Glomalin Production Research Articles

Effect of Arbuscular Mycorrizhal Fungi Inoculation on Glomalin, Growth and Rice Yield

TITLE : EFFECT OF ARBUSCULAR MYCORRIZHAL FUNGI INOCULATION ON GLOMALIN, GROWTH AND RICE YIELD. The aim of this study was to measure the glomalin production, growth and yield of rice in upland rice fields. The research used Completely Randomized Design with four treatments: two sterilization levels (no sterilisatio and with sterilization) and two levels of mycorrhizae inoculation ( no mycorrhizae and with mycorrhizae). Mycorrhizae (5 g/pot) was inoculated before planting rice seeds. The results showed that Glomalin Total (GT) and Glomalin easily extracted (GEE) were higher in mycorrhizae inoculation, increased by 16% and 20% in non-sterile soil and 25% and 11% in sterile soil compared to non-mycorrhizae inoculation. The content of the GT ranged from 4.95 to 9.74 mg/g soil and GEE 0.99 to 2.78 mg/g soil. Plant height, tillers number and the grain yield was increased by mycorrhizae inoculation significantly. Soil sterilization could reduce the effectiveness of mycorrhizae inoculated.

Manipulation of rhizosphere organisms to enhance glomalin production and C sequestration: Pitfalls and promises

Walley, F. L., Gillespie, A. W., Adetona, A. B., Germida, J. J. and Farrell, R. E. 2014. Manipulation of rhizosphere organisms to enhance glomalin production and C-sequestration: Pitfalls and promises. Can. J. Plant Sci. 94: 1025–1032. Arbuscular mycorrhizal fungi (AMF) reportedly produce glomalin, a glycoprotein that has the potential to increase soil carbon (C) and nitrogen (N) storage. We hypothesized that interactions between rhizosphere microorganisms, such as plant growth-promoting rhizobacteria (PGPR), and AMF, would influence glomalin production. Our objectives were to determine the effects of AMF/PGPR interactions on plant growth and glomalin production in the rhizosphere of pea (Pisum sativum L.) with the goal of enhancing C and N storage in the rhizosphere. One component of the study focussed on the molecular characterization of glomalin and glomalin-related soil protein (GRSP) using complementary synchrotron-based N and C X-ray absorption near-edge structure (XANES) spectroscopy, pyrolysis field ionization mass spectrometry (Py-FIMS), and proteomics techniques to characterize specific organic C and N fractions associated with glomalin production. Our research ultimately led us to conclude that the proteinaceous material extracted, and characterized in the literature, as GRSP is not exclusively of AMF origin. Our research supports the established concept that GRSP is important to soil quality, and C and N storage, irrespective of origin. However, efforts to manipulate this important soil C pool will remain compromised until we more clearly elucidate the chemical nature and origin of this resource.

Arbuscular mycorrhizal fungal communities and soil aggregation as affected by cultivation of various crops during the sugarcane fallow period

Management systems involving crop rotation, ground cover species and reduced soil tillage can improve the soil physical and biological properties and reduce degradation. The primary purpose of this study was to assess the effect of various crops grown during the sugarcane fallow period on the production of glomalin and arbuscular mycorrhizal fungi in two Latosols, as well as their influence on soil aggregation. The experiment was conducted on an eutroferric Red Latosol with high-clay texture (680 g clay kg-1) and an acric Red Latosol with clayey texture (440 g kg-1 clay) in Jaboticabal (São Paulo State, Brazil). A randomized block design involving five blocks and four crops [soybean (S), soybean/fallow/soybean (SFS), soybean/millet/soybean (SMS) and soybean/sunn hemp/soybean (SHS)] was used to this end. Soil samples for analysis were collected in June 2011. No significant differences in total glomalin production were detected between the soils after the different crops. However, total external mycelium length was greater in the soils under SMS and SHS. Also, there were differences in easily extractable glomalin, total glomalin and aggregate stability, which were all greater in the eutroferric Red Latosol than in the acric Red Latosol. None of the cover crops planted in the fallow period of sugarcane improved aggregate stability in either Latosol.

