Conserving and Enhancing Biological Control of Nematodes

Conservation biological control is the modification of the environment or existing practices to protect and enhance antagonistic organisms to reduce damage from pests. This approach to biological control has received insufficient attention compared with inundative applications of microbial antagonists to control nematodes. This review provides examples of how production practices can enhance or diminish biological control of plant-parasitic nematodes and other soilborne pests. Antagonists of nematodes can be enhanced by providing supplementary food sources such as occurs when organic amendments are applied to soil. However, some organic amendments (e.g., manures and plants containing allelopathic compounds) can also be detrimental to nematode antagonists. Plant species and genotype can strongly influence the outcome of biological control. For instance, the susceptibility of the plant to the nematode can determine the effectiveness of control; good hosts will require greater levels of suppression than poor hosts. Plant genotype can also influence the degree of rhizosphere colonization and antibiotic production by antagonists, as well the expression of induced resistance by plants. Production practices such as crop rotation, fallow periods, tillage, and pesticide applications can directly disrupt populations of antagonistic organisms. These practices can also indirectly affect antagonists by reducing their primary nematode host. One of the challenges of conservation biological control is that practices intended to protect or enhance suppression of nematodes may not be effective in all field sites because they are dependent on indigenous antagonists. Ultimately, indicators will need to be identified, such as the presence of particular antagonists, which can guide decisions on where it is practical to use conservation biological control. Antagonists can also be applied to field sites in conjunction with conservation practices to improve the consistency, efficacy, and duration of biological control. In future research, greater use should be made of bioassays that measure nematode suppression because changes in abundance of particular antagonists may not affect biological control of plant parasites.     

Soil carbon storage potential of direct seeding mulch-based cropping systems in the Cerrados of Brazil

No‐tillage cropping systems with direct seeding into a mulch of plant residues from cover crops – the so‐called direct seeding mulch‐based cropping (DMC) systems – have been adopted widely over the last 10–15 years in the Cerrado region of Brazil. They are replacing the traditional soybean monoculture with bare fallow using conventional tillage (CT) practices. The objective of this study was to examine how DMC practices affect soil organic carbon (SOC) dynamics and to assess their potential for enhanced soil carbon (C) storage. The approach was to determine soil C stocks along a chronosequence of fields under DMC, and then to apply the generic decomposition and yield (G'DAY) plant–soil model to analyse the soil C storage potential for a number of cropping systems. Forty‐five fields were selected on a plateau of Ferralsols in the central Cerrado region to represent a chronosequence of 0–12 years under continuous DMC. Before DMC the fields had been under CT soybean monoculture following the clearing of the native savannah. An average increase in SOC stocks of 0.83 Mg C ha^?1 yr^?1 in the 0–20 cm topsoil was measured. The corresponding increase in total soil nitrogen was 79 kg N ha^?1 yr^?1. The G'DAY model predicted a net accumulation of 0.70–1.15 Mg C ha^?1 yr^?1 in the 0–40 cm topsoil for the first 12 years, depending on the type of soil and DMC system. Model predictions showed that less soil C was accumulated under DMC systems that commenced immediately after clearing the native savannah. Gains in soil C under DMC were primarily due to the introduction of a second crop that caused higher net primary productivity, leading to higher plant C inputs to soil. A rough estimation shows that the conversion of 6 million ha of CT soybean monoculture to DMC in the Cerrados would enhance soil C storage by 4.9 Tg C yr^?1 during at least the first 12 years following the conversion to DMC.     

Suppression Effects on Pineapple Soil-Borne Pathogens by <i>Crotalaria juncea</i>, Dolomitic Lime and Plastic Mulch Cover on MD-2 Hybrid Cultivar

