The development and suppressive activity of soil microbial communities under compost amendment

Abstract

Soil is a highly complex system in which bacteria play a dominant role. Soil microorganism biodiversity is extremely important for sustaining the nutrient cycles of soil ecosystems. The diversity of soil bacterial and fungal communities can be influenced by agricultural management. The use of amendments, such as the incorporation of compost into the soil, strongly affects soil microbial communities directly or indirectly. The use of compost can be an important tool to control soil-borne pathogens. Certain groups of microorganisms (bacteria and fungi) present in compost produce metabolites, such as siderophores and antibiotics, with specific suppressive activity against soilborne pathogens: among these compost bacteria, species of Pseudomonas and Bacillus are very important. In this study, we investigated the effects of increasing doses of compost on the density of several cultivable soil microbial groups in an agricultural system of Southern Italy. The number of total bacteria, total fungi, siderophore-producing bacteria (principally Pseudomonas spp.) and spore-forming bacteria (principally Bacillus spp.) was evaluated over a period of five months. Moreover, we analyzed the ability of spore-forming bacteria isolated from soil and compost to inhibit, in vitro, five soil-borne phytopathogenic fungi (Rhizoctonia solani, Fusarium oxysporum, Sclerotinia minor, Fusarium solani, Pyrenochaeta lycopersici). The number of total bacteria and siderophore-producing bacteria was greater in the soil treated with compost than in soils treated with mineral fertilization or not manured, with an increase related to the dose of compost applied. Moreover, the compost used in this study produced a substantial increase in the number of spore-forming bacteria in the soil. Approximately 80% of these bacteria were able to inhibit the soil-borne phytopathogenic fungi Rhizoctonia solani, Fusarium oxysporum, Sclerotinia minor, Fusarium solani and Pyrenochaeta lycopersici. These results show that compost from the organic fraction of municipal solid wastes furnishes a high number of spore-forming bacteria exhibiting antibiotic activity against phytopathogenic fungi. The application of compost can change the composition of the soil microbial community, modifying the relationships among microorganisms, both competitive and/or antagonistic, producing a decrease in the activity of plant pathogens. These results were in agreement with the decrease in the symptoms of disease on tomato plants cultivated in the soils treated in this study.

Organic amendments as sustainable tool to recovery fertility in intensive agricultural systems

“…Scotti et al (2015) proposed compost application to soils under intensive farming systems combined with woody scraps to achieve significant changes in biological parameters. The authors found a rapid and intense boost of enzymatic activities (dehydrogenase, phosphomonoesterase and β-glucosidase) after organic amendments, especially after the second yearly amendment, demonstrating that repeated use of organic amendments should be planned to trigger microbial activity and functionality and improve consequently soil biological fertility.The use of compost can affect soil microbial diversity, as reported byZaccardelli et al (2013a) who showed a clear positive effect on the number of spore-forming bacteria, with an increase directly correlated with the dose of compost. Also in stressed soil, with high saline content, the use of compost can determine an improvement of biological fertility(Lakhdar et al, 2009).…”

“…In this scenario, a recovery of depleted soil organic matter and its maintenance to an adequate level is a critical task. It has been shown that application of organic amendments such as compost is a reliable and effective tool to ameliorate soil structure and both chemical and biological fertility of soils (Ros et al, 2003), as well as to suppress soilborne pathogens (Zaccardelli et al, 2013a).…”

Alpha and Beta-diversity of Microbial Communities Associated to Plant Disease Suppressive Functions of On-farm Green Composts

“…Microbial diversity may have a crucial role in sustaining ecosystem functions and maintaining the natural suppressive activities via compost amendment [30]. Compost microflora were found to be critical in protecting cucumber seedlings from Fusarium oxysporum f.sp.…”

Effect of different soil amendments on the microbial count correlated with resistance of apple plants towards pathogenicRhizoctonia solaniAG-5

“…Their results suggested that well-rotten farmyard manure induces the highest increase in microbial counts, potato yield and stem height. Another report, that of Zaccardelli et al [15], investigates the effects of increasing doses of compost on the density of several cultivable soil microbial groups in an agricultural system in Southern Italy. It shows that compost furnishes a high number of spore-forming bacteria exhibiting antibiotic activity against phytopathogenic fungi.…”