Glomalin Production and Infectivity of Arbuscular-Mycorrhizal Fungi in Response to Grassland Plant Diversity

Arbuscular-mycorrhizal fungi (AMF) are integral components of most terrestrial ecosystems, with complex interactions between plants and AMF. Our study assessed the impact of plant diversity of native grassland species on AMF infectivity and production of glomalin, an AMF hyphal glycoprotein that may play an important role in soil aggregation. The study was conducted over a 3-year period in field plots planted with 1, 2, 8, or 16 plant species. The mycorrhizal infection potential (MIP) of the plots was assayed in the greenhouse. Glomalin production and MIP were lowest in monocultures and were more closely correlated with plant diversity than with plant cover. Spore density was also greater in higher diversity plots. Lower AMF activity in monoculture plots may contribute to lower productivity and soil quality in plant monocultures. Immunoreactive glomalin levels varied seasonally, with higher levels in late summer than in late spring. Positive correlations were found between glomalin levels and spore density, and between MIP and spore density, but not between MIP and glomalin.

Selection of Aruscular Mycorrhizal Fungi (AMF) Indigeneus in Ultisol for Promoting The Production of Glmalin and Aggregate Formation Processes

The muatualism symbiosis of arbuscular mycorrhizal fungi ( AMF ) with plants are able to increase the capacity of plants to absorb nutrients and water from the soil. Recently, research was indicated that AMF hyphae containing glomalin as a glycoprotein that serves to glue the between dispersed soil particles. The content of glomalin in soil was positively correlated with soil aggregate stability. The research potential of AMF species indigenous of Ultisol Darmasraya District of West Sumatra and glomalin production in experimental pots of sterile sand medium has been carried out. The purpose of this study was to determine the diversity of AMF species on Ultisol and to seeking indigenous AMF isolates that have the best glomalin production capability. AMF spores were isolated and identified from the rhizosphere soil of corn in Ultisol. AMF species that have been identified experimentally tested culture medium pot of sand and zeolite (w / w 1:1) using corn crops. The results showed that the AMF species indigenous of Ultisol Darmasraya found 9 species, namely Acaulospora scrobiculata, Glomus etunicatum, Glomus luteum, Glomus mosseae, Glomus verruculosum, Glomus versiforme, Scutellospora gregaria, Scutellospora heterogama and Gigaspora sp. AMF species that showed better colonization ability in maize is G. luteum, G. verruculosum and G. versiforme. All three species can produce glomalin was significantly higher than the other species, ie 1.29 mg.g-1; 1.17 mg.g-1; 1.15 mg.g-1 respectively.

Glomalin: an arbuscular mycorrhizal fungal soil protein

Glomalin is abundant in soils and is closely correlated with aggregate water stability. Glomalin contains carbon and, hence, constitutes a non-trivial portion of the terrestrial carbon pool. Possibly far more importantly, however, stabilization of aggregates amplifies the role of glomalin in soils because carbonaceous compounds are protected from degradation inside of aggregates. Increased atmospheric CO2 can lead to increased production of glomalin because of the symbiotic association that exists between plants and producers of glomalin, arbuscular mycorrhizal fungi (AMF). Glomalin concentrations in soils are influenced by management practices, for example, in agroecosystems, further highlighting the role of this protein in carbon storage. Glomalin is an unusual molecule that has proven difficult to analyze biochemically due to its recalcitrance and complexity. Future research will be directed towards the elucidation of its structure and controls on its production.

Soil structural responses to alterations in soil microbiota induced by the dilution method and mycorrhizal fungal inoculation

Abstract This investigation examines the effect of manipulating soil microbial community composition and species richness on the development of soil structure over a seven month period in planted (with or without mycorrhizal fungi) and in unplanted macrocosms. The dilution method effectively resulted in soil communities with consistently contrasting levels of species (TRF) richness. In particular, the 10−6 dilution of field soil resulted in less rich communities in bare unplanted soil than did the 10−1 soil dilution. However, this was not the case in planted soils where root activity was a powerful influence on species richness. After seven months, principal components analysis (PCA) separated bacterial community composition primarily on planting regime; planted mycorrhizal, planted non-mycorrhizal and bare soil treatments all contained different bacterial community compositions. A consistent finding in planted and unplanted soils was that aggregate stability was positively correlated with small pore sizes. Mycorrhizal colonisation decreased plant biomass and also resulted in reduced soil bacterial species richness, lower percentage organic matter and smaller pore sizes relative to planted but non-mycorrhizal soils. However, soil aggregate stability and water repellency were increased in these (mycorrhizal) soils probably due to AMF hyphal activities including enmeshment and/or glomalin production. In contrast, bacterial TRF richness was positively correlated with aggregate stability in the bare and non-mycorrhizal planted soils. Soil organic carbon was an important factor in all treatments, but in the bare soil where there was no additional input of labile C from roots, the percentage C could be directly related to fungal TRF richness. The less species rich bare soil contained more organic C than the more species rich bare soil. This suggests a degree of redundancy with regard to mineralisation of organic matter when additional, more utilisable C sources are unavailable. Understanding the effects of microbial diversity on functional parameters is important for advancing sustainable soil management techniques, but it is clear that soil is a dynamic ecosystem.

