The nitrogen value of anaerobically digested sewage sludge applied to grassland during winter

The manurial value of liquid anaerobically digested sewage sludge (LAS), surface applied once at four different times during winter to contrasting swards, was assessed over each of three growing seasons by comparison with fertilizer N. Four nominal rates of N (0, 18, 36 and 54 kg ha⁻¹) were used based on the inorganic N content of LAS. Herbage dry matter (DM) and N uptake responses were measured by cutting three times per year.
Application of LAS in late winter compared with early winter led generally to greater N uptake and DM production. Herbage production response from LAS ranged from 5·4 to 30·1 kg DM kg⁻¹ N; within this range, larger responses were obtained from a sown sward than from permanent pasture. The apparent efficiency of LAS compared with fertilizer N ranged from 0·41 to 0·88 (permanent pasture) and 0·20 to 0·77 (sown sward) but occasionally mean apparent efficiencies of over 1·0 occurred because fertilizer N was poorly recovered. There was no residual effect on annual N uptake from applying sludge. It is concluded LAS is a useful nitrogenous manure when applied to grassland in late winter/early spring but more research is needed to elucidate the importance of pathways of N losses following the surface application of LAS, and to quantify these losses.     

Recycling of sewage sludge to grassland: a review of the legislation to control of the localization and accumulation of potential toxic metals in grazing systems

The recycling of sewage sludge or biosolids to grassland is strategically important in the European Union (EU) and its use is tightly regulated to control the risk of pathogen transfer to animals and the food chain. Sewage sludges not only contain valuable concentrations of beneficial nutrients, but also elevated concentrations of potentially toxic metals (PTM) compared with average background concentrations in the soil. The EC and UK regulations refer to six PTM, Cd, Pb, Cu, Zn, Ni and Hg, with provisional regulations for Cr, that have to be controlled to prevent detrimental effects on soil and animal health. Despite these regulations, there is still a danger that grazing animals may ingest elevated concentrations of PTM. Biosolids may adhere to herbage after the surface application of sewage sludge to grassland. The repeated surface application of sewage sludge to grassland can lead to elevated concentrations of PTM at the soil surface that may be ingested, together with soil and herbage, by grazing ruminants. This may lead to accumulation of Cd or Pb in liver or kidney. The risk to the human food chain is considered to be low, but the impact on the environment is still unknown. There is little information, for example, on the amount of soil and PTMs that may become incorporated into conserved grass. At present EU and UK legislation and voluntary codes of practice have been developed to protect animal from pathogens in sewage sludge and to minimize any potential risks from accumulation of PTM. The background and implementation of the legislation are examined in this review, and the source and mechanisms of accumulation of PTM by the grazing animal are evaluated.     

Growth and heavy metals accumulation potential of microalgae grown in sewage wastewater and petrochemical effluents

Microalgae exhibit a number of heavy metal uptake process by different metabolism. In this study, the ability of microalgae for removal of heavy metal from wastewater was studied. Growth and biochemical contents of microalgae were determined by spectrophotometer. Heavy metal analysis of wastewater effluents were performed by atomic absorption spectrophotometer before and after treatment at laboratory scale. The growth of Scenedesmus bijuga and Oscillatoria quadripunctulata in sewage wastewater was higher than those grown in synthetic medium. Whereas, the growth of S. bijuga and O. quadripunctulata in sterilized petrochemical effluents was slightly lower than that grown in the standard synthetic medium. The chlorophyll, carotenoid and protein content of S. bijuga and O. quadripunctulata grown in sterilized sewage wastewater were higher than those grown in the standard medium. Similarly S. bijuga and O. quadripunctulata grown in sterilized petrochemical effluents showed lower contents of pigments and protein than those grown in sewage and synthetic medium. Heavy metals copper, cobalt, lead and zinc were removed by 37-50, 20.3-33.3, 34.6-100 and 32.1-100%, respectively from sewage wastewater and petrochemical effluent using Ocillatoria culture. The metal absorption by S. bijuga were (Cu, Co, Pb, Zn) 60-50, 29.6-66, 15.4-25 and 42.9-50%, respectively from sewage and petrochemical effluents. Both species showed high level of heavy metal removal efficiency and metal sorption efficiency of both microalgae depended on the type of biosorbent, the physiological status of the cells, availability of heavy metal, concentration of heavy metal and chemical composition of wastewater.     

