Direct tracing of NH and NO emissions associated with urea fertilization approaches, using static incubation cells.

Nitrogen fertilization contributes significantly to crop production globally. However, low efficiency application management approaches lead to substantial N losses of which ammonia and nitrous oxide are known as environmental threats. Urea, the largest N fertilization source globally, is associated with high ammonia losses.

Reductions in root hydraulic conductivity in response to clay soil and treated waste water are related to PIPs down-regulation in Citrus.

Citrus hydraulic physiology and PIP transcript levels were characterized in heavy (clay) and light (sandy loam) soils with and without treated waste water (TWW) irrigation after a summer irrigation season and at the end of a winter rainy season recovery period. Consistent reductions in clay soils compared to sandy loam were found for fresh water (FW) and TWW irrigation, respectively, in root water uptake, as well as in hydraulic conductivity of whole plant (K plant), stem (K stem) and root (K root). Transcript levels of most PIPs down-regulated following TWW irrigation in both soils, but relative gene expression of three PIPs was significantly higher in summer for sandy soil and FW than for clay soil and TWW; their mRNA levels was significantly correlated to K root.

Impact of treated wastewater on growth, respiration and hydraulic conductivity of citrus root systems in light and heavy soils.

Roots interact with soil properties and irrigation water quality leading to changes in root growth, structure and function. We studied these interactions in an orchard and in lysimeters with clay and sandy loam soils. Minirhizotron imaging and manual sampling showed that root growth was three times lower in the clay relative to sandy loam soil.

Lower leaf gas-exchange and higher photorespiration of treated wastewater irrigated Citrus trees is modulated by soil type and climate.

Water quality, soil and climate can interact to limit photosynthesis and to increase photooxidative damage in sensitive plants. This research compared diffusive and non-diffusive limitations to photosynthesis as well as photorespiration of leaves of grapefruit trees in heavy clay and sandy soils having a previous history of treated wastewater (TWW) irrigation for >10 years, with different water qualities [fresh water (FW) vs TWW and sodium amended treated wastewater (TWW + Na)] in two arid climates (summer vs winter) and in orchard and lysimeter experiments. TWW irrigation increased salts (Na(+) and Cl(-) ), membrane leakage, proline and soluble sugar content, and decreased osmotic potentials in leaves of all experiments.

A continuous active monitoring approach to identify cross-connections between potable water and effluent distribution systems.

A continuous active monitoring approach was developed for identification of cross-connections between potable water supply systems and treated wastewater effluent reuse distribution systems. The approach is based on monitoring the oxidation reduction potential (ORP) at the potable water system while injecting sulfite (a reducing agent) into the effluent line. A sharp decrease in the ORP of the potable water would indicate a cross-connection event.