Knowledge of the effects of species diversity within taxonomic groups on nutrient cycling is important for understanding the role of soil biota in sustainable agriculture. We hypothesized that ...earthworm species specifically affect nitrogen mineralization, characteristically for their ecological group classifications, and that earthworm species interactions would affect mineralization through competition and facilitation effects. A mesocosm experiment was conducted to investigate the effect of three earthworm species, representative of different ecological groups (epigeic:
Lumbricus rubellus; endogeic:
Aporrectodea caliginosa tuberculata; and anecic:
Lumbricus terrestris), and their interactions on the bacterial community, and on nitrogen mineralization from
15N-labelled crop residue and from soil organic matter.
Our results indicate that
L. rubellus and
L. terrestris enhanced mineralization of the applied crop residue whereas
A. caliginosa had no effect. On the other hand,
L. rubellus and
A. caliginosa enhanced mineralization of the soil organic matter, whereas
L. terrestris had no effect. The interactions between different earthworm species affected the bacterial community and the net mineralization of soil organic matter. The two-species interactions between
L. rubellus and
A. caliginosa, and
L. rubellus and
L. terrestris, resulted in reduced mineral N concentrations derived from soil organic matter, probably through increased immobilization in the bacterial biomass. In contrast, the interaction between
A. caliginosa and
L. terrestris resulted in increased bacterial growth rate and reduced total soil C. When all three species were combined, the interaction between
A. caliginosa and
L. terrestris was dominant. We conclude that the effects of earthworms on nitrogen mineralization depend on the ecological traits of the earthworm species present, and can be modified by species interactions. Knowledge of these effects can be made useful in the prevention of nutrient losses and increased soil fertility in agricultural systems, that typically have a low earthworm diversity.
•Effects of four paired management practices on five soil quality indicators were analysed.•Yield was lower under NT and organic agriculture, but with environmental benefits.•SOM increased under NT, ...organic matter addition, crop rotation and organic farming.•Number of earthworms was the most sensitive indicator for the paired practices.•Soil pH appears to be the least sensitive indicator.
In this paper we present effects of four paired agricultural management practices (organic matter (OM) addition versus no organic matter input, no-tillage (NT) versus conventional tillage, crop rotation versus monoculture, and organic agriculture versus conventional agriculture) on five key soil quality indicators, i.e., soil organic matter (SOM) content, pH, aggregate stability, earthworms (numbers) and crop yield. We have considered organic matter addition, no-tillage, crop rotation and organic agriculture as “promising practices”; no organic matter input, conventional tillage, monoculture and conventional farming were taken as the respective references or “standard practice” (baseline). Relative effects were analysed through indicator response ratio (RR) under each paired practice. For this we considered data of 30 long-term experiments collected from 13 case study sites in Europe and China as collated in the framework of the EU-China funded iSQAPER project. These were complemented with data from 42 long-term experiments across China and 402 observations of long-term trials published in the literature. Out of these, we only considered experiments covering at least five years. The results show that OM addition favourably affected all the indicators under consideration. The most favourable effect was reported on earthworm numbers, followed by yield, SOM content and soil aggregate stability. For pH, effects depended on soil type; OM input favourably affected the pH of acidic soils, whereas no clear trend was observed under NT. NT generally led to increased aggregate stability and greater SOM content in upper soil horizons. However, the magnitude of the relative effects varied, e.g. with soil texture. No-tillage practices enhanced earthworm populations, but not where herbicides or pesticides were applied to combat weeds and pests. Overall, in this review, yield slightly decreased under NT. Crop rotation had a positive effect on SOM content and yield; rotation with ley very positively influenced earthworms’ numbers. Overall, crop rotation had little impact on soil pH and aggregate stability − depending on the type of intercrop; alternatively, rotation of arable crops only resulted in adverse effects. A clear positive trend was observed for earthworm abundance under organic agriculture. Further, organic agriculture generally resulted in increased aggregate stability and greater SOM content. Overall, no clear trend was found for pH; a decrease in yield was observed under organic agriculture in this review.
