the Al concentration in ryegrass, which was accompanied by an enhancement in root dry matter production. A reduced concentration of Si in plant tissues was also observed when plants were simultaneously supplied with Al and Si. Interestingly, Si transporter genes (Lsi1 and Lsi2) were down-regulated in roots after Si or Al was applied alone; however, both Lsi1 and Lsi2 were up-regulated as a consequence of Si application to Al-treated plants, denoting that there is an increase in Si requirement in order to cope with Al stress in ryegrass. Whereas Al addition triggered lipid peroxidation, Si contributed to an attenuation of Al-induced oxidative stress by increasing phenols concentration and modulating the activities of superoxide dismutase (SOD), catalase, peroxidase, and ascorbate peroxidase antioxidant enzymes. Differential changes in gene expression of SOD isoforms (Mn-SOD, Cu/Zn-SOD, and Fe-SOD) and the profile of peroxide (H2O2) generation were also induced by Si in Al-stressed plants. This, to the best of our knowledge, is the first study to present biochemical and molecular evidence supporting the effect of Si on the alleviation of Al toxicity in ryegrass plants.

Production of Biomass Crops Using Biowastes on Low-Fertility Soil: 2. Effect of Biowastes on Nitrogen Transformation Processes.

Increasing production of biowastes, particularly biosolids (sewage sludge), requires sustainable management strategies for their disposal. Biosolids can contain high concentrations of nutrients; hence, land application can have positive effects on plant growth and soil fertility, especially when applied to degraded soils. However, high rates of biosolids application may result in excessive nitrogen (N) leaching, which can be mitigated by blending biosolids with other biowastes, such as sawdust. We aimed to determine the effects of biosolids and sawdust on growth and N uptake by sorghum, rapeseed, and ryegrass as well as N losses via leaching. Plants were grown in a greenhouse over a 5-mo period in a low-fertility soil amended with biosolids (1250 kg N ha), biosolids-sawdust (0.5:1), or urea (200 kg N ha). Urea application increased biomass production of sorghum and ryegrass but proved insufficient for rapeseed on low-fertility soil. Biosolids application increased plant N concentrations in ryegrass and rapeseed and increased N uptake into the seeds of sorghum, increasing seed quality. Biosolids application did result in lower N leaching compared with urea, irrespective of plant species, and N leaching was unaffected by mixing the biosolids with sawdust. There was an indication of biological nitrification inhibition in the rhizosphere of sorghum. Rapeseed had similar growth and N uptake into biomass in biosolids and biosolids-sawdust treatments and hence was the most promising species with regard to recycling fresh sawdust in combination with high rates of biosolids on low-fertility soil.

Temperature and Plant Genotype Alter Alkaloid Concentrations in Ryegrass Infected with an Epichloë Endophyte and This Affects an Insect Herbivore.

Asexual Epichloë endophytes colonize agricultural forage grasses in a relationship which is mutually beneficial and provides the host plant with protection against herbivorous insects. The endophyte strain AR37 (Epichloë festucae var. lolii) produces epoxy-janthitrem alkaloids and is the only endophyte known to provide ryegrass with resistance against porina larvae (Wiseana cervinata (Walker)), a major pasture pest in cooler areas of New Zealand. This study examined the effect of temperature on concentrations of epoxy-janthitrems in AR37-infected ryegrass and determined how the resulting variations in concentration affected consumption, growth and survival of porina larvae. Twenty replicate pairs of perennial (Lolium perenne L.) and Italian ryegrass (L. multiflorum Lam.) plants with and without endophyte were prepared by cloning, with one of each pair grown at either high (20°C) or low (7°C) temperature. After 10 weeks, herbage on each plant was harvested, divided into leaf and pseudostem, then freeze dried and ground. Leaf and pseudostem material was then incorporated separately into semi-synthetic diets which were fed to porina larvae in a bioassay over 3 weeks. Epoxy-janthitrem concentrations within the plant materials and the semi-synthetic diets were analyzed by high performance liquid chromatography. AR37-infected ryegrass grown at high temperature contained high in planta concentrations of epoxy-janthitrem (30.6 μg/g in leaves and 83.9 μg/g in pseudostems) that had a strong anti-feedant effect on porina larvae when incorporated into their diets, reducing their survival by 25–42% on pseudostems. In comparison, in planta epoxy-janthitrem concentrations in AR37-infected ryegrass grown at low temperature were very low (0.67 μg/g in leaves and 7.4 μg/g in pseudostems) resulting in a small anti-feedant effect in perennial but not in Italian ryegrass. Although alkaloid concentrations were greatly reduced by low temperature this reduction did not occur until after 4 weeks of exposure. Alkaloid concentrations were slightly lower in Italian than in perennial ryegrass and concentrations were higher in the pseudostems when compared with the leaves. In conclusion, epoxy-janthitrems expressed by the AR37 endophyte show strong activity against porina larvae. However, when ryegrass plants are grown at a constant low temperature for an extended period of time in planta epoxy-janthitrem concentrations are greatly reduced and are less effective against this pasture pest.

