Cross-Site Soil Microbial Communities under Tillage Regimes: Fungistasis and Microbial Biomarkers

Abstract

The exploitation of soil ecosystem services by agricultural management strategies requires knowledge of microbial communities in different management regimes. Crop cover by no-till management protects the soil surface, reducing the risk of erosion and nutrient leaching, but might increase straw residue-borne and soilborne plant-pathogenic fungi. A cross-site study of soil microbial communities and Fusarium fungistasis was conducted on six long-term agricultural fields with no-till and moldboardplowed treatments. Microbial communities were studied at the topsoil surface (0 to 5 cm) and bottom (10 to 20 cm) by general bacterial and actinobacterial terminal restriction fragment length polymorphism (T-RFLP) and phospholipid fatty acid (PLFA) analyses. Fusarium culmorum soil fungistasis describing soil receptivity to plant-pathogenic fungi was explored by using the surface layer method. Soil depth had a significant impact on general bacterial as well as actinobacterial communities and PLFA profiles in no-till treatment, with a clear spatial distinction of communities (P < 0.05), whereas the depth-related separation of microbial communities was not observed in plowed fields. The fungal biomass was higher in no-till surface soil than in plowed soil (P < 0.07). Soil total microbial biomass and fungal biomass correlated with fungistasis (P < 0.02 for the sum of PLFAs; P < 0.001 for PLFA 18:26). Our cross-site study demonstrated that agricultural management strategies can have a major impact on soil microbial community structures, indicating that it is possible to influence the soil processes with management decisions. The interactions between plant-pathogenic fungi and soil microbial communities are multifaceted, and a high level of fungistasis could be linked to the high microbial biomass in soil but not to the specific management strategy.

Soil Fungistasis Against Fusarium Graminearum Under Different Crop Management Systems

“…Garbeva et al (2006) evaluated fungistasis against plant pathogenic Rhizoctonia solani in different soil management systems and found that conservationist management increased fungistasis. Likewise, Sipilä et al (2012) identified a positive correlation between no-tillage management and soil suppression of the pathogen Fusarium culmorum, concluding that soil management strategies have strong influences on soil microbiological processes, including suppression. It thus seems that the employment of suitable soil management and cropping systems favors the potential suppressive properties of some soils.…”

“…Because of these factors, cropping systems inevitably have impacts on soil processes, including fungistasis. Management practices, such as crop rotation (Mazzola and Gu, 2002) and soil tillage, have the capacity to affect the microbial populations involved in the control of soil pathogens, thus introducing the possibility of manipulating fungistasis by applying appropriate agronomic techniques (Sipilä et al, 2012).…”

Community structure of soil fungi in a novel perennial crop monoculture, annual agriculture, and native prairie reconstruction

“…This gradient tends to concentrate soil fungi at the surface and can lead to changes in community composition and diversity (richness and relative abundance) with depth [41].This is consistent with the trends observed in this experiment, as the overall and functional fungal community structure was distinct within each cropping system at each depth, and the overall OTU richness decreased with depth. Despite possible homogenization effects of tillage, distinct communities were found at both sampling depths in the annual agriculture system [14,42]. It is possible that a nutrient gradient was still present, or the deeper sample reached below the tillage depth.…”

“…In a cropping system with tillage, homogenization of the upper soil layers may lead to similar fungal communities throughout the entirety of disturbed soil [14,25]. In cropping systems without tillage, distinct fungal communities may be found at shallower depths due to a maintained gradient of resources [25,42].…”

Culture-Independent Molecular Tools for Soil and Rhizosphere Microbiology

“…Buyer and Sasser [126] have developed a new procedure with increased throughput and therefore a large number of PLFAs can be analyzed. The method has been used to detect changes and structure of soil microbial communities [127][128][129]. The PLFA method has been used recently to understand the formation of soil organic matter (SOM) and the involvement of microbial cell-envelope fragments in this process.…”