Irrigating and Fertigating with High Frequency Subsurface Drip Irrigation can prevent Drainage and Groundwater Contamination

摘要

It is essential to manage and quantify the movement of soil water and nitrate through and below the crop root zone to reduce the transport of nitrogen to the groundwater. High frequency subsurface Drip Irrigation (HF-SDI) has achieved these objectives when used with annual crops grown in clay loam soil. One objective of this research is to demonstrate the validity of the HF-SDI for irrigating perennial crops growing in sandy loam soils. A large weighing lysimeter filled with Hanford sandy loam soil (coarse-loamy, mixed, thermic Typic Xerorthents) has been used since 2010 to measure hourly evapotranspiration, irrigation and drainage in a pomegranate orchard irrigated with HF-SDI. In 2013, 8 calibrated heat dissipation soil matric potential sensors (SMP)were installed in the lysimeter in two columns of 4 SMP sensors each at depths of 0.61, 0.91, 1.22 and 1.52 m. from the soil surface. Hourly SMP measurements were used to calculate the hydraulic gradient and infer the leaching potential under HF-SDI. Since early 2013 when the SMP sensors were installed, the calculated hydraulic gradients have been close to zero and no deep percolation was measured by the lysimeter even though over 810 mm of irrigation water was applied to the lysimeter in 2014. This research shows that similar to previous reports for annual crops grown in a clay loam soil, the HFSDI systems were also capable of irrigating efficiently and controlling movement of water and nitrates under perennial crops being grown on coarse soils. In addition, yield data from the pomegranate orchard demonstrated that subsurface drip irrigation provides higher yields and water use efficiency compared to surface drip irrigated with the same frequency as subsurface drip.