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| Author(s): |
Fernando José Garbuio
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Piracicaba. |
| Institution: | Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC) |
| Defense date: | 2010-02-10 |
| Examining board members: |
Luis Reynaldo Ferracciú Alleoni;
Elke Jurandy Bran Nogueira Cardoso;
Antonio Costa;
Carlos Alexandre Costa Crusciol;
Luis Ignacio Prochnow
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| Advisor: | Luis Reynaldo Ferracciú Alleoni |
| Abstract | |
Soil acidity is a serious problem in tropical and subtropical regions of the world reducing root growth and crop yield. Surface liming is a common practice to ameliorate soil acidity in areas under no-till system (NTS). The subsoil acidity amelioration, as a result of surface liming, is affected by cover crop residues as well as N fertilization. Liming and crop residues play important roles on C and N cycles due to changes in soil biological attributes, such as microbial community and activity, quantity and quality of substrate to microorganisms. The aims of this study were to evaluate the effects of surface liming and black oat residues, with or without N addition, on (i) soil chemical attributes, ionic speciation, soybean nutrition and yield of a loamy, kaolinitic, thermic Rhodic Hapludox in an experiment carried out in Ponta Grossa, state of Paraná, Brazil (25º10S, 50º05W) under NTS; (ii) C and N pools, potentially mineralizable N and decomposition rate of amino acids; and (iii) to evaluate the initial soil pH and black oat residues placement on soil solution composition and microbial behaviour. Surface liming increased soil pH and contents of Ca and Mg throughout soil profile, and also it reduced Al content to a 60 cm soil depth, regardless of cover crop treatments. The addition of N caused soil acidification. The Al content in soil solution was found mainly complexed to dissolved organic compounds, in contrast to Ca and Mg, which were found in a free form. Soybean yield was increased by lime rates. Due to soil pH increase, surface liming stimulated soil microbial biomass, potentially mineralizable N and amino acids decomposition rate, mainly at soil surface layer. Amino acids released from the initial decomposition of black oat residues were immediately used by soil microorganisms. Surface liming, cover crop residues and N fertilization affected nutrients availability and microbial biomass composition and activity under NTS. (AU) | |