Soil properties and turf growth on a sandy soil amended with fly ash

Field lysimeters of a sandy soil were amended to a depth of 100 mm with four rates (0, 5, 10 and 20%, wt/wt) of fly ash, and effects on soil water content, nutrient leaching, turf growth and nutrition, and uptake of trace elements by turf were assessed. Measurements were taken for 70 days for lysimeters either planted with rhizomes of Cynodon dactylon(L.) Pers., cv. `Wintergreen', or left bare. When irrigated daily, soil water content increased progressively with increasing rates of fly ash and leachate volumes were decreased by 17–52% for lysimeters containing fly ash amended soil. Fertiliser was applied equivalent to 28.4 g N m<sup>–2</sup> and 10.3 g P m<sup>–2</sup> for the entire 70 days (including pre-plant application). Macronutrient concentrations in leaf tissue were within levels regarded as sufficient. Total dry mass (root plus shoot) decreased when fertiliser application rates were reduced by 25%, irrespective of fly ash treatment. In `bare' lysimeters containing fly ash amended soil, cumulative leaching of NO₃ ^–, NH₄ ⁺and P were 0.32–0.88 of the values in non-amended soil. When planted with turf, leaching of those nutrients was minimal (equivalent to 3% of total N applied) and leaching loses did not differ among fly ash rates. Extractable soil P levels were increased 2.5–4.5-fold in the fly ash amended zone, compared with non-amended soil. Root mass in the top 100 mm was 1.2–1.5-fold larger for turf in fly ash amended soil, compared to non-amended soil. The Se concentrations were higher in leaf tissue grown in fly ash amended soil (being at most 0.63 g g^–1), but there was no effect of fly ash amended soil on As, Ba, B, Cd, Co, Cr, Cu, Pb, Hg, Mn, Ni, Ag or Zn in leaf tissues. Thus, fly ash amendment may be a suitable management option for turf culture on sandy soils, since fly ash improved soil water holding capacity and root growth in the amended zone.     

粉煤灰改良砂姜黑土对麦田生态因子及重金属残留的影响

采用盆栽试验,研究了粉煤灰改良砂姜黑土对麦田生态因子及Cd、Cr、Pb、Hg和As残留的影响.结果表明,粉煤灰改良砂姜黑土可以降低土壤容重和土壤比重,减少土壤粘粒含量,增加土壤孔隙度和土壤渗透系数,提高耕层地温,促进土壤微生物活动和养分转化;土壤含水量高时具有散湿作用,土壤含水量低于10%后,具有保墒作用;在粉煤灰用量为6×10⁴～18×10⁴kg·hm^-2的条件下,土壤及小麦子粒中重金属元素的积累量远低于国际污染标准值,即在此范围内,施用粉煤灰改良砂姜黑土是安全可靠的.     

Growth and physiological response of lemongrass (Cymbopogon citratus (D.C.) Stapf.) under different levels of fly ash-amended soil

Revegetation with metal tolerant plants for management of fly ash deposits is an important environmental perspective nowadays. Growth performance, photosynthesis, and antioxidant defense of lemongrass (Cymbopogon citratus (D.C.) Stapf.) were evaluated under various combination of fly ash amended with garden soil in order to assess its fly ash tolerance potential. Under low level of fly ash (25%) amended soil, the plant growth parameters such as shoot, root, and total plant biomass as well as metal tolerance index were increased compared to the control plants grown on garden soil, followed by decline under higher concentration of fly ash (50%, 75% and 100%). In addition, leaf photosynthetic rate, stomatal conductance, and photosystem (PS) II activity were not significantly changed under low level of fly ash (25%) amended soil compared to the garden soil but these parameters were significantly decreased further with increase of fly ash concentrations. Furthermore, increase of activities of some antioxidant enzymes such as superoxide dismutase, ascorbate peroxidase, and guaiacol peroxidase over control were noticed in lemongrass under all fly ash treatments. Taken together, the study suggests that lemongrass can be used for phytoremediation of fly ash at 25% amended soil.     

