Microbiological attributes of a cultivated Plinthosol with sugarcane on different levels of straw

The objective of this work was to evaluate the microbiological attributes of a Plinthossol cropped with sugar cane in straw. The experiment was installed in União (04 ° 51’09”S and 42 ° 53’10 ‘’ W, altitude 52 m), northern region of Piauí state, Brazil. The experimental design was randomized blocks, with four replications, and treatments corresponding to different rates of straw (Mg.ha-1) (0, 4.19, 9.54, 13.04 and 18.38). Microbiological attributes were determined at a depth of 0-10 cm. Data was submitted to analysis of variance, cluster analysis and main components. An increase of straw in the soil influenced the stocks and contents of C, Cmic, Nmic, respiration and microbial and metabolic quotients. Cluster analysis combined the treatments into three distinct groups. 9.54 Mg.ha-1 of straw treatment was isolated from other treatments, being strongly correlated to the microbial quotient. The group formed by the treatments 13.04 and 18.38 Mg.ha-1 of straw correlated with most of the evaluated attributes, being the best proportions to be used to improve soil quality.

Soil quality indicators after conversion of “murundu” fields into no-tillage cropping in the Brazilian Cerrado

The objective of this work was to evaluate changes in soil quality due to different times of adoption of the no-tillage system in “murundu” (mound) fields converted to agriculture, as well as to identify the best indicators to explain these changes. The study was carried out on a Plinthic Altisol, in the municipality of Portelândia, in the state of Goiás, Brazil. The treatments consisted of different times of conversion and of adoption of the no-tillage system - 8, 12, and 17 years - and of native area between the mounds and on top of the mounds (reference area). After 17 years of the adoption of no-tillage, there was an increase in organic carbon and nitrogen, as well as in their particulate fractions in relation to the reference area. The microbiological attributes showed greater values in the 17-year no-tillage period compared with the native area. For soil aggregation, 12 years of adoption of the no-tillage system were enough to show an increase in this variable. The main attributes to be used as soil quality indicators are microbial biomass carbon, the carbon management index, and the microbial quotient.

Microbial biomass in a haplic gleysol in the Mato Grosso State Pantanal

The Pantanal is a biome that lives under water conditions and resists to two very distinct periods: flooded and drained. The objective of this study was to evaluate the behavior and quantify the microbial biomass during the flood period, in soils under riparian forest and cerrado vegetation in Mato Grosso State pantanal, at two depths. At depths of 0.00-0.05 m, the highest levels of C-BM and RB were found in cerrado soils; for the metabolic quotient no differences were observed in the two vegetations; the total organic carbon content was higher in riparian forest soils and the microbial quotient was higher in cerrado soils. Bacteria and fungi were found to be more abundant in the cerrado soil at the two evaluated depths and the actinomycetes in the forest. It is concluded that in the flood period there are the presence of active microorganisms which produce a differentiated biomass due to the phytophysiognomy of the location.

Microbial activities, carbon, and nitrogen in an irrigated Quartzarenic Neosol cultivated with cowpea in southwest Piauí

The aim of this study was to evaluate microbial biomass and total organic carbon and nitrogen of an irrigated Quartzarenic Neosol cultivated with two cowpea cultivars in Bom Jesus, Piauí, Brazil. The experiment was conducted in a randomized experimental block design in split plots. The plots consist of two cowpea cultivars (Aracê and Tumucumaque) and the subplots were composed of five different irrigation regimes (L1 = 108.2; L2 = 214.7; L3 = 287.9; L4 = 426.1, and L5 = 527.7 mm). Soil samples were collected at a depth of 0-0.20 m in order to evaluate basal soil respiration, microbial biomass carbon, metabolic quotient, microbial quotient, content, and storage of soil carbon and nitrogen. Basal soil respiration, microbial biomass carbon, microbial metabolic quotient, and microbial quotient are influenced by the interaction between cowpea cultivars and irrigation. The cultivar Aracê showed greater stimulus to the microbial community, while the irrigation regimes with 214.7 and 287.9 mm (60 and 90% of ETo, respectively) provided the best moisture conditions for microbial activities.

Microbiological activity and carbon mineralization in pampean soils with different agricultural use intensity

The processes involved in the flows of matter and energy of terrestrial ecosystems depends heavily on soil biological activity, the current conventional agricultural managements could alter the biological mechanisms involved in decomposition and nutrient cycling in agroecosystems. The aim of this study was to compare the activity levels and soil microbial biomass between different agricultural pampean soil uses and its relationship to carbon mineralization. 25 years of agricultural use were compared with 25 years of ecological reserve naturalized where each agroecosystem soil were collected at 61 - 125 - 183 - 236 - 302 - 368 - 431 - 488 days for measuring their moisture, organic matter, enzymatic activity, microbial biomass carbon, soil respiration, metabolic quotient, microbial quotient and carbon mineralization rate. The distance between agroecosystems is less than 800 m, thus assuming the same soil and climatic conditions. The data were evaluated by Friedman test finding significant differences in moisture, organic matter, enzymatic activity, soil respiration y microbial quotient (p< 0.01). Difference was also found in the microbial mineralization rate of carbon (p< 0.1).

