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.
Global warming, as a result of an increase in the mean temperature of the planet, might lead to catastrophic events for humanity. This temperature increase is mainly the result of an increase in the ...atmospheric greenhouse gases （GHG） concentration. Water vapor, carbon dioxide （CO2）, methane （CH4） and nitrous oxide （N20） are the most important GHG, and human activities, such as industry, livestock and agriculture, contribute to the production of these gases. Methane, at an atmospheric concentration of 1.7 gmol tool-1 currently, is responsible for 16% of the global warming due to its relatively high global warming potential. Soils play an important role in the CH4 cycle as methanotrophy （oxidation of CH4） and methanogenesis （production of CH4） take place in them. Understanding methanogenesis and methanotrophy is essential to establish new agriculture techniques and industrial processes that contribute to a better balance of GHG. The current knowledge of methanogenesis and methanotrophy in soils, anaerobic CH4 oxidation and methanotrophy in extreme environments is also discussed.
Improving food security, environmental preservation and enhancing livelihood should be the main targets of the innovators of today's farming systems. Conservation agriculture (CA), based on minimum ...tillage, crop residue retention, and crop rotations, has been proposed as an alternative system combining benefits for the farmer with advantages for the society. This paper reviews the potential impact of CA on C sequestration by synthesizing the knowledge of carbon and nitrogen cycling in agriculture; summarizing the influence of tillage, residue management, and crop rotation on soil organic carbon stocks; and compiling the existing case study information. To evaluate the C sequestration capacity of farming practices, their influence on emissions from farming activities should be considered together with their influence on soil C stocks. The largest contribution of CA to reducing emissions from farming activities is made by the reduction of tillage operations. The soil C case study results are not conclusive. In 7 of the 78 cases withheld, the soil C stock was lower in zero compared to conventional tillage, in 40 cases it was higher, and in 31 of the cases there was no significant difference. The mechanisms that govern the balance between increased or no sequestration after conversion to zero tillage are not clear, although some factors that play a role can be distinguished, e.g., root development and rhizodeposits, baseline soil C content, bulk density and porosity, climate, landscape position, and erosion/deposition history. Altering crop rotation can influence soil C stocks by changing quantity and quality of organic matter input. More research is needed, especially in the tropical areas where good quantitative information is lacking. However, even if C sequestration is questionable in some areas and cropping systems, CA remains an important technology that improves soil processes, controls soil erosion and reduces production cost.
Background, aim, and scope Although highly diverse and specialized prokaryotic and eukaryotic microbial communities in soil degrade polycyclic aromatic hydrocarbons (PAHs), most of these are removed ...slowly. This review will discuss the biotechnological possibilities to increase the microbial dissipation of PAHs from soil as well as the main biological and biotechnological challenges. Discussion and conclusions Microorganism provides effective and economically feasible solutions for soil cleanup and restoration. However, when the PAHs contamination is greater than the microbial ability to dissipate them, then applying genetically modified microorganisms might help to remove the contaminant. Nevertheless, it is necessary to have a more holistic review of the different individual reactions that are simultaneously taking place in a microbial cell and of the interactions microorganism-microorganism, microorganism-plant, microorganism-soil, and microorganisms-PAHs. Perspectives Elucidating the function of genes from the PAHs-polluted soil and the study in pure cultures of isolated PAHs-degrading organisms as well as the generation of microorganisms in the laboratory that will accelerate the dissipation of PAHs and their safe application in situ have not been studied extensively. There is a latent environmental risk when genetically engineered microorganisms are used to remediate PAHs-contaminated soil.
Densely populated, intensively cropped highland areas in the tropics and subtropics are prone to erosion and declining soil fertility, making agriculture unsustainable. Conservation agriculture in ...its version of permanent raised bed planting with crop residue retention has been proposed as an alternative wheat production system for this agro-ecological zone. A five years field experiment comparing permanent and tilled raised beds with different residue management under rainfed conditions was started at El Batán (Mexico) (2,240 m asl; 19.31°N, 98.50°W; Cumulic Phaeozem) in 1999. The objective of this study was to determine the soil quality status after five years of different management practices. The K concentration was 1.65 times and 1.43 times larger in the 0-5 cm and 5-20 cm profiles, respectively, for permanent raised beds compared to conventionally tilled raised beds. The Na concentration showed the opposite trend. Sodicity was highest for conventionally tilled raised beds and for permanent raised beds it increased with decreasing amounts of residue retained on the surface. Permanent raised beds with full residue retention increased soil organic matter content 1.4 times in the 0-5 cm layer compared to conventionally tilled raised beds with straw incorporated and it increased significantly with increasing amounts of residue retained on the soil surface for permanent raised beds. Soil from permanent raised beds with full residue retention had significantly higher mean weight diameter for wet and dry sieving compared to conventionally tilled raised beds. Permanent raised beds with full residue retention had significantly higher aggregate stability compared to those with residue removal. A lower aggregation resulted in a reduction of infiltration. Principal component analysis (PCA) was performed using these soil physicochemical variables that were significantly influenced by tillage or residue management. The PC1 and PC2 separated the conventionally tilled raised beds from the permanent raised beds and PC3 separated permanent raised beds with at least partial residue retention from permanent raised beds with no residue retention. These clear separations suggest that tillage and residue management have an effect on soil processes. The research indicates that permanent raised bed planting increases the soil quality and can be a sustainable production alternative for the (sub)tropical highlands. Extensive tillage with its associated high costs can be reduced by the use of permanent raised beds while at least partial surface residue retention is needed to insure production sustainability.