Occurrence of arbuscular mycorrhizal fungi after organic fertilization in maize, cowpea and cotton intercropping systems

The effect of organic manure on the community of mycorrhizal fungi (AMF) was evaluated in maize, cowpea and cotton intercropping systems in a semi-arid region of Brazil over two consecutive years. The experiment was conducted using a randomized block design with four replicates and six soil treatments: (M) goat manure incorporated in the soil before planting; (G) gliricidia prunings incorporated before planting; (M+G) manure and gliricidia incorporated before planting; (GS) gliricidia applied on the soil surface 45 days after planting; (M+GS) manure incorporated before planting and gliricidia applied to the surface 45 days after planting; and (C) control treatment without incorporation. It was not possible to identify the best treatment for both years in terms of spore density, mycorrhizal colonization and glomalin content. However, there was a significant effect from the fertilization treatments when compared to the control in most treatments. In both years, M+GS favored glomalin and AMF sporulation in the cotton plots. In the second year, which had low rainfall, there was an increase in production of spores, glomalin, colonization and AMF species richness irrespective of soil incorporation and culture. Plots that were fertilized with manure presented greater AMF species richness regardless of the year and crop type.

The influence of different stresses on glomalin levels in an arbuscular mycorrhizal fungus--salinity increases glomalin content.

Glomalin is a glycoprotein produced by arbuscular mycorrhizal (AM) fungi, and the soil fraction containing glomalin is correlated with soil aggregation. Thus, factors potentially influencing glomalin production could be of relevance for this ecosystem process and for understanding AM fungal physiology. Previous work indicated that glomalin production in AM fungi may be a stress response, or related to suboptimal mycelium growth. We show here that environmental stress can enhance glomalin production in the mycelium of the AM fungus Glomus intraradices. We applied NaCl and glycerol in different intensities to the medium in which the fungus was grown in vitro, causing salinity stress and osmotic stress, respectively. As a third stress type, we simulated grazing on the extraradical hyphae of the fungus by mechanically injuring the mycelium by clipping. NaCl caused a strong increase, while the clipping treatment led to a marginally significant increase in glomalin production. Even though salinity stress includes osmotic stress, we found substantially different responses in glomalin production due to the NaCl and the glycerol treatment, as glycerol addition did not cause any response. Thus, our results indicate that glomalin is involved in inducible stress responses in AM fungi for salinity, and possibly grazing stress.

Effects of arbuscular mycorrhizal inoculation on metallophyte and agricultural plants growing at increasing copper levels

A pot culture experiment was carried out to assay the behavior of different arbuscular mycorrhizal (AM) fungal inocula on plant growth and copper (Cu) uptake using two metallophytes (Oenothera picensis and Imperata condensata) and one agricultural plant (Helianthus annuus) grown at increasing Cu supply levels. Plants were established in a Cu polluted soil spiked with 0, 150, 300 or 450mg Cukg−1, and inoculated or not with: (i) Cu-adapted AM fungi (GA) or (ii) the Cu non-adapted strain Glomus claroideum (GC). Differences in plant biomass between inoculated and uninoculated plants were found, which were dependent on the AM fungal inocula used and the Cu level applied. Although the beneficial effect of AM fungi in promoting plant biomass production was not observed in metallophytes plants, a positive interaction between GA and H. annuus increased the shoot growth, especially at higher Cu levels. In addition, the Cu transfer from the roots to the shoots was low, remaining mostly at root level, especially in non-mycorrhizal plants; however AM fungi produced changes in Cu distribution increasing the translocation to the shoots. Differences in AM fungal parameters (root colonization, spore number and glomalin production) were strictly dependent on the Cu level and the AM fungal inoculum, suggesting the existence of certain compatibility, which was dependent on the particular combination AM-plant used. Specifically, the glomalin accumulation and Cu-bound to glomalin were significantly higher in AM colonized H. annuus plants, which could suggest a highly efficient way to reduce the Cu toxicity levels in soil. Therefore the use of H. annuus with AM fungal could promote phytostabilization processes.

