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C. Chen, R.J. Roseberg, D. Sugar and J.S. Selker

A study was undertaken to determine if microsprinkler irrigation (MI) can provide sufficient water and produce similar yield and quality of pear (Pyrus communis L.) fruit as flood irrigation (FI) in a cracking (shrinking-swelling) clay soil. Soil water content and fruit quality attributes were measured under MI and FI in 2 years. Water potential of the upper 120 cm (47 inches) of soil was maintained at 0.1 to 0.3 MPa (14.5 to 43.5 lb/inch2) through most of the growing season in both MI and FI treatments. MI and FI treatments did not differ in their effect on fruit size, yield, or firmness decline during cold storage. No consistent effect on fruit susceptibility postharvest fungal decay related to irrigation treatment was observed. MI has the potential to reduce chemical and water movement to groundwater, while providing sufficient water to produce satisfactory yield and fruit quality in a cracking clay soil.

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Shaun F. Kelly, J.L Green and John S. Selker

Time Domain Reflectometry (TDR) is used to measure in situ soil moisture content and salinity of porous media. Commercially available TDR systems used for field measurements have limited use in laboratory scale experiments where short high resolution probes are needed. A short TDR probe was designed for use with high bandwidth TDR instruments currently available. The probes are designed from SMA bulkhead connectors using gold-plated stainless steel wire 0.035 inches in diameter. A 20.GHz digital sampling oscilloscope (11801; Tektronix, Beaverton, Ore.) with an SD-24 TDR sampling head is used with the probes to determine water content and ion concentrations in porous media. The 7.5- and 3.0-cm-long probes were used to measure soil moisture content and ion concentrations in laboratory columns. Fertilizer and water gradients were observed by using bromide salts brought into contact with the top of laboratory columns, 7.6 cm in diameter and 18 cm long, packed with container media [1 peat: 1 vermiculite v/v)]. Soil moisture measurements in the presence of high concentrations of salts were made by insulating the probes with Teflon heat-shrinkable tubing to minimize conductivity losses.