The development and implementation of sustainable and environmentally friendly agricultural practices are indispensable as alternatives to pesticide use and to keep populations of soil-borne plant pathogens at levels that do not affect crop productivity. The present research evaluates the incidence of soil-borne phytopathogens on the pineapple variety MD-2, which was subjected to different treatments: Incorporation of Crotalaria juncea into the soil (organic amendment), application of dolomitic lime to soil (inorganic amendment), and the use of plastic mulch covering the soil. During the crop cycle (15 months), the following variables were evaluated: plant height (cm), fruit weight (kg·plant⁻¹ ), crop yield (ton·ha⁻¹ ), the bud root disease incidence caused by Phytophthora nicotianae, number of soil phytoparasitic nematodes and colony-forming-units (CFUs) of soil fungi and oomycetes. The results indicate that Crotalaria juncea treatment reduced the pathogen population (nematode and oomycetes) at levels that did not affect crop development, so that yield increased (18–20%). The incorporation of C. juncea into the soil as an organic amendment favors the populations of fungi disease suppressors (Trichoderma-Aspergillus). The phytoparasitic nematodes (Meloidogyne sp., Pratylenchus sp., and Mesocriconema sp.) and oomycetes (Phytophthora spp., and Pythium spp.) showed a reduction of their population levels by effects of organic amendment (C. juncea). The plastic mulch was also effective, probably due to the maintenance of optimal condition to crop growth and weed control. However, the dolomitic lime application had the poorest effect under the conditions of the study area on the variables analyzed. The described observations are characteristics of a system-based approach for the potential management of soil-borne pathogens of pineapple MD-2 in Veracruz, México.     

Effects of biocides and rotation breaks on soil organisms associated with the poor early growth of sugarcane in continuous monoculture

Glasshouse and field experiments were conducted to determine the effects of biocides and rotation breaks on deleterious soil organisms associated with the poor early growth and subsequent yield decline of sugarcane grown in continuous monoculture. Fumigation of a soil that had been under sugarcane monoculture with minimal breaks for more than 30 years markedly improved the health and growth of the sugarcane sett and shoot root systems, increased the growth of the primary shoot and stimulated more and larger secondary shoots. It also reduced populations of culturable fungi in the rhizosphere of the sett roots and reduced colonization of the sett and shoot roots by lesion nematode (Pratylenchus zeae). Exposure of the developing sett root system for 14 days to mono-cultured sugarcane soil was sufficient to significantly retard subsequent plant growth. In field experiments, fungicide and nematicide (mancozeb + aldicarb), when applied together to land under sugarcane monoculture, was as effective as fumigation in improving early sugarcane growth and increasing sugarcane yields. Rotation breaks (alternate crops, sown pasture, bare fallow) that were in place for 54 months, increased sugarcane establishment and increased sugarcane yields to levels similar to that obtained following fumigation of land under sugarcane monoculture. Fumigation of land that had been under the rotation breaks gave plant growth responses that were in addition to that achieved by the breaks alone. A mancozeb + aldicarb treatment was as effective as fumigation in increasing sugarcane yields after a bare fallow break but accounted for only a portion of the fumigation response following the crop and pasture breaks. Improved plant nutrition may be a factor in the fumigation response following the crop and pasture breaks. Plant growth responses to fumigation and the manocozeb + aldicarb treatments that were manifested in final sugarcane yields (after one years growth) were evident as plant growth responses (sett root, shoot root and primary shoot dry weight) measured 54 days after planting. The experimental results support the concept that when sugarcane is grown as a monoculture, deleterious fungi and nematodes retard plant establishment and early plant growth and that this leads to reduced sugarcane yields.     

有机肥和植被去除管理对人工林土壤节肢动物多样性的影响

施用有机肥和林下抚育（植被去除）是人工林重要的管理措施;土壤节肢动物物种丰富,是土壤生态系统的重要组成成分,对环境变化敏感,可以作为森林管理的指示生物。人工林植被去除和施肥管理影响土壤性质、资源输入量及微生物多样性,从而影响土壤节肢动物多样性,但是相关研究还十分缺乏。以沿海地区杨树人工林为对象,研究了施用有机肥和林下植被去除对土壤节肢动物的数量和多样性的影响。结果表明,有机肥和植被去除管理对不同土壤层土壤节肢动物的数量和多样性指标影响不一致。有机肥增加0-10 cm深度土壤节肢动物总数量、蜱螨目数量,降低土壤节肢动物群落物种丰富度、均匀度和Shannon多样性指数;植被去除减少0-10 cm深度土壤节肢动物总数量和弹尾目数量,降低均匀度指数。两种处理对10-20 cm深度土壤节肢动物群落的数量和各多样性指标影响不显著。总体来说（0-20 cm）,有机肥处理土壤节肢动物的数量显著增加,优势类群前气门亚目（Prostigmata）的数量增长为对照的4倍,但是土壤节肢动物群落的均匀度和Shannon多样性指数显著降低,这可能是土壤节肢动物优势类群前气门亚目密度急剧增加,而物种丰富度没有变化所导致;此外,施用有机肥增加了土壤有机质、总氮、有效磷的含量,降低土壤pH值,并且与前气门亚目密度显著相关。林下植被去除没有影响0-20 cm深度土壤节肢动物的数量和各多样性指标。     

