Long term effect of soil solarization on soil properties and cauliflower vigor

The effect of soil solarization on physical, chemical and biological properties of soil was studied, along with the response of cauliflower seedlings following solarization. Nursery beds were covered with transparent polyethylene sheet and soil temperature and moisture were recorded. Soil samples were collected five times for analysis. Three cauliflower nurseries were raised at 30-day intervals; germination was recorded 10 days after sowing and seedling length 30 days after sowing. The maximum temperature in solarized soil ranged from 40.2–47.2°C, with an increase of 5.2° to 9.9°C over non-solarized soil. There was a conservation of 5.48% moisture in solarized soil as compared with non-solarized. Solarization significantly increased electrical conductivity, organic carbon, nitrogen and potassium over pre-solarized soil. The mean pH, EC, Ca, Mg, N, P, K and C recorded in solarized soil was higher than in non-solarized. Soil solarization reduced the population of fungi from 25.68 x 10⁴ to 4.8 x 10⁴, bacteria from 20.28 x 10⁶ to 5.66 x 10⁶, actinomycetes from 31.60 x 10⁵ to 4.40 x 10⁵, and reduction in population was recorded even after 90 days, when compared with non-solarized soil. Solarization effectively reduced (>97%) population of plant parasitic and free living nematodes. Cauliflower seedlings in solarized soil had a better vigor index than non-solarized soil. Present findings reveal that soil solarization could be exploited for nutrient management and soilborne pests control, with a better vigor index of vegetable nursery.     

Suppression of Fusarium wilt of spinach with compost amendments

The effect of different organic composts on the suppression of wilt disease of spinach caused by Fusarium oxysporum f. sp. spinaciae was evaluated in a continuous cropping system in both containers and in microplot field trials. Test soils infested with the pathogen were amended with wheatbran, wheatbran and sawdust, coffee grounds, chicken manure, or mixture of different composts with and without 5% (w/w) crab shell powder either once (5%, w/w) or continuously (2.5%) into the test soils infested with the pathogen. In the container trials, the soil amended with composts became suppressive to disease development on the second and third cropping. The suppressive effect was notable in the soil amended with the mixture of compost with and without crab shell powder. The coffee compost lowered soil pH but became suppressive to the disease after modifying the soil pH. In the field trial using the mixture of the different composts containing 5% crab shell powder, a combination of 5% before the first cropping and 2.5% every second cropping gave stable disease control and promoted plant growth. After compost amendment, populations of fungi, bacteria and actinomycetes as measured by dilution plate counting and the total microbial activity as evaluated by fluorescein diacetate hydrolysis increased and population of the pathogen gradually decreased. These phenomena were especially notable in soils amended with the mixture of different composts. These results indicate that diversity in the organic materials promotes higher microbial activity and population in the soil thereby enhancing disease suppressiveness.     

Assessment of the differential response of weeds to soil solarization by two methods

The efficacy of solarization in weed control under field conditions of the United Arab Emirates was evaluated by two methods: on-farm weed assessment and a seed germination test. In the on-farm weed assessment method, the weed frequency, density, and dry weight were compared in the solarized and non-solarized plots that were cultivated with cabbage. Prior to solarization, the soil was artificially infested with the seeds of 10 weeds. Generally, the densities of seven species and dry weights of five species were significantly lower in the solarized plots as compared to the control. Launea mucronata , Capsella bursa-pastoris , and Echinochloa colona were very sensitive to solarization, as they did not appear in the solarized plots. However, Portulaca oleracea and Melilotus indica were not significantly affected by soil solarization. In the second method, the germination was assessed for the seeds of four weedy species buried at three depths for different durations of solarization. The results confirmed the great sensitivity of L. mucronata and C. bursa-pastoris seeds to solarization, as all had not germinated after 15 days of solarization, even at the 15 cm depth. The seeds of E. colona , however, were less sensitive after 15 days of solarization, especially at 7.5 cm and 15 cm, respectively. The seed germination method confirmed the resistance of the P. oleracea seeds to solarization. The results emphasized the importance of the germination test to provide accurate predictions about the spatial and temporal changes of the soil seed bank in solarized farms. This would help to determine the optimal duration of solarization in each farm, depending on the kind of weeds infesting the farm.     