Comparing response of ryegrass-white clover pasture to gibberellic acid and nitrogen fertiliser applied in late winter and spring

ABSTRACTThe objective of this study was to compare the effect of one or two applications of gibberellic acid (GA) or nitrogen (N) fertiliser on dry matter (DM) yield and composition of perennial ryegrass-white clover pasture. Pasture was treated with 0 or 8 g a.i./ha of GA and 0 or 50 kg/ha N fertiliser in a 2 × 2 factorial design in late winter and spring. One application of N fertiliser increased DM yield by increasing leaf mass and tiller density of perennial ryegrass while one application of GA increased DM yield by increasing perennial ryegrass and white clover yield. There was no DM yield response to two applications of GA, though two applications of N did increase DM yield. A single GA application in late winter increased fibre and reduced protein concentration in ryegrass. The use of GA to increase DM yield with reduced herbage protein concentration may have reduced environmental impact through reducing N intake of livestock.

Ergovaline, an endophytic alkaloid. 2. Intake and impact on animal production, with reference to New Zealand

On the basis of published reports, the daily intake of the alkaloid ergovaline from the consumption of endophyte-containing ryegrass in New Zealand ranges from 0.008 to 0.287 mg ergovaline/kg LW0.75.day. Most of the reports are based on the use of standard endophyte-containing ryegrass and, thus, it is difficult to disassociate the impact of ergovaline consumption from that of lolitrem B. However, physiological effects of ergovaline consumption, such as reduced circulating prolactin concentration, vasoconstriction and elevated core temperature, have been detected at fairly low ergovaline intake, whereas decreased feed intake, liveweight gain and milk production have not generally been observed in animals at an intake below 0.07 mg ergovaline/kg LW0.75.day. Intakes above this value represent only 17% of published values. There are insufficient data to suggest a threshold ergovaline intake associated with heat stress with animal-welfare implications. The relationship between published ergovaline intake and the corresponding ergovaline concentration in pasture is poor (R2 = 0.48), but on average an intake of 0.07 ergovaline/kg LW0.75.day is associated with an ergovaline concentration in ryegrass of 0.70 mg/kg DM. About 16–18% of published ergovaline concentrations in ryegrass pasture exceed this value. The ergovaline concentration in ryegrass is greater in the basal parts of the plant than in the leaf and during the late summer–autumn than in spring. Animals grazing in the lower sward horizons (horizontal grazing plane) are more at risk of high ergovaline intake, although the reduction in grazing intake induced by grazing at low pasture height aids in limiting ergovaline intake. As pasture growth rates decline in late summer, supplementary feed may be used to maintain stocking rate and, if such feeds have zero ergovaline concentration, they serve to dilute the mean dietary ergovaline intake. Ergovaline-containing ryegrass pastures are widely used in New Zealand. It appears that farmers consider the risks of depressed animal production on these pastures to be less than the benefits ergovaline bestows through its deterrent effect of specific insect attack and thus greater survival and pasture persistence.

Efficient remediation of PAH-metal co-contaminated soil using microbial-plant combination: A greenhouse study

A 2-year greenhouse study was conducted to remediate an actual wastewater-irrigated soil co-contaminated with polycyclic aromatic hydrocarbons (PAHs) and heavy metals (Cd and Zn). The remediation methods included microbial remediation, phytoremediation, and microbe-assisted phytoremediation. The maximum PAH removal (96.4%), PAH mineralization, and metal phytoextraction (36.1% Cd and 12.7% Zn) were obtained by interplanting ryegrass with Seduce alfredii with regular re-inoculation with Microbacterium sp. KL5 and Candida tropicalis C10 in the co-contaminated soil. The plants shoots were harvested at a 4-month interval. After 2 years, the concentrations of 16 individual PAHs were reduced to below the limit of Chinese soil quality standard for agricultural use (grade II, pH 6.5–7.5), and the metal concentrations in ryegrass shoots were below the Chinese national limit for animal feeds (GB13078-2001). The exogenous microbes gradually disappeared with time, and thus a 2-month re-inoculation interval was applied for a purpose to maintain high cell density and activity of the inoculants. KL5 introduction increased soil enzyme activity, plant growth, PAH removal and metal phytoextraction, while C10 promoted soil enzyme activity and removal of high-molecular-weight PAHs. Interplanting with S. alfredii reduced metal concentrations in ryegrass tissues. Ryegrass showed stronger rhizosphere effects than S. alfredii did.

