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Growth and decomposition of fine roots and soil quality under integration of agriculture, livestock and forestry systems (São Carlos-SP)

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Author(s):
Wanderlei Bieluczyk
Total Authors: 1
Document type: Doctoral Thesis
Press: Piracicaba.
Institution: Universidade de São Paulo (USP). Centro de Energia Nuclear na Agricultura
Defense date:
Examining board members:
Marisa de Cassia Piccolo; Alberto Carlos de Campos Bernardi; Roberto Botelho Ferraz Branco; José Leonardo de Moraes Gonçalves; Patrícia Perondi Anchão Oliveira
Advisor: Marisa de Cassia Piccolo; Marcos Gervasio Pereira
Abstract

Integrated farming systems (IS) diversify and intensify rural production, although there are still gaps in advancing and detailing of the processes and mechanisms involved in the soil-plant-atmosphere relations, which are essential to adapt and model these systems for the different eco-regions and edafoclimatic conditions. This study investigated the effects of the intensification of IS on the quantity, quality and origin of soil organic matter (SOM) and on root growth and decomposition dynamics of plant species during cropping and grazing periods. The experiment was conducted at Embrapa Pecuária Sudeste, state of São Paulo, southeast region of Brazil. Two IS were evaluated: integrated crop-livestock system (ICL) and integrated crop-livestock-forest system (ICLF). Two references areas were used: extensive grazing (not degraded) and a semideciduous seasonal forest (only for SOM evaluations). Two evaluation periods were considered: cropping (summer of 2014/15) and grazing period (winter of 2015 and summer and winter of 2015/16). The quantity (C and N contents and stocks), quality (C management indexes, light, particulate and mineral SOM fractions) and the origin (?13C and ?15N) of SOM in the 0-0.40 m layer, and the growth and decomposition of the root systems of the plant species and water flow in the soil profile (0-0.7 m) were evaluated during cropping and grazing periods. In addition, in ICLF also these parameters of plants and soils were evaluated at three distances of eucalyptus rows (1.9, 4.5 and 7.3 m). The conversion of extensive grazing to ICL system resulted in: (i) increased availability of nutrients (Ca, Mg, K and P) in the soil; (ii) increases in C and N stocks, as well as labile fractions of SOM; (iii) maintenance of greater water content in the soil; and (iv) cycling of C and N, with higher root production and decomposition, even in deeper layers of the soil. Implementing the ICLF under the area used for ICL promoted the following effects: (i) reduction in soil water content; (iii) limitations in the root production in the cropping season (mainly in places near the trees) and increases in the root decomposition, resulting in higher cycling rates of the roots in the soil; (iv) increases in C and N cycling; and, (v) occurrence of symbiotic associations with the roots, such as ectomycorrhizal fungi, which were perceptible by the technique of root analysis using minirhizotrons. According to the results, it is suggested that the arrangement of the trees in the ICLF system need to be restructured after the fourth year of age, when they limited the root growth and the amount of labile organic matter, besides reducing the contents of water in the soil. However, farming intensification is recommended under tropical conditions, as the SOM quantity and quality, and the productivity and deepening of the root system were increased during cultivations in the IS, especially in the ICL system (AU)

FAPESP's process: 14/17927-2 - Growth and decomposition of fine roots and soil quality under integration of agriculture, livestock and forestry systems (São Carlos, SP)
Grantee:Wanderlei Bieluczyk
Support type: Scholarships in Brazil - Doctorate