Fine sand soils important to Florida agriculture have volumetric soil water content values (θv) of <0.10 cm3 cm−3 after drainage due to gravity has ceased. Small changes in θv in the range of 0.02 to 0.08 cm3 cm−3 can greatly affect plant available water and, therefore, good calibration of soil water content sensors is necessary. The EnviroSCAN (Sentek Pty. Ltd., South Australia) is a multiple sensor capacitance probe capable of continuous measurement of soil water content by volume (θv). Many fine sand soils in Florida have plant available θv values of ≤0.08 cm3 cm−3 The manufacturer's calibration curve has very few data points <0.10 cm3 cm−3 θv and no data in the 0.02 to 0.04 cm3 cm−3 θv range. Because of the lack of data in this range, a calibration curve from 0.02 to 0.08 cm3 cm−3 θv was developed for Candler fine sand (hyperthermic, uncoated Typic Quartzipsamments), Apopka fine sand (loamy, siliceous, hyperthermic Grossarenic Paleudults), and Immokalee fine sand (sandy, siliceous, hyperthermic Arenic Alaquods) in two locations in Florida. Since calibration curves for the three soils did not differ significantly, data from the three soils were combined. An exponential calibration curve was developed This equation provides substantially different estimates of water content in the 0.02 to 0.08 range than values obtained from the manufacturer's calibration. This improved calibration extends the useful range of the EnviroSCAN to include an important group of soils with very low water holding capacity.

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Knowledge of crop response to temporary waterlogging is important in the development of effective water management practices. A field study was conducted to determine the response of soybean rGlvcine max. (L.) Merr] grown on a poorly drained, clayey soil to temporary flooding at three growth stages. The four treatments were soybean flooded for seven consecutive days at either VI, V4 or R2 growth stages at a flood height of 0.03 m above the soil surface and a well-watered control. Flooding for seven consecutive days wetted but did not saturate the lower parts of the soil profile. This was attributed to the swelling by the montmorillonitic clay and subsequent sealing of the soil near the surface. In general, Eh and ODR decreased gradually during the flood, but 1045 increased as the soil dried upon removal of the flood. Canopy heights and dry weights of the flooded soybeans were dependent on plant growth stage at flooding and time of measurement but were lower than the control. When flooded at the VI or V4 growth stages, concentrations of N and K in the above-ground plants were lower than the control after the flood. Three weeks after the flood was removed higher concentrations of these elements were found. When flooded at R2, concentrations of N and K were lower than in the control. Few differences were found in the plant concentrations of Ca, Mg, Mn, Fe, Al, and Na in the plant due to the flood, but by the end of the growing season, concentrations of Mn, Fe and Al were higher in the R2 flooded soybeans than in the other treatments. Seed yield response of the soybeans depended upon plant growth stage at flooding. The soybeans were particularly sensitive to the seven days of continuous flood at the R2 growth stage. Values of relative seed yield were 88, 83, and 44 % of the well watered-control for the VI, V4 and R2 growth stages, respectively.Differences in seed yield were found with cultivar and with cultivar*flood treatment.