Special Issue "Soil Biology and Its Importance in Soil Fertility"

Guest Editor
Prof. Dr. Les Copeland
Faculty of Agriculture, Food and Natural Resources, University of Sydney, NSW 2006, Australia
Website: http://sydney.edu.au/agriculture/staff/find_staff_member/staff_profiles/les_copeland.shtml
E-Mail: les.copeland@sydney.edu.au
Phone: +61 2 8627 1017
Interests: agricultural chemistry and biochemistry; cereals; food grains

Dear Colleagues,

The sustainability of agroecosystems depends on healthy soils. Although the biota comprise only a small fraction of soil mass, they play a crucial role in providing favourable conditions for plant growth. The microorganisms and micro-, meso- and macro-fauna that make up the soil biota are essential for soil fertility and the promotion of plant-soil interactions. Biological activity in soil is fundamental for plant growth: the biological nitrogen, phosphorus and sulphur cycles increase the bioavailability of nutrients, and the deposition of organic carbon contributes to soil structure, which is important for reducing erosion and improving water movement and retention. Enzymes and metabolites released into the soil help to solubilise essential mineral nutrients, promote the decomposition of plant and animal remains, and catalyse the degradation of xenobiotics. For these reasons, biological diversity is widely used as an indicator of a functioning “life support” system that the soil represents. It is therefore appropriate that this first issue of the MDPI journal Agriculture is devoted to soil biology.

Prof. Dr. Les Copeland
Guest Editor

Submission

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. Papers will be published continuously (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are refereed through a peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Agriculture is an international peer-reviewed Open Access quarterly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. For the first couple of issues the Article Processing Charge (APC) will be waived for well-prepared manuscripts. English correction and/or formatting fees of 250 CHF (Swiss Francs) will be charged in certain cases for those articles accepted for publication that require extensive additional formatting and/or English corrections.

• soil biology
• soil fertility
• soil biota, soil mass, microbial biomass
• microorganisms, micro-, meso- and macro-fauna
• soil organic matter
• biological nitrogen, phosphorus and sulphur cycles, mineralization
• bioavailability of nutrients
• organic carbon contributes
• plant-soil interactions
• soil structure, erosion, water movement and retention
• Enzymes and metabolites
• xenobiotics degradation

Manuscript ID: agriculture-13741
Type of Paper: Article
Title: Nitrogen and Phosphorus Acquisition at the Tree-Crop Interface: The effects of Shade on Uptake Strategies
Authors: Meighen Whitehead and Marney E. Isaac
Affiliation: Department of Physical and Environmental Sciences, University of Toronto, 1265 Military Trail, Toronto, Ontario, Canada, M1C 1A4.
Abstract: With increasing economic and environmental costs associated with fertilizer use, the need for low-input agroecological systems is on the rise. It is well documented that intercropping legumes can increase the supply of nutrients, through N₂-fixation and P mobilization. Concurrently, the integration of trees in the agricultural landscape shows increasing evidence of nutrient inputs through efficient biogeochemical cycles. However, little is known on the shade effects at the tree-crop interface on legume-crop performance. This research aims to determine whether intercropping of the legumes soybean (Glycine max L. Mer) and alfalfa (Medicago sativa) with durum wheat (Triticum turgidum durum) is beneficial for performance, particularly under shady conditions associated with tree-based intercropping. Test species were cultivated in hydroponics with a broad nutrient solution and steady state addition of N for 3 weeks. Individual plants were transferred to rhizoboxes with a 1mm zone of P sufficient soil for 16 days under i) full sun or ii) shade to mimic light levels at the tree-crop interface. In monoculture, shading was found to significantly decrease wheat biomass. Intercropping wheat with alfalfa under full sun had no negative effect on growth but did increase wheat P uptake as compared to wheat in monoculture. In contrast, intercropping wheat with soybean under full sun decreased wheat biomass, suggesting competition. However, under shade, this competitive effect was mitigated, as wheat exhibited similar biomass and higher N and P shoot concentration when associated with soybean as compared to monocultured wheat under lower light levels. This effect may be attributed to reduced biomass of soybean combined with higher soybean N₂-fixation under shade. Legume-based intercrops may increase nutrient supply but this beneficial effect will be dependent on matching species selection to light levels under tree-based intercropping.
Keywords: tree-based intercropping; ¹⁵N natural abundance; N₂-fixation; Ontario; rhizobox; shade effects

Manuscript ID: agriculture-13105
Type of manuscript: Review
Title: Levels of Sulfur as an Essential Nutrient Element in the Soil-Crop-Food System in Austria
Author: Manfred Sager *
Affiliation: Competence Centre for Elements, Austrian Agency for Health and Food Safety, Spargelfeldstrasse 191, Vienna A-1220, Austria
Abstract: Total sulfur data of various agricultural and food items done in the lab of the author, have been compiled to get an idea about sulfur levels and ecological cycling in Austria. As sulfur is not met among the quality criteria of soil and fertilizer composition, the database is rather small. Problems in analytical determinations of total sulfur, in particular digestions, are outlined. As a protein component, sulfur is enriched in matrices of animal origin, in particular in egg white. There is substantial excretion from animals and man via the urine. Organic fertilizers (manures, composts) might contribute significantly to the sulfur budget of soils, which is important for organic farming of crops with high sulfur needs. For soils, drainage is a main route of loss of soluble sulfate, thus pot experiments may yield unrealistic sulfur budgets.
Keywords: sulfur; food; feed; cereals; manure; fertilizer