A field experiment to investigate the interaction of soil fauna and organic resource quality in the applied organic material mass loss was conducted on a Eutric Cambisol in southern Burkina Faso ...during the 2000 rainy season. Plots were treated with the pesticides Dursban and Endosulfan or left untreated (main treatments). Sub-treatments consisted of surface-placed maize straw,
Andropogon straw or cattle dung. Organic materials were applied at a rate equivalent to the application of 40
kg
N
ha
−1. Litterbags and direct estimation methods were used to follow the litter mass loss of the different organic materials. Without soil macrofauna, 96% of
Andropogon straw, 70% of cattle dung and 34% of maize straw were not broken down 3 months after application, whereas in the presence of soil fauna only 19% of
Andropogon straw, 8% of cattle dung and 5% of maize straw remained 3 months after application. Soil depth (surface-placed or buried) had little or no influence on organic resource disappearance in the absence of soil fauna. The interaction between organic resource quality and soil macrofauna had a large influence on the timing of organic material disappearance. Termite density was strongly correlated with the remaining organic material, with organic material being preferred over easily decomposable organic resources. In semi-arid low-input agricultural systems, soil fauna (termites) determine the rate of decomposition of organic resources.
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•Organic soil management increases the abundance of all microbial groups in soil.•Organic soil management enhances total soil microbial catabolic activity.•Effects of organic soil ...management are amplified by oat as cover crop.•Organic soil management increases dissolved organic carbon of lower aromaticity.•Soil management effects on soil organic matter feed back to cover crop litter traits.
It is well recognized that organic soil management stimulates bacterial biomass and activity and that including cover crops in the rotation increases soil organic matter (SOM). Yet, to date the relative impact of different cover crop species and organic vs. non-organic soil management on soil bacteria and fungi and on SOM quantity and quality remains to be tested. We used a long-term (10 years) full-factorial field experiment to test the combined effects of organic vs. conventional soil management with different cover crop species (oat or rye) and the legacy effects of seven soil health treatments (SHTs: treatments with compost, chitin, marigold, grass–clover, biofumigation or anaerobic soil disinfestation (ASD), and fallow as control) on microbial community biomass, structure and catabolic activity and on SOM quantity and quality (dissolved organic carbon (DOC), aromaticity and water repellency).
Microbial community traits were assessed using PLFA/NLFA analyses and multi-substrate induced respiration. We found that organic soil management enhanced total microbial biomass by increasing bacterial, saprotrophic and arbuscular mycorrhizal fungal biomass; and increased total microbial catabolic activity, associated with maintaining high microbial efficiency (low qCO2). Effects of organic management were amplified by oat as cover crop, which enhanced the abundance of saprotrophic fungi resulting in a higher fungal:bacterial ratio. Total SOM concentration was similar among treatments, however the most easily accessible fraction, i.e. DOC, was higher in organic compared to conventional soils. Also, the aromaticity of the DOC was lower in organic than in conventional systems, which was associated with lower water repellency. There was a legacy effect of SHTs on fungal:bacterial ratio in that chitin and marigold showed higher fungal:bacterial ratio compared to compost, biofumigation and ASD even 6 years after the last application.
We conclude that organic soil management enhances the abundance of all microbial groups and their total catabolic activity, associated with a higher concentration and lower aromaticity of dissolved organic matter. These effects can be enlarged by the growth of specific cover crops and the application of certain soil health treatments.
