Clay Mineralogy of Subtropical Soils under Long-Term Organic Fertilization in No-Tillage Systems

Abstract

Organic fertilization effect on physical-chemical properties in no-tillage systems in tropical soils has been widely investigated, but little is known about the effects of this practice on the mineralogy of the clay fraction. This study aimed to evaluate the clay-fraction mineralogy of two subtropical soils, fertilized with organic residues in long-term no-tillage systems. An Alfisol fertilized with 0, 40, and 80 m 3 ha-1 yr-1 pig slurry was evaluated for eight years, and an Oxisol with 0, 8, and 16 Mg ha-1 of wood shavings with pig slurry, for six years. Soil samples from the layers 0.00-0.04, 0.04-0.08, and 0.16-0.20 m were collected and subjected to chemical extractions with DCB and oxalate, X-ray diffractometry, and thermal analysis. No mineralogical changes in the clay fraction were observed in either the Alfisol or Oxisol. The chemical dissolution data indicated no significant differences among the tested treatments with regard to the re-precipitation of low-crystallinity oxides. However, the increase in zinc extracted by DCB and zinc extracted by oxalate in the treatments with residue application was clear. The crystallinity data efficiently indicated the effects of residue rates on soil mineralogy only in the Alfisol; the increasing slurry rates induced a reduction in the percentage of hematite, increase in the percentage of goethite, increase in the Gt/Gt+Hm ratio and decreased the mean crystal diameter of goethite and hematite.

Magnetic susceptibility in the prediction of soil attributes in southern Brazil

“…The amplitude verified in the dataset, which was reflected in the calibration and validation models, is related to the lithological, climatic, geomorphological, and pedological diversity of the state of RS (Ministério da Agricultura. Departamento Nacional de Pesquisa Agropecuária, Brazil, 1973;Maluf, 2000;Streck et al, 2018) and was also observed in several other studies carried out in this state (Bertolazi et al, 2017;Coblinski et al, 2020;Da Silva, Fruett, Zinn, Inda, & do Nascimento, 2019;Moura-Bueno et al, 2019;Pedron, Lourenzi, Ceretta, Lorensi, & Cancian, 2018;Ramos et al, 2017).…”