Aims
In this study, the species indicator test was used to identify key bacterial taxa affected by changes in the soil environment as a result of conservation agriculture or conventional practices.
...Methods and Results
Soils cultivated with wheat (Triticum spp. L.) and maize (Zea mays L.) under different raised bed planting systems for 20 years, that is, varying crop residue and fertilizer management, were used. Taxonomic‐ and divergence‐based 16S‐metagenomics, and IndVal analysis were used to study the bacterial communities and identify indicator taxa (genus and OTU97) affected by agricultural practices. Although, some phyla were affected significantly by different treatments, the taxonomic assemblages at phylum level were similar. Bacterial taxa related to different processes of the N‐cycle were indicators of different fertilization rates, for example, Azorhizobium, Nostoc and Nitrosomonas. A large number of OTU97 were indicators for conventionally tilled beds and their distribution was defined by soil organic carbon. IndVal analysis identified different taxa in each of the residue management systems. This suggests that although the same organic material remains in the field, crop residue management affects specific taxa. The taxa indicator of the burned residues belonged mainly to the order SBR1031 (Anaerolineae, Chloroflexi), and the genera Bacillus and Alicyclobacillus.
Conclusions
N‐fertilizer application rates affected N‐cycling taxa. Tillage affected Actinobacteria members and organic matter decomposers. Although the same crop residue was retained in the field, organic material management was important for specific taxa.
Significance and Impact of the Study
In this study, we report that agricultural practice affected soil bacterial communities. We also identified distinctive taxa and related their distribution to changes in the soil environment resulting from different agricultural practices.
Vinasses are a residual liquid generated after the production of beverages, such as mezcal and tequila, from agave (
Agave
L.), sugarcane (
Saccharum officinarum
L.
)
or sugar beet (
Beta vulgaris
...L.). These effluents have specific characteristics such as an acidic pH (from 3.9 to 5.1), a high chemical oxygen demand (50,000–95,000 mg L
−1
) and biological oxygen demand content (18,900–78,300 mg L
−1
), a high total solids content (79,000 and 37,500 mg L
−1
), high total volatile solids 79,000 and 82,222 mg L
−1
, and K
+
(10–345 g L
−1
) content. Vinasses are most commonly discarded onto soil. Irrigation of soil with vinasses, however, may induce physical, chemical and biochemical changes and affect crop yields. Emission of greenhouse gases (GHG), such as carbon dioxide, nitrous oxide and methane, might increase from soils irrigated with vinasses. An estimation of GHG emission from soil irrigated with vinasses is given and discussed in this review.
Polycyclic aromatic hydrocarbons (PAHs) such as phenanthrene, anthracene and Benzo
apyrene (BaP) are toxic for the environment. Removing these components from soil is difficult as they are resistant ...to degradation and more so in soils with high pH and large salt concentrations as in soil of the former lake Texcoco, but stimulating soil micro-organisms growth by adding nutrients might accelerate soil restoration. Soil of Texcoco and an agricultural Acolman soil, which served as a control, were spiked with phenanthrene, anthracene and BaP, added with or without biosolid or inorganic fertilizer (N, P), and dynamics of PAHs, N and P were monitored in a 112-day incubation. Concentrations of phenanthrene did not change significantly in sterilized Acolman soil, but decreased 2-times in unsterilized soil and >25-times in soil amended with biosolid and NP. The concentration of phenanthrene in unsterilized soil of Texcoco was 1.3-times lower compared to the sterilized soil, 1.7-times in soil amended with NP and 2.9-times in soil amended with biosolid. In unsterilized Acolman soil, degradation of BaP was faster in soil amended with biosolid than in unamended soil and soil amended with NP. In unsterilized soil of Texcoco, degradation of BaP was similar in soil amended with biosolid and NP but faster than in the unamended soil. It was found that application of biosolid and NP increased degradation of phenanthrene, anthracene and BaP, but to a different degree in alkaline–saline soil of Texcoco compared to an agricultural Acolman soil.
Metal concentrations were measured in plants growing on heavily contaminated tailings from a mine active since about 1800 in San Luis Potosí (Mexico).
Viguiera dentata (Cav.) Spreng.,
Parthenium ...bipinnatifidum (Ort.) Rollins,
Flaveria angustifolia (Cav.) Pers.,
F. trinervia (Spreng.) C. Mohr. and
Sporobolus
indicus (L.) R. Br. were tolerant to high As, Cu, Pb and Zn concentrations. Of those,
S.
indicus excluded heavy metals from its shoots, while
P. bipinnatifidum and
F. angustifolia accumulated them.
V. dentata and
P. bipinnatifidum were accumulators of As, but not hyperaccumulators. It was found that
V. dentata,
P. bipinnatifidum,
F. angustifolia,
F. trinervia and
S.
indicus, could be used to vegetate soils contaminated with As, Cu, Pb and Zn.
Ambrosia
artemisifolia could be used to remediate soils contaminated with Zn,
S. amplexicaulis those with Cu and
F. angustifolia and
F. trinervia those with As, as they have a strong capacity to accumulate those metals.
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