PHYSICAL QUALITY OF A YELLOW LATOSSOL UNDER INTEGRATED CROP-LIVESTOCK SYSTEM

Soil physical quality is essential to global sustainability of agroecosystems, once it is related to processes that are essential to agricultural crop development. This study aimed to evaluate physical attributes of a Yellow Latossol under different management systems in the savanna area in the state of Piaui. This study was developed in Urucui southwest of the state of Piaui. Three systems of soil management were studied: an area under conventional tillage (CT) with disk plowi and heavy harrow and soybean crop; an area under no-tillage with soybean-maize rotation and millet as cover crop (NT + M); two areas under Integrated Crop. Livestock System, with five-month pasture grazing and soybean cultivation and then continuous pasture grazing (ICL + S and ICL + P, respectively). Also, an area under Native Forest (NF) was studied. The soil depths studied were 0.00-0.05, 0.05-0.10 and 0.10-0.20 m. Soil bulk density, as well as porosity and stability of soil aggregates were analyzed as physical attributes. Anthropic action has changed the soil physical attributes, in depth, in most systems studied, in comparison to NF. In the 0.00 to 0.05 m depth, ICL + P showed higher soil bulk density value. As to macroporosity, there was no difference between the management systems studied and NF. The management systems studied changed the soil structure, having, as a result, a small proportion of soil in great aggregate classes (MWD). Converting native forest into agricultural production systems changes the soil physical quality. The Integrated Crop-Livestock System did not promote the improvement in soil physical quality.34371772

Changes in Soil Organic Carbon and Nitrogen Stocks in Long-Term Experiments in Southern Brazil Simulated with Century 4.5

ABSTRACT The Century model has successfully simulated soil organic matter dynamics in many agroecosystems. However, initial applications in southern Brazil produced mixed results. The objective of this study was to calibrate and validate Century 4.5 to simulate soil carbon (C) and nitrogen (N) dynamics under diverse soil management practices in subtropical Brazil. Soil C and N data from two long-term experiments established on a degraded Acrisol in the early 1980s were used. Treatments were conventional or no-tillage; grass or grass/legume cropping systems; and corn with or without mineral N fertilizer. The calibration process iteratively modified model parameters to match simulated values of C additions and Soil Organic Carbon (SOC) and Soil Organic Nitrogen (SON) stocks to field data measured throughout the 25 years of the experiments. Improved fit between measured and observed data was obtained after key parameter changes. Soil C and N stocks were simulated accurately after these modifications were implemented. Other experimental treatments were used to validate the model. Century successfully simulated increases in C and N stocks under no-tillage cropping systems including legumes. However, the model overestimated Soil Organic Matter (SOM) decomposition in treatments with low N availability, like oat/corn without N fertilizer. Overall, Century version 4.5 showed adequate performance in simulating C and N trajectories of contrasting cropping systems commonly found in southern Brazil. The few discrepancies between measured and modeled SOC stocks do not preclude using Century in regional-scale applications to assess impacts of agricultural practices on soil C and N in southern Brazil

Relação entre macrofauna edáfica e atributos químicos do solo em diferentes agroecossistemas

O objetivo deste trabalho foi avaliar o efeito do uso do solo sobre a densidade e a diversidade da macrofauna invertebrada, bem como a relação dessa com atributos químicos do solo em diferentes agroecossistemas. Foram estudados cinco agroecossistemas: sistema ecológico com três anos de adoção (SE3), sistemas agroflorestais com seis (SAF6) e dez (SAF10) anos de adoção; agricultura de corte e queima (ACQ), e floresta nativa (FN). Em cada sistema, foram coletadas aleatoriamente cinco amostras solo, em forma de blocos (25x25 cm), na profundidade de 10 cm, nas épocas seca (outubro, 2006) e chuvosa (maio, 2007). A relação entre os atributos químicos e a macrofauna edáfica, nos diferentes sistemas de uso do solo, foi determinada por meio da análise da coinércia. Maior abundância da macrofauna foi observada na época chuvosa. Os sistemas SE3, SAF6 e SAF10 apresentaram maior riqueza de espécies e índices de Shannon e Pielou, independentemente da época de coleta. O manejo agroflorestal favoreceu a ocorrência de "engenheiros do ecossistema". Os sistemas agroflorestais propiciam melhores características químicas do solo e aumentos na abundância e riqueza da macrofauna invertebrada do solo