Concentrations In Ryegrass Research Articles

Calcium water treatment residue reduces copper phytotoxicity in contaminated sandy soils

Calcium water treatment residue (Ca-WTR), an industrial by-product, was found to be effective in decreasing Cu availability in contaminated soils and transport to the environment. In this study, a greenhouse study was conducted to test the ability of Ca-WTR to reduce the toxicity and uptake of Cu by ryegrass ( Lolium perenne L.) and lettuce ( Lactuca sativa L.) as indicator crop plants in Cu-contaminated sandy soils. Eight weeks growing period was observed in Alfisol and Spodosol amended with different levels of Ca-WTR (5–100 g kg −1 soil). Plant biomass yields increased with WTR application rates at the low levels (5–20 g kg −1 for Alfisol, pH 5.45 and 5–50 g kg −1 for Spodosol, pH 4.66), and decreased at the high levels (>20 g kg −1 for Alfisol and >50 g kg −1 for Spodosol). The maximum growth of ryegrass with Ca-WTR was 133% and 149% of the control (without Ca-WTR) for the original Alfisol and Spodosol (without spiked Cu), respectively, while the corresponding values for lettuce was 145% and 206%. Copper concentrations in ryegrass shoots decreased significantly with increasing Ca-WTR application rates. For lettuce, Cu concentration decreased only at high Ca-WTR rates (>50 g kg −1). In addition, ryegrass had a greater potential for Cu uptake and translocation than lettuce in both soils.

Utilização de Lolium Perenne L. na fitoestabilização controlada de solos degradados por actividades mineiras

We studied the application of Lolium perenne L. and of different organic residues in the assisted phytostabilization of mine-contaminated soils (Aljustrel Mine Area, Iberian Pyrite Belt). Although the application of the organic residues led to immobilization of Cu, Pb, and Zn in the soil, decreasing their effective available fraction, their concentrations in the above-ground plant material did not change. The accumulation factors (AF) obtained were AF(Cu) and AF(Pb) <<1, and AF(Zn) <1, allowing its election as a possible candidate for phytostabilization purposes. However, Pb and Cu concentrations in ryegrass shoots were considered toxic, which suggests that there is a risk of contamination of the human food chain. Multivariate statistical analysis emphasized sewage sludge as the organic residue with the greatest capacity to correct soil acidity, and to improve soil characteristics, followed by the compost obtained from municipal solid waste residues. However, an impaired growth was obtained when using the highest application rate (100 Mg ha-1) of both residues. All garden waste compost rates were unable to correct general soil constraints to plant growth.

Effects of short-term pH fluctuations on cadmium, nickel, lead, and zinc availability to ryegrass in a sewage sludge-amended field

In this field experiment, sewage sludge was applied at 0, 5, 10, and 50 t ha −1, and the availability of Cd, Ni, Pb, and Zn was assessed both by ryegrass uptake and by DTPA extractions. The aim was to investigate the role of important soil parameters, particularly pH, on heavy metal availability. It was found that metal uptake and extractability increased significantly in the 50 t ha −1 treatment. In the 16th week of the experiment there was a significant, although temporary, increase in DTPA-extractable Cd, Ni, and Zn concentrations. Metal concentrations in ryegrass were also significantly elevated in week 20 compared to the subsequent cuttings. These fluctuations in both DTPA and ryegrass uptake occurred only at 50 t ha −1 and were probably induced by a sudden pH decrease measured in the same treatment in week 16. This suggests that soils which have received high applications of sewage sludge may be prone to fluctuations in metal availability.

