Brazilian soil science: from its inception to the future, and beyond

The present essay is meant to provide some background on the evolution of the soil science community in Brazil, since its inception, to describe its current situation, and to outline a number of opportunities and challenges facing the discipline in decades to come. The origin of Brazilian agronomy dates back to the beginning of the 19th century as a subdiscipline of botany, and its association with chemistry would later establish it as a science. In the middle of the 19th century, agricultural chemistry was born as a result of this association, leading to the establishment of edaphology, a branch of Soil Science. Another branch of Soil Science, known as pedology, was established as an applied and scientific knowledge in Brazil during the middle of the 20th century. During the same period, the Brazilian Soil Science Society (SBCS) was created, merging the knowledge of both branches and gathering all scientists involved. Twenty years after the SBCS foundation, the creation of Graduate Programs made Brazilian Soil Science enter the modern era, generating crucial knowledge to reach the current levels of agricultural productivity. Part of a community composed of 25 Soil Departments, 15 Graduate Programs and a great number of institutions that promote research and technology transfer, Brazilian soil scientists are responsible for developing solutions for sustainable development, by generating, adapting and transferring technology to the benefit of the country. The knowledge produced by SBCS members has been particularly significant for Brazil to achieve the status of most competitive tropical agriculture in the world. In the future decades, Soil Science will still remain topical in discussions regarding environment care and production of food and fibers, in addition, it will be essential and strategic for certain issues, such as water quality, reducing poverty and development of renewable sources of energy.

Sulfur in agriculture

Sulfur (S) deficiency in soils is becoming increasingly common in many areas of the world as a result of agronomic practices, high biomass exportation and reduced S emissions to the atmosphere. In this review, the incidence and commercial exploitation of S pools in nature are discussed, as well as the importance of S for plants and the organic and inorganic S forms in soil and their transformations, especially the process of microbiological oxidation of elemental sulfur (S0) as an alternative to the replenishment of S levels in the soil. The diversity of S0-oxidizing microorganisms in soils, in particular the genus Thiobacillus, and the biochemical mechanisms of S0 oxidation in bacteria were also addressed. Finally, the main methods to measure the S0 oxidation rate in soils and the variables that influence this process were revised.

LAYERED DOUBLE HYDROXIDES: NANOMATERIALS FOR APPLICATIONS IN AGRICULTURE

The current research aims to introduce Layered Double Hydroxides (LDH) as nanomaterials to be used in agriculture, with particular reference to its use as storage and slow release matrix of nutrients and agrochemicals for plant growing. Structural characteristics, main properties, synthesis methods and characterization of LDH were covered in this study. Moreover, some literature data have been reported to demonstrate their potential for storage and slow release of nitrate, phosphate, agrochemicals, besides as being used as adsorbent for the wastewater treatment. This research aims to expand, in near future, the investigation field on these materials, with application in agriculture, increasing the interface between chemistry and agronomy.

Arbuscular mycorrhizal fungi in soil aggregates from fields of "murundus" converted to agriculture

The objective of this work was to evaluate the spore density and diversity of arbuscular mycorrhizal fungi (AMF) in soil aggregates from fields of "murundus" (large mounds of soil) in areas converted and not converted to agriculture. The experiment was conducted in a completely randomized design with five replicates, in a 5x3 factorial arrangement: five areas and three aggregate classes (macro-, meso-, and microaggregates). The evaluated variables were: spore density and diversity of AMF, total glomalin, total organic carbon (TOC), total extraradical mycelium (TEM), and geometric mean diameter (GMD) of soil aggregates. A total of 21 AMF species was identified. Spore density varied from 29 to 606 spores per 50 mL of soil and was higher in microaggregates and in the area with 6 years of conversion to agriculture. Total glomalin was higher between murundus in all studied aggregate classes. The area with 6 years showed lower concentration of TOC in macroaggregates (8.6 g kg-1) and in microaggregates (10.1 g kg-1). TEM was greater at the top of the murundus in all aggregate classes. GMD increased with the conversion time to agriculture. The density and diversity of arbuscular mycorrhizal spores change with the conversion of fields of murundus into agriculture.