Assessing long-term impacts of cover crops on soil organic carbon in the central US Midwestern agroecosystems

Cover crops have been reported as one of the most effective practices to increase soil organic carbon (SOC) for agroecosystems. Impacts of cover crops on SOC change vary depending on soil properties, climate, and management practices, but it remains unclear how these control factors affect SOC benefits from cover crops, as well as which management practices can maximize SOC benefits. To address these questions, we used an advanced process-based agroecosystem model, ecosys, to assess the impacts of winter cover cropping on SOC accumulation under different environmental and management conditions. We aimed to answer the following questions: (1) To what extent do cover crops benefit SOC accumulation, and how do SOC benefits from cover crops vary with different factors (i.e., initial soil properties, cover crop types, climate during the cover crop growth period, and cover crop planting and terminating time)? (2) How can we enhance SOC benefits from cover crops under different cover crop management options? Specifically, we first calibrated and validated the ecosys model at two long-term field experiment sites with SOC measurements in Illinois. We then applied the ecosys model to six cover crop field experiment sites spanning across Illinois to assess the impacts of different factors on SOC accumulation. Our modeling results revealed the following findings: (1) Growing cover crops can bring SOC benefits by 0.33 ± 0.06 MgC ha⁻¹ year⁻¹ in six cover crop field experiment sites across Illinois, and the SOC benefits are species specific to legume and non-legume cover crops. (2) Initial SOC stocks and clay contents had overall small influences on SOC benefits from cover crops. During the cover crop growth period (i.e., winter and spring in the US Midwest), high temperature increased SOC benefits from cover crops, while the impacts from larger precipitation on SOC benefits varied field by field. (3) The SOC benefits from cover crops can be maximized by optimizing cover crop management practices (e.g., selecting cover crop types and controlling cover crop growth period) for the US Midwestern maize–soybean rotation system. Finally, we discussed the economic and policy implications of adopting cover crops in the US Midwest, including that current economic incentives to grow cover crops may not be sufficient to cover costs. This study systematically assessed cover crop impacts for SOC change in the US Midwest context, while also demonstrating that the ecosys model, with rigorous validation using field experiment data, can be an effective tool to guide the adaptive management of cover crops and quantify SOC benefits from cover crops. The study thus provides practical tools and insights for practitioners and policy-makers to design cover crop related government agricultural policies and incentive programs for farmers and agri-food related industries.     

The soil quality concept as a framework to assess management practices in vulnerable agroecosystems: A case study in Mediterranean vineyards

Land management aiming to sustain ecosystem services is an important issue, especially in biodiversity hot spots such as found in Mediterranean areas. In Mediterranean areas, viticulture is an important land use. Vineyards are frequently found on inherently poor soils and are submitted to intensive management practices, which threaten soil functioning and associated ecosystem services. To encourage winegrowers and stakeholders to be reflective and adapt their vineyard practices, we evaluated the effects of three soil management practices (inter row plant cover duration, weeding and fertilization strategies) on soil functioning in 146 commercial plots distributed in Southern France, by a complementary set of biological and physico-chemical indicators. We used the concept of soil dynamic quality to evaluate some soil management practices on soil functioning. The influence of inherent soil properties derived from pedogenesis on soil dynamic indicator response was accounted for by considering the response of soil indicators for three soil groups differing in their stoniness and Ca carbonate content. The three soil management practices systematically influenced some nematode-based indicators, whereas other indicators were ascribable to a specific soil type or practice. We demonstrated that the potential of soil management practices to enhance soil functioning is restricted by soil type. In particular for calcareous soils, the soil functioning is very stable limiting effects of soil management practices. The presence of a cover crop, even temporary, in the inter row, is the only practice which benefits soil functioning whatever the soil type whereas organic fertilization and chemical weeding exhibit contrasting results on soil functioning.     

