► This study compared soil quality indices based on 3 sets of indicators. ► The effects of land management practices on soil functions were evaluated. ► Soil quality was best assessed using a set of ...29 indicators. ► However, fewer-indicators sets (8 and 4) showed the same trends. ► Soil quality index approach provides great information for land management decisions.
Efforts to define and quantify soil quality are not new, but establishing consensus about a set of standardized indicators remains difficult. Also, the view of land managers is usually not taken into account when evaluating various sets of indicators. Our objective was to compare, in functional terms, soil quality assessments based on 29 indicators, a subset with 8 of those indicators, and 4 indicators selected independently by farmers, based on their perceptions of soil quality. The assessments were made for three different rice management systems in Camaquã, Rio Grande do Sul state, Brazil, on soils of four soil textural classes based on clay content (<200, 200–400, 400–600, or >600gkg−1). The effects of land management practices on soil functions (water infiltration, storage and supply; nutrient storage, supply and cycling; and sustained biological activity) were evaluated. Soil quality was best assessed using the entire set of 29 indicators, but use of smaller indicator sets showed the same trends among management systems, textural classes, and soil functions, thus providing meaningful information on soil quality for land managers.
•Mouldboard ploughing negatively affected earthworm abundances in short term.•Earthworm populations in mouldboard ploughing recuperated by the following spring.•In medium term, reduced tillage in ...organic farming decreased A. caliginosa.•In medium term, reduced tillage in conventional farming increased L. rubellus.
Earthworms play an important role in many soil functions and are affected by soil tillage in agricultural soils. However, effects of tillage on earthworms are often studied without considering species and their interactions with soil properties. Furthermore, many field studies are based on one-time samplings that do not allow for characterisation of temporal variation. The current study monitored the short (up to 53 days) and medium term (up to 4 years) effects of soil tillage on earthworms in conventional and organic farming. Earthworm abundances decreased one and three weeks after mouldboard ploughing in both conventional and organic farming, suggesting direct and indirect mechanisms. However, the medium-term study revealed that earthworm populations in mouldboard ploughing systems recovered by spring. The endogeic species Aporrectodea caliginosa strongly dominated the earthworm community (76%), whereas anecic species remained <1% of all earthworms in all tillage and farming systems over the entire study. In conventional farming, mean total earthworm abundance was not significantly different in reduced tillage (153m−2) than mouldboard ploughing (MP; 130m−2). However, reduced tillage in conventional farming significantly increased the epigeic species Lumbricus rubellus from 0.1m−2 in mouldboard ploughing to 9m−2 averaged over 4 years. Contrastingly, in organic farming mean total earthworm abundance was 45% lower in reduced tillage (297m−2) than MP (430m−2), across all sampling dates over the medium-term study (significant at 3 of 6 sampling dates). Reduced tillage in organic farming decreased A. caliginosa from 304m−2 in mouldboard ploughing to 169m−2 averaged over 4 years (significant at all sampling dates). Multivariate analysis revealed clear separation between farming and tillage systems. Earthworm species abundances, soil moisture, and soil organic matter were positively correlated, whereas earthworm abundances and penetration resistance where negatively correlated. Variability demonstrated between sampling dates highlights the importance of multiple samplings in time to ascertain management effects on earthworms. Findings indicate that a reduction in tillage intensity in conventional farming affects earthworms differently than in organic farming. Differing earthworm species or ecological group response to interactions between soil tillage, crop, and organic matter management in conventional and organic farming has implications for management to maximise soil ecosystem functions.
Nematodes, the earth’s most abundant metazoa, are ubiquitous in the soil environment. They are sufficiently large to be identifiable by light microscopy and sufficiently small to inhabit water films ...surrounding soil particles. They aggregate around and in food sources. They include component taxa of the soil food web at several trophic levels. They can be categorized into functional guilds whose members respond similarly to food web enrichment and to environmental perturbation and recovery. Indices derived through nematode faunal analysis provide bioindicators for disturbance of the soil environment and condition of the soil food web. We enhance the resolution of faunal analyses by providing a weighting system for the indicator importance of the presence and abundance of each functional guild in relation to enrichment and structure of the food web. Graphical representations of food web structure, based on nematode faunal analyses, allow diagnostic interpretation of its condition. Simple ratios of the weighted abundance of representatives of specific functional guilds provide useful indicators of food web structure, enrichment, and decomposition channels.