Effect of Ash Pond Soil and Amendments on the Growth and Arbuscular Mycorrhizal Colonization of Allium cepa and Germination of Arachis hypogaea,Lycopersicon esculentum,and Vigna mungo Seeds

The effect of fly ash pond soil on the growth and yield of onion (Allium cepa var. microaggregatum) plants grown in pots was investigated. The fly ash pond soil was amended with combinations of red soil and press mud, a waste product from sugar mills. Water-holding capacity of ash pond soil amended with press mud increased; however, addition of press mud delayed onion bulb development. Onion bulb germination took place rapidly in ash pond soil; however, subsequent bulb development declined. The addition of red soil and press mud increased the growth and yield of onion plants. In all the soils and amendments, onion plant roots were colonized by native arbuscular mycorrhizal species. Both vesicles and arbuscules were present in the roots. Colonization was low in ash pond soil but increased with the addition of red soil. Effect of fly ash pond soil on germination of groundnut (Arachis hypogaea), tomato (Lycopersicon esculentum), and black gram (Vigna mungo) seeds was evaluated and compared with red soil in the laboratory. Ash pond soil increased the germination of tomato seeds but did not affect the germination of groundnut and black gram seeds.     

Characteristics of boron accumulation by fly ash application in paddy soil

Fly ash has a high content of plant available silicate which is strongly needed for rice cultivation in Korea. One concern for plants grown on soils amended with fly ash is boron (B) toxicity because most of the fresh fly ash contains considerable B. This study was conducted in paddy soil to determine B uptake by rice and characteristics of B accumulation in soil after fly ash application (0, 40, 80, and 120 Mg fly ash ha⁻¹). In all fly ash treatments, B content in rice leaves and available B in soil at all growing stage were higher than those of control, but were not exceeded a toxicity levels. Boron occluded in amorphous Fe and Al oxides comprised ca. 20–39% of total B and was not affected by fly ash application. Most of the B was accumulated by fly ash application as a residual B which is plant-unavailable form, comprised >60% of the total B in soil. Thus, fly ash can be a good soil amendment for rice production without B toxicity.     

Inorganic materials as ameliorants for soil remediation of metal toxicity to wild mustard (Sinapis arvensis L.)

The ameliorating effects of different inorganic materials were investigated on a soil originating from a zinc smelter dumping site contaminated by toxic metals. Wild mustard (Sinapis arvensis L.) was used as a test plant. The soil was amended with different doses of mining sludge, Perferric Red Latosol (LVj), steel shots, cyclonic ash, silifertil, and superphosphate. The most effective amendments improved plant growth with 45% and reduced metal uptake by over 70% in comparison to untreated soil. Reductions in availability as estimated by BaCl2-extractable metals reached up to 90% for Zn and 65% for Cd as compared to unamended soil. These reductions were associated with lower shoot and root metal contents. Shoot Zn content was reduced from 1,369 microg g(-1) in plants grown on untreated soil to 377 microg g(-1) when grown on cyclonic ash amended soil while Cd decreased from 267 to 44 microg g(-1) in steel shots amended soil. Superphosphate addition had no ameliorating effect. On the contrary, it increased BaCl2-extractable amounts of Zn. Considering all parameters we determined, steel shots, cyclonic ash and silifertil are the most promising for remediating metal contaminated soil in the tropics. Further studies evaluating impacts, cost-effectiveness and durability of effects will be conducted.     

