The interactions and hierarchical effects of long-term agricultural stressors on soil bacterial communities

Soils are subjected to multiple anthropogenic modifications, but the synergistic impacts of simultaneous environmental stressors on below-ground communities are poorly understood. We used a large-scale (1152 plots), long-term (26 years), multi-factorial grassland experiment to assess the impact of five common agricultural practises (pesticides, herbicide, liming, fertilizers and grazing exclusion) and their interactive effects on the composition and activity of soil microbial communities. We confirmed that pH strongly impacts belowground communities, but further demonstrate that pH strongly mediates the impacts of other management factors. Notably, there was a significant interaction between liming and the effect of pesticide application, with only half of the taxa responding to pesticide being shared in both limed and unlimed treatments. Likewise, nutrient amendments significantly altered bacterial community structure in acidic soils. Not only do these results highlight an hierarchy of effect of commonly used agricultural practices but also the widespread interactions between treatments: many taxa were significantly affected by interactions between treatments, even in the absence of significant main effects. Furthermore, the results demonstrated that chemical amendments may not percolate deeply into physically unperturbed soils with effects concentrated between 0 and 30 cm, despite 20+ years of treatment. The research shows that future changes to agricultural practices will need to consider interactions among multiple factors

Land use driven change in soil pH affects microbial carbon cycling processes

Soil microorganisms act as gatekeepers for soil–atmosphere carbon exchange by balancing the accumulation and release of soil organic matter. However, poor understanding of the mechanisms responsible hinders the development of effective land management strategies to enhance soil carbon storage. Here we empirically test the link between microbial ecophysiological traits and topsoil carbon content across geographically distributed soils and land use contrasts. We discovered distinct pH controls on microbial mechanisms of carbon accumulation. Land use intensification in low-pH soils that increased the pH above a threshold (~6.2) leads to carbon loss through increased decomposition, following alleviation of acid retardation of microbial growth. However, loss of carbon with intensification in near-neutral pH soils was linked to decreased microbial biomass and reduced growth efficiency that was, in turn, related to trade-offs with stress alleviation and resource acquisition. Thus, less-intensive management practices in near-neutral pH soils have more potential for carbon storage through increased microbial growth efficiency, whereas in acidic soils, microbial growth is a bigger constraint on decomposition rates

Test sorghumrassen op vier proeflocaties

De droogtetolerantie en ziekteresistentie van sorghum maken het gewas steeds geschikter voor teelt en gebruik als ruwvoer in Nederland. Het gewas is echter nog niet uitontwikkeld. Veredelaars zetten elk jaar stappen om betere sorghumrassen te ontwikkelen voor Nederland. Zo wordt momenteel gezocht naar rassen die in het Nederlandse klimaat opbrengst combineren met een redelijk zetmeelgehalte en een goede verteringscoëfficiënt

Volatile-mediated suppression of plant pathogens is related to soil properties and microbial community composition

There is increasing evidence that the soil microbial community produces a suite of volatile organic compounds that suppress plant pathogens. However, it remains unknown which soil properties and management practices influence volatile-mediated pathogen suppression. The aim of this study was to relate soil properties to growth suppression of three plant pathogens by soil volatiles. We measured the effect of volatiles emitted from a broad range of agricultural soils on the in vitro growth of the plant pathogenic fungi Rhizoctonia solani and Fusarium oxysporum, and the oomycete Pythium intermedium. Growth suppression of pathogens by soil volatiles could be linked to various soil properties, and some aspects of microbial community composition and field history, using multiple linear regression. Volatile-mediated suppression of mycelial development occurred for each pathogen type, but the magnitude of inhibition differed among soils as well as pathogens. On average R. solani and P. ultimum appeared more sensitive to volatile suppression than F. oxysporum. Suppression of R. solani by volatiles was positively correlated with organic matter content, microbial biomass and proportion of litter saprotrophs in the microbial community, but negatively correlated with pH, microbial diversity (Shannon), and the proportion of Acidobacteria in the community. R. solani, F. oxysporum, and P. intermedium suppression by volatiles was affected by various management practices occurring in the soil's field history, such as reduced tillage, the presence of certain crops in the crop rotation, and the application of solid manure. P. intermedium suppression was also negatively correlated with soil sulphur content. This study identifies pathogen-specific drivers of growth-suppressive volatiles, a critical step in integrating soil volatiles into prediction and management of soil-borne plant diseases. Keywords • Soil microbial ecology; • Phytopathology; • Volatile organic compounds; • Soil-borne plant pathogens; • Rhizoctonia solani; • Pythium intermedium; • Fusarium oxysporumstatus: publishe

Effecten van sorghum en mais op bodem en gewas op een verdichte zandgrond

Volgens buitenlands onderzoek is gebleken dat sorghum beter dan mais in staat is om dieper te wortelen in droge, verdichte zandgronden. Omdat sorghum voor Nederland nog een vrij nieuw gewas is, is een proef uitgevoerd in Brabant om na te gaan of sorghum ook hier dieper wortelt dan mais op een verdichte zandgrond. Gegevens zijn verzameld over bodem- en gewasparameters en ook over nitraatresidu aan het eind van het seizoen

Volatile-mediated suppression of plant pathogens is related to soil properties and microbial community composition