Diagnóstico mineral en forraje y suero sanguíneo de bovinos lecheros en dos épocas en el valle central de México

Analysis was done for Ca, P, K, Na, Mg, Cu, Fe, Zn, and Mn concentrations in rye grass (Lolium perenne) forage, feeds and the blood serum of Holstein cows (16.6±3.6 L of milk d-1). Forages, feeds and cows in small-scale production systems were sampled during the dry (April-May) and rainy (August-September) seasons. Blood samples were taken from 139 cows from twelve production units at four sites in the Toluca Valley, Mexico. Site, season and the site/season interaction affected mineral concentrations (P<0.05). Forage calcium was low during the rainy season, although feed and serum Ca were high. Forage P was low during the dry season at three sites. The forage Ca:P ratios at all four sites were below 2:1, but were higher in the serum. Forage and serum K was normal during both seasons. Forage Na was low at two sites, but was adequate in the serum. Serum Mg was adequate. Serum Cu was deficient at all four sites during the dry season. Forage Fe was high at all four sites during both seasons, but serum Fe was highest in the rainy season. Forage and serum Zn were deficient at all four sites during both seasons. Forage Se was low during both seasons, but was adequate in the serum. The studied forages and feeds exhibited mineral imbalances that can affect the corresponding serum mineral concentration, and consequently cow health and performance.

High nutrient supply and carbohydrate content reduce endophyte and alkaloid concentration

Two controlled environment experiments were performed to test the effects of nitrogen, phosphorus and carbohydrates on endophyte (Neotyphodium lolii) and alkaloid concentrations in ryegrass (Lolium perenne). Three perennial ryegrass cultivars ('high sugar grasses' AberDove and AberDart; control Fennema) that differ in carbohydrate content were infected with three strains of N. lolii (common strain, CS; AR1; AR37). Infected and uninfected plants were grown under high (9 mM) and low (2.25 mM) nitrogen (AberDove, Fennema; CS, AR1, AR37) or under high (2 mM KH2PO4) and low (0.05 mM KH2PO4) phosphorus (AberDart, Fennema; CS, AR1). Quantitative realtime Polymerase Chain Reaction (qPCR) was used to estimate endophyte concentrations in harvested leaf tissues. High N and P supply as well as high carbohydrate content of the host grass reduced endophyte concentrations. Alkaloid production was also reduced under both increased N supply and in the high sugar cultivar, and was linearly related to endophyte concentration (except ergovaline). The results stress the need for wider quantification of fungal endophytes in the grassland/ foliar endophyte context, and have implications for how introducing new cultivars, novel endophytes, or increasing nutrient inputs, affect the role of endophytes in grassland ecosystems. Keywords: Neotyphodium lolii, foliar endophyte, Lolium perenne, perennial ryegrass, qPCR, high sugar ryegrass, nitrogen, phosphate, carbohydrate, AR1, AR37, alkaloids

Speciation of Cd and Zn in contaminated soils assessed by DGT-DIFS, and WHAM/Model VI in relation to uptake by spinach and ryegrass

A pot experiment was carried out to investigate the impact of Cd and Zn extractability in soil and speciation in pore water of industrial contaminated soils, on metal concentration in a metal sensitive species like spinach ( Spinacia oleracea) and a more metal tolerant species like Italian ryegrass ( Lolium multiflorum). For chemical speciation of Cd and Zn in pore water, WHAM/Model VI version 6.0 was used. The DGT technique was used to determine the effective concentration, C E, of Cd and Zn in soils. The free ion activity in pore water correlated well with the contents in plants, and there was a linear relationship between the C E values and the concentration of Cd and Zn in both spinach and ryegrass in the non-toxic range. However, the C E values usually overestimated the plant contents when plants, particularly the spinach plants, were subjected to toxic concentration in the pore water. Metal uptake decreased in plants affected by toxicity, whereas metal binding to the Chelex resin did not. Thus, we found no linear relationship between the C E and metal contents in spinach, whereas a linear relationship was found between C E-Zn and the Zn concentration in ryegrass ( r 2 = 0.96, p < 0.001). For Cd in ryegrass this relationship was weak ( r 2 = 0.53, p = 0.18). This study indicates that the transport of metals from labile metal pools to the DGT-resin is linearly related to plant uptake only when plants are growing well, and that the applicability of DGT as an indicator for plant uptake seems species dependent.