Suitability of Brahmi (Bacopa monnieri L.) cultivation on fly ash-amended soil for better growth and oil content

Abstract

Sustainable application of fly ash and its management in agriculture is a major challenge nowadays. A pot culture experiment was conducted to find out the most suitable level of fly ash application for soil amendments that can improve the plant growth and productivity of Brahmi (Bacopa monnieri L.). After growing seedlings of B. monnieri under different levels of fly ash for 90?days, a significant increase in plant biomass, essential oil content and tolerance index (more than 100%) was observed under 25% of fly ash amended soil in comparison to garden soil and higher fly ash treatments. Leaf chlorophyll content and photosynthetic parameters were remained unchanged under 25% of fly ash as compared to seedlings grown on garden soil. However, these parameters were significantly declined under higher concentrations of fly ash treatments. Higher levels of fly ash caused oxidative damage and the induction of some antioxidative enzymes activities in B. monnieri indicates its capability to endure oxidative stress tolerance. Overall, our study showed that 25% of fly ash can be used as soil amendment for cultivation of B. monnieri L. leading to enhance plant biomass and essential oil production.     

Gypsum amendment to soil can reduce selenium uptake by alfalfa grown in the presence of coal fly ash

Experiments in the field and greenhouse were conducted in the presence of coal fly ash to determine whether gypsum can reduce Se concentration in alfalfa (Medicago sativa L.). In the field experiment, conducted at a coal fly ash landfill, 11.2 t ha^-1 gypsum was applied to soil as a top dressing to test the effect of gypsum in reducing selenium (Se) concentration in aboveground plant tissue. There were four treatment combinations of gypsum over a two year period, 1990 and 1991: (0, 0), (0, 11.2) (11.2, 0) and (11.2, 11.2). In 1991, the Se concentration was lower in alfalfa grown with gypsum regardless of whether the gypsum was applied in both years or in only one year, indicating that the effect of gypsum application in the first year persisted into the second year. Since there was no increase in aboveground biomass with added gypsum, differences in Se concentration reflect a competitive interaction between S and Se. In the greenhouse experiment, 12 soil treatments were tested: three levels of fly ash (0, 10 and 20%) in combination with each of four levels of gypsum (0, 2.5, 5, and 7.5%). The Se concentration in alfalfa grown in 10% fly ash declined linearly with increasing gypsum dose, resulting in a reduction in Se concentration of 0.04±0.02 μg g^-1 for each 1% gypsum added for the first harvest and 0.06±0.03 μg g^-1 for each 1% gypsum added in the second harvest. Based on these results, gypsum may prove useful as a management tool to reduce the uptake of Se by plants growing on coal fly ash landfills. ei]H Lambers     

Effect of fly ash, organic wastes and chemical fertilizers on yield, nutrient uptake, heavy metal content and residual fertility in a rice-mustard cropping sequence under acid lateritic soils

A field experiment was conducted for two years in sandy loam acid lateritic soil to study the direct effect of fly ash, organic wastes and chemical fertilizers on rice (Oryza sativa) and their residual effect on mustard (Brassica napus var glauca) grown in sequence. Rice yields were higher when fly ash, organic wastes and chemical fertilizers were used in an integrated manner as compared to sole application of chemical fertilizers. Yields of mustard were also higher under the residual effect of the former rather than the latter. However, this beneficial residual effect under integrated nutrient sources was inadequate for the mustard crop in the low fertility test soil. Hence, direct application of fertilizers was needed, in addition to residual fertility. The effect of fly ash on mean rice equivalent yield of the rice–mustard cropping sequence was highest (up to 14%) when it was used in combination with organic wastes and chemical fertilizers. While the yield increase was 10% when it was used in combination with only chemical fertilizers. The minimum yield advantage, 3%, occurred when fly ash was applied alone. The equivalent yield of the rice–mustard cropping sequence was equally influenced by either of the organic wastes. Cadmium and Ni content in rice grain and straw were less under the direct effect of fly ash. The residual effect on mustard was similar for Ni content in seed and stover; however, Cd content was increased. Beneficial residual soil chemical properties in terms of pH, organic carbon and available N, P and K were noted for integrated nutrient treatments involved fly ash, organic wastes and chemical fertilizers as compared to continuous use of only chemical fertilizers. Application of fly ash alone was effective in raising soil available P. Thus, integrated use of fly ash, organic wastes and chemical fertilizers was beneficial in improving crop yield, soil pH, organic carbon and available N, P and K in sandy loam acid lateritic soil.     