土壤质量与土壤质量指标及其评价

土壤作为一种重要的自然资源可以为人类生产食物和纤维,并维持地球生态系统.土壤也是植物生长的媒介、水、热和化合物的源、水分的过滤器和废物分解的生物介质.土壤与水、气和植物互作并抑制环境的波动.土壤可以调节很多控制水气质量和促进植物生长的生态过程.土壤质量概念的引入使我们更全面地理解土壤,也有助于合理地使用和分配劳力、能源、财政和其它投入.土壤质量也提供了一个通用的概念使得专业人员、生产者和公众明白土壤的重要性.此外,它也是一个评价管理措施和土地利用变化对土壤影响的评价工具.土壤质量由土壤的物理、化学和生物性质组成,MDS已被科学家们提出用于土壤质量评价.国际上比较常用的评价方法主要有多变量指标克立格法、土壤质量动力学方法、土壤质量综合评分法和土壤相对质量法.人类对土地不和谐地利用和管理可以导致全球生物地球化学循环发生改变和加快土壤性质变化的速度,当前世界各地土壤退化相当严重,已日益威胁到人类赖以生存的土地资源.在探讨相关概念的基础上综述了近年来土地利用变化对土壤理化质量和生物质量的影响进展,以引起国内外学者对土地利用变化对土壤质量影响研究的重视,从而为探讨土地利用对土壤质量影响的机理和规律以及退化土地的恢复和区域土地资源管理以及土地的持续利提供理论依据.土壤质量未来的研究应该集中在土壤质量指标与评价方法;土壤质量变化的发生条件、过程、影响因素及其作用机理与时空规律性;尺度问题的研究;土壤质量保持与提高的途径及其关键技术研究.     

Influence of agricultural practices and seasons on the abundance and community structure of culturable pseudomonads in soils under no-till management in Argentina

Background and aims

Members of the genus Pseudomonas are common inhabitants of rhizospheres and soils, and it is known that soil types and crop species influence their population density and structure. 20?×?10⁶ ha are cultivated under no-tillage in Argentina and there is a need to find new biologically-based soil quality indexes to distinguish between sustainable and non-sustainable agricultural practices. Pseudomonads abundance and community structure were analyzed in no-till soils with different agricultural practices, in productive fields along 400 km of Argentinean Pampas.

Methods

We sampled soils and root systems from agricultural plots in which sustainable or non-sustainable agricultural practices have been applied. Samples were collected in summer and winter during 2010 and 2011. Culturable fluorescent and total pseudomonads were enumerated by plating on Gould’s selective medium S1. Colonies from these plates served as DNA source to carry out PCR-RFLP community structure analysis of the pseudomonads-specific marker genes oprF and gacA.

Results

Abundance of total and fluorescent culturable pseudomonads in bulk soils was influenced by seasonal changes and agricultural practices. Rhizospheric counts from the same crop were affected by agricultural treatments. Also, crop species influenced pseudomonads density in the rhizosphere. Combined PCR-RFLP profile of both genes showed a seasonal grouping of samples.

Conclusions

Sustainable soil management seems to promote pseudomonads development in soils, favoring root colonization of crops from those plots. Crop species influence total pseudomonads load of rhizospheres and its community structure. Total or relative pseudomonads load could function as soil quality indicator of good agricultural practices.     

Mycorrhizal Interactions in Sustainable Agriculture

Abstract

Vesicular-arbuscular mycorrhizal (VAM) fungi are an intimate link between the roots of most crop plants and soils, thereby affecting the development of host plants and host soils. The role of VAM fungi in improving plant nutrition and their interactions with other soil biota have been investigated with reference to host plant growth, but little is known about how these interactions affect soil structure. The impact of cultural practices and the particular role that VAM fungi play in improving soil structure are discussed in the context of sustainable farming.     