Manurial value of septic-tank sludge on grassland

About 5% of the UK population is served by septic tanks and cesspits. In some districts this is applied to farmland. The Water Research Centre and South-West Water collaborated in establishing a field trial to provide knowledge of the manurial value of septic-tank sludge. The trial was designed to investigate the value of nitrogen (N), phosphorus (P) and potassium (K) contained in the sludge and applied over a 3-year period to grassland. The approximate proportions of total nutrients present in the sludge applied which became available to ryegrass as inorganic fertilizer nutrients were:
Barley grown in the fourth year when no sludge was applied showed a significant response to residual sludge N and P remaining in the soil. It is concluded that septic-tank sludge can supply useful amounts of N and P, and, unlike other forms of sewage sludge, significant quantities of K to grassland. Estimates of the nutrient value should be based on analysis for dry solids, and total N, P and K. Septic-tank sludge is usually low in metal content and no metal contamination problems should arise when it is applied to land.     

Improved membranes for the extraction of heavy metals

This work presents a series of experimental tests on new practical approaches in membrane design to improve extraction capacity and rate. We chose an extraction system involving Aliquat 336 as the extractant and Cd(II) as the metal ion to be extracted to demonstrate these new approaches. The core element in the new membrane assembly was the extractant loaded sintered glass filter. This membrane assembly provided a large interface area between the extractant and the aqueous solution containing metal ions. By recycling the aqueous solution through the membrane assembly, the extraction rate was significantly improved. The membrane assembly also offered good extraction capacity.     

Mineral concentrations in herbage and soil in a Pinus radiata silvopastoral system in north-west Spain after sewage sludge and lime application

Silvopastoral systems in north-west Spain can reduce the risk of fires and promote multi-purpose forest land use. Fertilizer application is important for optimal pasture and tree production. The application rate of sewage sludge as a fertilizer is regulated and is based on its nutrient concentration, especially nitrogen. The aim of this study was to assess the effect of three consecutive years of application of different application rates of sewage sludge and inorganic fertilizer, with or without lime (2·5 t CaCO₃ ha⁻¹) on the ammonium, nitrate and exchangeable K, Ca and Mg contents in soil, and on the crude protein (CP), K, Ca and Mg concentrations in herbage in a silvopastoral system established under a 5-year-old Pinus radiata D. Don plantation with a density of 1667 trees ha⁻¹. The experiment was started in autumn 1997, when a pasture mixture was sown (25 kg ha⁻¹ Lolium perenne , 10 kg ha⁻¹ Dactylis glomerata and 4 kg ha⁻¹ Trifolium repens ). Changes in ammonium and nitrate content in the soil in response to liming and sewage sludge application reflected the initial pH of the soil. In general, liming increased the available Ca and Mg content in soil, and CP and Ca concentrations in herbage, but reduced exchangeable K content in the soil in the first year. Application of sewage sludge increased all of the measured nutrients in both soil and herbage.     

Distribution of heavy metals in the sediments of agricultural fields adjacent to urban areas in Central Taiwan

In 2002, the Environmental Protection Administration of Taiwan began a detailed survey of heavy metals in soils, to determine the scope of the contaminated lands in the Changhua County’s agricultural fields. It was found that agricultural lands have been seriously polluted with Cr, Hg, Cu, Ni, and Zn, due to industrial wastewaters. This study, characterized the processes associated with heavy metal pollution by analyzing heavy metal contents in sediments within two periods, 2002 and 2010. This study employed geostatistical and multivariate statistics to obtain spatio-temporal variations of heavy metal pollution in paddy fields. The results indicate that, changes in industrial types have been altered the characteristics of pollutions, such as reducing the number of plants in industries (i.e., electroplating, surface treatments, metal works, chemicals, papermaking, etc.). Their wastewaters contained a large number of Ni, making the pollution composition of driven factors have been changed that can be indicated in this study. Pollution distribution and irrigation systems are positively correlated and concentrations of Cr, Cu, Ni, and Zn were inversely proportional to the scale of irrigation channels.     

Influence of nitrogen and sewage sludge on botanical composition of an old hay field†

Applications of either sewage sludge or N as ammonium nitrate were made to a 15-year-old hayfield over a 2-year period. The original seeding mixture was unknown but was believed to be timothy (Phleum pratense L.) and red clover (Trifolium pratense L.). During the second year, botanical separations indicated that applications of both N and sewage sludge resulted in reduced proportions of red and volunteer white clover (Trifolium repens L.) as well as volunteer Kentucky bluegrass (Poa pratensis L.). During the growing season a decline in proportion of timothy (Phleum pratense L.) was observed for the control as well as for the N and sludge treatments. In contrast, quackgrass (Agropyron repens (L.) Beauv.) was markedly stimulated by the treatments and the proportion of it in the hay increased during the growing season.     