粉煤灰基质上草坪草苗期生长状况及其评价

在未施肥的条件下,采用盆栽试验对粉煤灰、粉煤灰 泥炭土、粉煤灰 黄砂土、泥炭土、黄砂土5种基质上8种草坪草的苗期生长状况进行了研究。结果表明,白三叶、红三叶、黑麦草、高羊茅和马蹄金种子在粉煤灰基质上出苗快,其出苗率、苗高、分蘖数均高于粉煤灰 泥炭土和粉煤灰 黄砂土基质;但在后期出现叶片纤细、叶绿色浅淡。剪股颖在粉煤灰基质上出苗率低,结缕草和紫羊茅在粉煤灰基质上不出苗。     

Effect of cadmium on fungi and on interactions between fungi and bacteria in soil: influence of clay minerals and pH.

Fungi (Rhizopus stolonifer, Trichoderma viride, Fusarium oxysporum f. sp. conglutinans, Cunninghamella echinulata, and several species of Aspergillus and Penicillium) tolerated higher concentrations of cadmium (Cd) when grown in soil than when grown on laboratory media, indicating that soil mitigated the toxic effects of Cd. In soil amended with clay minerals, montmorillonite provided partial or total protection against fungistatic effects of Cd, whereas additions of kaolinite provided little or no protection. Growth rates of Aspergillus niger were inhibited to a greater extent by 100 or 250 mug of Cd per g in soil adjusted to pH 7.2 than in the same soil at its natural pH of 5.1. However, there were no differences in the growth rates of Aspergillus fischeri with 100 or 250 mug of Cd per g in the same soil, whether at pH 5.1 or adjusted to pH 7.2. Growth of A. niger and A. fischeri in a soil contaminated with a low concentration of Cd (i.e., 28 mug/g), obtained from a site near a Japanese smelter, did not differ significantly from growth in a soil collected some distance away and containing 4 mug of Cd per g. Growth of A. niger in sterile soil amended with 100 mug of Cd per g and inoculated with Bacillus cereus or Agrobacterium tumefaciens was reduced to a greater extent than in the same soil containing 100 mug of Cd per g but no bacteria. The inhibitory effects of Agrobacterium radiobacter to A. niger were slightly reduced in the presence of 100 mug of Cd per g, whereas the inhibitory effects of Serratia marcescens were enhanced.     

Effects of fly ash and Helminthosporium oryzae on growth and yield of three cultivars of rice

A 120-day greenhouse experiment was conducted to study the effects of various fly ash concentrations (0%, 20%, 40%, 60%, 80% and 100% vol/vol) with normal field soil and Helminthosporium oryzae on the growth and yield of three cultivars (Pusa Basmati, Pant-4 and Pant-10) of rice, Oryza sativa L. Application of 20% and 40% fly ash with soil caused a significant increase in plant growth and yield of all the three cultivars. Forty percent fly ash caused a higher increase in growth and yield than did 20%. Sixty percent, 80% and 100% fly ash had an adverse effect on growth and yield of all the three cultivars, the maximum being with 100% fly ash. Inoculation of H. oryzae had an adverse effect on the growth and yield, Pant-10 suffered higher damage by H. oryzae than Pusa Basmati and Pant-4. Pant-10 also exhibited higher infected leaf area and greater disease symptoms of H. oryzae than did Pusa Basmati and Pant-4. Plants grown in 100% fly ash suffered higher reductions in growth and yield with H. oryzae than plants grown in pure soil or in 20% or 40% fly ash. In general, plant growth was best in Pusa Basmati followed by Pant-4 and Pant-10, while yield was higher in Pant-4 followed by Pant-10 and Pusa Basmati.     

