Effect of Organic Management of Soils on Suppressiveness to <Emphasis Type="Italic">Gaeumannomyces graminis</Emphasis> var. <Emphasis Type="Italic">tritici</Emphasis> and its Antagonist, <Emphasis Type="Italic">Pseudomonas fluorescens</Emphasis>

Organic management of soils is generally considered to reduce the incidence and severity of plant diseases caused by soil-borne pathogens. In this study, take-all severity on roots of barley and wheat, caused by Gaeumannomyces graminis var. tritici, was significantly lower in organically-managed than in conventionally-managed soils. This effect was more pronounced on roots of barley and wheat plants grown in a sandy soil compared to a loamy organically-managed soil. Fluorescent Pseudomonas spp. and in particular phlD⁺ pseudomonads, key factors in the take-all decline phenomenon, were represented at lower population densities in organically-managed soils compared to conventionally-managed soils. Furthermore, organic management adversely affected the initial establishment of introduced phlD⁺ P. fluorescens strain Pf32-gfp, but not its survival. In spite of its equal survival rate in organically- and conventionally-managed soils, the efficacy of biocontrol of take-all disease by introduced strain Pf32-gfp was significantly stronger in conventionally-managed soils than in organically-managed soils. Collectively, these results suggest that phlD⁺ Pseudomonas spp. do not play a critical role in the take-all suppressiveness of the soils included in this study. Consequently, the role of more general mechanisms involved in take-all suppressiveness in the organically-managed soils was investigated. The higher microbial activity found in the organically-managed sandy soil combined with the significantly lower take-all severity suggest that microbial activity plays, at least in part, a role in the take-all suppressiveness in the organically-managed sandy soil. The significantly different bacterial composition, determined by DGGE analysis, in organically-managed sandy soils compared to the conventionally-managed sandy soils, point to a possible additional role of specific bacterial genera that limit the growth or activity of the take-all pathogen.     

Effect of soil amendments and biological control agents (BCAs) on soil-borne root diseases caused by <Emphasis Type="Italic">Pyrenochaeta lycopersici</Emphasis> and <Emphasis Type="Italic">Verticillium albo-atrum</Emphasis> in organic greenhouse tomato production systems

The effect of different soil amendments and biological control agents on soil-borne root diseases that cause significant economic losses in organic and other soil-based tomato production systems (Pyrenochaeta lycopersici and Verticillium albo-atrum) was compared. Organic matter inputs (fresh Brassica tissue, household waste compost and composted cow manure) significantly reduced soil-borne disease severity (measured as increased root fresh weight) and/or increased tomato fruit yield, with some treatments also increasing fruit number and/or size. Soil biological activity also increased with increasing organic matter input levels and there were significant positive correlations between soil biological activity, root fresh weight and fruit yield. This indicates that one mechanism of soil-borne disease control by organic matter input may be increased competition by the soil biota. Chitin/chitosan products also significantly reduced soil-borne disease incidence and increased tomato fruit yield, number and/or size, but had no effect on soil biological activity. Biological control products based on Bacillus subtilis and Pythium oligandrum and commercial seaweed extract (Marinure) and fish emulsion (Nugro)-based liquid fertilisers had no positive effect on soil-borne disease incidence and fruit yield, number and size. The use of ‘suppressive’ organic matter inputs alone or in combination with chitin/chitosan soil amendments can therefore be recommended as methods to control soil-borne diseases in organic and other soil-based production systems.     

Potato brown rot incidence and severity under different management and amendment regimes in different soil types