Untersuchungen zum Einfluss einer Pflanzenschutzmittelspritzfolge auf das Rückstandsverhalten von Terbutryn und die mikrobielle Aktivität im Boden. Teil II. Beeinflussung der mikrobiellen Aktivität

Studies on the effect of a pesticide spray sequence on the behaviour of terbutryn residues and on soil microbial activity. Part II. Influence on microbial activity In laboratory incubation experiments (at 10 and 20°C and 30 and 60% soil water-holding capacity) soil microbial activities (dehydrogenase, respiration after glucose amendment and nitrogen transformations) were scarcely affected by 20·9 and 28·0 mg kg^?1, respectively, of terbutryn in two soils of different sorption properties. In contrast, dinosebacetate, alone or mixed with terbulryn, triadimefon or parathion, inhibited dehydrogenase activity and respiration even at a low rate of application (2·87 mg kg^?1). Following application of a 10 times higher rate to a highly adsorbent soil there was an initial inhibition of nitrification followed by an enhanced rate of nitrogen mineralization. Triadimefon and parathion, alone and in combination with other pesticides, caused both stimulation and inhibition of microbial activity; the reason is not clear. The effects on dehydrogenase and respiration were confirmed in field experiments. Dehydrogenase activity was the most sensitive and so could be a useful test for the side-effects of pesticides on soil micro-organisms. Additional work on nitrogen transformations is needed to interpret the results.     

Suppression of Rhizoctonia solani on Impatiens by Enhanced Microbial Activity in Composted Swine Waste-Amended Potting Mixes

ABSTRACT Peat moss-based potting mix was amended with either of two composted swine wastes, CSW1 and CSW2, at rates from 4 to 20% (vol/vol) to evaluate suppression of pre-emergence damping-off of impatiens (Impatiens balsamina) caused by Rhizoctonia solani (anastomosis group-4). A cucumber bioassay was used prior to each impatiens experiment to monitor maturity of compost as the compost aged in a curing pile by evaluating disease suppression toward both Pythium ultimum and R. solani. At 16, 24, 32, and 37 weeks after composting, plug trays filled with compost-amended potting mix were seeded with impatiens and infested with R. solani to determine suppression of damping-off. Pre-emergence damping-off was lower for impatiens grown in potting mix amended with 20% CSW1 than in CSW2-amended and nonamended mixes. To identify relationships between disease suppression and microbial parameters, samples of mixes were collected to determine microbial activity, biomass carbon and nitrogen, functional diversity, and population density. Higher rates of microbial activity were observed with increasing rates of CSW1 amendment than with CSW2 amendments. Microbial biomass carbon and nitrogen also were higher in CSW1-amended mixes than in CSW2-amended potting mixes 1 day prior to seeding and 5 weeks after seeding. Principal component analysis of Biolog-GN2 profiles showed different functional diversities between CSW1- and CSW2-amended mixes. Furthermore, mixes amended with CSW1 had higher colony forming units of fungi, endospore-forming bacteria, and oligotrophic bacteria. Our results suggest that enhanced microbial activity, functional and population diversity of stable compost-amended mix were associated with suppressiveness to Rhizoctonia damping-off in impatiens.     

Degradation of isoproturon and bentazone in peat- and compost-based biomixtures

BACKGROUND: The composition and properties of a biomixture used in a biobed are decisive for pesticide sorption and degradation. This study was performed to investigate the capability of compost‐based substrates in mixtures with citrus peel and vine branch straw and peat‐based substrates in mixtures with soil and vine branch straw at different levels in order to degrade isoproturon and bentazone. RESULTS: Dissipation and mineralisation rates of both pesticides were determined, and metabolic activity was followed as respiration. Compost‐based substrates showed faster pesticide dissipation in the presence of lignocellulosic materials, as in garden compost and vine branch straw. The increasing content of vine branch straw in peat‐based substrates does not seem to affect dissipation of the parent compounds. Low mineralisation rate was observed in all treatments. CONCLUSION: Higher pesticide degradation was observed in the lignocellulosic substrates, probably because of the development of lignin‐degrading microorganisms which have shown to be robust and are able to degrade recalcitrant pesticides. Copyright © 2010 Society of Chemical Industry     