Effects of different treatments of fly ash and mining soil on growth and antioxidant protection of Indian wild rice

The aim of the present study was investigation of the effects of fly ash and mining soil on growth and antioxidant protection of two cultivars of Indian wild rice (Oryza nivara and Oryza rufipogon) for possible phytoremediation and restoration of metal-contaminated site. In this study, Indian wild rice showed significant changes in germination, growth, and biochemical parameters after exposure to different ratio of fly ash and mining soil with garden soil. There was significant reduction of germination, fresh weight, dry weight, leaf chlorophyll content, leaf area, Special Analysis Device Chlorophyll (SPAD) Index, proteins, and activities of antioxidant enzymes in both cultivars of the wild rice grown in 100% fly ash and mining soil compared to the plants grown in 100% garden soil. Results from this study showed that in both cultivars of wild rice, all growth and antioxidant parameters increased when grown in 50% fly ash and mining soil. Taken together, Indian wild rice has the capacity to tolerate 50% of fly ash and mining soil, and can be considered as a good candidate for possible phytoremediation of contaminated soils.     

Turf culture under declining volume and frequency of irrigation on a sandy soil amended with fly ash

The effects of four rates (0, 5, 10 and 20%, wt/wt) of fly ash amendment in a sandy soil (top 100–120 mm) on soil properties, turf (Cynodon dactylon (L.) Pers., cv. Wintergreen) water relations, growth and colour, were assessed during 84 days of irrigation treatments (irrigated daily, every 3^rd day, or every 4^th day) imposed during summer in a Mediterranean-type climate. In plots irrigated at 40% of net evaporation summed and applied every 3^rd day: (i) soil water contents were 14–33% higher in the fly ash amended soil zone when compared to values in plots with non-amended soil; (ii) soil water content below the root zone (i.e., 1500 mm) during that period remained low (being only 1–2% above the permanent wilting point), indicating minimal, if any, deep drainage. Extractable soil P was 2.0- to 3.8-fold higher in the fly ash amended soil compared to non-amended soil. By contrast extractable P was 1.7- to 2.1-fold higher in the soil 100–500 mm below the surface in non-amended plots, compared with fly ash amended plots. Irrigation at 40% replacement of net evaporation summed and applied every 3^rd day did not adversely impact on turf growth or colour, when compared to plots irrigated daily, irrespective of fly ash treatments. However, extending irrigations (at 40% of net evaporation) to every 4^th day reduced turf growth and colour, but the turf recovered fully from the mild water stress within 21 days of being irrigated daily at 100% replacement of net evaporation. Therefore, 40% replacement of net evaporation summed and applied every 3^rd day was a suitable watering schedule for maintenance of turf, with minimal risks of deep drainage.     

Effect of two biodegradable chelates on metals uptake,translocation and biochemical changes of Lantana Camara growing in fly ash amended soil

The present work had two purposes firstly to evaluate the potential of Lantana Camara for phytoextraction of heavy metals from fly ash amended soil and to assess the suitability of a proper biodegradable chelating agent for chelate assisted phytoextraction. Plants were grown in manure mixed soil amended with various concentration of fly ash. Two biodegradable chelating agents were added (EDDS and MGDA) in the same dose separately before maturation stage. Sampling was done at different growing stages. The plant took up metal in different plant parts in the following order: for Cu, and Zn leaf >root >stem, for Cr and Mn leaf>stem >root, for Ni root >leaf>stem and for Pb root≈leaf>stem respectively. For Cu, Zn, Cr and Mn Lantana camara acted as phytoextractor. Translocation factor and bioaccumulation coefficient was>1 signifying enrichment and translocation of metals in the plant. Morphological studies showed no toxicity symptom in the plant. Among biochemical parameters protein and nitrate reductase activity decreased, whereas, chlorophyll and peroxidise activity increased with the growth stages. Finally, it was evident from the results that Lantana Camara can be used as efficient phytoextractor of metals, with proper harvesting cycle and both chelate were proved as effective chelators for phytoextraction of metals.     