Ralstonia solanacearum race 3 biovar 2, the causative agent of potato brown rot (bacterial wilt), is an economically important disease in tropical, subtropical and temperate regions of the world. In view of previous reports on suppression of the disease by organic amendments, and the expansion of organic agriculture, it was timely to compare the effects of organic and conventional management and various amendments on brown rot development in different soils (type: sand or clay; origin: Egypt or the Netherlands). Brown rot infection was only slightly reduced in organically compared to conventionally managed sandy soils from Egypt, but organic management significantly increased disease incidence and pathogen survival in Dutch sandy and clay soils, which correlated with high DOC contents in the organic Dutch soils. There was no correlation between disease incidence or severity and bacterial diversity in the potato rhizosphere in differently managed soils (as determined by 16S DGGE). NPK fertilization reduced bacterial wilt in conventional Egyptian soils but not in Dutch soils. Cow manure amendment significantly reduced disease incidence in organic Dutch sandy soils, but did not affect the bacterial population. However, cow manure did reduce densities of R. solanacearum in Egyptian sandy soils, most probably by microbial competition as a clear shift in populations was detected with DGGE in these and Dutch sandy soils after manure amendment. Amendment with compost did not have a suppressive effect in any soil type. The absence of a disease suppressive effect of mineral and organic fertilization in Dutch clay soils may be related to the already high availability of inorganic and organic nutrients in these soils. This study shows that the mechanism of disease suppression of soil-borne plant pathogens may vary strongly according to the soil type, especially if quite different types of soil are used.     

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.     

Characterization of the Suppressiveness of Hairy Vetch-Amended Soils to Thielaviopsis basicola

ABSTRACT Factor(s) involved in soil suppressiveness to Thielaviopsis basicola when hairy vetch was used as a green manure were studied in a cotton production system. Soil suppressiveness was assessed in vitro at hairy vetch amendment levels of 0, 0.25, and 0.75% (wt/wt) by observing chlamydospores, using a nylon fabric technique. Chlamydospore germination in all soils was below 5%, and microscopic examination showed no germ tube lysis or visible propagule destruction. Viability (chlamydospore germination on T. basicola-carrot-etridiazol-nystatin [TB-CEN] medium) was reduced by 29% within 48 h after hairy vetch amendment. Viability also was reduced in atmospheres of amended soils, suggesting that the suppressiveness was due to a volatile factor. In a field study, chlamydospore viability in amended soils was reduced by 16%. T. basicola hyphal growth was more sensitive to ammonia than Rhizoctonia solani or Pythium ultimum, and chlamydospore mortality of T. basicola was 100% in petri dish atmospheres with 0.4 ppm of ammonia (50% lethal dose = 0.15 ppm). Soil atmospheric ammonia was 0.08 and 0.10 ppm for 0.25 and 0.75% amendment levels, respectively, both at 3 and 7 days after incorporation. In the field, 0.11 and 0.14 ppm of ammonia were detected in soil atmospheres 3 and 7 days after incorporation, respectively. The levels of ammonia detected were sufficient to account for the loss in T. basicola chlamydospore viability, indicating that ammonia is responsible for the suppressiveness observed.     

Suppression of Rhizoctonia solani in potato fields. 1. Occurrence

A search was made forRhizoctonia solani-suppressive soils by establishing many small experimental plots, half of which were planted withRhizoctonia-infected seed potatoes and the other half with disinfected seed stock. The sclerotium index of the harvested tubers was compared witht that of the seed potatoes. In suppressive soils, the sclerotium index of the harvest is much lower than that of the seed potatoes. None of the plots on holocene marine soils (loamy sand, sandy loam, clay loam and clay) proved to be suppressive in 1978 and 1979. Only on pleistocene, slightly acid sandy soil suppressiveness was observed. In 1978, four out of twelve plots showed suppressiveness when the plots were planted with seed potatoes produced on a sandy soil. In 1979, only two out of thirtyone plots were slightly suppressive when planted with seed potatoes produced on a young clay loam from a new polder. A higher percentage of sclerotia on tubers from sandy soils proved to be infected with antagonistic fungi (73%) than of those on tubers from marine clay or loam soils (25%). Factors that influence suppressiveness are suggested.     