Assessment of organic compost and biochar in promoting phytoremediation of crude-oil contaminated soil using Calendula officinalis in the Loess Plateau,China

The Loess Plateau, located in Gansu Province, is an important energy base in China because most of the oil and gas resources are distributed in Gansu Province. In the last 40 a, ecological environment in this region has been extremely destroyed due to the over-exploitation of crude-oil resources. Remediation of crude-oil contaminated soil in this area remains to be a challenging task. In this study, in order to elucidate the effects of organic compost and biochar on phytoremediation of crude-oil contaminated soil(20 g/kg) by Calendula officinalis, we designed five treatments, i.e., natural attenuation(CK), planted C. officinalis only(P), planted C. officinalis with biochar amendment(PB), planted C. officinalis with organic compost amendment(PC), and planted C. officinalis with co-amendment of biochar and organic compost(PBC). After 152 d of cultivation, total petroleum hydrocarbons(TPH) removal rates of CK, P, PB, PC and PBC were 6.36%, 50.08%, 39.58%, 73.10% and 59.87%, respectively. Shoot and root dry weights of C. officinalis significantly increased by 172.31% and 80.96% under PC and 311.61% and 145.43% under PBC, respectively as compared with P(P0.05). Total chlorophyll contents in leaves of C. officinalis under P, PC and PBC significantly increased by 77.36%, 125.50% and 79.80%, respectively(P0.05) as compared with PB. Physical-chemical characteristics and enzymatic activity of soil in different treatments were also assessed. The highest total N, total P, available N, available P and SOM(soil organic matter) occurred in PC, followed by PBC(P0.05). C. officinalis rhizospheric soil dehydrogenase(DHA) and polyphenol oxidase(PPO) activities in PB were lower than those of other treatments(P0.05). The values of ACE(abundance-based coverage estimators) and Chao 1 indices for rhizospheric bacteria were the highest under PC followed by PBC, P, PB and CK(P0.05). However, the Shannon index for bacteria was the highest under PC and PBC, followed by P, PB and CK(P0.05). In terms of soil microbial community composition, Proteiniphilum, Immundisolibacteraceae and Solimonadaceae were relatively more abundant under PC and PBC. Relative abundances of Pseudallescheria, Ochroconis, Fusarium, Sarocladium, Podospora, Apodus, Pyrenochaetopsis and Schizothecium under PC and PBC were higher, while relative abundances of Gliomastix, Aspergillus and Alternaria were lower under PC and PBC. As per the nonmetric multidimensional scaling(NMDS) analysis, application of organic compost significantly promoted soil N and P contents, shoot length, root vitality, chlorophyll ratio, total chlorophyll, abundance and diversity of rhizospheric soil microbial community in C. officinalis. A high p H value and lower soil N and P contents induced by biochar, altered C. officinalis rhizospheric soil microbial community composition, which might have restrained its phytoremediation efficiency. The results suggest that organic compost-assisted C. officinalis phytoremediation for crude-oil contaminated soil was highly effective in the Loess Plateau, China.     

Adsorption and degradation of thiazopyr in compost‐amended and non‐amended soils

Adsorption and degradation of thiazopyr on two unamended soils and a soil amended annually during 8 years with compost were studied under laboratory conditions and compared with the results obtained on soils amended with fresh sewage sludge compost. The adsorption isotherms fitted the Freundlich equation well and a marked sorption increase was found in amended soils. Degradation data followed first‐order kinetics and thiazopyr had a half‐life of about 75 days at 25 °C and 60% water‐holding capacity of soil. The addition of fresh compost markedly decreased the rate of thiazopyr degradation, whereas the compost mineralised in the field after annual additions had only a small influence. Incubation studies with sterile soils showed a very significant decrease of the degradation rate, indicating that degradation by micro‐organisms was the main pathway of thiazopyr degradation in the soils studied. © 2001 Society of Chemical Industry     

Einfluss von herbizidem Citronella-Öl und Neem (Azadirachtin) auf mikrobielle Aktivitäten im Boden