Changes in macro‐ and micronutrient contents of grasses and forbs following Miscanthus x giganteus feedstock,hydrochar and biochar application to temperate grassland

Biochar and hydrochar application to soil holds promise for climate change mitigation. This study provides first insights into the nutrient concentration and removal of grassland vegetation after addition of various carbon compounds together with pig slurry. Four treatments: control (no carbon application), feedstock, hydrochar and biochar from Miscanthus x giganteus were applied at a permanent grassland site near Giessen, Germany. Changes in plant functional groups, biomass production and nutrition status were monitored over 2 years. Total biomass production was not affected by the carbon amendments. However, biochar favoured growth of forbs over grasses, while legume growth was increased by all carbon amendments. The initial nutrient concentrations of the carbon compounds were enriched according to their degree of carbonization, potentially providing nutrients to plants. The plant biomass from hydro‐ and biochar amended plots, added up over 2 years, exhibited higher potassium concentrations compared to biomass from feedstock and control plots. All carbon amendments led to lower sodium concentrations in total biomass, compared to the control. Uncarbonized feedstock led to increased manganese concentrations in total biomass, while the concentrations of all other heavy metals were not influenced by any carbon amendment, compared to the control. From a plant and animal nutritional point of view, none of the carbon amendments reduced grassland yield or fodder quality. The study suggests that hydrochar and, even more so, biochar may provide a source of potassium to plants.     

Sodium fertilizer application to pasture. 8. Turnover and defoliation of leaf tissue

The effects of application of sodium fertilizer on the turnover and defoliation of leaf tissue were investigated in a perennial ryegrass (Lolium perenne) pasture grazed by dairy cows. Eight plots were allocated to treatments either with or without sodium fertilizer, with the former receiving 32 kg Na ha^–1 applied in five applications of NaNO₃ over the grazing season. An equivalent amount of nitrogen was given to the controls as ammonium nitrate, the application of which was reduced in the sodium treatment to equate nitrogen fertilizer applications for the two treatments. In nine periods between April and September, marked tillers were recorded to measure leaf turnover, leaf lamina growth and specific leaf weight and, when combined with tiller density measurements, gave an estimate of herbage flux for the sward. The defoliation and net growth of the marked tillers were monitored at 3-day intervals and the data were combined with tiller density and specific leaf weight data to determine the intake of the expanding, penultimate and oldest live leaf laminae. Sodium fertilizer application did not affect the rate at which leaves appeared, but it retarded their rate of disappearance. The extension rate and the specific weight of green laminae were both increased by sodium fertilizer application and therefore the net gravimetric growth rate was increased. Tiller density was not affected by sodium fertilizer application and hence the estimated herbage growth and net herbage flux were increased by sodium fertilizer application. Application of sodium fertilizer did not affect lamina length, and in both treatments the penultimate laminae were approximately twice as long as expanding and oldest live laminae. Defoliation frequency decreased from the expanding to the oldest live laminae in the control treatment without sodium. Sodium fertilizer application increased the frequency of defoliation of the oldest live leaf and also increased the length of the expanding leaf that was defoliated. For penultimate leaf laminae sodium fertilizer application reduced the defoliation frequency and length of foliage grazed. The dry-matter (DM) intake of the oldest live laminae was increased by the application of sodium fertilizer. It is concluded that sodium fertilizer application increases net herbage growth both by increased extension rate of leaf laminae and specific leaf weight and by delayed laminae senescence, and that it increases herbage DM intake by increasing the defoliation frequency of the oldest live leaf laminae.     

The removal of heavy metals in aqueous solution by hydroxyapatite/cellulose composite

Hydroxyapatite has an excellent ion-exchangeability and is expected to be used as an agent for the removal of heavy metal ions in wastewater. However, the pure hydroxyapatite is very difficult to use because it exists in the form of white powder. Thus, the pure hydroxyapatite was mixed with cellulose to utilize its ion-exchangeability. In this research, a method for dispersion of hydroxyapatite in cellulose matrix is described and its dispersion is observed with scanning electron microscopy. The removal ratios of some heavy metal ions with hydroxyapatite composite are examined with regard to reaction time and amount of hydroxyapatite composite. The ion-exchangeability of hydroxyapatite composite did not seem to be interfered by cellulose matrix during removing heavy metal ions.     

