This article presents the results of a study aimed at evaluating the behavior of water in the soil based on measurements of humidity in the soil profile. Soil humidity data were acquired in the period between June 16 and September 08, 2009, using a set of 96 Watermark TM sensors installed at three soil depths, 20, 60, and 120 cm and in two plots. One plot (with 48 sensors) located in a four-year old Eucalyptus area and the other plot located in an adjacent native forest area. Both plots have the same slope and aspect characteristics. Soil physical and chemical characteristics were determined at the laboratory using collected samples. Results indicate that under Eucalyptus cover at the intermediate soil layer (60 cm) the humidity conditions is more stable. When precipitation occurs the top and intermediate layers respond more rapidly and the deeper layer requires more time to respond. Comparison between Eucalyptus and native forest cover indicate that forest cover had consistently higher water content in the soil at all three depth layers in this short term of observation.

The management of spatial arrangement in soybean culture (Glycine max L., Merrill) from seeding density and row spacing is an important tool that contributes to yield growth. The objective of this study was to evaluate the influence of spatial arrangement in the development and the production components of soybean in the Piauí Cerrado savanna. The experimental design was completely randomized, with subdivided plots and four replicates. The main plots consisted of different row spacing (17.5 cm, 25 cm, 50 cm and 76 cm) and subplots consisted of plant populations as follows: recommended (280,000 plant/ha); 50% below recommended; 50% and 100% higher than recommended. The subdivided plots had six lines of five metres in length. The highest growth component values (plant height, stem diameter and number of nodes) were observed in the larger spacing (50 cm and 76 cm) and lower populations (recommended and 50% below recommended). The highest component yield values (number of grains per pod, number of grains per plant, number of pods per plant, weight of one thousand seeds and productivity) were observed in the larger spacing (50 cm and 76 cm) and in the recommended population for the cultivar.

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