Modelling 137Cs uptake in plants from undisturbed soil monoliths

A model predicting 137Cs uptake in plants was applied on data from artificially contaminated lysimeters. The lysimeter data involve three different crops (beans, ryegrass and lettuce) grown on five different soils between 3 and 5 years after contamination and where soil solution composition was monitored. The mechanistic model predicts plant uptake of 137Cs from soil solution composition. Predicted K concentrations in the rhizosphere were up to 50-fold below that in the bulk soil solution whereas corresponding 137Cs concentration gradients were always less pronounced. Predictions of crop 137Cs content based on rhizosphere soil solution compositions were generally closer to observations than those based on bulk soil solution composition. The model explained 17% (beans) to 91% (lettuce) of the variation in 137Cs activity concentrations in the plants. The model failed to predict the 137Cs activity concentration in ryegrass where uptake of the 5-year-old 137Cs from 3 soils was about 40-fold larger than predicted. The model generally underpredicted crop 137Cs concentrations at soil solution K concentration below about 1.0 mM. It is concluded that 137Cs uptake can be predicted from the soil solution composition at adequate K nutrition but that significant uncertainties remain when soil solution K is below 1 mM.

Uptake of trifluralin and lindane from water by ryegrass

Understanding of the plant uptake of organic chemicals is essential to assessing contaminant mobility in the ecosystem, exposure to humans, and phytoremediation technologies. In this study, we measured the uptake of trifluralin and lindane from water by ryegrass as a function of uptake time for periods of 96 and 120 h, respectively. Trifluralin concentration in ryegrass increased sharply at the early stage of uptake and reached the maximum at 10 h, and then decreased with uptake time. 14C-labelled trifluralin uptake displayed a similar trend but a higher 14C-concentration than that of extracted parent compound, indicating metabolism and formation of bound residues following trifluralin uptake. Lindane concentration in ryegrass slowly increased with uptake time and approached a plateau, indicating minimal metabolism and formation of bound residues. The difference in the uptake characteristics of these two chemicals may be related to the differences in their lipophilicity, and chemical and biological reactivities. A two-compartment model accounting for the contributions of transpiration, metabolism and formation of bound residues to overall uptake was developed to assess the uptake kinetics. The model adequately described the uptake of trifluralin and lindane into ryegrass by providing the first-order rate constants of uptake, release, transpiration, and metabolism and formation of bound residues. These rate constants are used in calculating plant concentration factor (PCF). The ratios of trifluralin concentrations in ryegrass to its aqueous concentrations are between the PCF at thermodynamic equilibrium and the PCF at steady state, suggesting the utility of both PCF values.

Estimating leaf nitrogen concentration in ryegrass ( Lolium spp.) pasture using the chlorophyll red-edge: Theoretical modelling and experimental observations

Chlorophyll red-edge descriptors have been used to estimate leaf nitrogen concentration in ryegrass ( Lolium spp.) pasture. Two-layer model calculations have been used to predict the influence of chlorophyll content and Leaf Area Index (LAI) on the shape and location of the peaks observed in the derivative spectra of a ryegrass canopy. The complex structure of the resulting derivative spectra precluded extracting red-edge wavelengths by fitting inverted Gaussian curves to reflectance profiles. Fitting a combination of three sigmoid curves to the calculated reflectance spectra provided a better representation of subsequent derivative spectra. The derivative spectra in the vicinity of the chlorophyll red-edge is predicted to contain two peaks (∼705 and ∼725 nm), which on increasing the canopy LAI is generally found to shift to longer wavelengths. However, for a canopy containing leaves of low chlorophyll content and LAI>5, the wavelength of the first peak becomes insensitive to changes in LAI. The same phenomenon is predicted for high-chlorophyll leaves of LAI>10. The role of multiple scattering, primarily due to increased leaf transmittance at higher wavelengths, has also been verified. In subsequent experiments, the predicted shape of the derivative spectra was observed and the use of three sigmoid curves to better represent this shape verified. Changes in the descriptors used to describe the chlorophyll red-edge were observed to explain 60% and 65% of the variance of leaf nitrogen concentration and total leaf nitrogen content, respectively. The resulting regression equation was found to predict leaf nitrogen concentration, in the range of 2-5.5%, with a standard error of prediction (SEP) of 0.4%. The confounding influence of canopy biomass on the red-edge determination of leaf nitrogen concentration was found to be significantly less at higher canopy biomass, confirming both theoretical predictions and the potential of using the chlorophyll red-edge as a biomass-independent means of estimating leaf chlorophyll, and hence nitrogen, concentration in high-LAI ryegrass pastures.

