Biochemical and microbiological agriculture soil analyses at the aggregate level in no-till field assays in Argentina. Effects of crop rotation

ROBLEDO B; GABBARINI L; WALL LG

Valparaiso

Congreso; 1st ISME Latin America Congress; 2019

ISME

Agriculture is one of the most important economic activities in Argentina and means more than 20 million cultivated hectares under no-till management. Soybean monocropping practices (more than 80%) lead to soil compaction and many other problems as soil-borne diseases and resistant weeds invasion. Physical structure of the soil has been related to fauna activity (i.e.: earthworms) but recently, bacteria and fungi have been recognized as main factors for soil aggregation. No-till crop rotation is considered a basic good agriculture practice. Moreover, the increase in diversity and intensity of crop rotation, estimated as a rotation intensification index (RII), leads to highest yields and better soil health, supported by biological and biochemical data that we measured, in cooperation with farmers leading the field assays: 5 different levels of RII, replicated in three locations. Soil fractionation was adjusted to be reproducible and scalable. RII modified the proportion of soil macro and microaggregates fractions increasing the values of the bigger as the RII increases. Looking into soil health parameters at the microaggregate level we look for different soil enzyme activities and found differential enzymatic profiles according to soil aggregate size. Preliminary 16s barcoding soil DNA sequencing, at the aggregate level, shows differential bacterial community structure between aggregates and bulk soil. Bacterial community appears to be different at the aggregate level when monocropping is compared to intense crop rotation. Whole soil fatty acid signature at the aggregate level is under study and will be discussed. All together, we think it will be possible to find bacterial responders to treatment or biochemical indicators of soil health, that would help more precise soil evaluations that will allow farmers to take decisions about management practices much earlier than chemical and physical indexes as soil organic matter and apparent density values are shifted in soil.