长期施用绿肥对小麦玉米间作土壤微生物的影响

利用Biolog微平板法和高通量测序技术，研究小麦玉米间作条件下，不同长期施肥处理土壤微生物对不同碳源的利用差异以及土壤微生物群落在门、属水平上的变化，探明长期施用绿肥对土壤微生物群落多样性及代谢功能的影响。结果表明：长期施用绿肥可显著提高土壤有机质、速效磷和速效钾含量，降低土壤pH值，增强土壤微生物碳源代谢能力。不同施肥条件下，放线菌门(Actinobacteria)和变形菌门(Proteobacteria)为土壤优势菌群，绿肥处理的放线菌门丰度最高(29.94%),农家肥处理最低(22.95%);秸秆还田处理的变形菌门丰度最高(22.32%),对照处理最低(18.85%);酸杆菌门(Acidobacteriota)、绿弯菌门(Chloroflexi)、厚壁菌门(Firmicutes)在各个处理中的相对丰富度较高，分别为13.39%～19.71%、10.85%～14.56%、3.54%～12.98%。长期施用绿肥有效提高了土壤放线菌门、厚壁菌门、芽孢杆菌属(Bacillus)以及假节杆菌属(Pseudarthrobacter)的丰度，降低了酸杆菌门的丰度，增加了土壤微生物种群数量。综...     

Effect of prior tillage and soil fertility amendments on dispersal of Phytophthora capsici and infection of pepper

Organic soil amendments including composted cotton gin trash, composted poultry manure, an incorporated rye-vetch green manure, or synthetic fertilizer were applied to subplots, and main plots were either tilled frequently or surface-mulched in experimental field plots between 1997 and 2004. Soil from each replication of the tillage and fertility treatments was sampled in August of 2001, 2002, and 2003, brought to the greenhouse, and infested with Phytophthora capsici to study the effect of previous soil treatments on disease incidence and dispersal of the pathogen. Both the previous tillage and fertility amendments affected the incidence of disease and dispersal of the pathogen. Final disease incidence, AUDPC and the distance of pathogen spread were significantly greater in soils with previous surface mulch applications than in frequently tilled soils. Final disease incidence, AUDPC and the distance of pathogen spread were also significantly higher in soils amended with cotton gin trash, than rye-vetch green manure, poultry manure, or synthetic fertilizer. Soils amended with cotton gin trash had higher soil water content, lower bulk density, higher humic matter content, higher porosity and higher levels of mineralizable N, than soils with other fertility amendments. Soil water content, soil porosity, humic matter content, and net mineralizable levels nitrogen were positively correlated and bulk density was negatively correlated with final incidence of disease.     

Dynamics of the root/soil pathogens and antagonists in organic and integrated production of potato

Microbial communities in the root, rhizoplane, and rhizosphere and non-rhizosphere soil in potato, in organic and integrated production systems, were compared at the emergence and flowering phases of plant development. Microorganisms were identified on the basis of their morphology. The dominant groups included Clonostachys + Gliocladium + Trichoderma, Fusarium + Gibberella + Haematonectria + Neonectria, Paecilomyces, Penicillium and Phoma. Microbial density at the flowering phase was often significantly greater in roots and non-rhizosphere soil than in the rhizoplane and rhizosphere. Diversity of the communities often remained stable or was greater at the emergence phase. The density of bacteria changed with time. The density of Pseudomonas often decreased while Streptomyces significantly increased with time. Changes in densities of pathogens and antagonists decreased the suppressiveness of the habitat towards soil-borne potato pathogens at the flowering phase. The study contributes information that will help to: (a) understand the epidemiology of some potato diseases, (b) make decisions on the economic and ecological aspects of chemical control in potato, (c) develop strategies for manipulation of the soil microbial environment as a viable crop management technique, and (d) develop prognosis models for potato diseases in central Europe.     

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.     

Influence of abiotic factors,inoculum source,and cultivar susceptibility on the potato tuber blemish diseases black dot (Colletotrichum coccodes) and silver scurf (Helminthosporium solani)

