Dear Colleagues,

Soil is usually rich in plant nutrients, measured with total analysis, but plants commonly suffer from deficiencies, unless fertilized, owing to a shortage of plant available nutrients. Many studies have shown that microbes can help to mobilize sparingly soluble nutrient reserves by various mechanisms.

Mycorrhizae, symbiotic associations between a fungus and a plant, increase the effective rooting volume and dissolve sparingly soluble sources of phosphorus (P). The host plant receives P from the fungus, which receives carbohydrates from the plant as a payment. There is an array of plant growth-promoting microorganisms (PGPM) that have already been commercialized. One of them is Penicillium bilaji, which lives in the rhizosphere and dissolves P in the first place. Many other microorganisms also do well in the rhizosphere, where they have a supply of carbohydrates available as root exudates and died root cells. Microbial activity decreases redox potential in the rhizosphere and results in the dissolution of iron and manganese, which thus become available to plants. Nitrogen fixation is probably the best-known plant–microbe symbiosis, most commonly involving leguminous plants and Rhizobia that take N₂ from soil air. Furthermore, decomposition of organic matter and organic residues can be regarded as plant–microbe–soil interaction, possibly being quantitatively the most important in the recycling of nutrients. Finally, plant–microbe–soil interaction can also play a role in the phytoremediation of contaminated soils. 

Soil properties have an effect on the interactions mentioned above. The plants benefit the mycorrhizae only in soils that are poor in P; in P-rich soils, this nutrient would be sufficiently available without the fungus, and the mycorrhiza turns out to be only a cost. On the other hand, we can assume that bacteria that solubilize P may be particularly effective in soils that contain large reserves of residual fertilizer P. It is also well known that in addition to different Rhizobium species for different crops, various strains differ in the efficiency of N₂ fixation. In many developing countries with a strongly negative nutrient balances in soil, N₂ fixation may be hampered by the deficiency of other nutrients, such as P, K, S, and micronutrients. Salinity problems are increasing in many parts of the world, and it is not well established how plant–microbe–soil interactions are affected by increasing soil salinity. In general, there is a need for more knowledge about the soil properties that result in favorable interactions between the different organisms in the agroecosystem. This knowledge is vital to be able to utilize these interactions more effectively in sustainable agriculture.

In this Special Issue, authors are encouraged to submit papers at the cutting edge of plant–microbe–soil interaction, particularly with applications to sustainable agriculture. How important are these interactions quantitatively from the plant’s point of view? How do soil properties influence the benefit to the plant? Which interactions can be utilized in developing countries, often with soils of low fertility, and which ones may be important in industrial countries where soils have a history of heavy fertilization?

Dr. Mahmoud F. Seleiman
Prof. Dr. Markku Yli-Halla (retired)
Guest Editors

Manuscript Submission Information

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. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short 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 thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Sustainability is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

• plant–soil–microbe interactions
• soil fertility
• sustainable agriculture
• crop production
• mycorrhiza
• soil amendments
• abiotic stress
• biofertilizers
• nanofertilizers
• symbiotic bacteria
• physiological and biochemical traits
• quality