Within plant protection the products from citronella oil and neem mostly were used against pests. Their application for weed control is still at the beginning. This special application, however, needs higher dosages. The possible soil contamination and the missing microbiological-ecotoxicological information initiated our laboratory trial. The dosages used were relatively high as was necessary for weed control. They allowed the investigation of dose-effect relationships. In a loamy sand soil the biomass-related dehydrogenase activities as well as the carbon mineralization (actual and cumulative CO₂ formation) were measured. Because a soil with and without lucerne meal amendment was used the specific activity increase (=?LIA) could be calculated for both microbial parameters. Mostly both microbial activities were dose-dependently stimulated by the neem compound. Citronella oil at the beginning inhibited with the higher dosages and later on stimulated these activities. Most of the stimulations may be caused by the microbial decomposition of the organic compounds amended to the soil, which overlie some expected biocidal effects. This allows a preliminary estimation of the microbiological-ecotoxicological effects as less critical. Depending on the very high amounts needed for weed control, however, a final evaluation should consider additional investigations with further microbial activities and other soil organisms.     

The effects of soil solarization on sclerotial populations of Sclerotinia sclerotiorum

Solarization reduced the populations of sclerotia of Sclerotinia sclerotiorum in soil and reduced the ability of the surviving sclerotia to form apothecia. The greatest reductions occurred in the top 5 cm layer of soil but significant effects were seen at 10 and 15 cm depths. These reductions were due mainly to microbial colonization and degradation of sclerotia weakened by the sublethal temperatures produced by solarization. A beneficial side-effect was a significant reduction in the population of weeds in solarized plots.     

Limited survival of Ralstonia solanacearum Race 3 in bulk soils and composts from Egypt

Survival of Ralstonia solanacearum race 3 biovar 2 (phylotype II sequevar 1) in Egyptian soils and compost was studied under laboratory and field conditions. Survival of the pathogen under laboratory conditions varied with temperature, water potential and soil type, with temperature being the major determinant of survival of the pathogen. The effects of temperature and moisture content were variable between different experiments, but survival was generally longer at 15°C than at 4, 28 and 35°C respectively. Survival was also longer when moisture levels were constant compared with varying moisture levels at all temperatures. In experiments to compare the effects of progressive drying in sandy and clay soils there was a difference in survival times between the two soil types. In sandy soils, the pathogen died out more rapidly when soil was allowed to dry out than in controls where the soil was kept at constant water potential. In clay soils there was little difference between the two treatments, possibly due to the formation of a hard impermeable outer layer during the drying process, which retarded water loss from within. Survival in mature composts at 15°C was of the same order of magnitude as in soils but shorter at 28°C, possibly owing to increased biological activity at this temperature, or a resumption of the composting process, with concomitant higher temperatures within the compost itself. The maximum survival time recorded over all soil types and conditions during in vitro studies was around 200 days. In field studies, the maximum survival time in both bare sand and clay was around 85 days at depths up to 50 cm. The survival time was reduced in field experiments carried out in summer to less than 40 days and in one study when the ground was flooded for rice cultivation, the bacterium could not be detected 14 days after flooding. The maximum survival time of R. solanacearum in infected plant material or in infested soil samples incorporated into compost heaps was less than 2 weeks. At the culmination of field soil and compost experiments, no infection was detected in tomato seedlings up to 10 weeks after transplanting into the same soils or composts under glasshouse conditions at a temperature of 25°C.     