In situ immobilization of metals in contaminated or naturally metal-rich soils

The chemical behaviour of metals is primarily governed by their retention and release reactions of solute with the soil matrix. Liming increased the soil pH, resulting in increased adsorption of Zn, Cu, and Cd in soils, which in consequence decreased the concentration of easily soluble Cd fraction in the soils and the uptake of this metal by wheat (Triticum aestivum) and carrots (Daucus carota). Metal adsorption also depended on the presence of clay and organic matter, and thus the soils having highest amounts of clay (e.g., alum shale) and (or) organic matter (e.g., peat soil) showed the highest adsorption for these metals. Among the materials (Fe and Mn oxides and aluminosilicates) having high binding capacity for metals, the immobilizing capacity of birnessite (MnO2) was higher than that of other materials. Addition of synthetic zeolites significantly reduced the metal uptake by plants. Application of zeolite to a soil resulted in increased dissolved organic carbon (DOC) concentration in the leachate, which in consequence increased the leaching of Cd and Zn. Addition of beringite (an aluminosilicate) to a Zn-contaminated soil resulted in increased shoot length and leaf area of bean (Phaseolus vulgaris) and a significant reduction in Zn concentration in leaves (from 350 to 146 mg kg-1). Cadmium concentration in ryegrass and the concentrations of diethylenetriaminepentaacetic acid (DTPA)- extractable Cd, Cu, Ni, and Zn in the soil decreased significantly (P &lt; 0.05) with increasing amounts of organic matter (peat soil and cow manure) added to soils. These effects were assumed to be related to immobilization of metals due to formation of insoluble metal--organic complexes and increased cation exchange capacity (CEC). An overview of the results showed that the products tested (lime, Fe/Mn-containing compounds, aluminosilicates, and organic matter products) can reduce the solubility and the plant uptake of metals but their immobilizing capacity is limited (sometimes through their side effects). Key words: aluminosilicates, contaminated soils, in situ immobilization, leaching, metal oxides, organic matter, plant uptake.

GRAVEL SLUDGE AS AN IMMOBILIZING AGENT IN SOILS CONTAMINATED BY HEAVY METALS: A FIELD STUDY

Field plot studies were conducted on sandy loam soils in Dottikon, Rafz and Giornico contaminated by Zn, Cu and Cd to investigate the effectiveness of gravel sludge as an in situ immobilization additive. In addition to NaNO3-extractable heavy metal concentrations in the soil, metal concentrations in ryegrass (Lolium perenne L.) and lettuce (Lactuca sativa L.) were analyzed at two application doses of gravel sludge. Application of gravel sludge increased pH in all three topsoils by up to 0.6 units and reduced NaNO3-extractable Zn concentrations by more than 65%. No effect was seen for the NaNO3-extractable Cu concentrations in Rafz and even an increase resulted in Giornico. In Dottikon, gravel sludge additions decreased the NaNO3-extractable Cu concentrations from 0.97 to 0.7 mg kg−1 and reduced the concentrations of Zn and Cu by more than 35% in ryegrass. For lettuce grown in Giornico and Dottikon, we found reductions of Zn and Cd concentrations by 22 to 48%, whereas in Rafz, no significant variations were found. Immobilization by gravel sludge was most efficient in soils with high total/NaNO3-extractable heavy metal ratio and more effective for ryegrass than for lettuce. Part of the immobilization effect was due to a pH increase, caused by CaCO3 in gravel sludge.