There is increasing evidence that the soil microbial community produces a suite of volatile organic compounds that suppress plant pathogens. However, it remains unknown which soil properties and management practices influence volatile-mediated pathogen suppression. The aim of this study was to relate soil properties to growth suppression of three plant pathogens by soil volatiles. We measured the effect of volatiles emitted from a broad range of agricultural soils on the in vitro growth of the plant pathogenic fungi Rhizoctonia solani and Fusarium oxysporum, and the oomycete Pythium intermedium. Growth suppression of pathogens by soil volatiles could be linked to various soil properties, and some aspects of microbial community composition and field history, using multiple linear regression. Volatile-mediated suppression of mycelial development occurred for each pathogen type, but the magnitude of inhibition differed among soils as well as pathogens. On average R. solani and P. ultimum appeared more sensitive to volatile suppression than F. oxysporum. Suppression of R. solani by volatiles was positively correlated with organic matter content, microbial biomass and proportion of litter saprotrophs in the microbial community, but negatively correlated with pH, microbial diversity (Shannon), and the proportion of Acidobacteria in the community. R. solani, F. oxysporum, and P. intermedium suppression by volatiles was affected by various management practices occurring in the soil's field history, such as reduced tillage, the presence of certain crops in the crop rotation, and the application of solid manure. P. intermedium suppression was also negatively correlated with soil sulphur content. This study identifies pathogen-specific drivers of growth-suppressive volatiles, a critical step in integrating soil volatiles into prediction and management of soil-borne plant diseases

Microbiota in Dung and Milk Differ Between Organic and Conventional Dairy Farms

Organic farming is increasingly promoted as a means to reduce the environmental impact of artificial fertilizers, pesticides, herbicides, and antibiotics in conventional dairy systems. These factors potentially affect the microbial communities of the production stages (soil, silage, dung, and milk) of the entire farm cycle. However, understanding whether the microbiota representative of different production stages reflects different agricultural practices – such as conventional versus organic farming – is unknown. Furthermore, the translocation of the microbial community across production stages is scarcely studied. We sequenced the microbial communities of soil, silage, dung, and milk samples from organic and conventional dairy farms in the Netherlands. We found that community structure of soil fungi and bacteria significantly differed among soil types, but not between organic versus conventional farming systems. The microbial communities of silage also did not differ among conventional and organic systems. Nevertheless, the dung microbiota of cows and the fungal communities in the milk were significantly structured by agricultural practice. We conclude that, while the production stages of dairy farms seem to be disconnected in terms of microbial transfer, certain practices specific for each agricultural system, such as the content of diet and the use of antibiotics, are potential drivers of shifts in the cow’s microbiota, including the milk produced. This may reflect differences in farm animal health and quality of dairy products depending on farming practices

Microarthropod communities and their ecosystem services restore when permanent grassland with mowing or low-intensity grazing is installed

The current focus on intensification and maximizing productivity in agriculture can endanger soil biota and the ecosystem services they provide in such a way that it acts counterproductive and increases the dependence on external inputs. In this study, we aimed to identify the factors that are most limiting for the restoration of soil biota and their ecosystem services on sandy soils. To this end, we assessed microarthropod communities, their relationship with the aboveground food web and their effect on organic matter decomposition, in two land-use types: grasslands with agricultural land use and grasslands with nature land use. The latter are grasslands converted from agricultural land use, for the development of the Dutch National Ecological Network. For these land-use types, we took into account two main factors of disturbance: the number of years since the last tillage (i.e., plowing event), and the current grassland management (mowing or grazing). We found that the diversity of microarthropods was higher in nature grasslands than in agricultural grasslands. The abundance of microarthropods increased with time since last tillage for grasslands that were mown, but not for grasslands that were grazed. An agricultural grassland without tillage since 39 years had a microarthropod abundance similar to reference natural grasslands reported in previous research. The number of predatory beetles increased with a higher microarthropod abundance in mown grasslands, but not so in grazed grasslands. The number of fungivorous and herbofungivorous grazer microarthropods positively influenced the decomposition of soil organic matter as measured with the Tea Bag Index. Furthermore, we found a negative effect of Difenyl and total fungicide concentrations in the soil on (herbo)fungivorous grazers. Contrary to our expectations, we found more pesticide residues in nature grasslands than in agricultural grasslands. In conclusion, to restore the soil microarthropods and the ecosystem services they contribute to, the best practice is to strive for permanent grassland (without tillage) with mowing or low-intensity grazing (without compaction of the topsoil)

Bacteriën en schimmels op melkveebedrijf in beeld

De samenstelling van de bacterie- en schimmelgemeenschap als geheel is specifiek voor elk onderdeel van de kringloop op een melkveebedrijf. Dat laat een verkennend onderzoek gefinancierd door de Triodos Foundation zien. Zo is de bacterie- en schimmelgemeenschap in de bodem heel anders dan die in de mest. In de mest en melk was er een verschil te zien tussen gangbare en biologische bedrijven

Achtergronden bij informatie in de BOOT-lijst factsheets

Vanuit het Bestuurlijk Overleg Open Teelt en Veehouderij (BOOT) is de zogenaamde BOOT-lijst opgesteld met maatregelen die emissie naar water vanuit landbouwbedrijven verlagen. De praktijkrijpe maatregelen worden via het Deltaplan Agrarisch Waterbeheer (DAW) verder uitgerold. Factsheets over 24 van de maatregelen geven inzicht in het productievoordeel, het milieuvoordeel en de kosten en in de praktische inpasbaarheid. Dit rapport voorziet in achtergrondinformatie en onderbouwing van de factsheets en geeft aan in hoeverre er consensus is over de gepresenteerde inzichten. Bij veel maatregelen is er behoefte aan versterking van de empirische onderbouwing. Adviezen over te nemen maatregelen kunnen aan overtuigingskracht winnen als resultaten van veldonderzoek beschikbaar zijn. Een aantal maatregelen heeft betrekking op verandering van bodemaspecten (zoals het bodem organische stofgehalte) zonder dat de relatie van deze doelen met waterkwaliteit voldoende duidelijk is uitgewerkt. De effectiviteit van deze maatregelen op uiteindelijke waterkwaliteitsdoelen moet scherper in het vizier komen