Effects of Synthetic Fertilizer on Coffee Yields and Ecosystem Services: Parasitoids and Soil Glomalin in a Costa Rican Coffee Agroecosystem

We explored the relationships between synthetic fertilizer use, yield, and ecosystem services in a coffee agroecosystem in the Tarrazú region in the central highlands of Costa Rica. Working in nine farms ranging from 0.3 to 2.7 ha in the CoopeTarrazú farmers' cooperative, we focused on two important indicators of ecosystem services: biological control agents and mycorrhizal fungi. Biological control agents (especially parasitoid wasps) are essential for population regulation of herbivorous arthropods that reside in coffee agroecosystems. Mycorrhizal fungi contribute to plant nutrition and disease resistance and produce a highly stable protein, glomalin, which is critical for soil aggregation. Soil aggregates hedge against erosion, particularly in sloping soils, by improving porosity. Slopes in this study ranged from 4% to 66%. We manipulated synthetic fertilizer levels in experimental plots ranging from 6.9% increase to 53.3% decrease in total N relative to control plots that received a standard amount of fertilizer. The effects on coffee yields, soil glomalin production by mycorrhizal fungi, and wasp diversity were examined. Yield and glomalin decreased, but parasitoid diversity increased with greater reductions in fertilizer application six months after application. Reducing fertilizer use may bolster biological control assemblages, while glomalin is more directly dependent on plant production.

Establishment of endomycorrhizal fungi on micropropagated teak (Tectona grandisL.f.)

Background Commercial micropropagation of teak (Tectona grandisL.f.) has been achieved for a number of years in countries such as Thailand, India and Malaysia. This has led to the availability of elite genotypes for large scale plantation production. Teak has been shown to develop arbuscular mycorrhizal (AM) fungal associations [1], and this has been attributed to increasing productivity [2]. It is likely that the establishment of mycorrhiza, through the introduction of Glomusspecies, on the roots of micropropagated plantlets will improve the productivity of selected clones. Established hyphal networks can speed up plant colonization [3] and in the long term may also increase carbon storage through glomalin production [4].Our research is pursuing the development of a mycorrhization protocol for micropropagated teak at the acclimatization stage.

Glomalin production and accumulation in soilless pot cultures

This study was designed to determine how glomalin production relates to accumulation in three sequential greenhouse culturing periods using a soilless potting medium. The data indicated that this stable glycoprotein was washed out the pot bottom, and did not accumulate in the hyphal chamber.

Glomalin Production and Microbial Activity in Soils Impacted by Gypsum Mining in a Brazilian Semiarid Area

Problem statement: Mining activities involve the removal of the veget al cover and the soil organic layer, causing a severe environmental impac t. In Northeast Brazil, 40% of the world's crude gypsum is found in a semiarid area, making this reg ion responsible for 95% of the gypsum demand in the national market. Although economically important, this activity is harmful to the environment. Studies of soil microbiological and biochemical att ributes can help in the identification of the limitations of impacted ecosystems, providing data to define strategies for sustainability of such environments. Approach: To evaluate and compare the biological state of pr eserved and mining degraded semiarid soils, a native preserved area an d areas impacted by gypsum mining were selected at the Araripina Experimental Station, located in t he semiarid region of Pernambuco State, Northeast Brazil. The four sampling areas included: (1) A nat ive, preserved caatinga area with spine bearing trees and shrubs and some characteristic xerophytic plants (AN); (2) An area surrounding the mine, presenting the same type of vegetation although alr eady degraded (AM); (3) A waste deposit area (AR); (4) Interface area between the waste deposit and a mining degraded area (AI). Samples were taken in each area (1000 m 2 ) during two periods: wet (December/2003, Rainfall = 28.7 mm) and dry (September/2004, Rainfall = 1.3 mm). Results: Fluorescein diacetate hydrolysis values, microbial biomass C and basal respiration were higher in the preserved caatinga than in the impacted areas. The gypsum mining activity reduced the concentration of easily extractable glomalin in relation to the native caatinga area in both sampling periods. Hi gher deposits of total glomalin also occurred in th e native area, however, mainly during the wet period. Conclusion: The mining activity produced a negative impact on the soil microbiota, reducing th e total enzymatic activity. The microbial biomass was significantly lower in the waste deposit area t han in the native and interface areas. The results indicated that the mining activity is harmful to th e soil microbiota in this area and that glomalin ca n be a useful indicator of soil disturbance.