► Within conventional tillage, residue retention did not lead to earthworm proliferation. ► Increased earthworm abundance under conservation agriculture (CA) resulted in changes in soil ...micromorphology. ► CA resulted in soil organic carbon stratification, topsoil aggregation and increased direct surface infiltration. ► Soil bulk density was a poor indicator for soil compaction across tillage systems. ► Soil quality changes were not translated into stable yields increases and significant soil C sequestration under CA.
Crop residue mulching combined with zero tillage and crop rotation, known as conservation agriculture (CA), is being promoted as an alternative system to revert soil degradation in maize-based farming in the central highlands of Mexico. The goal of this paper was to determine the effects of CA vs. conventional tillage systems on soil quality, with a special focus on the role of earthworms in affecting the soil structure morphology, and on crop yield. For the conventional tillage system, the effect of crop residue retention (CONV+RES) was also compared to the conventional farmers’ practice (residues removed; CONV). CA resulted in four times higher earthworm abundance when compared to CONV. Residue retention per se (CONV+RES) did not favor earthworm abundance. In all cases the earthworm community was dominated by exotic species. CA increased total N and soil organic C concentrations relative to CONV, but only at 0–5cm soil depth. Nevertheless, the more pronounced vertical stratification of soil organic carbon content under CA favored soil surface aggregation and aggregate stability as expressed by the aggregate mean weight diameter after dry sieving (MWDds=2.6mm for CA and 1.6mm for CONV) and wet sieving (MWDws=0.9mm and 0.6mm, respectively). Also, CA improved topsoil water stable macroaggregation (WSA=415mgg−1) when compared to CONV (251mgg−1). Residue retention within conventional tillage (CONV+RES) led to small increases in topsoil aggregate stability (i.e. MWDds and WSA). Soil structural improvements were accompanied by a higher direct surface water infiltration. Micromorphological analysis of thin sections indicated a loose and highly biogenic soil microstructure in CA, whereas CONV was characterized by a physicogenic microstructure, despite similar soil bulk densities (SBD). SBD is thus a poor indicator of soil physical quality when comparing different tillage systems. Redundancy analysis illustrated that CA resulted in improvement in most parameters related to soil quality, especially at the soil surface, but significant yield increases were recorded only in 2004. CONV+RES lead to marginal improvements in soil quality with no yield increases.
▶ Earthworms and termites were favored by warm and dry conditions. ▶ Cropping negatively affected earthworms more than termites. ▶ Management leading to low soil C supported fewer earthworm and ...termite taxa.
Earthworm and termite diversity were studied in 12 long-term agricultural field trials across the sub-humid to semi-arid tropical zones of Eastern and Western Africa. In each trial, treatments with high and low soil organic C were chosen to represent contrasts in long-term soil management effects, including tillage intensity, organic matter and nutrient management and crop rotations. For each trial, a fallow representing a relatively undisturbed reference was also sampled. Earthworm taxonomic richness decreased in the direction fallow>high-C soil>low-C soil and earthworm abundance was higher in fallow than under continuous crop production. Termite abundance was not significantly different between fallow and high and low-C treatments and termite taxonomic richness was higher in fallow soil than in the two cropping systems. We concluded that fewer species of earthworms and termites were favored under agricultural management that led to lower soil C. Results indicated that the soil disturbance induced by continuous crop production was more detrimental to earthworms than to termites, when compared to the fallow.