Concentration of selected heavy metals in spices,dry fruits and plant nuts

Different spices, dry fruits and plant nuts commonly consumed in Pakistan were assayed for the heavy metals cadmium, lead, copper, zinc, iron and manganese by the potentiometric stripping analysis and AA spectrophotometry. The results revealed wide variation in heavy metal content among different biological materials. Mixed spices generally exhibited higher value for trace metals specially lead (6.6–9.2 µg/g), cadmium (0.65–1.34 µg/g), iron (142.3–285.0 µg/g) and zinc (64.2–65.8 µg/g). Dry fruits contained relatively lesser amounts of heavy metals than plant nuts. Almonds contained higher levels of lead (1.02 µg/g) and cadmium (0.24 µg/g) than other nuts and dry fruits.     

Silage fermentation characteristics of three common grassland species in response to advancing stage of maturity and additive application

This study investigated the effects of advancing stage of maturity and additive treatment on the fermentation characteristics of three common grassland species. Perennial ryegrass (PRG; Lolium perenne L., var. Gandalf), timothy (Phleum pratense L., var. Erecta) and red clover (Trifolium pratense L., var. Merviot) were harvested at three dates in the primary growth (11 May, 8 June and 6 July; Harvests 1–3) and ensiled with the following additive treatments: (1) control (i.e. no treatment), (2) formic acid‐based additive, (3) homofermentative lactic acid bacterial (LAB) inoculant and (4) heterofermentative LAB inoculant. Additive application to the PRG (irrespective of harvest date), the late‐harvest timothy (Harvest 3) and the red clover (Harvests 2 and 3) herbages had little impact on silage fermentation characteristics, where a lactic acid dominant fermentation already prevailed. However, the application of the formic acid‐based additive to the Harvest 1 and 2 timothy and Harvest 1 red clover herbages, where the silage fermentation characteristics were poorer, resulted in an increase in the proportion of lactic acid in total fermentation products and a decrease in pH. In contrast, the heterofermentative LAB inoculant had a negative impact on silage fermentation characteristics where a poor preservation prevailed in the corresponding control silage.     

Removal of heavy metals in aqueous solution using Antarctic krill chitosan/hydroxyapatite composite

Discarded Antarctic krill shells can be used to prepare chitosan and adsorption materials in an attempt to save resource and protect environment. The optimal conditions of composite materials preparation were as follows: mass ratio of CS and HA was 2:1 at 40 °C, pH 10–10.5, volume ratio of chitosan and Ca(NO₃)₂ was 2:1 over a period of 1 day. Under these conditions, the Cr (VI) removal rate was about 75±8 %. SEM, TEM, XRD, FTIR, DT-TGA analysis indicated that CS/HA composite was made up of CS and HA and it possessed good mechanical strength and thermal stability. The ability to remove Cd (II), Cr (III) and Cu (II) in aqueous was high, and the optimal conditions were as follows: a contact time of 60 min at 35 °C and pH 6–7. The removal rates of all three heavy metals were above 90 %.     

Low‐ammonia‐emission application methods can increase the opportunity for application of cattle slurry to grassland in spring in Ireland

Application of slurry in spring to grassland in north‐west Europe increases the efficiency of nitrogen recovery compared with the application in summer. In Ireland, however, more than 0·50 of slurry is applied in the summer. The splash‐plate method of application, most commonly used in Ireland, can make application in spring difficult because of the risk of contamination of grass with slurry, affecting subsequent silage quality and grazing preferences. This study evaluated the potential of low‐emission spreading methods to increase the opportunity for spring application of slurry using an agro‐meteorological modelling approach. Weather data from two weather stations were combined with data on grass growth from two nearby sites. Using three soil‐drainage classes (well, moderate and poor), each with a typical regime of grassland management, a database of soil moisture deficits, drainage, patterns of grazing and cover of grass herbage was developed for three hypothetical management systems, one for each soil drainage class, at each site. Simulations of four slurry application methods [splash‐plate (SP), band‐spreader (BS), trailing‐shoe (TS) and shallow‐injection (SI)], subject to a series of constraints, were compared over an 8‐year period (1998–2005) in order to determine the number of days during the period from 1 January to approximately 10 May of each year, when it was considered that grassland was suitable for application of slurry. These constraints were: (i) restrictions on spreading imposed by current legislation in Ireland; (ii) the period before occurrence of drainage or overland flow; (iii) soil trafficability; (iv) the time‐lag before a subsequent grazing or harvest event; and (v) herbage mass of the pasture. On well and moderately drained soils, the model predicted that the highest number of days available for slurry spreading was found for the TS method followed by the BS, SI and SP methods. There was no difference between application methods in the number of available days on poorly drained soils.     