Responses of Ryegrass (Lolium perenne L.) Grown in Mudflats to Sewage Sludge Amendment

Sewage sludge amendment (SSA) is an alternative waste disposal technique and a potential way to increase fertility of mudflats for crop growth. The present study aimed to assess the suitability of SSA by assessing the nitrogen (N) and phosphorous (P) uptakes, heavy metal accumulation, growth, biomass, and yield response of ryegrass (Lolium perenne L.) at 0, 30, 75, 150, and 300 t ha−1 SSA rates at various growth stages. The results showed that the highest biomass of ryegrass at seedling and vegetative stages were at 300 and 150 t ha−1 SSA rate, respectively. The increments of ryegrass yield at reproductive stage at 30, 75, 150, and 300 t ha−1 SSA rates were 98.0, 122.6, 88.1, and 61.2%, compared to unamended soil. N and P concentrations in ryegrass increased with increasing SSA rates at all stages except N and P in roots dropped significantly at 300 t ha−1 rate at vegetative stage. The metal concentration for Mn, Cu, Zn, Ni, Cd, Cr, and Pb in shoot of ryegrass at 300 t ha−1 SSA rate increased by 0.63-, 2.34-, 15.02-, 0.97-, 10.00-, 0.01- and 1.13-fold, respectively, compared to unamended soil. However, heavy metal concentrations in shoot of ryegrass were lower than the standard for forage products in China. The study suggested that sewage sludge amendment in mudflat soils might be feasible. However, the impacts of sludge application on edible crop plants and soil environment need further investigations.

Evaluation of Different Amendments to Stabilize Cadmium, Zinc, and Copper in a Contaminated Soil: Influence on Metal Leaching and Phytoavailability

The contamination of soils with heavy metals is a global disaster that is related to human activities. Phytostabilization basically refers to the use of metal-tolerant plants and inexpensive mineral or organic soil amendments to reduce the concentrations or toxic effects of contaminants in the environment. Here, we tested the effects of four cost-effective amendments (CaCO3, phosphate rock, activated carbon, and exhausted olive cake ash) on Cd, Zn, and Cu leaching and uptake by ryegrass (Lolium perenne L.). The results showed that all amendments reduced Cd, Zn, and Cu leaching, mainly due to the alkalinity increase. Among all amendments tested, CaCO3 was the most effective treatment in decreasing both the heavy-metal leaching and concentrations in ryegrass shoots. Results obtained suggest the efficacy of several amendments, but further work is needed to gain insight into their possible synergetic effects.

Evaluation of fermentation parameters, microbiological composition and aerobic stability of grass and whole crop maize silages treated with microbial inoculants

experiments were conducted in 2011-2012 to evaluate the fermentation parameters, microbiological composition and aerobic stability of grass and whole crop maize silages treated with microbial inoculants, different blends of the selected bacterial strains and blend of the selected bacterial strains in combination with sodium benzoate. Wilted ryegrass:timothy and whole crop maize with 265 and 276 g kg -1 dry matter (DM) content were ensiled in 3 litre laboratory silos. The mean water soluble carbohydrate (WSC) concentration, buffer capacity and nitrate concentration in ryegrass:timothy and whole crop maize were 101.8 and 98.9 g kg -1 DM, 355 and 217 mEq kg -1 DM, and 153.2 and 841.1 mg kg -1 DM, respectively. Silages treated with the tested inoculants were characterized by higher concentrations of DM compared with the untreated silage. Ryegrass:timothy and maize herbage inoculant treatments before ensiling significantly decreased (P < 0.05) pH, significantly reduced butyric acid, ammonia-N concentrations and DM loss compared with control silage. Ryegrass:timothy and maize silages inoculated with homofermentative bacteria blends produce higher (P < 0.05) lactic acid compared with that of the control silage. Butyric acid, alcohols and N-NH 3 fraction concentrations were significantly (P < 0.05) decreased by inoculation. When compared with control silage, increased (P < 0.05) acetic acid concentration and decreased lactic acid concentration were observed in ryegrass:timothy silages and maize silages inoculated with heterofermentative lactic acid bacteria (LAB) strain Lactobacillus buchnery. The LAB blends used in our experiment significantly suppressed yeast and moulds growth reflected in the lower concentration of alcohols, generally correlated to yeast activity in silages. Inoculation increased the aerobic stability of ryegrass:timothy and maize silages, compared with control silage. The aerobic stability of inoculated ryegrass:timothy and maize silages was improved by 66-312 hours compared to control silage.