Knowledge of the effects of cow diet on manure composition is required to improve nutrient use efficiency and to decrease emissions of N to the environment. Therefore, we performed an experiment with ...nonlactating cows to determine the consequences of changes in cow rations for the chemical characteristics and the traits of the microbial community in the feces. In this experiment, 16 cows were fed 8 diets, differing in crude protein, neutral detergent fiber, starch, and net energy content. These differences were achieved by changing dietary ingredients or roughage to concentrate ratio. After an adaptation period of 3 wk, fecal material was collected and analyzed. Observed results were compared with simulated values using a mechanistic model that provides insight into the mechanisms involved in the effect of dietary variation on fecal composition. Feces produced on a high-fiber, low-protein diet had a high C:N ratio (>16) and had lower concentrations of both organic and inorganic N than feces on a low-fiber, high-protein diet. Fecal bacterial biomass concentration was highest in high-protein, high-energy diets. The fraction of inorganic N in the feces was not significantly different between the different feces. Microbial biomass in the feces ranged from 1,200 to 8,000μg of C/g of dry matter (average: 3,700μg of C/g of dry matter). Bacterial diversity was similar for all fecal materials, but the different protein levels in the feeding regimens induced changes in the community structure present in the different feces. The simulated total N content (Ntotal) in the feces ranged from 1.0 to 1.5 times the observed concentrations, whereas the simulated C:Ntotal of the feces ranged from 0.7 to 0.9 times the observed C:Ntotal. However, bacterial biomass C was not predicted satisfactorily (simulated values being on average 3 times higher than observed), giving rise to further discussion on the definition of microbial C in feces. Based on these observations, it was concluded that diet composition affected fecal chemical composition and microbial biomass. These changes may affect the nutrient use and efficiency of the manure. Because the present experiment used a limited number of dry cows and extreme diet regimens, extrapolation of results to other dairy cow situations should be done with care.
Though soil physical and soil biological properties are intrinsically linked in the soil environment they are often studied separately. This work adds value to analyses of soil biophysical quality of ...tillage systems under organic and conventional farming systems by correlating physical and biological data otherwise left unexplored. Multivariate redundancy analysis was used to relate data on soil water, soil structure, soil carbon, crop yield, and earthworm species abundances (Aporrectodea caliginosa, Aporrectodea rosea, Eiseniella tetraedra, Lumbricus rubellus). Structural equation modelling was then used to infer causal relations amongst the variables. Effects of tillage system (i.e., mouldboard ploughing (MP) and non-inversion tillage (NIT)) on soil physical parameters and on the earthworm species Lumbricus rubellus were similar in organic and conventional farming. Despite sampling times in different seasons and different crops present at the time of sampling NIT correlated positively with L. rubellus, soil organic matter content, plant-available water content, soil aggregate stability, soil water content, and penetration resistance. Field-saturated hydraulic conductivity was negatively correlated with NIT and was negatively, or not correlated at all, with earthworm species abundances, possibly due to the absence of Lumbricus terrestris in these fields. In the comparison of organic fields, earthworms were positively correlated with the soil's ability to hold water but loosening by ploughing appears to have benefited the conduction of water through soil more than earthworms. Tillage systems and farming systems were found to have both direct and indirect influences on soil parameters. Organic farming increased soil organic matter content, soil water content, and both endogeic and epigeic earthworm species abundances. Non-inversion tillage increased crop yield, soil organic matter content, and soil penetration resistance. This study demonstrates that multivariate techniques can integrate and add value to data otherwise analysed separately.
•Data were explored and causal links modelled using multivariate analyses.•Mouldboard ploughing and infiltration correlated positively.•Non-inversion tillage increased crop yield and soil organic matter.•Organic farming increased soil organic matter and earthworm abundances.
Knowledge of the interactions between organisms within trophic groups is important for an understanding of the role of biodiversity in ecosystem functioning. We hypothesised that interactions between ...bacterivorous nematodes of different life history strategies would affect nematode population development, bacterial community composition and activity, resulting in increased N mineralization. A microcosm experiment was conducted using three nematode species (Bursilla monhystera, Arcobeloides nanus and Plectus parvus). All the nematode species interacted with each other, but the nature and effects of these interactions depended on the specific species combination. The interaction between B. monhystera and A. nanus was asymmetrically competitive (0,-), whereas that between B. monhystera and P. parvus, and also A. nanus and P. parvus was contramensal (+, -). The interaction that affected microcosm properties the most was the interaction between B. monhystera and P. parvus. This interaction affected the bacterial community composition, increased the bacterial biomass and increased soil N mineralization. B. monhystera and P. parvus have the most different life history strategies, whereas A. nanus has a life history strategy intermediate to those of B. monhystera and P. parvus. We suggest that the difference in life history strategies between species of the same trophic group is of importance for their communal effect on soil ecosystem processes. Our results support the idiosyncrasy hypothesis on the role of biodiversity in ecosystem functioning.