Differential growth response of Rytidosperma species (wallaby grass) to phosphorus application and its implications for grassland management

Rytidosperma species (formerly Austrodanthonia) are native grasses common in temperate grasslands of southern Australia. Nine Rytidosperma species, Lolium perenne and Bromus hordeaceus were grown as microswards in pots in a glasshouse, and their growth response to six levels of applied P was measured. Shoot yield differed up to twofold between the highest‐ and lowest‐yielding Rytidosperma species. Some Rytidosperma species were slow growing with minimal ability to respond to increased soil P availability. However, three species, Rytidosperma duttonianum, Rytidosperma racemosum and Rytidosperma richardsonii, had a similar shoot yield to L. perenne. Species that grew well at high P also grew well at low P, except B. hordeaceus, which was the lowest‐yielding species at low P, but had among the highest yields at high P. No species showed evidence of P toxicity. The species exhibited a range in critical external P requirement (i.e. amount of P applied for 90% maximum yield). Among the fast‐growing Rytidosperma species, R. richardsonii was notable because it had a low critical external P (16·3 mg P pot^?1) and high agronomic P‐use efficiency (94·1 g DW g^?1 P applied). In contrast, R. duttonianum had a higher critical external P requirement (22·4 mg P pot^?1) and lower agronomic P‐use efficiency (85 g DW g^?1 P applied). It was concluded that it is important to know which Rytidosperma species are present in a grassland to understand how it may respond to P fertilization. The results help to explain the diverse opinions expressed about the productivity of pastures containing Rytidosperma species.     

湖北省典型茶园土壤重金属污染状况及评价

通过对湖北省61个典型茶园的土壤重金属Cu、Ph、As、Hg、Cd和Cr的含量测定,明确了湖北省典型茶园土壤重金属污染状况.结合土壤环境质量评价国家标准,采用单因子污染指数和内梅罗综合污染指数法,对湖北省典型茶园土壤重金属污染状况进行了分析评价.结果表明,湖北省茶园土壤环境质量状况良好,符合国家土壤环境质量标准(二级),处于清洁和尚清洁级标准的茶园比例分别为85.25%和13.11%,仅有1个茶园出现中度污染.茶园土壤重金属Pb、As和Hg的含量均未超标,个别茶园土壤重金属Cu、Cd和Cr出现超标现象.     

钾素水平对油菜酶活性的影响

利用盆栽试验研究不同钾素施用水平对油菜薹期酶活性的影响。结果表明 ,钾素缺乏和过量均可导致油菜叶片POD含量上升 ,CAT和SOD含量下降。不同施钾水平条件下 ,油菜下部叶的酶活性差异比上部叶更明显     

松阳县高速公路粉尘对茶叶重金属含量影响程度的探讨

在浙江省松阳县新兴镇茶区选一段山脚下高速公路,在其中200 m路段的路边种植3m高的小松树作为绿篱,从绿篱伸向5°山坡上茶园深处500 m设为绿篱区;相连的200 m路段不种植绿篱,从其路边伸向山坡上茶园500 m为对照(CK)区。在种植绿篱前、后1.5年,采集1芽1叶嫩梢、成叶和表土,检测铅、砷、镉、铬、铜、镁、锰、钠、镍和锌10种元素含量。结果:(1)种植绿篱前后,无论绿篱区还是CK区,嫩梢、成叶和表土的铅等10种元素含量范围皆没有明显改变,比如绿篱区内,种绿篱之前距路边0 m、100 m、200 m、300 m、400 m和500 m的1芽1叶嫩梢、成叶和表土的铅含量范围分别为0.25～0.55 mg/kg、0.47～2.11 mg/kg和23.11～37.46 mg/kg,种植绿篱1.5年之后,则分别为0.23～0.56 mg/kg、0.45～2.13 mg/kg以及23.05～37.42 mg/kg;(2)种植绿篱前、后,未有距离路边愈远,重金属含量呈递减的趋势;(3)铅、砷、铬和锰在嫩梢中含量明显小于在成叶中含量,4者在成叶中有累积效应;铜、镁、锌和镍在嫩梢中含量明显大于在成叶中含量。认为:现阶段高速公路汽车尾气和扬尘对于路边茶园的重金属污染可忽略。