Whole soil fatty acid lipidic signature discriminates agriculture intensification in no-till systems

Abstract

Argentinean farmers are adopting alternative agricultural systems based on diversification and intensification of crop rotations in no-till agriculture in order to improve soil health and recover degraded soils after years of monocropping. This is achieved by reducing fallow periods, increasing the intensity of crop rotations with maize and soybean in summer, and establishing different winter crops, including cover crops. We evaluated whole soil fatty acids (WSFA) signature in agricultural cropping systems with different levels of intensification in three on-farm experiments in Argentinean Argiudolls soils, along an on-field 8-year assay and measuring at 5 and 8 years after the beginning of the intensification. Contrasted treatments were: typical rotation, intensified rotation with cereals and intensified rotation with legumes. They were compared to an implanted pasture, and a pasture converted to intensified rotation. Eight years after the beginning of the trial, the intensified crop rotations were separated from the typical rotation by multivariate analysis of WSFA. This technique was able to distinguish between agricultural treatments with subtle differences in management, separating the intensified rotations, which later showed higher crop productivity. Conversion of pasture back to agriculture showed a delay of three years before changing the lipidic signature according to WSFA-based indicators. The outstanding conclusion is that mono-unsaturated fatty acids (MUFA) are the most relevant fatty acid functional group for land use discrimination, with a similar potency to the whole lipidic pattern. Within the MUFA group, the fatty acids 16:1w5c and 18:1w5c, appeared as potential biomarkers of these alternative agricultural practices.