Black dot and silver scurf are potato blemish diseases whose economic impact has increased in recent years. Because their symptomatology on tubers is visually similar, disease assessment does not usually differentiate between the two pathogens, which share the same ecological niche. The epidemiology of black dot has been extensively studied, especially in the UK, but the factors that influence silver scurf have been less investigated. In this study, the influence of cultivar, source of inoculum, and environmental conditions on both diseases was studied in field trials over a three-year period (2016–2018) in Switzerland. Planting minitubers did not prevent either disease in daughter tubers, indicating the contribution of soil as an inoculum reservoir. An arbitrary threshold of Colletotrichum coccodes soil inoculum could be set to discriminate between low and high disease risk. For the first time, Helminthosporium solani DNA was detected in stolons, and infections appeared earlier in stolons than in tubers. H. solani stolon and tuber infections usually appeared later in the season than those of C. coccodes. Black dot severity correlated positively with precipitation, while silver scurf severity correlated positively with temperature. Table potato cultivars commonly grown in Switzerland exhibited significant differences in susceptibility to both diseases, and cultivars with low susceptibility to both silver scurf and black dot were identified. These results gave new insights into understanding the factors driving the epidemiology of potato blemish diseases and may contribute to building a risk assessment scheme to manage both diseases simultaneously.     

Mixtures of organic amendments and biochar promote beneficial soil microbiota and affect Fusarium oxysporum f. sp. lactucae,Rhizoctonia solani and Sclerotinia minor disease suppression

The use of soil fumigants and fungicides to control soilborne pathogens is reduced due to awareness of their negative drawbacks. Long-term application of such agrochemicals negatively affects soil microbiota and reduces natural soil suppressiveness. We investigated long-term impacts of biochar and not-pyrogenic organic amendment (OAs: manure, alfalfa straw and glucose), on disease suppression compared with conventional management in three pathosystems: Fusarium oxysporum f. sp. lactucae (FOL)–lettuce, Rhizoctonia solani–tomato and Sclerotinia sclerotiorum–lettuce, by conditioning soil for 2 years. Soil analyses included pH, electrical conductivity, organic carbon, total nitrogen, C:N ratio, N-NO₃⁻, N-NH₄⁺, cation exchange capacity, available phosphorus, Ca²⁺, Mg²⁺, K⁺, Na⁺, fluorescein diacetate (FDA), and total and active limestone. Soil microbiota was characterized by combining BIOLOG EcoPlates with next-generation sequencing of 16S and 18S rRNA genes. Soil amended with OAs generally suppressed disease by S. sclerotiorum and FOL compared to fumigants and synthetic fertilizers. However, the incidence of R. solani infection was lower in soil treated with synthetic fertilizers than soil amended with OAs. EC, pH, C:N, N-NO₃⁻, N-NH₄⁺, FDA and BIOLOG were significantly correlated with disease, depending on pathosystem. Bacterial richness and diversity, presence of some genera like Acidobacteria, Chloracidobacteria, Solibacteres, Anaerolineae, Nitrospira and Deltaproteobacteria were negatively related to disease incidence of FOL and S. sclerotiorum, whereas damping-off caused by R. solani was negatively affected by the presence of Flavobacterium and Chitinofagha. Therefore, we concluded that long-term application of OAs can effectively improve soil suppressiveness and reduce disease incidence against root pathogens, although the effects vary considerably depending upon pathosystem.     

Evaluation of fungicide application rates,spray schedules and alternative management options for rust and angular leaf spot of snap beans in Uganda

Yield losses due to rust and angular leaf spot (ALS) of snap beans may reach 100% in Eastern Africa. Where susceptible varieties are grown, farmers control these diseases with routine fungicide applications. To determine an optimum application rate and spray schedule for Orius® (tebuconazole 250 g/L), we sprayed 10 mL and 20 mL Orius® per 15 L spray water twice at two trifoliate leaf stage and 50% flowering, and three times at the same stages, with an additional application at pod initiation. In farmers’ fields, we tested the effect of fungicide sprays, use of resistant variety, intercropping, increased plant spacing and farmyard manure on rust and ALS diseases. Application three times of 20 mL Orius® per 15 L spray water reduced rust severity scores by 5.7 and 2.4 in 2010 and 2011, respectively. Lowest rust and ALS severities were observed when a resistant variety, fungicide or farmyard manure was used. Pod yield increments due to disease management ranged between 13% and 242%. Prophylactic fungicide application, use of resistant varieties and farmyard manure can be used to reduce disease severity and improve snap bean quality on smallholder farms.     