转基因抗草甘膦大豆叶片降解对土壤微环境的影响

转基因作物具有良好的商业价值和优良的性状品质,为世界带来了巨大经济效益与社会效益,但转基因产品存在未知的环境风险使其安全性颇具争议,对其进行相关研究必不可少。以转入G2-EPSPS和GAT双价基因抗草甘膦大豆GE-J12、受体Jack、常规主栽品种ZH37为研究对象,利用生物试验的方法,于2018―2020连续3年跟踪调查分别埋有3种大豆叶片的土壤中可培养微生物数量及土壤酶活性变化,旨在明确转基因抗草甘膦大豆叶片在土壤降解过程的土壤环境安全性。结果表明：（1）以2019年测定结果为例,从整个90 d的调查期来看,同一年份3种大豆叶片在土壤中降解过程中真菌、放线菌和细菌数量变化趋势相似,无显著性差异;3个处理对土壤脱氢酶、土壤脲酶、土壤蔗糖酶影响也相似,仅在处理后10 d,GE-J12的土壤蔗糖酶活性显著低于ZH37,但与受体Jack相比无显著性差异,且该差异并不会在整个调查期持续出现。（2）不同年份转基因大豆叶片在土壤中降解过程中土壤真菌、放线菌和细菌数量,土壤脱氢酶、土壤脲酶和土壤蔗糖酶活性变化趋势相似,并没有发生数量或活性值突然骤增或骤降的现象。从整体上看,2018年的微生物数量高...     

Inactivation of Macrophomina phaseolina Propagules during Composting and Effect of Composts on Dry Root Rot Severity and on Seed Yield of Clusterbean

Survival of a heat-tolerant pathogen Macrophomina phaseolina, causing dry root rot of clusterbean, was studied by incorporation and retrieval of infected residue samples at various stages of the composting process of pearl millet (Pennisetum glaucum) and clusterbean (Cyamopsis tetragonoloba) residues. During the heating phase, temperatures varied from 48–51°C at 30cm and 60–62°C at 60cm depth in compost pits. Reduction in survival of M. phaseolina propagules (13–23%) was significantly higher in the residues enriched with 4% urea-N and kept at 60cm compared to 2% urea-N and at 30cm. However, a heat phase (48–62°C) was not enough to completely eradicate M. phaseolina propagules from infected residues. Further reductions (54–61%) in survived propagules were achieved by sub-lethal temperatures (48–53°C) when moistened compost materials were exposed to heat during summer days. Beneficial effects of composts were ascertained on dry root rot intensity, seed yield of clusterbean and densities of M. phaseolina, Nitrosomonas and antagonists in soil. In a two-year field study, all the composts significantly reduced plant mortality due to dry root rot and increased the yield of clusterbean. The highest disease suppression and yield promotion were recorded in soil amended with pearl millet compost and cauliflower leaf residue compost, respectively. Soil amendment with compost also lead to a significant reduced density of M. phaseolina and an increased density of antagonistic actinomycetes, lytic bacteria and Nitrosomonas. Among composts, greater potential of cauliflower compost in enhancing population of antagonists in soil was discernible.     

异噁唑草酮对玉米根际土壤微生物量碳、氮和酶活性的影响

为明确异噁唑草酮对玉米根际土壤微生物碳、氮及酶活性的影响, 采用田间试验的方法, 以1倍、5倍和10倍田间推荐剂量为供试除草剂剂量, 测定了异噁唑草酮土壤封闭处理对玉米根际土壤微生物量碳、氮及土壤脲酶、过氧化氢酶、蔗糖酶、脱氢酶和中性磷酸酶活性的影响。结果表明:推荐剂量的异噁唑草酮对玉米根际土壤微生物量碳、氮含量无显著影响, 5倍和10倍推荐剂量的异噁唑草酮对玉米根际土壤微生物量碳、氮含量具有抑制作用。推荐剂量的异噁唑草酮对玉米根际土壤脲酶、过氧化氢酶和蔗糖酶影响较小, 5倍和10倍推荐剂量的异噁唑草酮对其具有明显的抑制作用。异噁唑草酮对土壤脱氢酶活性具有抑制作用, 且施用剂量越高, 抑制作用越强。异噁唑草酮对土壤中性磷酸酶活性的影响表现为前期促进, 后期抑制, 且施用剂量越大, 促进或抑制作用越强。研究表明:推荐剂量的异噁唑草酮对玉米根际土壤微生物量碳、氮及土壤脲酶、过氧化氢酶和蔗糖酶活性的影响较小, 但对土壤脱氢酶、中性磷酸酶活性有影响。     

The influence of soil properties on the rates of degradation of metamitron,metazachlor and metribuzin