Molecular characterization and glomalin production of arbuscular mycorrhizal fungi colonizing a heavy metal polluted ash disposal island, downtown Venice

In this work the arbuscular mycorrhizal (AM) fungal communities colonizing a polluted ash dump island, downtown Venice, were studied by using a multimodal approach. The island, Sacca San Biagio, was covered with a thick layer of municipal solid waste residues produced by an incinerator operating from 1973, to 1984. Such residues contained high levels of heavy metals (Cu, Pb and Zn). We characterized the AMF communities present in soils on Sacca San Biagio island by using molecular methods. Nine AM fungal sequence types were detected in the roots of three plant species, representative of the dominant flora, by using partial SSU ribosomal RNA genes. The most abundant sequence types corresponded to Glomus intraradices/ Glomus fasciculatum, and to Glo18, a sequence detected so far only in planta. Two sequences were new to science. Glomalin-related soil protein (GRSP), extracted from rhizosphere soil of dominant plant species, ranged from 1.6 to 2.3 mg g −1. The occurrence of an active AM fungal community able to live in such harsh environment was evinced by the correlation between mycorrhizal colonization and GRSP content.

Uso de vermicomposto favorece o crescimento de mudas de gravioleira (Annona muricata L. 'Morada') associadas a fungos micorrízicos arbusculares

A gravioleira, cujos frutos apresentam elevado potencial para exportação, é de fácil adaptação ao Semi-Árido nordestino, e a sua produção, economicamente importante, vem sendo estimulada. O uso de adubos orgânicos associados à inoculação com fungos micorrízicos arbusculares (FMA) pode ser útil na formação de mudas frutíferas, porém o efeito da adição de adubo na simbiose com gravioleira (Annona muricata L. 'Morada') não é conhecido. Foi investigado o efeito de FMA multiplicado em substrato com resíduo orgânico na formação de mudas de gravioleira mantidas em substratos com fertilizante. O delineamento foi inteiramente casualizado, em fatorial de 2×5: 2 substratos (solo sem ou com 10% de vermicomposto) e cinco tratamentos de inoculação (Acaulospora longula Spain & Schenck e Gigaspora albida Schenck & Smith produzidos em substratos com ou sem resíduo orgânico e controle não inoculado), com quatro repetições. Após 102 dias, avaliou-se: massa seca da parte aérea e radicular, altura, diâmetro do caule, taxa de crescimento, produção de esporos de FMA e de glomalina, atividade enzimática do solo, respiração microbiana, colonização micorrízica total, arbuscular e hifálica. Em geral, a inoculação com FMA estimulou o crescimento, mas no tratamento adubado as mudas em simbiose com G. albida não foram beneficiadas pela associação. O uso de vermicomposto estimulou a colonização micorrízica, a respiração microbiana, a atividade enzimática e a produção de glomalina no solo, porém reduziu a esporulação de A. longula. A utilização de FMA e vermicomposto pode constituir alternativa na produção de mudas de gravioleira, pois reduziu à metade o tempo de formação das mudas e pode reduzir em 75% a dose de adubo a ser aplicada. No entanto, a escolha de FMA compatíveis com o hospedeiro é indispensável para garantir respostas positivas. A aplicação conjunta de FMA e adubo orgânico também pode melhorar a qualidade do solo, contribuindo para a produção sustentável de mudas desta e de outras fruteiras.

