Do coffee agroforestry systems favor carbon and glomalin input in soil biogenic aggregates?

[Display omitted] •Coffee cultivation is not reflected in changes in the quantity and distribution of biogenic and physiogenic aggregates and intermediates in the soil;•Soil biogenic aggregates are predominant in coffee crops, as well as in native forests;•The coffee agroforestry system (AFS) with grevillea is more favorable to maintaining organic carbon and glomalin contents in biogenic aggregates;•AFS with cedar and coffee monoculture negatively impacts carbon and glomalin contents in soil and aggregates. Glomalin is a glycoprotein produced by mycorrhizal fungi and is an important biotic agent in forming soil aggregates. Despite this, few studies have focused on its contribution to stabilizing soil organic carbon (SOC), especially in coffee cultivation systems. We aim to answer the following questions: do agroforestry and coffee monoculture systems influence the aggregate formation pathways? How is this influence reflected in the organic carbon and glomalin contents of biogenic and physiogenic soil aggregates? Thus, three coffee cultivation systems were evaluated (AFSG – coffee agroforestry system with grevillea, AFSC – coffee agroforestry system with cedar, and CM – coffee monoculture), and a native forest (NF) used as a reference. Soil was collected by removing monoliths which were subjected to dry aggregate fractionation in the field. The > 6 mm fractions were separated according to their morphological pattern (biogenic, physiogenic and intermediate aggregates). The SOC, labile carbon (LC), easily extractable glomalin and total glomalin (TG) contents were determined in the morphological classes. AFSG presented the highest carbon contents in whole soil (67.4 g kg−1), maintaining similar values to NF, while AFSC and CM did not vary from each other (average of 44.6 g kg−1). AFSG was also the coffee system with the highest root mass, LC and TG. The coffee systems did not affect the aggregate formation and distribution. AFSG proved to be more favorable to maintaining SOC and glomalin contents associated with biogenic and physiogenic aggregates.