Soil microbiological attributes of an agricultural area following disposal of tannery sludge

Author(s)

André Shigueyoshi Nakatani

• Document type: Doctoral Thesis
• Press: Piracicaba.
• Institution: Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC)
• Defense date: 2010-12-20

Examining board members

Elke Jurandy Bran Nogueira Cardoso; Fernando Dini Andreote; Carlos Eduardo Pellegrino Cerri; Marco Antonio Nogueira; José Paulo Filipe Afonso de Sousa

• Advisor: Elke Jurandy Bran Nogueira Cardoso

Abstract

Tannery sludge is a residue with a high content of nutrients and soil acidity neutralization power, which allow its use in agricultural areas and could be an advantageous alternative for its final disposal and recycling. Furthermore, the accumulation in soil of high concentrations of certain elements, such as nitrogen, sodium and chromium, typically present in tannery sludge can provide negative impacts on the environment. Microorganisms play a very important role in soil sustainability and plant nutrition, as well as, respond quickly to environmental changes. Thus, it becomes important to study the impact of a material resulting of the mixture of sludge from the liming process and the primary sludge from the wastewater treatment plant, with a low level of chromium, on soil biological attributes. This study aimed to evaluate the microbial soil attributes after application of tannery sludge doses (0, 3,4, 13,5, 23,6, and 33,7 Mg ha-1 in 2006 and 0, 2,3, 9,0, 15,8, and 22,6 Mg ha-1 in 2007) based on total N content of sludge, with doses equivalent to 0 up to 1200 kg ha-1 total N. Tannery sludge application modified the genetic structure of the bacterial community mainly right after each sludge application. There was a clear separation between the bacterial communities in different treatments, being that each dose of sludge imposed a specific community different from the control. It was verified that the effect of sludge on these bacterial populations is more extended in the first year of application, when the effect remained until after 300 days of application. In the second year of sludge application, there was no difference in the bacterial community among the smallest doses and the control after 260 days of the application. The same result was observed regarding soil biological activity. The most influenced properties by the application of tannery sludge were asparaginase and urease activities (both are related to the N cycle). Changes in the structure of the bacterial community were directly related to changes of biological activity in this soil. The AMF spore density decreased with increasing doses of tannery sludge. The rate of AMF root colonization was high (64%) and stayed unaffected by the sludge. Eighteen AMF species belonging to six genera (Acaulospora, Glomus, Gigaspora, Scutellospora, Paraglomus and Archaeospora) were recorded. At the highest doses of sludge we observed decreased AMF species diversity and changes in their relative frequencies. Furthermore, the tannery sludge altered AMF species composition, modifying the mycorrhizal status of this soil. High doses of tannery sludge modified the microbial community structure based on the phospholipids fatty acids (PLFA) profile. The carbon substrate consumption by the microbial community was accelerated and intensified by sludge application, showing that the metabolic potential of this community was different from that of the control. The changes observed in the microbial attributes are related to modifications in the soil chemical attributes, mainly to the increases of inorganic N and soil pH. (AU)

• FAPESP's process: 07/06903-1 - Microbial ecological attributes of soil under disposal of tannery sludge
• Grantee: André Shigueyoshi Nakatani
• Support Opportunities: Scholarships in Brazil - Doctorate