Physical fractions of organic matter and mineralizable soil carbon in forest fragments of the Atlantic Forest

This study determined the physical granulometric fractionation evaluated the mineralizable carbon within and around forest fragments of the Atlantic Forest biome located in the state of Paraná. Soil samples were collected at three three internal points of the fragments: the edge (E), the half radius (HR) and the center (CF); and one point in no-tillage system (NTS) areas around the fragments, in four replicates. The contents of total organic carbon (TOC), particulate fraction carbon (C-POM) and mineral fraction (C-MOM) were determined, and the %POM and %MOM and the stocks of POM (StockPOM) and MOM (StockMOM) were calculated, in addition to the indices: carbon stock index (CSI), lability (L), lability index (LI) and carbon management index (CMI), also evaluating CO2 emission, daily and accumulated. The highest TOC levels were observed in the CF point. The highest C-POM contents were observed in the E and CF points of fragment 1, in the CF point of fragment 2, and the highest C-MOM contents were expressed in the CF points of both fragments. CMI showed a distinct pattern among the fragments. The NTS areas showed lower C-CO2 emissions, with 39.8% and 28.3% less total emission compared to CF. The results of physical granulometric fractionation show the CF point favors the quality of SOM and the mineralizable carbon analysis indicated that the conversion of native areas into NTS compromises soil microbial activity.

Soil Carbon Stock and Pools in Acid Sulphate Soils of Kerala

A study was conducted to assess the soil carbon storage as different soil carbon pools in acid sulphate soils of Kuttanad, Kerala under different land uses and mapping of carbon stock using GIS. Surface soil samples (0-15 cm) were collected from three agricultural land use systems namely rice, coconut and rice-fish from six acid sulphate soil series viz. Ambalapuzha, Purakkad, Thakazhi, Thuravur, Thottapalli and Kallara and were analysed for soil carbon pools like organic carbon, labile carbon, water soluble carbon, particulate organic carbon, microbial biomass carbon and mineralizable carbon using standard procedures .The carbon stock in soil was also computed and mapped using Arc GIS software. The highest organic carbon content of 9.38% was recorded in Kallara series under rice land use. The water soluble carbon ranged from 44.38 to 208.68 mg kg-1. Labile carbon in soil varied form 4.36 mg g-1 to 13.06 mg g-1. Particulate organic carbon was the highest in rice land use in Kallara series (7.23%). The mineralizable carbon ranged from 2.17 mg kg-1 to 2.91 mg g-1. The microbial biomass carbon varied between 71 mg kg-1 and 488 mg kg-1. The humic acid content varied from 0.20% to 6.09% and the fulvic acid content ranged from 0.09% to 20.10%. The active and passive carbon pools and their contribution to total soil carbon pool was the highest in Kallara series. Among the different land uses, coconut had the highest active pool, while rice land use recorded the highest passive pool of carbon. The soil organic carbon stock (115.96 Mg ha-1) and carbon pool index (2.10) were the highest in Kallara series. The proportion of POC to SOC was the highest in Kallara series (0.62) under rice land use indicating it as a potential carbon sink. The carbon turnover rate was found to be the highest in Thottapalli series (1.15) under coconut land use indicating it as a potential carbon source.

Evolution and accumulation of C-CO2 in biogenic and physiogenic aggregates of different agroecological management systems

Determination of mineralizable carbon (C) is based on the evolution of C-CO2, reflecting the activity of soil biota in soil organic matter (SOM) decomposition, and can be used as a testing parameter in agroecological production systems. The objective of the present work was to quantify mineralizable C in aggregates of different biogenic and physiogenic formation pathways in agroecological management systems in the city of Seropédica, state of Rio de Janeiro. Five sampling areas were selected: (1) 10-year agroforestry system (AFS), (2) 15-year full sun coffee (C-SUN), (3) 15-year shaded coffee (C-SHA), (4) 10-year phlegm alleles (FLE), and (5) 6-year no-till planting system with corn and eggplant (NT) in Red-Yellow Argissolo in Seropédica-RJ.Morphological patterns were used to identify the formation pathway (biogenic and physiogenic) of aggregates. In these, fertility, total organic carbon (TOC), and total nitrogen (TN) were evaluated. The evolution and accumulation of C-CO2were determined in the laboratory after 35 days of incubation. The NT area under agroecological management present higher C-CO2 accumulation between the systems with biogenic aggregates and less accumulation in the physiogenic aggregates.