Mechanisms of Carbon Sequestration in Soil Aggregates

Soil and crop management practices have a profound impact on carbon (C) sequestration, but the mechanisms of interaction between soil structure and soil organic C (SOC) dynamics are not well understood. Understanding how an aggregate stores and protects SOC is essential to developing proper management practices to enhance SOC sequestration. The objectives of this article are to: (1) describe the importance of plants and soil functions on SOC sequestration, (2) review the mechanisms of SOC sequestration within aggregates under different vegetation and soil management practices, (3) explain methods of assessing distribution of SOC within aggregates, and (4) identify knowledge gaps with regards to SOC and soil structural dynamics. The quality and quantity of plant residues define the amount of organic matter and thus the SOC pool in aggregates. The nature of plant debris (C:N ratio, lignin content, and phenolic compound content) affects the rate of SOC sequestration. Mechanisms of interaction of aggregate dynamics with SOC are complex and embrace a range of spatial and temporal processes within macro- ( > 250 μ m e.c.d.) and microaggregates ( < 250 μ m e.c.d.). A relevant mechanism for SOC sequestration within aggregates is the confinement of plant debris in the core of the microaggregates. The C-rich young plant residues form and stabilize macroaggregates, whereas the old organic C is occluded in the microaggregates. Interactions of clay minerals with C rich humic compounds in correlation with clay mineralogy determine the protection and storage of SOC. Principal techniques used to assess the C distribution in aggregates include the determination of total organic C in different aggregate size fractions, isotopic methods to assess the turnover and storage of organic C in aggregates, and computed tomography and X-ray scattering to determine the internal porosity and inter-aggregate attributes. The literature is replete with studies on soil and crop management influences on total organic C and soil aggregation. However, research reports on the interactions of SOC within aggregates for C sequestration are scanty. Questions still remain on how SOC interacts physically and chemically with aggregates, and research is needed to understand the mechanisms responsible for the dynamics of aggregate formation and stability in relation to C sequestration.     

Agronomic Practices for Improving Gentle Remediation of Trace Element-Contaminated Soils

The last few decades have seen the rise of Gentle soil Remediation Options (GRO), which notably include in situ contaminant stabilization (“inactivation”) and plant-based (generally termed “phytoremediation”) options. For trace element (TE)-contaminated sites, GRO aim to either decrease their labile pool and/or total content in the soil, thereby reducing related pollutant linkages. Much research has been dedicated to the screening and selection of TE-tolerant plant species and genotypes for application in GRO. However, the number of field trials demonstrating successful GRO remains well below the number of studies carried out at a greenhouse level. The move from greenhouse to field conditions requires incorporating agronomical knowledge into the remediation process and the ecological restoration of ecosystem services. This review summarizes agronomic practices against their demonstrated or potential positive effect on GRO performance, including plant selection, soil management practices, crop rotation, short rotation coppice, intercropping/row cropping, planting methods and plant densities, harvest and fertilization management, pest and weed control and irrigation management. Potentially negative effects of GRO, e.g., the introduction of potentially invasive species, are also discussed. Lessons learnt from long-term European field case sites are given for aiding the choice of appropriate management practices and plant species.     

Soil and water erosion under different plant species in a semiarid river valley, SW China: the effects of plant morphology

