SOIL FORMATION FACTORS

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Earthworm mucus increases dissolved carbon 9.8%–37.5%

Earthworm mucus increases dissolved carbon 9.8%–37.5% and accelerates mineralization and humification of organics.

Plant worms. Prime carbon. Increase nutrient cycling.

Role of earthworms’ mucus in vermicomposting system: Biodegradation tests based on humification and microbial activity http://www.sciencedirect.com/science/article/pii/S0048969717321022

Abstract

During vermicomposting, the organic wastes can be recycled into high-value products as mediated by earthworms through gut digestion, burrowing, casting and mucus excretion. However, to date, few studies have been done on the role of mucus in vermicomposting system compared to the effects of the other activities. Hence, this study investigated the potential role of earthworms’ mucus in the decomposition and humification of organic wastes. For this, the mucus of Eisenia fetida was extracted and inoculated into three vermicomposting substrates using cow dung (CD), fruit and vegetable wastes (FVW), and sewage sludge (SS). The results obtained after a 20 day experiment showed that the mucus could accelerate the mineralization and humification rates of organic components. The dissolved carbon showed 9.8%–37.5% increase in treatments containing mucus, higher than those in substrates without mucus. Moreover, the mucus significantly stimulated the microbial activity and bacterial abundance, showing the greatest increases in FVW treatments. In addition, the mucus positively stimulated growth of Proteobacteria, but negatively affected the Firmicutes during decomposition. This result suggests that the earthworms’ mucus significantly accelerated the decomposition and humification of vermicomposting materials, and could even promote microbial activity, growth, and increase community diversity in vermicomposting systems.

 

Earthworm Burrows Create Microbial Hotspots with 4-20x The Nutrients

A new study of earthworm burrows finds:

Earthworm burrows provide not only the linkage between top- and subsoil for carbon and nutrients, but strongly increase microbial activities and accelerate soil organic matter turnover in subsoil, contributing to nutrient mobilization for roots.

Rolling in the deep: Priming effects in earthworm biopores in topsoil and subsoil

Highlights

•Mechanisms regulate microbial activities in biopores vs. bulk soil, topsoil vs. subsoil.
•Earthworms homogenize SOM quality in topsoil and subsoil.
Priming effect in earthworm burrows was 4–20 times higher than in bulk soil.
•Biopores and bulk soil showed higher priming effect in subsoil than topsoil.

Abstract

Priming effect is the change of soil organic matter (SOM) decomposition due to the addition of labile carbon (C) sources. Earthworms incorporate organic matter into their burrow-linings thereby creating preferred habitats for microorganisms, but the roles of such burrows in priming effect initiation is unknown. Here we study the mechanisms driving SOM decomposition in top- and subsoil biopores and additionally in the rhizosphere. Given the topsoil was newly formed after ploughing 10 months prior to sampling, we hypothesized that (1) SOM accessibility, enzyme activities and efficiency of enzymatic reaction (Ka) are main drivers of different priming effect in biopores vs. bulk soil and rhizosphere, subsoil vs. topsoil and (2) the production of microbial enzymes in biopores depends on microbial community composition. To test these hypotheses, biopores formed by Lumbricus terrestris L. and bulk soil were sampled from topsoil (0–30 cm) and two subsoil depths (45–75 and 75–105 cm). Additionally, rhizosphere samples were taken from the topsoil. Total organic C (Corg), total N (TN), total P (TP) and enzyme activities involved in C-, N-, and P-cycling (cellobiohydrolase, β-glucosidase, xylanase, chitinase, leucine aminopeptidase and phosphatase) were measured. Priming effects were calculated as the difference in SOM-derived CO2 from soil with or without 14C-labeled glucose addition.

Enzyme activities (Vmax) and the catalytic efficiency (Ka) were higher in biopores compared to bulk soil and the rhizosphere, indicating that the most active microbial community occurred at this site. Negative correlations between some enzymes and C:N ratio in bulk soil are explained by higher content of fresh organic C in the topsoil, and the corresponding C and nutrient limitations in the subsoil. The positive correlation between enzyme activities and Corg or TN in biopores, however, was associated with the decrease of C and TN with pore age in the subsoil. In the subsoil, priming effect in biopores was 2.5 times higher than bulk soil, resulting from the favorable conditions for microorganisms in biopores and the stimulation of microbial activities by earthworm mucus. We conclude that earthworm burrows provide not only the linkage between top- and subsoil for C and nutrients, but strongly increase microbial activities and accelerate SOM turnover in subsoil, contributing to nutrient mobilization for roots.