Isolation of the most common Fusarium species and the effect of soil solarisation on main pathogenic species in different climatic zones of Iran

Understanding the distribution pattern of the Fusarium species can help prevent crop diseases and large yield losses. While several approaches have been used to control soil-borne pathogens, soil solarisation has shown promising results in managing these pathogens. The main objectives of this study were to: (i) describe the biogeography of Fusarium species in four different climatic zones in Iran and (ii) explain the effect of soil solarisation on main pathogenic Fusarium species in wheat grains, beans and date palms. A total of 12 sub-samples were collected from four different climatic zones including, Rasht (humid), Zanjan (semi-arid), Isfahan (extra-arid) and Ahwaz (arid). For precise identification, molecular-phylogenetic analyses of the species were also performed. From these four sites 17 Fusarium species were recovered. F. solani complex, F. oxysporum and F. equiseti were the only species found in all four regions; whereas F. compactum, F. sambucinum and F. fujikuroi were restricted to Ahwaz, Zanjan and Rasht, respectively. Furthermore, soil solarisation treatments were applied to F. pseudograminearum, F. solani and F. oxysporum, as the main cause of root rot pathogens and wilt disease of wheat, bean and date palm, respectively. After 6 weeks of soil solarisation application, the population densities of these species were decreased from 900 to 100 CFU g^?1 in F. solani, from 600 to 50 CFU g^?1 in F. oxysporum and from 550 to 0 CFU g^?1 in F. pseudograminearum showing a promising result in controlling soil-borne pathogens. Mycogeography of Fusarium species and the effect of soil solarisation can help improve the management control strategies of these soil-borne fungi.     

A new large scale soil DNA extraction procedure and real-time PCR assay for the detection of Sclerotium cepivorum in soil

A real-time PCR assay specific for Sclerotium cepivorum, the causal agent of white rot in onions, was developed for use with a new DNA extraction method capable of processing up to 1?kg of soil in weight. The assay was specific for S. cepivorum when tested against 24 isolates representative of 14 closely related species and other pathogens of onion. The assay was highly sensitive when used with soil DNA extracted using the new DNA extraction procedure. In three different field soils tested, a good relationship between cycle threshold (Ct) and number of sclerotia was observed (R2?=?0.89). Twenty-nine soil samples from onion and leek crops were obtained and the pathogen was detected in four samples. All four positive samples were associated with current or past outbreaks of white rot of onion. Additional assays were also used on the 29 field soil samples, Botrytis aclada and Rhizoctonia solani AG8 were also detected, in one soil sample each. Rhizoctonia solani AG2-1 was more widespread and was detected in eight different soil samples. The method is therefore suitable to quantify levels of S. cepivorum in soil samples, with the added advantage that the technique allows other soil pathogens of interest to be assayed from the same DNA sample. The bulk soil DNA extraction method described here has the potential to be used to detect soil-borne pests and pathogens for other crops in a wide range of soil types.     

Available alkalinity and N mineralization are key factors regulating soil pH value of an organically amended Iranian agricultural soil

This study was conducted to evaluate short- and long-term effects of poultry and sheep manures, as well as sunflower, canola, and potato residues, which commonly are being used as organic amendments (OAs) in agricultural soils, on the pH value, buffering capacity, and nitrogen (N) turnover of a sub-alkaline agricultural soil using laboratory incubation. The tested OAs had pH values ranging from alkaline (manures) to acidic (plant residues), and their effects of the short- and log-term on soil pH value were assessed by fractionation of the OAs alkalinity and evaluating the contribution of OA-borne N mineralization to soil acidity. On average, 45% of potential alkalinity in tested OAs was available for acid-base reactions, soluble alkalinity accounted for 58, 80, 32, 50, and 50% of the excess cations for poultry manure, sheep manure, sunflower, canola, and potato residues, respectively. Buffering capacity of the tested OAs was higher for sunflower residues, potato residues, and poultry manure and lower for canola residues and sheep manure. The tested OAs showed different N mineralization potential, and during the 100 days of incubation, soils amended with sheep manure, poultry manure, and potato residues released 107, 118, 129, and 240?mg?N?kg^?1 soil, respectively, more than double than that released from unamended soil. Our results demonstrated that long-term impact of OAs on the soil pH value is not related to the initial OAs pH value and soluble alkalinity and that available alkalinity and N mineralization are key factors regulating the soil pH value on the long-term.     