Influence of soil-applied coal combustion by-products on growth and elemental composition of annual ryegrass

The total annual production of coal combustion by-products in the USA is expected to exceed 150 million Mg by the year 2000. Agricultural utilisation may offer a partial solution to disposal problems, but the benefits and risks associated with using these materials must be assessed. Four coal combustion by-products, bed ash (BA) and fly ash (FA) from a fluidised-bed combustion furnace and stabilised scrubber sludge (SS) and a high gypsum content by-product (G) from flue gas desulphurisation processes were added to two soils at rates of 0, 20, 40 and 80 g kg-1. The growth and elemental composition of ‘Gulf’ annual ryegrass (Lolium multiflorum L.) were evaluated in the treated soils. Adding FA, SS and G to both soils at application rates of up to 80 g kg-1 was not detrimental to the growth of ryegrass and resulted in higher yields than controls in some instances. Adding BA created a high alkalinity, high soluble-salt environment that initially inhibited seedling germination and significantly reduced (p<0.05) yields of dry matter, so it will probably need to be restricted to rates of lime requirement. Ryegrass concentrations of Cu, Zn, Ni, Pb, Cd and Cr were similar in control and treated soils, but levels of B, Se, As and Mo were raised in treatments. Based on low trace-element concentrations in ryegrass shoots and in soil solution, Se from FA application may be the only potential food-chain risk associated with application of the four coal combustion by-products used in this investigation.

Availability of fluoride to plants grown in contaminated soils

Two pot experiments were carried out to study uptake of fluoride (F) in clover and grasses from soil. Fluoride concentrations in t Trifolium repens (white clover) and t Lolium multiflorium (ryegrass) were highly correlated with the amounts of H2O− and 0.01 t M CaCl2−extractable F in soil when increasing amounts of NaF were added to two uncontaminated soils (r=0.95–0.98, t p<0.001). The amounts of H2O− or 0.01 t M CaCl2−extractable F did not explain the F concentrations to a similar extent in t Agrostis capillaris (common bent) grown in 12 soils (Cambic Arenosols) collected from areas around the Al smelters at A: rdal and Sunndal in Western Norway (r=0.68–0.78). This may be due to variation in soil pH and other soil properties in the 12 soils. Soil extraction with 1 t M HCl did not estimate plant−available F in the soil as well as extraction with H2O or 0.01 t M CaCl2. Fluoride and Al concentrations in the plant material were positively correlated in most cases. Fluoride and Ca concentrations in the plant material were negatively correlated in the first experiment. No consistent effects were found on the K or Mg concentrations in the plant material. The F accumulation in clover was higher than in the grasses. The uptake from soil by grasses was relatively low compared to the possible uptake from air around the Al smelters. The uptake of F in common bent did not exceed the recommended limit for F contents in pasture grass (30 mg kg−1) from soil with 0.5−28 mg F(H2O) kg−1 soil. The concentration in ryegrass was about 50 mg F kg−1 when grown in a highly polluted soil (28 mg F(H2O) kg−1 soil). Concentrations in clover exceeded 30 mg F kg−1 even in moderately polluted soil (1.3–7 mg F(H2O) kg−1 soil). Liming resulted in slightly lower F concentrations in the plant material.

