Roney Berti de Oliveira

Optimum size in grid soil sampling for variable rate application in site-specific management

The importance of understanding spatial variability of soils is connected to crop management planning. This understanding makes it possible to treat soil not as a uniform, but a variable entity, and it enables site-specific management to increase production efficiency, which is the target of precision agriculture. Questions remain as the optimum soil sampling interval needed to make site-specific fertilizer recommendations in Brazil. The objectives of this study were: i) to evaluate the spatial variability of the main attributes that influence fertilization recommendations, using georeferenced soil samples arranged in grid patterns of different resolutions; ii) to compare the spatial maps generated with those obtained with the standard sampling of 1 sample ha -1 , in order to verify the appropriateness of the spatial resolution. The attributes evaluated were phosphorus (P), potassium (K), organic matter (OM), base saturation (V%) and clay. Soil samples were collected in a 100 × 100 m georeferenced grid. Thinning was performed in order to create a grid with one sample every 2.07, 2.88, 3.75 and 7.20 ha. Geostatistical techniques, such as semivariogram and interpolation using kriging, were used to analyze the attributes at the different grid resolutions. This analysis was performed with the Vesper software package. The maps created by this method were compared using the kappa statistics. Additionally, correlation graphs were drawn by plotting the observed values against the estimated values using cross-validation. P, K and V%, a finer sampling resolution than the one using 1 sample ha -1 is required, while for OM and clay coarser resolutions of one sample every two and three hectares, respectively, may be acceptable.

Modelagem de um complexo de inundação por meio de sistema de informações geográficas

MODELLING A FLOOD COMPLEX THROUGH GEOGRAPHICAL INFORMATION SYSTEM The Parana River is the main stream forming the Prata basin. Significant part of the basin is included in Environmental Protection Area (APA) Ilhas e Varzeas do Rio Parana. The compartmentalization of these areas is intermittent, which over time changes to reorder the environmental system. This is because this region is frequently flooded annually, either by rivers or by direct rainfall. Therefore, the objective of this work was the establishment of the occurrence period of flooding of Ivai river, a tributary of Parana river and the affected areas by them. The studies focused on the Querencia do Norte, State of Parana, where altimetry and land use survey was conducted. The use of GIS data and orbital landsat images allowed construction of a numerical terrain model to represent the surface. The results showed altimetric variation greater than 100 meters and seasonal variation of the flooding 4 meters above the normal river level (9 meters in the scale), characterizing the crops grown in there as in regular situation. The seasonal flooding of the Ivai river is 235.04 m above sea level.

LEVANTAMENTO E CARACTERIZAÇÃO DOS SOLOS EM UMA REGIÃO DE VÁRZEAS DA APA DAS ILHAS E VÁRZEAS DO RIO PARANÁ

O objetivo deste trabalho foi o de mapear os solos numa regiao de varzeas do municipio de Querencia do Norte e as alteracoes sofridas pelos mesmos em funcao da ocorrencia de cheias. Para tanto, foram realizadas coletas de solo em locais representativos da paisagem e enviados para laboratorio para realizacao de analises fisicas e quimicas. Os resultados possibilitaram o mapeamento e classificacao detalhada dos solos, alem da analise da distribuicao de alguns atributos no espaco. Dessa forma, obteve-se uma gama de 10 classes de solo na regiao de estudos e concluiu-se que estas sofrem influencia direta de fatores do ambiente desde sua formacao ate a situacao atual.