Title: Sorption of Tannin and Related Phenolic Compounds and Effects on Extraction of Soluble-N in Soil Amended with Different Carbon Sources
Authors: Jonathan J. Halvorson ¹, Hero T. Gollany ², Javier M. Gonzalez ¹, Stewart B. Wuest ² and Ann Hagerman ³
Affiliations: ¹ USDA-ARS, Beaver, WV, USA 
² USDA-ARS, Pendleton, OR, USA
³ Miami University, Oxford, OH, USA
Abstract: Some tannins, phenolic substances produced by plants, sorb to soil and reduce the extraction of soluble-N and thus could influence soil organic matter (SOM) and nutrient cycling. However, we know little about how these compounds interact with organic amendments in soil. Surface soil (0-5 cm) from plots, amended annually with various carbon substances (C-source), was treated with water (Control) or solutions containing tannins or related phenolic subunits. Treatments included a polymeric flavonoid-based proanthocyanidin (SOR), catechin (CAT), tannic acid (TA), β-1,2,3,4,6-penta-O-galloyl-D-glucose, (PGG), gallic acid (GA), and methyl gallate, (MG). We determined soluble-C and N in supernatants after application and a subsequent incubation in hot water (16 hr, 80 oC), to uncover evidence for sorption or effects on extraction of soil-N. Sorption was low for non-tannin phenolics, less than 15%, for MG, GA, and CAT, and unaffected by C-source. Sorption of SOR, TA and PGG was higher, about 23%, 42% and 63%, and impacted by C-source, greatest in plots amended with biosolids and manure, lowest in those amended with grass, wood, compost, wheat residue, sucrose, cellulose, or unamended soil. Extraction of soluble-N was little affected by C-source or by CAT, SOR, or MG, but reduced 18-24% by PGG, TA and GA. Total soil-C remaining in control samples and the CAT, SOR and PGG treatments was comparable to predicted values but low in the MG, GA and TA treatments, associated with the acidity of the solution pH. Soil cation exchange capacity increased following treatment with PGG by 5.3%, but decreased by about 6.5% with GA, irrespective of amendment. This study indicates different kinds of tannins, but not related phenolics, readily affix to soil and are influenced by C-source. Some of these compounds can reduce solubility of soil-N. Tannins and other phenolic compounds appear to have a role in the management of soils.

Type of Paper: Review
Title: Soil Biology, Productivity, Ecology and Function
Authors: Michelle M. Wander and Carmen M. Ugarte
Affiliation: Department of Natural Resources and Environmental Sciences, University of Illinois, 1102 S. Goodwin Ave., Urbana, IL 61801, USA
Abstract: This article will review current approaches and interpretive frameworks being used to measure and manage biologically-based fertility. We will: (1) consider the potential for direct measures of biochemical fractions, and bio-indicators to provide meaningful information about the status and function of the soil resource and (2) compare these to physico-chemical measures that describe the soil habitat, before (3) evaluating their current and potential utility for agronomic and ecological-decision making.

Type of Paper: Article
Title: Biological and Ecological Characteristics of Two Earthworm Populations (Oligochaeta, Glossoscolecidae) in a Natural and a Protected Savanna from Fire and Cattle Raising Activities in Central Llanos, Venezuela
Author: Danilo López-Hernández
Affiliation: Universidad Central de Venezuela, Instituto de Zoología Tropical, Laboratorio de Estudios Ambientales, Apdo 47058, Caracas 1041A, Venezuela
Abstract: To study the effect on earthworm populations of long term-protection of fire and agricultural management in savannas, we compared the general aspects on the biology and ecology of earthworm populations in: a protected savanna (PS) from fire and cattle raising for forty years located at Estación Biológica de los Llanos, Venezuela (EBLL), and in an adjacent natural savanna (NS) under burning and cattle raising. In each ecosystem plots of 90 × 90 m five sampling units were selected at random remaining fixed during sampling. At sampling point one soil monolith of 25 × 25 × 30 cm was collected from unit. Earthworms were extracted using a hand sorting extraction method. The floatation method was used to estimate the density of the cocoons. The earthworms were classified in ecological categories considering its pigmentation, size and profile distribution. The main physical, chemical, biochemical and microbial activities properties of soils in the systems were estimated.  As a result of the protection of the savanna most of the studied parameters were modified in relation to SNI. The increase in earthworm biomass in NS is much related to a beneficial increase in soil fertility.

Type of Paper: Review
Title: Roles of Microbes in Soil Macroaggregate Formation and Stabilization and Inter-aggregate Nutrient Cycling
Authors: Kristine A. Nichols, TheCan Caesar-TonThat and Jonathan J. Halvorson
Affiliation: USDA-ARS, Northern Great Plains Research Laboratory, 1701 10th Ave SW, P.O. Box 459, Mandan, ND 58554, USA
Abstract: The average composition of soil is about 45–50% mineral particles, 1–5% organic matter, and 50% pore space. Macro- and micro-aggregates bind the mineral particles together to create pore space. Pore space allows air and water movement in and out of soils and reduces compaction while soil aggregates themselves stimulate microbial growth, soil organic matter (SOM) turnover, and nutrient cycling. These processes impact erosion, root development and growth, plant health and vigor, water availability, nutrient availability, and leaching. Despite the important roles aggregates play in the soil, little is understood about how macroaggregates form and where their stability comes from. We hypothesize that the forces—physical, chemical, and biological—play different roles in macroaggregate formation than those involved in stabilization.  To illustrate this, we will be focusing on the processes and forces involved in aggregation, particularly the roles of plant roots and arbuscular mycorrhizal (AM) and russuloid basidiomycete fungi; the quality of SOM fractions; and microbial biomolecules such as glomalin, extracellular polymer substances (EPS), and polysaccharides.