Tillage and no-tillage effects on prokaryote communities, soil physiology, lipidic profiles and soil aggregation in semi-arid soils in Argentina

WALL LG

Montevideo

Workshop; INIA-JKI organized workshop. Towards more sustainable agriculture through managing the soil microbiome; 2019

INIA-JKI

Soil tillage in the semiarid south-western Argentine pampas is pushing ecosystems towards desertification processes because of the exhaustion of agricultural lands. A long-term field experiment was installed to compare the effects of conventional tillage (CT) vs. no-till (NT) agriculture on the soil of side-by-side plots, excluding plant and crop effects. In partial plots, soil managements were shifted one to another. Soil enzymes, soil respiration, bacterial diversity by 16S soil DNA sequencing and physical properties were analyzed in three consecutive samplings along 30 months. The results provide strong evidence that soil functions are rapidly modified according to the soil mechanical management and tend to stabilize in a profile according to a long-term soil practice, much earlier than the microbial structure as a whole. Many bacterial OTUs responders were found; i.e.: related to NT we found OTUs closed to Bacillus nealsonii, Candidatus Nitrosocosmicus, Candidatus Udaeobacter copiosus, or related to CT as Arthrobacter sp., Nitrososphaera viennensis and Chloroflexi bacterium. The dynamics of responders? bacterial change according to new management show different rate of change suggesting that CT induced a longer-term soil disruption than NT. The stratification of microbial diversity was significant for NT soil and different to CT soil on the basis of Bray Curtis dissimilarities. Although the microbial structure as a whole evolved to a transient status after shift of management, 30 months were enough for new NT soils to recover the levels of dissimilarities by stratification. A Spearman correlation analyses of functional and microbial structures, corroborated by random forest tests, revealed coherent structure-functional elements for soils. These findings contribute to better understanding fundamental mechanisms underlying soil microbiology, and may allow farmers to adopt conservative soil management strategies in Argentina.