A field experiment was conducted at Kaibo in southern Burkina Faso on an Eutric Cambisol during the 2000 rainy season to assess the interaction of organic amendment quality and soil fauna, affecting ...soil organic carbon and sorghum (Sorghum bicolor L. Moench) performance. Plots were treated with the pesticides Dursban and Endosulfan to exclude soil fauna or left untreated. Sub-treatments consisted of surface-placed maize straw (C/N ratio = 58), Andropogon straw (C/N ratio = 153), cattle dung (C/N ratio = 40), sheep dung (C/N ratio = 17) or compost (C/N ratio = 10) and the control. Organic amendments were applied at a dose equivalent to the application of 40 kg N ha-¹. The presence of soil fauna increased soil total carbon by 32% and grain yield production by 50%. The interaction between high C/N ratio organic amendment, Andropogon straw (SA), and soil fauna reduced soil carbon build-up. We suggest that this is due to a priming effect of SA on soil organic matter in the presence of soil fauna. We also suggest that the interaction between soil fauna and easily decomposable organic amendment led to the smallest decrease in soil carbon build-up. It is concluded that in semi-arid West Africa, in the presence of soil fauna, soil carbon build-up is more affected by the quality of organic amendments than the quantity of carbon inputs. Sorghum grain yield production was significantly reduced in the absence of soil fauna. High C/N ratio organic amendment interacted negatively with soil fauna in its effects on crop performance. We propose that the effect of soil fauna on soil carbon build-up and crop performance can be optimised by using high quality organic matter or supplementing low-quality organic matter with inorganic nitrogen in semi-arid West Africa.
Summary
Biodiversity is responsible for the provision of many ecosystem services; human well‐being is based on these services, and consequently on biodiversity. In soil, earthworms represent the ...largest component of the animal biomass and are commonly termed ‘ecosystem engineers’. This review considers the contribution of earthworms to ecosystem services through pedogenesis, development of soil structure, water regulation, nutrient cycling, primary production, climate regulation, pollution remediation and cultural services. Although there has been much research into the role of earthworms in soil ecology, this review demonstrates substantial gaps in our knowledge related in particular to difficulties in identifying the effects of species, land use and climate. The review aims to assist people involved in all aspects of land management, including conservation, agriculture, mining or other industries, to obtain a broad knowledge of earthworms and ecosystem services.
Permanent grassland soils can act as a sink for carbon and may therefore positively contribute to climate change mitigation and adaptation. We compared young (5–15 years since latest grassland ...renewal) with old (>20 years since latest grassland renewal) permanent grassland soils in terms of carbon stock, carbon sequestration, drought tolerance and flood resistance. The research was carried out on marine clay soil at 10 dairy farms with young and old permanent grassland. As hypothesized, the carbon stock was larger in old grassland (62 Mg C ha−1) topsoil (0–10 cm) than in young grassland topsoil (51 Mg C ha−1). The carbon sequestration rate was greater in young (on average 3.0 Mg C ha−1 year−1) compared with old grassland (1.6 Mg C ha−1 year−1) and determined by initial carbon stock. Regarding potential drought tolerance, we found larger soil moisture and soil organic matter (SOM) contents in old compared with young grassland topsoils. As hypothesized, the old grassland soils were more resistant to heavy rainfall as measured by water infiltration rate and macroporosity (at 20 cm depth) in comparison with the young grassland soils. In contrast to our hypothesis we did not find a difference in rooting between young and old permanent grassland, probably due to large variability in root biomass and root tip density. We conclude that old grasslands at dairy farms on clay soil can contribute more to the ecosystem services climate change mitigation and climate change adaptation than young grasslands. This study shows that under real farm conditions on a clay topsoil, carbon stock increases with grassland age and even after 30 years carbon saturation has not been reached. Further study is warranted to determine by how much extending grassland age can contribute to climate change mitigation and adaptation.
Highlights
We studied the effect of young versus old grassland on a range of soil properties related to climate change mitigation and adaptation.
Old, more than young, grassland soils offer potential to mitigate and adapt to climate change.
This finding gives farmers insight into the merits of extending grassland age on clay soils.
Soil carbon stock determines carbon sequestration rate more than grassland age.