Density dependence and interspecific interactions between arbuscular mycorrhizal fungi mediated plant growth, glomalin production, and sporulation

Functional differences between the arbuscular mycorrhizal fungi Glomus intraradices Schenk and Smith and Scutellospora heterogama Nicolson and Gerdemann as they affect Persea americana Mill. growth, glomalin, and fungal sporulation were examined by varying the composition and relative density of the two fungi over a gradient of available phosphorus (P). The plant benefit provided by these mycorrhizal fungi together was not a simple sum of the benefits provided by each fungus in monoculture at its respective density. Glomus intraradices and S. heterogama interacted to reduce plant growth rates and uptake of P, zinc (Zn), and iron (Fe) relative to plants inoculated with G. intraradices alone. Thus, for plant growth and nutrition, no evidence for functional complementarity was detected. Instead, interspecific interactions between mycorrhizal fungi resulted in a negative feedback on plants. Under high available P, fungal functional differences were reduced, whereas the overall difference between mycorrhizal and nonmycorrhizal plants was greatest. Overall, S. heterogama produced more glomalin than did G. intraradices. In a mixture, sporulation of the inferior mutualist, S. heterogama, was lower than that of the superior mutualist, G. intraradices, but interspecific fungal interactions increased the sporulation of both fungi. Despite the negative impact of interspecific interactions on plants, supporting multiple arbuscular mycorrhizal fungi was of greater benefit than being nonmycorrhizal.

Glomalin production by an arbuscular mycorrhizal fungus: a mechanism of habitat modification?

We report on a novel mechanism by which arbuscular mycorrhizal fungi may be able to modify a sub-optimal growth environment to their advantage by secreting the glycoprotein glomalin, which is highly correlated with soil aggregate water stability. Here we used glass beads of different sizes to simulate different hyphal growing space conditions. With small beads (<106 μm; simulating a non-aggregated soil) fungal hyphal length was reduced over 80% compared to large beads (710–1180 μm; simulating an aggregated soil). Conversely, glomalin yield (immunoreactive protein) was more than seven times higher in the small bead growing space. The results challenge our thinking about soil aggregation as a consequence of general biological activity in soil, and uncover a new aspect of the biology of these ecologically important soil fungi.

Aggregate stability and glomalin in alternative crop rotations for the central Great Plains

Land productivity, along with improvement or maintenance of soil health, must be evaluated together to achieve sustainable agricultural practices. Winter wheat-fallow (W-F) has been the prevalent cropping system in the central Great Plains for 60 years where moisture is a limitation to crop production. Alternative cropping systems show that producers can crop more frequently if residue management and minimum tillage are used. The impact of different crops, crop rotations and tillage management practices on soil quality was assessed by measuring aggregate stability and glomalin production by arbuscular mycorrhizal (AM) fungi in soil from cropping trials established in 1990. Crops were wheat (W), corn (C), proso millet (M), and sunflower (S). Rotations sampled were W-F, W-C-M, W-C-M-F, W-C-F, and W-S-F. In the same area as the cropping trials, soils were taken from a perennial grass (crested wheatgrass) and from a buffer area that had been planted to Triticale for the past 2 years but prior to that had been extensively plowed for weed control. We found that aggregate stability and glomalin were linearly correlated (r=0.73, n=54, P<0.001) across all treatments sampled. Highest and lowest aggregate stability and glomalin values were seen in perennial grass and Triticale soils, respectively. Aggregate stability in W-S-F was significantly lower than in the other crop rotations (P≤0.03), while W-C-M had significantly higher glomalin than the other rotations (P<0.05). Differences between crop rotations and the perennial grass indicate that selected comparisons should be studied in greater detail to determine ways to manage AM fungi to increase glomalin and aggregate stability in these soils.

Changes in Aggregate Stability and Concentration of Glomalin during Tillage Management Transition

Improvement in structure of degraded soils or prevention of degradation of structure in healthy soils requires an understanding of processes contributing to aggregate stability. The impact of cropping systems on a specific molecule that contributes to aggregate stability is part of the process that has not been elucidated. The relationship between aggregate stability and glomalin, a glycoprotein produced by arbuscular mycorrhizal (AM) fungi, was studied during the first 3 yr in transition from plow tillage (PT) to no tillage (NT) maize (Zea mays L.). Results showed a high linear correlation between glomalin concentration in aggregates and aggregate stability. Increases in both aggregate stability and glomalin were measurable from year to year in NT plots, but NT was significantly higher than PT after 2 or 3 yr (P &lt; 0.05). Comparison of NT plots after 3 yr with nearby soil in grass cover indicated that there was 20% greater stability and 45% higher concentration of glomalin in the grass‐covered soil. Comparison of PT and NT (3 yr) interrow samples with intrarow samples indicated that plant roots and NT management may have a synergistic effect on aggregate stabilization. These results show that cropping systems should be evaluated for the impact on production of glomalin by AM fungi.