The rates of degradation of metamitron, metazachlor and metribuzin were measured in 12 mineral soils and the first order rate constants were compared with soil properties by regression analysis. Rates of metamitron degradation were best described by a multiple regression involving the silt content of the soil and the fraction of the total herbicide content which was available in the soil solution. Metazachlor degradation was best described by a multiple regression involving the sand content of the soil, the availability of the herbicide in the soil solution and soil microbial respiration. There was evidence that metribuzin degradation in any one soil was closely related to microbial activity, and rate constants per unit microbial respiration were derived for each soil. These rate constants were best described by a multiple regression involving the Freundlich adsorption constant and the sand content of the soils. The best regression equations for each herbicide were tested against observed degradation rates in an additional group of six soils. The calculated rates compared favourably with those observed for both metamitron and metazachlor, but with metribuzin, there was good agreement with one soil only.     

The crucial role of calcium interacting with soil pH in enhanced biodegradation of metam-sodium

Enhanced biodegradation of soil-applied pesticides has long been correlated with soil pH above ca 6.5-7.5, but the possibility of confounding or interdependence with calcium, given that soil calcium concentration increases exponentially as pH rises above that range, has not previously been studied. Enhanced biodegradation of the broad-spectrum biocide metam-sodium was readily induced de novo in a naturally acid sandy soil (pH 4.2 measured in 0.01 M CaCl2) by multiple treatments, but only when the pH and calcium concentration were raised simultaneously using calcium carbonate (lime). Enhanced biodegradation was not induced when soil pH alone was raised with magnesium carbonate, nor when calcium alone was raised using calcium chloride. In limed sand treated monthly for 12 months, the degradation rate increased to where dissipation was complete within 24 h of application after the fifth metam-sodium treatment at pH 7.8 and after the eighth metam-sodium treatment at pH 6.8. Pesticide concentration was reduced, but not eliminated, at pH 5.8 and was unchanged at pH 4.8. When metam-sodium was applied bi- and tri-monthly, the degradation rate also increased when soil pH was raised with calcium carbonate, but to a lesser extent than with monthly applications. In an acid loam soil amended to the same pH values with calcium carbonate and treated monthly, there was no correlation between soil pH or calcium concentration and degradation. The results reveal the crucial interdependence of pH and calcium concentration in enhancement of biodegradation of soil-applied pesticides, but confirm that the phenomenon ultimately depends on interaction with soil type and frequency of application factors, all of which probably together act to affect the abundance, composition and activity of the soil microbial biomass.     

Solarization of soil in piles for the control of Meloidogyne incognita in olive nurseries in southern Spain

The potential of solarization to control Meloidogyne incognita in piles of soil used at olive nurseries in southern Spain was studied in 1999 and 2000. Kaolin and soil infested with free eggs and egg masses of the nematode in nylon bags were buried 20 and 40 cm deep inside conical piles of soil 80 cm high and with a base diameter of 1 m. Soil piles were solarized for 3 weeks in July and August. The effect of various periods of solarization was assessed by egg hatch bioassays in sterile water, and by infectivity to tomato plants. Maximum soil temperature at 20 cm depth in solarized piles was 47·4°C in 1999 and 48·2°C in 2000, compared with 32·9°C and 31·7°C in nonsolarized piles. Solarization reduced egg hatch by > 95% compared with nonsolarized samples, irrespective of type, burial depth and location of inocula in a soil pile. Egg hatch of egg mass-infested samples buried at 20 cm depth was higher than that of free eggs buried at the same depth. The differential effect associated with burial depth and type of inoculum was not found in solarized piles. In nonsolarized piles, hatch of free eggs from samples buried at 40 cm depth was higher than that from samples buried at 20 cm depth. Egg hatch in samples from solarized piles was lower than that from nonsolarized piles. A bioassay of tomato plants in 2000 confirmed the reduction in infectivity of free eggs buried in solarized soil piles. Under the conditions in southern Spain, solarization of 40 cm-high piles of soil for 3 weeks can therefore be used for the control of root-knot nematodes in potting soil for olive nursery production.     

