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United States Department of Agriculture

Agricultural Research Service

Research Project: Reuse of Municipal Waste Waters for Irrigation: Plant Response and Impact on Soil Properties
2013 Annual Report


1a.Objectives (from AD-416):
To determine the impact of treated municipal waste water and other waste waters on soil physical and chemical properties and plant response (biomass, marketable yield and growth/appearance (turfgrass) and compare this response to that of degraded low organic natural waters.


1b.Approach (from AD-416):
To conduct laboratory and field research as needed to evaluate the use of treated municipal waste waters and other waste waters for irrigation of crops and turfgrass. This will include measurement of soil physical properties and plant growth and yield characteristics. Documents SCA with University of California - Riverside.


3.Progress Report:

The project is also related to objective 2 of the parent project, "Improve our ability to predict the impact of degraded waters on infiltration into soils and plant response to irrigation with these waters, c) develop decision tools for use of waters impacted by salinity and potentially toxic elements, with emphasis on boron. In this project we examine the impact of combined drought and salinity stress, utilizing degraded waters on turfgrass quality and crop yield".

We have completed an experiment on the cooperator fields, University of California, Riverside, California (UCR) to evaluate the combined effects of drought and degraded water (saline and sodic) on turfgrass production and quality. Salinity and water sensors and soil solution samplers were monitored and water and soil samples were analyzed. The field was planted in ryegrass, a relatively salt sensitive grass, but one commonly utilized as a winter overseeding grass in arid regions when Bermuda grass is used in either golf fairways or recreational lands irrigated with treated municipal waste water. The line source sprinkler system had alternating lines of fresh and degraded water (electrical conductivity of 3 deciSiemens per metre (dS/m) - thus generating a continuum of salinities from one line in the field to the next. Along the line source we used sprinklers of 4 different output volumes in different regions, from 130% of evapotranspiration to 60% of optimal evapotranspiration. Each water quantity treatment was replicated, thus enabling study of different irrigation quantities (under a range of salinity conditions. Results after over one year of study indicated that stresses were cumulative, with the worst conditions being saline and water stressed. Reductions in water application below 100% of evapotranspiration resulted in reduction in biomass production, reduction in visual appearance, and loss of vegetative cover. These results indicate that there is little opportunity to irrigate ryegrass to below 100% of evapotranspiration needs, and the best strategy is to pursue use of alternative, drought and salt tolerant grasses.

We initiated and completed a study on the response of spinach to salinity with two water compositions. We conducted the experiments in the outdoor sandtank facility at the Salinity Laboratory in late fall. Plots were instrumented with sensors to monitor water potential, and salinity was maintained constant in each plot. We report that the baby spinach variety tested was much more salt tolerant than indicated for spinach in the salt tolerance database and there was no effect of irrigation water composition on plant yield. The experiment was repeated under warmer climatic conditions in the spring of 2013. Under warmer conditions the crop salt tolerance was reduced, consistent with the greater transpirational demands during that season.


Last Modified: 8/22/2014
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