Microbial enzymatic activity and thermal effect in a tropical soil treated with organic materials

Abstract

Bacteria and fungi are the most active decomposers of organic materials in soil. They directly affect plant nutrient availability, and chemical and physical properties of soils. This investigation aimed at quantifying the effect of several organic materials on microbial activity of a Rhodic Eutrudox. Soil samples were incubated over a period of 91 days with the following organic materials: cattle manure (CM), earthworm humus (HM), and city sewage sludge from Barueri (BA) and Franca (FR). The activities of cellulase, protease and urease enzymes, the soil microbial carbon content (by fumigation-extraction method) and the exothermal effect were evaluated. Experimental design was randomized and arranged as factorial scheme five treatments × seven samplings with five replications. Organic materials promoted oscillations in microbial carbon (mg C g -1 soil), and enzyme activities -cellulase (µg glucose g -1 soil 24 h ) e no efeito térmico total (J g -1 solo), na seguinte ordem decrescente: (1) 655.90; 49.68; 24.55; 477.90; 367.70; 32.76; 10.66; 426.29; 273.40; 18.77; 19.35; 368.00; (4) 261.00; 17.05; 9.02; 202.79; (5) controle. Correlações foram obtidas entre o carbono microbiano e as enzimas celulase e protease (r = 0.54; p < 0.001), e entre o efeito exotérmico e a protease (r = 0.34; p < 0.005). A atividade de enzimas esteve diretamente relacionada à microbiota do solo, refletindo, dessa forma, no efeito térmico total. Palavras-chave: enzimas, carbono da biomassa, materiais orgânicos, microrganismos do solo, microcalorimetria

Changes of soil labile organic carbon fractions and their relation to soil microbial characteristics in four typical wetlands of Sanjiang Plain, Northeast China

“…The production of extra cellular enzymes related to microbial biomass enhancement (Albiach et al, 2000). Cenciani et al (2008) also concluded that soil microbial carbon significant correlated to cellulose activities. This inferred that any change in soil enzymes activity would strongly influenced soil organic C pools.…”

Enzymatic activity measured by microcalorimetry in soil amended with organic residues

“…The overall cellulase activity in the soil samples containing earthworm casts was relatively low (261 μg glucose g -1 soil 24 h -1 ), when compared with other organic materials, but values were significantly higher than of the unamended control. These results are probably due to the relatively humified and stable composition that characterizes the earthworm humus (Cenciani et al, 2008). The sum of cellulase activity was lower in the sludge from Franca (273.4 μg glucose g -1 soil 24 h -1 ) than in sewage sludge from Barueri (367.7 μg glucose g -1 soil 24 h -1 ) (Table 2a), despite the high carbon contents in both sludges (Table 1).…”

“…It is possible that the pH influences these processes. In relatively acidic soil, as in FR sludge with pH 6.0, several ions are hydrolyzed and can react with organic compounds to form organic-complexes (Cenciani et al, 2008), differently from the Barueri sludge, with an alkaline pH of around 12 (Table 1).…”

“…In microbial communities, where growth is limited not only by substrates, but also by physical factors such as diffusion processes and porosity, the anabolic enthalpy change (biosynthesis, microbial growth) is likely to be small when compared to catabolic reactions (breakdown of organic substrates, enzymatic activity). Consequently the thermal effect in soils is closely related to respiration, ATP content, microbial biomass, and enzyme activity (Barros & Feijóo, 2003;Critter et al, 2004a,b;Cenciani et al, 2008).…”

“…An isothermal environment is a positive factor for the establishment of adequate conditions for microbial growth and metabolism, and also for measuring the thermal effect (Critter et al, 2001). This is one of reasons to the fact that heat conduction or isothermal microcalorimeters have been recently used in several calorimetric studies, such as in the efficiency of C utilization by soil microorganisms (Barros & Feijóo, 2003), microbial activity in composts using microcalorimetry (Laor et al, 2004), thermal effect resulting from the influence of agrochemicals on soil microorganisms (Prado & Airoldi, 2000;Critter et al, 2004a) and in applications of microcalorimetry and the respiration rate to investigate microbial growth and activity (Critter et al, 2001(Critter et al, , 2002Cenciani et al, 2008).…”