Growth characteristics, nutrient uptake, and metal accumulation of ryegrass (Lolium perenne L.) in sludge-amended mudflats

The objective of this study was to investigate the impact of sewage sludge amendment (SSA), with the rates of 0, 30, 75, 150, and 300 t ha−1, on soil chemical properties and biomass, aboveground and root growth, and nitrogen and phosphorus uptake of ryegrass (Lolium perenne L.) seedling grown on a mudflat soil. Results showed that SSA modified the chemical properties of mudflat soil by decreasing soil salinity and pH, increasing soil organic matter, total and available N and P, and heavy metals. The biomass of root and aboveground parts of ryegrass showed increments with increasing SSA rates. Maximum increases of 5.6- and 1.3-fold in fresh weight of aboveground parts and root of ryegrass were observed at 300 t ha−1 rate. Root grown at all SSA rates showed positive response to higher nutrient availability in the mudflat soil with increasing root average diameter and volume. The root length and surface area at 30 t ha−1 SSA rate was significantly higher than those in other treatments. The sewage sludge amendment increased N and P content in both aboveground and root parts of ryegrass. Cd, Cr, Cu, Mn, Ni, and Zn accumulation in ryegrass was positively correlated with SSA rates. However, heavy metal concentrations in ryegrass did not exceed the safety standard for feed in China (GB 13078-1999), except for Cd at 300 t ha−1 SSA rate. The study suggests that sewage sludge can be applied for mudflat soil amendment, which provides an innovative solution pertaining to new arable land resources and solid waste disposal. The optimum SSA rate is 150 t ha−1 with maximum plant yield yet permissible metal accumulation.

Effect of Sewage Sludge Amendment on Heavy Metal Uptake and Yield of Ryegrass Seedling in a Mudflat Soil

Mudflat soil amendment by sewage sludge is a potential way to dispose of solid wastes and increase fertility of mudflat soils for crop growth. The present study aimed to assess the impact of sewage sludge amendment (SSA) on heavy metal accumulation and growth of ryegrass ( L.) in a seedling stage. We investigated the metal availability, plant uptake, and plant yield in response to SSA at rates of 0, 30, 75, 150, and 300 t ha. The SSA increased the metal availability in a mudflat soil and subsequently metal accumulation in ryegrass. The SSA increased the bioavailable fraction of the metals by 4550, 58.8, 898, 189, 35.8, and 84.8% for Zn, Mn, Cu, Ni, Cr, and Cd, respectively, at an SSA rate of 300 t ha as compared to unamended soil. Consequently, the metal concentrations in ryegrass increased by 1130, 12.9, 355, 108, 2230, and 497% in roots and by 431, -4.3, 92.6, 58.3, 890, and 211% in aboveground parts, for Zn, Mn, Cu, Ni, Cr, and Cd, respectively, at the 300 t ha rate as compared to unamended soil. The enhanced metal accumulation, however, did not induce growth inhibition of ryegrass. Fresh weight of aboveground parts and roots of ryegrass at 300 t ha SSA rate increased by 555 and 128%, respectively, as compared to those grown in unamended soil. The study suggests that SSA can promote yield of ryegrass seedlings grown in mudflat soils. None of metal concentrations at all SSA rates was above the Chinese permissible limits. Despite the data at only the seedling stage, our results indicate that SSA in mudflat soils might be a potential way for mudflat soil fertility improvement and sewage sludge disposal. Further study at plants' maturity stage is warranted to fully assess the suitability of sewage sludge amendment on mudflat soils.

Short term effects of heating a lateritic podzolic soil on the availability to plants of native and added phosphate

We studied the impact of heating on minerals in a lateritic podzolic soil from Bakers Hill, Western Australia and consequent effects on phosphate availability and plant growth. This forest soil was heated at 250, 350 and 500°C, which are temperatures attained by topsoil during bushfires. Heating soil caused kaolinite, gibbsite and goethite to dehydroxylate and to partly alter into metakaolinite, amorphous alumina and hematite respectively. Heating increased soil pH, from 4.63 for unheated soil to 4.67, 5.40 and 5.45 for soil heated at 250, 350 and 500°C respectively. Electrical conductivity (EC) values also increased on heating to 250°C, although EC then relatively decreased for 350°C and 500°C heating. A glasshouse study determined the effect of heating soils on their pH and EC values after cropping and on P uptake by ryegrass. Yield of ryegrass decreased with increasing temperature of heating for unfertilized soil and for heated soils supplied with phosphate (P) fertilizer. The P concentration in ryegrass for each of three harvests ranged from 0.03% to 0.3% and decreased in the same sequence as for yield (i.e. unheated soil >250°C>350°C>500°C heated soil). Clearly heating of soil by bushfires may reduce the availability to plants of native and added phosphate.