Extractability and bioavailability of heavy metals in surface soils derived from dredged sediments

ABSTRACTAccumulation of heavy metals by plants causes concern because it is a major pathway by which metals can enter into the food chain. Extractability and bioaccumulation in rye grass of Cd, Cu, Mn, Pb and Zn in dredged sediment derived surface soils were studied in a greenhouse experiment. The soils were extracted with 0.01 mol L−1 CaCl2, 1 mol L−1 NH4OAc, 0.02 mol L−1 NH4OAC—EDTA, 0.005 mol L−1 DTPA and 0.1 mol L−1 HCI. Extracted metal contents were correlated with concentrations in rye grass, harvested after 1 and after 2 months. The extractability of Cd, Mn and Zn decreased in the order NH4OAC-EDTA > HCI > DTPA > NH4OAC > CaCl2. For Cu and Pb, the order was similar except that DTPA extracted higher amounts than HCI. No significant differences in dry matter yield were observed between the soils upon the first harvest. In the second harvest, the dry matter yield was significantly lower for the soils highest in clay content. Elevated concentrations of Cd and Zn were observed in the plant material and ...

Testing a low‐quality urban compost as a fertilizer for arable farming

Abstract. A coarse urban compost, low in organic matter but mature, was tested for agricultural use. The response of Tewera ryegrass to this compost (applied at 12 and 48 t/ha) was evaluated in a field trial over two years. For a satisfactory yield the larger dose was necessary. This dose also gave greater values for the apparent recovery of N in both years. However, the N concentration in ryegrass was always below the sufficiency ranges proposed for N. The values of the potentially mineralizable N of the compost showed that the applied N at the greater rate of compost application was not sufficient to cover crop removal of N. In contrast, concentrations of P, S, K, Mn and Zn were within their corresponding sufficiency ranges. The dose of 48 t/ha did not increase Cu, Ni, Pb and Cd concentrations in the ryegrass.

Dynamics of potassium fractions in the soil‐plant system after the application of an acid potassium‐rich effluent

We did a greenhouse experiment focused on the application of olive oil mill wastewater on potassium dynamics in the soil‐plant system. Two doses of wastewater and two of K fertilizer containing amounts of potassium equivalent to those in the wastewater treatments were tested and compared with the results of control and control plus mineral fertilizer lacking K. The application of wastewater and of K fertilizer significantly increased initial exchangeable K in soil in comparison with control values, although the effect of wastewater was weaker than that of fertilizer. Treatments with wastewater or K fertilizer, but not with mineral fertilizer lacking K, kept K concentrations in ryegrass above the critical level during all three harvests. In both control treatments the K requirements of the crop, represented by cumulative K uptake, led to the mobilization of assimilable K from the reserve of nonexchangeable K in soil. This was not observed in treatments with industrial wastewater or K fertilizer: initial ex...

Effect of different forms and sources of arsenic on crop yield and arsenic concentration

Two greenhouse experiments were conducted to investigate the effects of different sources of As application on the yield of ryegrass (Lolium perenne L.) and barley (Hordeum vulgare L.) and the arsenic concentration in crop tissue. The soils used were a sand and a loam soil. In the first experiment (3 yr), As was applied either as sodium arsenite or as disodium hydrogen arsenate at the rate of 0, 2, 10, 50, and 250 mg As kg−1 soil in year 1. In years 2 and 3, only the residual effect of As applied in year 1 was investigated. In the second experiment (5 yr), a NPK(16-7-12) fertilizer containing 10, 100 and 3000 mg As kg−1 as sodium arsenite was applied at rates of 750 and 600 mg kg−1 to ryegrass and barley, respectively, with lime and without lime. Arsenite had more inhibitory effect on crop yield than arsenate. Although the residual effect persisted up to year 3, it was found to be dependent on As application rate, soil type, and crop species. Only minor differences in As concentration in crops between arsenite and arsenate sources were observed. The yield reduction and the increase of As concentration in crops was highly related to As application rates. The As rates of 50 and 250 mg As kg−1 resulted in significant yield reduction and marked increase of As concentration in both crops and these rates could be considered as critical for both crops. The application of As containing fertilizer had little or no effect on crop yield. The As concentration in both crops was little affected by the fertilizer containing up to 100 mg As kg−1 but the concentration increased several folds when the fertilizer containing 3000 mg As kg−1 was applied. The application of additional P to the treatment containing 3000 mg As kg−1 fertilizer only slightly increased crop yields but it increased As concentration in ryegrass markedly. The repeated application of As containing fertilizer up to a period of 5 yr, even at 3000 mg As kg−1 level, generally did not affect either the yields or the As concentration in both crops although a slight increase of As concentration in barley grain over the years was observed. In both experiments, the yield reduction and the increase in As concentration in crop tissue were lower in the loam soil than in the sand and barley straw cointained much higher As than barley grains, indicating that greater proportion of the As taken up by this crop was retained in the vegetative organs.

