Beno Wendling

Organic-Matter Pools of Soil under Pines and Annual Cultures

When submitted to different uses and managements, soils can suffer alterations in the amount and in the quality of carbon and nitrogen present in the soil. This studys objective was to evaluate carbon and nitrogen in different compartments of the organic matter of the soil under savannah, 30-year-old pine plantation, and annual cultivations with corn and soy under conventional preparation and direct planting after 10 years of age. The substitution of the savannah for the pines and annual cultures reduces the carbon and total nitrogen in the soil. Among the compartments, only the particulate-free light fraction is not reduced in the Pinus in relation to the savannah. No tillage presents potential for improvement of the quality of the soil to make the fractions of carbon more labile in the soil. The more labile fractions reflect the alterations well imposed in the use and management of the soil, and they can be used as sensitive and premature indicators of the quality of the soil. They can be used for calculation of the carbon management index.

CO2 emissions from soil incubated with sugarcane straw and nitrogen fertilizer

The decomposition/mineralization of organic material from crop residues constitutes an important nutrient reservoir for plants. This process produces CO 2 and is influenced by biophysical and environmental conditions such as temperature, oxygen availability and the chemical composition of the crop residue. We studied the effect of temperature and nitrogen fertilization on CO 2 emissions and the distinct contributions of C from sugarcane residue either left on the surface or incorporated into the red-yellow Oxisol. Incorporated sugarcane residue and N applications produce higher total organic carbon (TOC) mineralization rates when compared to application on the soil surface and without N. Nevertheless, there was no difference between TOC and C in the humin fraction (C-HU) 80 days after incubation. CO 2 emissions peaked at 5.45, 10.82, 14.00, 11.92 and 11.20, 14.47, 15.98, and 14.74 µg mol of CO 2 g -1 s -1 within the first four days of incubation for unincorporated and incorporated residues, respectively. After these first four days, emissions decreased until stabilizing at 40 days after incubation. Keywords: Greenhouse gases, organic matter, urea. African Journal of Biotechnology , Vol 13(31) 3376-3384

Influence of Phosphorus and Carbon on Soil Microbial Activity in a Savannah Agroecosystem of Brazil

The microbial activity of soil plays an important role in the regulation of the transformation of carbon (C) and phosphorus (P). However, the activity of soil microbes is strongly related to the type of land-use system. The present work aimed to compare the microbial activity and metabolic responses of three different land-use systems to P (0 to 600 mg kg−1 of dry soil) and C additions in an Oxisol of the Brazilian savannah. The land-use systems studied were savannah vegetation (SV), 32-year-old pine plantation (PP), and 11-year-old no-tillage system (NT). The following analyses were carried out: amount of C carbon dioxide (CO2) evolved, total organic carbon (TOC), total glucose (TG), microbial biomass carbon (MBC), and metabolic yields (Y) from P and C additions to the soil. The different land-use systems affected the respiratory activity of microbiota, indicating an increase in SV and a decrease in PP when compared to the SV system under incubation for 17 days. The addition of P resulted in an increase of respiratory activity. The responses were adjusted by the Michaelis–Menten equation for all three land-use systems. The greatest TOC and lowest MBC were observed in NT and PP, respectively, when compared to SV. However, a lower content of TG was observed in NT in comparison to SV. Under bioassay conditions, the results confirm the greater microbial demand for P in PP and SV than in NT. The NT system showed greater metabolic yields when glucose was applied to the soil, suggesting that the response of microbiota in this system depends on easily available forms of C, as shown by the sugar content. The results showed expressive metabolic differences among the systems, suggesting that different soil uses change the dynamic of the responses of soil microorganisms.

Simulation using the Century Model of the Carbon and Nitrogen Stocks in Latosols of the Brazilian Cerrado

O uso de modelos matematicos pode ser util para o entendimento das alteracoes do uso e manejo do solo e fornecem subsidios para testar cenarios futuros, possibilitando desenvolver estrategias de manejo menos impactantes ao meio ambiente. Os objetivos deste trabalho foram: (a) usar o modelo Century v4.5 para simular os efeitos dos usos e manejos sobre os estoques de carbono e nitrogenio do solo em diferentes compartimentos, (b) comparar os estoques medidos e simulados pelo Century, e (c) testar impacto de cenarios futuros ate o ano de 2100. Os tratamentos avaliados foram Pinus, plantio direto e plantio convencional, com historico das areas ate o momento da coleta de solo (2004). Para o Pinus foram testados tres cenarios futuros, um deles simulando o mesmo manejo adotado ate o momento da coleta de solo, outro reduzindo os eventos de fogo, alem do uso sem preparo do solo para o replantio. Para o plantio direto e plantio convencional, simularam-se dois cenarios futuros, um com rotacao milho/soja e outro com monocultura de milho. O modelo Century foi sensivel as mudancas de manejo adotadas, os compartimentos mais labeis apresentam maior sensibilidade (ativo e lento), do que o mais estavel (passivo). Em relacao ao estoque de C, o modelo simulou estoques proximos aos medidos no campo, com um erro minimo de 0,36%. Para os estoques de N, os valores simulados apresentaram erro de 5,71% para os compartimentos mais labeis. Os cenarios futuros mostraram a importância de se evitar queimadas no Pinus e o uso de monocultivo.