Plant uptake and phytotoxicity of boron in Australian fly ashes

Summary French bean (Phaseolus vulgaris cv. Redland Pioneer) and Rhodes grass (Chloris gayana cv. Pioneer) were grown in glasshouse experiments to examine the potential for phytotoxicity of B in a range of Australian fly ashes. In each experiment, the ashes used were either untreated, leached or adjusted to pH 6.5 and subsequently leached.In the first eperiment, the yield and B status of plants grown on five fly ashes mixed (5 and 10% by weight) with an acid-washed sand were measured and, with the exception of one ash, yield differences among ash sources and among ash treatments were attributed to differences in the degree of B toxicity. In a subsequent experiment, a fly ash with properties representative of most Australian ashes was mixed (0, 15, 30, 70 and 100% by weight) with a sandy loam, and the yield and mineral composition of plants grown on these mixtures determined. Although the available water capacity of the soil was substantially increased by fly ash addition, incorporating large proportions of untreated fly ash resulted in poor plant growth primarily due to B toxicity. In both experiments, leaching the ash reduced the potential for B toxicity, whereas adjustment of the pH to 6.5 and subsequent leaching of the fly ash resulted in plants with normal levels of B.There were marked differences in both the tissue levels of B and the extent of B toxicity symptoms between the two species. Rhodes grass appeared to be able to tolerate higher B contents in the growing medium by taking up much less of the element than French bean. The results indicate that phytotoxicity of B would be a major problem in establishing vegetation on ash dams and in the agronomic utilization of unweathered fly ashes in Australia.     

海南稻田土壤硒与重金属的含量、分布及其安全性

采集了海南省18个市(县)代表性的稻田土壤耕作层(0—20cm)样品280个,研究了硒(Se)和5种有毒重金属元素(Hg、Cd、Cr、Pb和As)的含量、分布及其相关关系,并对Se和重金属的安全性进行评价,可为合理区划清洁且富Se稻田提供理论依据。结果表明:海南稻田土壤中Hg、Cd、Cr、Pb和As平均含量均低于国家土壤环境质量一级标准值和全国土壤背景值,以绿色食品产地环境技术条件限量标准为标准,用单项污染指数法和内梅罗综合污染指数法评价海南稻田土壤重金属的污染状况,结果都是清洁的。但以海南省土壤背景值做参比值,Hakanson潜在生态危害指数达到211.54,属于强生态危害,从潜在生态危害系数来看,Hg(102.61)和Cd(98.89)达到强生态危害,分别比海南省土壤背景值增加1.56和2.3倍,今后应注意控制Hg和Cd污染源。稻田土壤Se含量从痕量到1.532mg/kg之间,平均值为0.211mg/kg,占47.5%的稻田土壤Se含量处于中等及以上水平(>0.175mg/kg)。Se含量高的稻田土壤主要集中在东北部的海口及其周边的澄迈、定安、文昌和琼海,还有东南部的万宁和保亭。由于重金属平均含量还比较低,可暂时忽略重金属污染,故可在上述Se含量高的稻田土壤上种植富Se水稻。稻田土壤Se含量与Hg、Cd和As含量呈极显著或显著正相关,因此今后应加强研究稻田土壤Se与Hg、Cd和As的有效性及其相互作用,以便生产出绿色的富Se优质大米。     

Effect of Cadmium on Fungi and on Interactions Between Fungi and Bacteria in Soil: Influence of Clay Minerals and pH

Fungi (Rhizopus stolonifer, Trichoderma viride, Fusarium oxysporum f. sp. conglutinans, Cunninghamella echinulata, and several species of Aspergillus and Penicillium) tolerated higher concentrations of cadmium (Cd) when grown in soil than when grown on laboratory media, indicating that soil mitigated the toxic effects of Cd. In soil amended with clay minerals, montmorillonite provided partial or total protection against fungistatic effects of Cd, whereas additions of kaolinite provided little or no protection. Growth rates of Aspergillus niger were inhibited to a greater extent by 100 or 250 μg of Cd per g in soil adjusted to pH 7.2 than in the same soil at its natural pH of 5.1. However, there were no differences in the growth rates of Aspergillus fischeri with 100 or 250 μg of Cd per g in the same soil, whether at pH 5.1 or adjusted to pH 7.2. Growth of A. niger and A. fischeri in a soil contaminated with a low concentration of Cd (i.e., 28 μg/g), obtained from a site near a Japanese smelter, did not differ significantly from growth in a soil collected some distance away and containing 4 μg of Cd per g. Growth of A. niger in sterile soil amended with 100 μg of Cd per g and inoculated with Bacillus cereus or Agrobacterium tumefaciens was reduced to a greater extent than in the same soil containing 100 μg of Cd per g but no bacteria. The inhibitory effects of Agrobacterium radiobacter to A. niger were slightly reduced in the presence of 100 μg of Cd per g, whereas the inhibitory effects of Serratia marcescens were enhanced.     