It is frequently hypothesised that high soil fungal/bacterial ratios are indicative for more sustainable agricultural systems. Increased
F
/
B
ratios have been reported in extensively managed ...grasslands. To determine the shifts in fungal/bacterial biomass ratio as influenced by grassland management and to find relations with nitrogen leaching potential, we sampled a two-year-old field experiment at an organic experimental farm in the eastern part of The Netherlands. The effect of crop (grass and grass-clover), N application rate (0, 40, 80,
120
kg
N
ha
-
1
) and manure type (no manure, farm yard manure and slurry) on the
F
/
B
ratio within three growing seasons was tested, as well as relations with soil and crop characteristics, nitrate leaching and partial N balance. Biomass of fungi and bacteria was calculated after direct counts using epifluorescence microscopy. Fungal and bacterial biomass and the
F
/
B
ratio were higher in grass than in grass-clover. The
F
/
B
ratio decreased with increasing N application rate and multiple regression analysis revealed a negative relationship with pH. Bacterial activity (measured as incorporation of
3Hthymidine and
14Cleucine into bacterial DNA and proteins) showed the exact opposite: an increase with N application rate and pH. Leaching increased with N application rate and was higher in grass-clover than in grass. Partial N balance was more positive at a higher N application rate and showed an inverse relationship with fungal biomass and
F
/
B
ratio. We conclude that the fungal/bacterial biomass ratio quickly responded to changes in management. Grasslands with higher N input showed lower
F
/
B
ratios. Grass-clover had a smaller fungal biomass and higher N leaching than grass. In general, a higher fungal biomass indicated a lower nitrogen leaching and a more negative partial N balance (or smaller N surplus), but more observations are needed to confirm the relationship between
F
/
B
ratio and sustainability.
Production ecology and conservation biology have long focused on providing the knowledge base for intensive food production and biodiversity conservation, respectively. With increasing global food ...insecurity and continuing biodiversity decline, we show that the largely separate development of these fields is counterproductive. Scenario analyses suggest that feeding the world is possible without further encroachment of agriculture into natural ecosystems. Without ignoring the necessary demographic, socio-economic, institutional and governance requirements, we make the case for a science that develops the best ecological means to produce food in a way that has substantially less negative effects on biodiversity and associated ecosystem services and, indeed, should be able to contribute to their persistence and enhancement. Recent developments in trait-based ecology should soon make it possible to adapt and (re-)design agroecosystems to meet both goals of biodiversity conservation and food security. However, there are real tensions between, on the one hand, the opportunity costs of biodiversity conservation (for direct use and for conversion to agriculture) and on the other hand, the ecosystem service values and option values associated with biodiversity. We elaborate the management of plant genetic resources as a metaphor of the tensions between such values of biodiversity and ecosystem services in general. We conclude that significant changes in policies, institutions and practices are necessary to make advances in ecology work for reconciling biodiversity conservation and food security.
Soil biodiversity for agricultural sustainability Brussaard, Lijbert; de Ruiter, Peter C.; Brown, George G.
Agriculture, ecosystems & environment,
07/2007, Letnik:
121, Številka:
3
Journal Article, Conference Proceeding
Recenzirano
We critically highlight some evidence for the importance of soil biodiversity to sustaining (agro-)ecosystem functioning and explore directions for future research. We first deal with resistance and ...resilience against abiotic disturbance and stress. There is evidence that soil biodiversity does confer stability to stress and disturbance, but the mechanism is not yet fully understood. It appears to depend on the kind of stress and disturbance and on the combination of stress and disturbance effects. Alternatively, community structure may play a role. Both possible explanations will guide further research. We then discuss biotic stress. There is evidence that soil microbial diversity confers protection against soil-borne disease, but crop and soil type and management also play a role. Their relative importance as well as the role of biodiversity in multitrophic interactions warrant further study. Henceforth, we focus on the effects of plant and soil biodiversity on nutrient and water use efficiencies as important ecological functions in agroecosystems. The available evidence suggests that mycorrhizal diversity positively contributes to nutrient and, possibly, water use efficiency. Soil fauna effects on nutrient and water use efficiencies are also apparent, but diversity effects may be indirect, through effects on soil structure. We present a conceptual diagram relating plant and soil biodiversity with soil structure and water and nutrient use efficiencies as a framework for future studies. We then consider how cropping systems design and management are interrelated and how management options might be interfaced with farmers’ knowledge in taking management decisions. Finally, we attempt to express some economic benefits of soil biodiversity to society as part of a wider strategy of conserving and using agrobiodiversity.
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