Related: Restoring Construction Soils with Compost, Earthworms and Plants – Permie Flix

Soil Substrate Comparison: Water Retention

Bonsai Soil Tests: Part 1: Water Retention

Note:
Retention Values (g @ %) given after 5.25-hour
Rank given for 24-hour Retention based on values.

Organic Rankings:
1. Coconut Coir: 129g @ 14.57% loss
2. Pine Bark: 22g @ 14.86% loss
3. Compost: 26g @ 31.58% loss
4. Commercial Peat Moss: 6g @ 40% loss

Inorganic Rankings:
1. Diatomaceous Earth: 37g @ 30.19% loss
2. Akadama: 22g @ 26.67% loss
3. Pumice: 22g @ 29.03% loss
4. LECA (Turface): 30g @ 36.17% loss
5. Vermiculite: 28g @ 41.67% loss
6. Perlite: 14g @ 36.36% loss
7. Sand: 12g @ 67.56% loss
8. Lava Rock (Scoria): 4g @ 76.47% loss
9. Expanded Shale: 2g @ 84.62% loss
10. Granite Chips: 1g @ 94.44% loss

Quick Correction: Diatomaceous earth is not calcined clay, like Oil-Dri. It is silica based, formed from fossilized algae.

Microbes On Meteorites

Do Bacteria Live On Meteorites?? | SimplyScience by Kristie Tanner

Kristie summaries a paper that can be found here

Much more interesting than I thought it would be. The iron and sulphur makes me think about the amount of energy those elements provide to form reactions that sustain life(scroll down for pictures), and how differing amounts of those elements may influence the colonization.
I’m also reminded of the sea monster at the bottom of the carbon food chain where there’s little oxygen and energy is scarce.
To the other extreme where oxygen is rich and where historically moisture rich microbes respire excess carbon from soils.

Bonus video:

Why So Many Meteorites Come From The Same Place

Restoring Construction Soils with Compost, Earthworms and Plants

Urban soils at the scene of construction where subsoil has been brought to the surface, mixed or that have had the topsoil removed and construction materials like sand, stone, brick etc. embedded in them can pose a challenge to regenerate. Stabilising these soils such that rain and flood doesn’t cause erosion is also an important task.

To help understand what contributes to soil aggregate formation and the stability of these soils researchers studied the “Interactive effects of compost, plants and earthworms on the aggregations of constructed Technosols” and found increasing amounts of compost needed increasing amounts of plants or earthworms to make a difference.

Aggregation is an important physical process to study during the early formation of Technosols. It is known to be influenced both by the organic matter content and soil biota. Constructed Technosols represent good models to test the importance of these factors since their composition can be easily manipulated by mixing different proportions of parent materials and introducing soil organisms. In this study, we performed a 5 month mesocosm experiment, using excavated deep horizons of soils (EDH) as mineral material mixed with green waste compost (GWC) at six different proportions (from 0 to 50%) in the presence or absence of plants and/or earthworms. After 21 weeks of incubation, aggregation was characterized by: 1) determining the size fraction and morphology, 2) measuring the distribution of organic carbon (OC) in each fraction and 3) testing the aggregate stability. Results showed that organisms accounted for 50% of soil aggregation variance while green waste compost (GWC) was responsible for only 5% of the variance. The percentage of total variance of OC distribution in aggregates explained by organisms, GWC, and the interaction of the two was similar (28%, 22% and 26%, respectively). The effect of GWC on structural stability was negligible (2%) compared to that of organisms (70%). The effect of earthworms combination with plants was complex: plants had a dominant effect on the distribution of the size of aggregates by disrupting earthworm casts, but earthworms had a dominant effect over plants for aggregate stability under fast wetting only when the percentage of compost was low. This study underlines the importance of considering the interaction of the organic matter and soil biota: in this case, increasing compost proportion in a Technosol has significant effects on aggregation only in the presence of plants or earthworms.

Interactive effects of compost, plants and earthworms on the aggregations of constructed Technosols