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When irrigation management is not properly conducted in irrigation areas, especially in semi-arid regions, soil may be salinized and sodiumized, with decrease in agricultural productivity. Investigation of spatial variation of the factors that condition the processes is extremely important in agricultural planning. Current analysis mapped the space variability of salinity and sodiumized in an area with irrigated mango trees in the Vale do Açu (RN), Brazil. Statistical and geostatistical techniques were applied by GeoR and Vesper software. The sampling grid was performed in a rectangular area of 100 m x 64 m (6,400 m²), points distanced 16 m x 10 m, totaling 40 samples. Variables Ca2+, Mg2+, K+, Na+, pH, CE, PST and RAS were determined. Results indicate that the area has low risk in salinity and sodiumization. Attributes behaved heterogeneously, with the exception of K+ and pH presenting a low variation coefficient. Spatial dependence was weak for Na+, K+ and RAS, moderate for attributes pH, CE and PST, and strong for Ca and Mg only. Geo-statistics proved to be a tool capable of delimiting the areas with higher and lower concentrations in unsampled sites, contributing to the rational use of soil and water. [ABSTRACT FROM AUTHOR]

So that one may obtain the economic value of an environmental resource, its monetary value should be estimated in relation to other goods/services available in the economy. Environmental valorization methods currently used are relatively new and the variables in the process may not be known or partially known. One method is the Reposition Cost that calculates the value of reparation from a damage. Current paper applied the reposition cost method in the economic valorization of nutrient loss by soil erosion in the hydrographic basin of the river Una, Brazil, through geoprocessing to evaluate spatially the area under analysis. Thirty-five samples were collected and the soil´s nutrients quantified, Ca, Mg, P and K. Concentrations were spatialized and annual loss estimated, with reposition costs. In more than 89% of the studied area, the reposition cost of K, P, Ca and Mg of the three fertilizers employed (potassium chloride, potassium chlorate, simple superphosphate and lime) reached about R$ 0.01 per m². Total reposition cost was R$ 352,846.43. The spatialization of reposition costs showed which areas required special attention of the government with regard to monitoring and proposition of sustainability. [ABSTRACT FROM AUTHOR]

The photogrammetry techniques are known to be accessible due to its low cost, while the geometric accuracy is a key point to ensure that models obtained from photogrammetry are a feasible solution. This work evaluated the discrepancies in 3D (DSM) and 2D (orthomosaic) models obtained from photogrammetry using control points (GCPs) near a reflective/refractive area (water body), where the objective was to evaluate these points, analysing the independence, normality and randomness and other basic statistic. The images were obtained with a 16 MP Canon PowerShot ELPH 110S with a modified NiR band and a multispectral sensor Parrot Sequoia, both embedded in a hex-rotor UAV in flight over the Unisinos University's artificial lake in the city of São Leopoldo, Rio Grande do Sul, Brazil. Due the distribution of the data found to be not normal, we applied non-parametric tests Chebyshev's Theorem and the Mann-Whitney's U test, where it showed that the values obtained from Sequoia DSM presented significant similarities with the values obtained from the GCP's considering the confidence level of 95%; however, this was not confirmed for the model generated from a Canon camera, showing that we found better results using the multispectral Parrot Sequoia. [ABSTRACT FROM AUTHOR]