The small-scale effects of plant morphology in improving soil quality and reducing runoff and soil loss have remained unclear, especially in some arid environments with sparse vegetation. We selected three representative species with contrasting morphologies (Artemisia gmelinii; Ajania potaninii; Pulicaria chrysantha) to examine the effects of plant morphology on soil quality, runoff, and soil loss in the dry-warm river valley of the upper reach of Minjiang River, SW China. Runoff events were monitored from July through October 2006 using runoff plots on a micro scale (<40 × 40 cm²) on a south-facing slope. The observation duration for rainfall and runoff events can be divided into two stages. Higher runoff depth, but lower soil loss per event occurred at the second stage as compared with the first stage due to the differences in rainfall, plant, and soil surface characteristics. The two herbs, A. gmelinii and P. chrysantha, had greater improvements on soil quality yielding high soil nutrient content and low soil compactness, while the effectiveness of the small shrub, A. potaninii, was minimal. Relative to bare surface (control treatment), the effectiveness of reducing runoff depth per event was 64.9, 66.6 and 38.0%, and reducing soil loss 65.5, 59.3 and 69.9% for A. gmelinii, A. potaninii, and P. chrysantha, respectively. All three plant species can improve soil quality and reduce runoff and soil loss, but their effects vary, which implies that plant morphology has to be considered while selecting species for ecosystem restoration.     

Soil temperature in a sugar-cane crop as a function of the management system

Air and soil temperatures are, by far, the most important state variables of agroecosystems. In the case of sugar-cane (Saccharum officinarum L.) they affect plant development, maturation and a series of biological and physical-chemical soil processes. This paper presents a comparative study of three management practices, applied to the first ratoon of a sugar-cane crop established on a Rhodic Kandiudox (Terra Roxa Estruturada) of Piracicaba, SP, Brazil. The management practices are: (i) interrow with bare soil; (ii) trash mulching, maintaining harvest residues (straw+tips) on the soil; (iii) soil with residues from burning the prior crop. Soil temperature was measured with digital stick thermometers driven into the soil down to the depths of 0.03, 0.06 and 0.09 m, meter by meter, close to the crop row, along an 84-point transect that covered all treatments and borders. The measurements were performed from November 1998 (right after the first harvest of the planted cane) to June 1999. The effects of the treatments on soil temperature were, evidently, more prominent in the period November/February when the plants had a smaller height, not closing interrows. Data that were collected on typical days, chosen along the development cycle of the crop, always from 11:00 to 12:00 a.m., show significant differences, mainly between mulched and non mulched treatments, reaching values as high as 7 °C for the average of the three depths. A comparative analysis is made between treatments and their effects are discussed in relation to the sugar-cane crop.     

干旱区绿洲农田不同种植模式和秸秆管理下土壤质量评价

研究干旱区绿洲农田不同种植模式和秸秆管理下土壤有机碳及其酶活性的变化,揭示农业管理措施对土壤质量的影响,以期为干旱区农业资源高效利用及可持续发展提供理论依据.在作物种植规划区,选择新疆主要农作物棉花、小麦、玉米,设计长期连作及轮作试验.结果表明:轮作处理土壤有机碳(SOC)、微生物生物量碳、易氧化有机碳、水溶性有机碳、热水溶性有机碳含量较连作处理分别提高了3.6%~9.9%、41.8%~98.9%、3.3%~17.0%、11.1%~32.4%、4.6%~27.5%;秸秆还田处理较秸秆不还田处理分别提高了12%~35.9%、22.4%~49.7%、30.7%~51.0%、10.6%~31.9%、41.0%~96.4%.轮作处理土壤过氧化氢酶、脱氢酶、β-葡萄糖核苷酶、蔗糖酶、纤维素酶活性较连作处理分别提高了6.4%~10.9%、6.6%~18.8%、5.9%~15.3%、10.0%~27.4%、28.1%~37.5%;秸秆还田处理较-秸秆不还田处理分别提高了31.4%~47.5%、19.9%~46.6%、13.8%~20.7%、19.8%~55.6%、54.1%~70.9%.相关性分析表明,SOC及其活性组分与土壤酶活性之间有极显著的正相关关系,利用土壤活性有机碳组分和酶活性变化可有效表征农田SOC和土壤质量变化.通过因子分析综合评价得知,在干旱区农业生产中,短期连作棉花兼实施秸秆还田可提高SOC及其活性组分含量和酶活性,合理轮作可有效缓解连作障碍,使土壤质量得到进一步改善,有利于农田土壤的可持续利用.     

