RESUMO A calibração de modelos é fator fundamental para a obtenção de elevadas acurácias na estimativa do crescimento e rendimento das culturas. Este estudo teve como objetivo parametrizar os coeficientes genético e de ecotipo do modelo DSSAT/Canegro para cinco cultivares de cana-de-açúcar mantidas sob três manejos hídricos, além de avaliar a precisão do modelo na estimativa da produtividade de colmos, produtividade de açúcar e altura de colmos. Foram utilizados dados experimentais de campo obtidos em dois anos de cultivo (2016 e 2017) na FCAV/Universidade Estadual Paulista, Jaboticabal, SP. As cultivares foram mantidas sob irrigação suplementar, irrigação deficitária e não irrigadas. Foram utilizados os dados do tratamento de irrigação suplementar (sem estresse) para a parametrização de cada cultivar. A acurácia do modelo foi verificada pela correlação de Pearson (r), raiz do erro quadrático médio (RMSE), erro médio (MBE), índice de concordância (d) e coeficiente de confiança (c). O modelo DSSAT/Canegro apresenta elevada acurácia na predição da produtividade de colmos e de açúcar da cana-de-açúcar cultivada sob regimes hídricos, apresentando-se como alternativa viável na simulação do rendimento da cultura. Para melhor performance do modelo DSSAT/Canegro, é necessário a parametrização das variáveis relacionadas ao ecotipo das cultivares, além dos coeficientes específicos das cultivares.

ABSTRACT Model calibration is a fundamental factor to obtain high accuracy in the estimation of crop growth and yield. This study aimed to parameterize the genetic and ecotype coefficients of the DSSAT/Canegro model for five sugarcane cultivars kept under three water managements, besides evaluating the accuracy of the model in predicting sugarcane stalk yield, sugar yield and height. Experimental field data were obtained from two years (2016 and 2017) of cultivation at FCAV/Universidade Estadual Paulista, Jaboticabal, SP, Brazil. The cultivars were maintained under supplementary irrigation, deficit irrigation and no irrigation. Data of the supplementary irrigation treatment (without stress) were used for the parameterization of each cultivar. Model accuracy was assessed by Pearson correlation (r), root mean squared error (RMSE), mean bias error (MBE), index of agreement (d) and confidence coefficient (c). The DSSAT/Canegro model is highly accurate in predicting stalk and sugar yields of sugarcane grown under water regimes, presenting itself as a viable alternative in sugarcane yield simulation. For better performance of the DSSAT/Canegro model, it is necessary to parameterize the variables related to the ecotype of the cultivars, besides the specific coefficients of the cultivars.

ABSTRACT The elaboration of maps to characterize the spatial variability of soil attributes assists in the strategic planning and decision making of agricultural managers. Precision and accuracy of maps are related to the ideal sampling density to characterize the variability pattern. This study was conducted with the aim of identifying the sampling density to represent the variability of soil physical quality using attributes with different magnitudes of variation in an area cultivated with coffee. Three approaches were used to find the most adequate sampling density (geostatistical analysis, percentage of error associated with the sampling density, and coefficient of variation). A total of 145 soil samples were collected at a depth of 0-0.20 m at the crossing points of a regular grid with a spacing of 50 m. The percentage of clay, silt, and sand, macroporosity, microporosity, total pore volume, and soil density were determined. The data were submitted to descriptive statistical analysis. For elaborating the variability maps with up to 15% error and soil attributes with a coefficient of variation close to 50%, a sampling density of 3 points ha−1 is suggested.

ABSTRACT Inadequate and intensive management of soils can promote changes in their chemical attributes and impair the quality of surface and groundwater, especially in hillside areas. Therefore, the aim of this study was to identify possible changes in soil and water chemical composition of hillside areas cultivated with horticulture. For this, chemical attributes of three soil depths (0-10, 10-30, and 30-60 cm) were determined in three hillside positions (upper, middle, and lower thirds) of five hillside and adjacent forest areas, as well as water from reservoirs for agricultural use and human consumption. Compared with the forest area, horticultural areas present soil with lower organic matter content and CEC, but higher values of pH, base saturation, and contents of P, Ca, and K. In cultivated areas, CEC decreases from the upper to the lower hillside, without significant changes in other soil fertility parameters. Soil fertility decreases with depth, regardless of soil management and hillside position. Water from reservoirs adjacent to hillside areas with horticulture is more acidic and has a higher nitrate content, especially during rainy periods.