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The objective of this study was to assess, during three years, the spatial arrangement that will enhance the morpho-productive development of Jatropha curcas L. in association systems with staple crops. It was hypothesized that the association of crops is a factor that determines the behavior of the species and the development of agroenergetic farms, considering rainy and low rainfall periods. A quasi-experimental design was used, and four treatments were tested: 1) J. curcas (Jc) in monoculture; 2) 50 % of the area with Jc and 50 % planted with food crops in rotation (CA); 3) Jc intercropped with CA; and 4) area planted with CA. A principal component statistical analysis was performed with the variables fruit yield and associated crop yield using 95 % confidence intervals from a Student's t-test. The number of bunches and total fruit and seeds harvested from Jc were shown to be the most important and had a positive correlation for the first component in each period. As for fruit yield, the highest values were achieved in monoculture. Although high yields were not attained in CA, the relationship is regarded favorable since the use of polycultures is viable, fundamentally in the arrangement of 50 % Jc + 50 % CA, being positive the biological efficiency given by the diversification and the best equivalent land use. [ABSTRACT FROM AUTHOR]

Mechanical actions exerted by diverse categories of machines are used to take the soil to the most desirable physical state. The mechanical operations are carried out in the soil with or without the plant and on the plant for harvesting with high yields. All these actions can affect the soil microstructure, its density and content of organic matter, as well as its capacity of cation exchange, its fertility and productivity. To value the behavior of these properties, Lixiviated Red Ferrallitic soils were studied in areas without cultivating, cultivated with sugar cane (Saccharum officinarum L.) during twelve and seventy-five years, cultivated with medicinal plants for twenty years and cultivated with varied crops for eighteen years, with irrigation. It was found that the pH (H2O and KCl) and the hydrolytic acidity increased as years of sugar cane cultivation increased, which did not happen in the areas without cultivating and in soils dedicated to medicinal plants. In the Red Ferrallitic Lixiviated fields with several cultivations and irrigation, the pH reached values above seven due to the high content of calcium in irrigation waters derived from karst region, effect generated by the climate change. [ABSTRACT FROM AUTHOR]