Subsurface soil water redistribution on the South African Tukulu, also referred as the Cutanic Luvisols in other countries, was evaluated following single run irrigation （20, 40, 80 and 160 L/min inflow rates） in 90...Subsurface soil water redistribution on the South African Tukulu, also referred as the Cutanic Luvisols in other countries, was evaluated following single run irrigation （20, 40, 80 and 160 L/min inflow rates） in 90 m furrows. Changes in soil water content （SWC） at three horizons were monitored using neutron water meter. Measurements were made every 10 m starting 5 m from the furrow inlet for 455 h. HYDRUS-2D software was used to estimate soil hydraulic parameters through inverse optimization algorithms for redistribution at the inlet, midpoint and furrow end. Optimized model parameters compared with initial estimates recorded satisfactory agreement between measured and predicted soil water content, despite spatial variability. Effective hydraulic conductivity （Keff） for 0-600 mm and 0-850 mm profile flow domains demonstrated linearity with SWC although inconsistencies under field conditions were inevitable. The underlying layer restricted gravity and augmented redistribution with Keff assuming a steeper gradient than normal. Conversion of KCff and soil water content into a ratio assisted in quantifying rate of redistribution at 0-600 mm and 0-850 mm profile depth. Vertical redistribution was found to be limited within the upper 600 mm depth thus providing the opportunity to develop furrow irrigation with confidence that water productivity is optimized.展开更多
文摘Subsurface soil water redistribution on the South African Tukulu, also referred as the Cutanic Luvisols in other countries, was evaluated following single run irrigation （20, 40, 80 and 160 L/min inflow rates） in 90 m furrows. Changes in soil water content （SWC） at three horizons were monitored using neutron water meter. Measurements were made every 10 m starting 5 m from the furrow inlet for 455 h. HYDRUS-2D software was used to estimate soil hydraulic parameters through inverse optimization algorithms for redistribution at the inlet, midpoint and furrow end. Optimized model parameters compared with initial estimates recorded satisfactory agreement between measured and predicted soil water content, despite spatial variability. Effective hydraulic conductivity （Keff） for 0-600 mm and 0-850 mm profile flow domains demonstrated linearity with SWC although inconsistencies under field conditions were inevitable. The underlying layer restricted gravity and augmented redistribution with Keff assuming a steeper gradient than normal. Conversion of KCff and soil water content into a ratio assisted in quantifying rate of redistribution at 0-600 mm and 0-850 mm profile depth. Vertical redistribution was found to be limited within the upper 600 mm depth thus providing the opportunity to develop furrow irrigation with confidence that water productivity is optimized.