Chemistry of Cr in some Swedish soils

The effect of Si(OH)4 on Cr toxicity and elemental concentrations in ryegrass were investigated in a growth chamber using an acid and a neutral mineral soil. Each soil was treated with 50 mg Cr, as CrO3, kg−1 soil dry weight, singly, or in combination with 25 mg Si as Si(OH)4. Plants growing in unamended soils were used as controls.

Seasonal variations in total nonstructural carbohydrate and major element levels in perennial ryegrass and paspalum in a mixed pasture

Abstract In the first of two experiments, above-and below-ground organs of paspalum (Paspalum dilatatum Poir.) and ryegrass (Lolium perenne L.) growing in a mixed dairy pasture were sampled over 12 months and their total nonstructural carbohydrate (soluble sugars and starch) and major element (N, P, K, S, Mg, Na) concentrations were determined. In the second experiment, biomass of ryegrass and paspalum were monitored over 12 months. Pasture biomass was dominated in all seasons by paspalum, primarily because of the size of its below-ground rhizome which more than doubled from December (1.6 t dry matter (DM)/ha to May (4.4 t DM/ha) coinciding with an increasing concentration (6-19% of DM) of nonstructural carbohydrates. In contrast, nonstructural carbohydrate concentrations in ryegrass were highest (13% of DM) in above-ground organs (leaves and “stems”) during winter followed by a decline before heading in spring. Seasonal variations in elemental concentrations in ryegrass organs were small. This was also true for paspalum leaves and roots but rhizome and “stem” nitrogen concentrations during autumn, winter, and early spring were almost double their summer levels of about 2% of DM. Paspalum had a larger total biomass and more reserves Received 21 September 1987; accepted 11 January 1989 than ryegrass. Climatic and management constraints which reduce ryegrass biomass and reserves may increase ryegrass mortality and the pasture area occupied by paspalum.

Zinc, copper and nickel concentrations in ryegrass grown on sewage sludge‐contaminated soils of different pH

AbstractSewage sludges containing high concentrations of zinc, copper and nickel were added separately to samples of two soils, a silty clay loam and a sandy loam, on which pH levels between 4.5 and 7.5 had been established; there were also treatments with sludge of low metal content or no‐sludge. Soil‐sludge mixtures were either continuously cropped with ryegrass or kept uncropped in pots in the glasshouse for 6 months. Zinc and nickel concentrations in 0.1 μM calcium chloride extracts of soils from the cropped pots and in solutions displaced from the fallow pots decreased with increasing pH over the range tested, but copper concentrations remained steady above pH 5.5; individual metal concentrations in ryegrass tops followed the same pattern with pH as those in extracted solutions. Squared correlation coefficients (R7) between shoot metal concentrations and concentrations of metals in EDTA, DPTA or calcium chloride extracts or displaced solutions, when taken over all soil, pH and sludge treatments, were &gt;0.60 (P&lt;0.001). Ryegrass yield reductions occurred on soils contaminated with each of the three metal sludges when soil pH was 5.5 or below.