Soil Organic Carbon and Nitrogen Stocks under Tropical Organic and Conventional Cropping Systems in Northeastern Brazil

• Published in: Communications in soil science and plant analysis Vol. 40; no. 19-20; pp. 2975 - 2994
• Main Authors: Xavier, F. Alisson da S, Maia, Stoecio Malta F, Oliveira, Teogenes Senna de, Mendonca, Eduardo de Sa
• Format: Journal Article
• Language: English
• Published: Philadelphia, PA Taylor & Francis Group, LLC 01-01-2009; Taylor & Francis
• Subjects: Agronomy. Soil science and plant productions; Biological and medical sciences; carbon; Carbon management index; Chemical, physicochemical, biochemical and biological properties; Fundamental and applied biological sciences. Psychology; General agronomy. Plant production; green manure fertilization; green manures; humic substances; nitrogen; Organic matter; organic production; Other nutrients. Amendments. Solid and liquid wastes. Sludges and slurries; oxidizible C fractions; Physics, chemistry, biochemistry and biology of agricultural and forest soils; sandy soils; soil chemical properties; soil fertility; soil management; soil nutrient dynamics; soil organic matter; soil quality; Soil science; Soil-plant relationships. Soil fertility. Fertilization. Amendments; tillage; tropical soils; Brazil; South America; America; Organic carbon; Organic nitrogen; Green manure; Tropical zone; Cropping system; green manure fertilization; Conventional agriculture; Organic fertilization; humic substances; sandy soils; Sandy soil; Organic acids; soil quality; Humic substance; oxidizible C fractions; Carbon management index
• DOI: 10.1080/00103620903261304
• EISSN: 1532-2416
• ISSN: 0010-3624

Soil organic matter (SOM) is an essential ecosystem component whose dynamics are affected by soil management practices. To evaluate the impact of two agricultural systems (organic and conventional) on soil organic carbon (C) and nitrogen (N) stocks in a sandy soil, samples were collected from the Amway Nutrilite Brazil farm and from the Central Pivot Horticultural Farmers Association farm, both situated in the Chapada da Ibiapaba region, Cear State, Brazil. The first area has a large-scale Caribbean Cherry fruit production system under organic management, whereas the second represented a conventional soil cultivation condition, characterized by the use of chisel plow and disc plow, mineral fertilization, and herbicides application. Plots with and without green manure fertilization were compared in the organically cultivated systems by using soil samples collected in the rows and between the rows. Areas under native forest were also sampled to determine the steady-state condition. Total organic C and N contents in the soil (SOC, TN) and in the humic substances were determined at the 0- to 5-, 5- to 15-, 15- to 30-, and 30- to 50-cm soil layers. In addition, oxidizible organic C fractions were measured to calculate the carbon management index (CMI). In general, total SOC levels were low, ranging from 2.5 to 12.6 g kg-1 in the whole soil profile among the organic systems. In the upper soil layer, SOC and TN stocks were greater in the rows in response to organic fertilization. The conventional system presented lower variation on the SOC contents throughout soil layers when compared to the native forest area, indicating the direct effect of plowing on the downward SOC distribution. The CMI data confirmed the reestablishment of SOM levels in the rows of the organic managed systems in relation to the reference area, whereas the reduction of the CMI in the conventional system suggests a decline in the soil quality and greater potential for increased C losses to the atmosphere.