Arbuscular mycorrhizal fungal community of wheat under long-term mineral and organic amendments in semi-arid Mediterranean Turkey

A minimal amount of information is currently available concerning arbuscular mycorrhizal (AM) fungal associations with crops in semi-arid zones on Leptosols in Turkey. Therefore, using molecular ecological techniques, we studied the effects of different management practices (without fertilization, chemical fertilization, farmyard manure, and plant compost amendments) on AM fungal communities associated with wheat roots. Experiments were conducted in a field established in 1996 in southern Mediterranean Turkey where soil productivity is low owing to unfavorable climatic effects and soil characteristics. We determined 201 partial sequences of AM fungal nuclear ribosomal large subunit genes. The higher AM fungal richness was found in the control treatment without fertilization and plant compost treatments compared with the chemical fertilization and farmyard manure treatments. Clones related to Rhizophagus were found in all treatments and accounted for 37% of the total AM fungal clones, whereas those of Funneliformis were dominant under chemical fertilization. Redundancy analysis based on the frequency of operational taxonomic units revealed that AM fungal communities were divided into three groups, namely, the control treatment, the chemical fertilization treatment, and the organic treatments (farmyard manure and plant compost treatments). Although different organic amendments supported relatively similar AM fungal communities, plant compost induced higher AM fungal richness than farmyard manure fertilization.     

The effects of soil solarization and soil fumigation on Fusarium wilt of watermelon grown in plastic house in south-eastern Spain

The effects of pre-planting solarization or fumigation with metham-sodium of sand-mulched soil on fusarium wilt of watermelon in plastic house culture were investigated at Almeria, south-eastern Spain. In two trials, 2 months' solarization increased the average maximum soil temperature by c. 5°C to 44-48° C at 10 cm depth and by 4-5° C to 40-42° C at 20-30 cm. The amount of Fusarium oxysporum in the upper 15 cm of a naturally infested soil was reduced by solarization and by fumigation. During the 9 months following treatment, the F. oxysporum population stabilized at a low level in soil solarized for 2 months, but fluctuated in soil solarized for 1 month and increased in fumigated soil. The amount of wilt in watermelon sown into this soil after treatment was generally low; plants growing in solarized or fumigated soil suffered less wilt than plants in untreated soil but the differences were not significant. In a soil artificially infested with the highly pathogenic race 2 of F. oxysporum f. sp. niveum, F. oxysporum populations were greatly reduced following solarization or fumigation, and fluctuated erratically thereafter. Solarization for 2 months completely controlled wilt in watermelon and gave a fruit yield almost five times that of plants in untreated soil. Solarization for 1 month only slowed disease development slightly but gave a yield more than twice that in untreated soil. Fumigation with metham-sodium retarded disease development considerably and tripled fruit yield. Plant performance was significantly better in soil solarized for 2 months than in uninfested control soil, suggesting beneficial effects of this treatment additional to wilt control.     

噻酮·异噁唑对玉米根际土壤微生物量碳、氮和酶活性的影响

为明确噻酮·异噁唑对玉米根际土壤微生物量碳、氮及酶活性的影响,采用田间试验的方法,测定了田间推荐剂量、5倍推荐剂量和10倍推荐剂量的噻酮·异噁唑土壤封闭处理对玉米根际土壤微生物量碳、氮及土壤脲酶、过氧化氢酶、蔗糖酶、中性磷酸酶和脱氢酶活性的影响。结果表明,推荐剂量的噻酮·异噁唑处理后,玉米根际微生物量碳、氮与对照无显著差异,处理后28 d, 5倍推荐剂量和10倍推荐剂量处理的玉米根际土壤微生物量碳、氮受到抑制,与对照有显著差异。推荐剂量的噻酮·异噁唑对玉米根际土壤酶活性影响小,与对照无显著差异,5倍和10倍推荐剂量的噻酮·异噁唑对土壤脲酶、过氧化氢酶、蔗糖酶和脱氢酶活性具有抑制作用,但试验后期可恢复到对照水平,5倍和10倍推荐剂量的噻酮·异噁唑对中性磷酸酶活性有显著的抑制作用,施药后不可恢复到对照水平。研究表明:推荐剂量的噻酮·异噁唑对玉米根际土壤微生物量碳、氮及土壤酶活性的影响小,试验后期可恢复到对照水平。