Microbiological activity and carbon mineralization in pampean soils with different agricultural use intensity

The processes involved in the flows of matter and energy of terrestrial ecosystems depends heavily on soil biological activity, the current conventional agricultural managements could alter the biological mechanisms involved in decomposition and nutrient cycling in agroecosystems. The aim of this study was to compare the activity levels and soil microbial biomass between different agricultural pampean soil uses and its relationship to carbon mineralization. 25 years of agricultural use were compared with 25 years of ecological reserve naturalized where each agroecosystem soil were collected at 61 - 125 - 183 - 236 - 302 - 368 - 431 - 488 days for measuring their moisture, organic matter, enzymatic activity, microbial biomass carbon, soil respiration, metabolic quotient, microbial quotient and carbon mineralization rate. The distance between agroecosystems is less than 800 m, thus assuming the same soil and climatic conditions. The data were evaluated by Friedman test finding significant differences in moisture, organic matter, enzymatic activity, soil respiration y microbial quotient (p< 0.01). Difference was also found in the microbial mineralization rate of carbon (p< 0.1).

Reviews and syntheses: Soil resources and climate jointly drive variations in microbial biomass carbon and nitrogen in China's forest ecosystems

Microbial metabolism plays a key role in regulating the biogeochemical cycle of forest ecosystems, but the mechanisms driving microbial growth are not well understood. Here, we synthesized 689 measurements on soil microbial biomass carbon (Cmic) and nitrogen (Nmic) and related parameters from 207 independent studies published up to November 2014 across China's forest ecosystems. Our objectives were to (1) examine patterns in Cmic, Nmic, and microbial quotient (i.e., Cmic / Csoil and Nmic / Nsoil rates) by climate zones and management regimes for these forests; and (2) identify the factors driving the variability in the Cmic, Nmic, and microbial quotient. There was a large variability in Cmic (390.2 mg kg−1), Nmic (60.1 mg kg−1, Cmic : Nmic ratio (8.25), Cmic / Csoil rate (1.92 %), and Nmic / Nsoil rate (3.43 %) across China's forests. The natural forests had significantly greater Cmic (514.1 mg kg−1 vs. 281.8 mg kg−1) and Nmic (82.6 mg kg−1 vs. 39.0 mg kg−1) than the planted forests, but had less Cmic : Nmic ratio (7.3 vs. 9.2) and Cmic / Csoil rate (1.7 % vs. 2.1 %). Soil resources and climate together explained 24.4–40.7 % of these variations. The Cmic : Nmic ratio declined slightly with Csoil : Nsoil ratio, and changed with latitude, mean annual temperature and precipitation, suggesting a plasticity of microbial carbon-nitrogen stoichiometry. The Cmic / Csoil rate decreased with Csoil : Nsoil ratio, whereas the Nmic / Nsoil rate increased with Csoil : Nsoil ratio; the former was influenced more by soil resources than by climate, whereas the latter was influenced more by climate. These results suggest that soil microbial assimilation of carbon and nitrogen are jointly driven by soil resources and climate, but may be regulated by different mechanisms.

Soil resources and climate jointly drive variations in microbial biomass carbon and nitrogen in China's forest ecosystems

Microbial metabolism plays a key role in regulating the biogeochemical cycle of forest ecosystems, but the mechanisms driving microbial growth are not well understood. Here, we synthesized 689 measurements on soil microbial biomass carbon (Cmic) and nitrogen (Nmic) and related parameters from 207 independent studies published during the past 15 years across China's forest ecosystems. Our objectives were to (1) examine patterns in Cmic, Nmic, and microbial quotient (i.e., Cmic / Csoil and Nmic / Nsoil rates) by climate zones and management regimes for these forests; and (2) identify the factors driving the variability in the Cmic, Nmic, and microbial quotient. There was a large variability in Cmic (390.2 mg kg−1), Nmic (60.1 mg kg−1), Cmic : Nmic ratio (8.25), Cmic / Csoil rate (1.92 %), and Nmic / Nsoil rate (3.43 %) across China's forests, with coefficients of variation varying from 61.2 to 95.6 %. The natural forests had significantly greater Cmic and Nmic than the planted forests, but had less Cmic : Nmic ratio and Cmic / Csoil rate. Soil resources and climate together explained 24.4–40.7 % of these variations. The Cmic : Nmic ratio declined slightly with the Csoil : Nsoil ratio, and changed with latitude, mean annual temperature and precipitation, suggesting a plastic homeostasis of microbial carbon-nitrogen stoichiometry. The Cmic / Csoil and Nmic / Nsoil rates were responsive to soil resources and climate differently, suggesting that soil microbial assimilation of carbon and nitrogen be regulated by different mechanisms. We conclude that soil resources and climate jointly drive microbial growth and metabolism, and also emphasize the necessity of appropriate procedures for data compilation and standardization in cross-study syntheses.