Earthworm species contribute to soil ecosystem functions in varying ways. Important soil functions like structural maintenance and nutrient cycling are affected by earthworms, thus it is essential to ...understand how arable farm management influences earthworm species. One aim of arable field margin strips and non-inversion tillage is to enhance agrobiodiversity, however their influence on earthworm species assemblages remains unclear. In particular, on-farm studies conducted over multiple years that capture variability across the landscape are rare. The current study monitored earthworm species assemblages on 4 farms in Hoeksche Waard, The Netherlands, from 2010 to 2012. It was hypothesised that arable field margin strips (FM) and non-inversion tillage (NIT; a reduced tillage system that loosens subsoil at 30−35 cm depth) would have higher earthworm species abundances (epigeics and anecics in particular), soil organic matter, and soil moisture than adjacent mouldboard ploughing (MP) fields, and that earthworm numbers would decrease with distance away from FM into arable fields (MP only). FM contained a mean total earthworm abundance of 284 m−2 and biomass of 84 g m−2 whereas adjacent MP arable fields had only 164 earthworms m−2 and 31 g m−2. Aporrectodea rosea, Lumbricus rubellus, Lumbricus terrestris, and Lumbricus castaneus were significantly more abundant in FM than adjacent arable soil under MP. However, no decreasing trend with distance from FM was observed in earthworm species abundances. A tillage experiment initiated on the farms with FM showed that relative to MP, NIT significantly increased mean total earthworm abundance by 34% to 275 m−2 and mean total earthworm biomass by 15% to 51 g m−2 overall sampling dates and farms. L. rubellus, A. rosea, and L. terrestris were significantly more abundant overall in NIT than MP. FM and NIT positively affected earthworm species richness and abundances and it is noteworthy that these effects could be observed despite variation in environmental conditions and soil properties between samplings, farms, and crops. Higher top-soil organic matter and less physical disturbance in FM and NIT likely contributed to higher earthworm species richness and abundances. The anecic species L. terrestris (linked to water infiltration and organic matter incorporation) was more abundant in FM, but densities remained very low in arable soil, irrespective of tillage system.
•Arable farm management can enhance earthworm species diversity.•Field margin strips and non-inversion tillage benefitted earthworm abundances.•Anecics were very rare in arable fields despite presence in field margin strips.•These effects were discerned despite variation between crops, farms, and seasons.
We analyzed the dynamics of dominant plant species in a grazed grassland over 17 years, and investigated whether local shifts in these dominant species, leading to vegetation mosaics, could be ...attributed to interactions between plants and soil-borne pathogens. We found that Festuca rubra and Carex arenaria locally alternated in abundance, with different sites close together behaving out of phase, resulting in a shifting mosaic. The net effect of killing all soil biota on the growth of these two species was investigated in a greenhouse experiment using gamma radiation, controlling for possible effects of sterilization on soil chemistry. Both plant species showed a strong net positive response to soil sterilization, indicating that pathogens (e.g., nematodes, pathogenic fungi) outweighed the effect of mutualists (e.g., mycorrhizae). This positive growth response towards soil sterilization appeared not be due to effects of sterilization on soil chemistry. Growth of Carex was strongly reduced by soil-borne pathogens (86% reduction relative to its growth on sterilized soil) on soil from a site where this species decreased during the last decade (and Festuca increased), while it was reduced much less (50%) on soil from a nearby site where it increased in abundance during the last decade. Similarly, Festuca was reduced more (67%) on soil from the site where it decreased (and Carex increased) than on soil from the site where it increased (55%, the site where Carex decreased). Plant-feeding nematodes showed high small-scale variation in densities, and we related this variation to the observed growth reductions in both plant species. Carex growth on unsterilized soil was significantly more reduced at higher densities of plant-feeding nematodes, while the growth reduction in Festuca was independent of plant-feeding nematode densities. At high plant-feeding nematode densities, growth of Carex was reduced more than Festuca, while at low nematode densities the opposite was found. Each plant species thus seems to be affected by different (groups of) soil-borne pathogens. The resulting interaction web of plants and soil-borne pathogens is discussed. We hypothesize that soil disturbances by digging ants and rabbits may explain the small-scale variation in nematode densities, by locally providing "fresh" sand. We conclude that soil-borne pathogens may contribute to plant diversity and spatial mosaics of plants in grasslands.
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