Field management effects on damping-off and early season vigor of crops in a transitional organic cropping system

Transitioning farmland to certified organic vegetable production can take many paths, each varying in their costs and benefits. Here, the effects of four organic transition strategies (i.e., tilled fallowing, mixed-species hay, low-intensity vegetables, and intensive vegetable production under high tunnels), each with and without annual compost applications for 3 years prior to assessment, were characterized. Although transition cropping strategies differed in soil chemistry (P < 0.05), the magnitude of the changes typically were marginal and pairwise comparisons were rarely significant. In contrast, the compost amendment had a much greater impact on soil chemistry regardless of cropping strategy. For example, percent C and total P increased by 2- to 5-fold and K increased from 6- to 12-fold. Under controlled conditions, damping-off of both edamame soybean (cv. Sayamusume) and tomato (cv. Tiny Tim) was reduced from 2 to 30% in soils from the mixed-hay transition. In the field, damping-off of both crops was also significantly lower in plots previously cropped to hay (P < 0.05). Although not always significant (P < 0.05), this pattern of suppression was observed in all four of the soybean experiments and three of the four tomato experiments independent of compost application. The compost amendments alone did not consistently suppress damping-off. However, plant height, fresh weight, and leaf area index of the surviving seedlings of both crops were greater in the compost-amended soils regardless of the transitional cropping treatment used (P < 0.05 for most comparisons). These data indicate that mixed-hay cropping during the transition periods can enhance soil suppressiveness to damping-off. In addition, although compost amendments applied during transition can improve crop vigor by significantly enhancing soil fertility, their effects on soilborne diseases are not yet predictable when transitioning to certified organic production.     

Replacing methyl bromide in annual strawberry production with glucosinolate-containing green manure crops

The use of biocidal green manure crops is an agronomic technique for amending soil with fresh organic matter containing volatile compounds active in controlling some soil-borne pests and diseases. Two new selections of the Brassicaceae family were cultivated, incorporated before planting strawberries and tested as an alternative to fumigation with methyl bromide. Two biocidal green manure crops (Brassica juncea L sel ISCI20, Eruca sativa Mill cv Nemat) containing glucosinolate-myrosinase systems, a conventional green manure (barley), untreated soil and a fumigated control were evaluated during two seasons. The effect of these soil management systems on subsequent strawberry performance was evaluated by monitoring yield and plant growth parameters. In both years, biocidal plant green manure treatments led to a fruit yield lower than with methyl bromide, but higher than with conventional green manure or untreated soil. These results confirm the good prospects for biocidal green manures, not only as an environmentally friendly alternative to methyl bromide in conventional agriculture, but also in organic agriculture as an alternative to conventional green manure crops.     

Use of organic amendments to reclaim saline and sodic soils: a review

Soil salinity and sodicity are land degradation processes that strongly alter soil quality and consequently plant productivity. The reclamation of soils affected by salinity and/or sodicity is an important goal to maintain the sustainability of production. The objectives of this review were (1) to investigate the effectiveness of different organic amendments to reclaim saline/sodic soils and improve environmental quality and productivity of agro-ecosystems and (2) to provide useful information on the most appropriate waste management for minimizing any potential risks. To achieve these aims, recently published literature, related to field and laboratory studies, considering the effects of a wide range of organic amendments on main soil properties, was collected. Results of these studies underline that input of exogenous organic matter (manure, plant residues, by-product of farming or municipal activities, etc.) can be a feasible way to reclaim soils with serious problems of salinity and sodicity. Optimal rates (not greater than 50 t ha^?1) of different organic amendments can improve physical (soil structure, permeability, water holding capacity, etc.) and chemical (pH, cation exchangeable capacity, etc.) soil properties, favoring plant growth and microbial activity, without any risks for the environment (subsoil and groundwater contamination). Of course, it is very important to characterize carefully the organic wastes before their use in agriculture and optimize their management, for avoiding further land degradation.