Application of Aspergillus niger-treated agrowaste residue and Glomus mosseae for improving growth and nutrition of Trifolium repens in a Cd-contaminated soil

The microbial transformation of sugar beet (SB) agrowaste with or without rock-phosphate (RP) has utility for the improvement of plant growth in a Cd (5 microg g-1) artificially contaminated soil, particularly when the soil is co-inoculated with arbuscular mycorrhizal (AM) fungus Glomus mosseae isolated from a Cd-polluted area. Under such Cd-polluted conditions, the limited growth, mineral nutrition, symbiotic developments (nodulation and AM-colonization) and soil enzymatic activities were stimulated using SB or SB+RP as soil amendments and G. mosseae as inoculant. G. mosseae enhanced plant establishment in a higher extent in amended soil; it is probably due to the interactive effect increasing the potential fertility of such compounds and its ability for decreasing Cd transfer from soil to plant. The amount of Cd transferred from soil solution to biomass of AM-colonized plants ranged from 0.09 microg Cd g-1 (in SB+RP-amended soil) to 0.6 microg Cd g-1 (in non-amended soil). Nodule formation was more sensitive to Cd than AM-colonization, and both symbioses were stimulated in amended soils. Not only AM-colonization but also amendments were critical for plant growth and nutrition in Cd-polluted soil. The high effectiveness of AM inoculum increasing nutrients and decreasing Cd in amended soil indicated the positive interaction of these treatments in increasing plant tolerance to Cd contamination.     

The potential of soil amendment with insect exuviae and frass to control the cabbage root fly

Reliable options to control the cabbage root fly, Delia radicum L., are lacking in many countries as restrictions on insecticide use have tightened due to environmental concerns. Although microbial control agents are often considered as a sustainable alternative, their application in agriculture is constrained by inconsistent efficacy owing to low field persistence. To stimulate naturally occurring beneficial microbes, soil amendment with the residual streams of insect production has been suggested as an alternative to synthetic fertilization and a new approach to microbial crop protection. In a set of greenhouse experiments, exuviae and frass of black soldier fly larvae, Hermetia illucens L., house crickets, Acheta domesticus L. and exuviae of mealworms, Tenebrio molitor L., were added to soil from an organically managed field. Exuviae and frass treatments were compared to treatments with synthetic fertilizer. Brussels sprouts, Brassica oleracea L., plants were grown in amended soil for 5 weeks before being infested with cabbage root fly larvae. Insect and plant performance were assessed by recording cabbage root fly survival, biomass and eclosion time and seed germination and plant biomass, respectively. Whereas soil amendment with black soldier fly frass or exuviae reduced cabbage root fly survival and biomass, respectively, amendment with house cricket or mealworm residual streams did not negatively affect root fly performance. Furthermore, seed germination was reduced in soil amended with house cricket exuviae, while amendment with either residual stream derived from black soldier fly larvae or house crickets resulted in lower plant shoot biomass compared with the synthetic fertilizer treatment. Amending soil with black soldier fly residual streams could become a novel and low-cost tool to be integrated in cabbage root fly management programmes, especially where methods currently available are insufficient. Therefore, the mechanisms underlying the effects of insect-derived soil amendments described here should be the focus of future research.