三峡库区消落带重建植被下土壤微生物生物量碳氮含量特征

为探究三峡库区消落带植被重建后,土壤微生物生物量含量特征及影响因素,对忠县消落带人工重建植被土壤及裸地土壤(作为对照)微生物生物量碳氮含量进行了调查研究。结果表明:(1)在消落带165-175 m高程土壤微生物生物量碳含量草地林地农耕地裸地,微生物生物量氮含量规律与微生物生物量碳一致,农耕地明显提高;土壤微生物生物量总体呈现出草地最高、林地和农耕地次之,裸地最低的趋势,表明进行消落带植被恢复对土壤微生物生物量有显著的促进作用。(2)不同植被类型下,土壤微生物生物量碳氮比变化范围为8.02-10.25,土壤微生物生物量碳、氮占土壤有机碳、全氮的百分比范围分别是2.40%-4.60%和2.13%-3.58%,其中林地对土壤碳、氮库贡献显著高于裸地(P0.05)。(3)土壤微生物生物量碳、氮与土壤有机碳、全氮和pH值呈现显著相关性,与土壤含水量呈现极显著相关性,说明消落带重建植被土壤的这些理化性质对土壤微生物生物量碳、氮含量有强烈的影响。因此,在三峡库区消落带进行植被恢复重建能显著提高土壤微生物生物量及土壤质量,对加强三峡库岸生态系统的稳定性具有重要意义。     

土壤健康的生物学表征与调控

如何有效判定土壤健康状态是实现农业绿色发展的基本问题。在现有的土壤健康评价体系中,很少考虑土壤生物在维持土壤健康方面的作用。基于此,本文论述了土壤健康的内涵,从土壤生物健康的角度,总结了土壤健康的生物学表征指标,阐述了土壤微生物、土壤酶活性、土壤微食物网及蚯蚓对土壤健康的指示作用。基于上述生物指标,从作物和土壤管理等方面探讨了不同农田管理措施对土壤健康状况的调控途径,并对土壤生物健康的未来发展趋势进行了展望。本文旨在增强科学家和决策者对维护土壤生物健康的认识,充分发挥土壤生物在生态系统服务中的重要作用。     

Harnessing microbial volatiles to replace pesticides and fertilizers

Global agricultural systems are under increasing pressure to deliver sufficient, healthy food for a growing population. Seasonal inputs, including synthetic pesticides and fertilizers, are applied to crops to reduce losses by pathogens, and enhance crop biomass, although their production and application can also incur several economic and environmental penalties. New solutions are therefore urgently required to enhance crop yield whilst reducing dependence on these seasonal inputs. Volatile Organic Compounds (VOCs) produced by soil microorganisms may provide alternative, sustainable solutions, due to their ability to inhibit plant pathogens, induce plant resistance against pathogens and enhance plant growth promotion. This review will highlight recent advances in our understanding of the biological activities of microbial VOCs (mVOCs), providing perspectives on research required to develop them into viable alternatives to current unsustainable seasonal inputs. This can identify potential new avenues for mVOC research and stimulate discussion across the academic community and agri-business sector.     

Soil seed bank contributes significantly to genetic variation of Hypericum sinaicum in a changing environment

The contribution of soil seed bank of a desert endemic plant species in maintaining genetic diversity has been addressed in this paper through investigating the differences in genetic diversity and structure (using AFLP markers) between plants grown from soil seed bank and standing crop plants within and among five populations of H. sinaicum growing at St. Katherine Protectorate, southern Sinai, Egypt. Standard genetic diversity measures showed that the molecular variation within and among populations was highly significantly different between standing crop and soil seed bank. While soil seed bank had lower genetic diversity than standing crop populations, pooling soil seed bank with standing crop samples resulted in higher diversity. The results revealed also that soil seed bank had lower differentiation (7 %) than among populations of the standing crop (18 %). Results of neighbor-joining, Bayesian clustering and principal coordinate analysis showed that soil seed banks had a separate gene pool different from standing crop. The study came to the conclusion that the genetic variation of the soil seed bank contributes significantly to the genetic variation of the species. This also stresses the importance of elucidating the genetic diversity and structure of the soil seed bank for any sound and long-term conservation efforts for desert species. These have been growing in small-size populations for a long time that any estimates gained only from aboveground sampling of populations may be ambiguous.