break down into carbon dioxide, water, and microbial biomass in soil under controlled laboratory conditions. Various BDMs have been shown to degrade after soil incorporation in the field; yet following breakdown in the soil to completion warrants further
Jenny C. Moore, Brian Leib, Zachariah R. Hansen, and Annette L. Wszelaki
J.P. Mitchell, C. Shennan, D. Peters, and R.O. Miller
Sustainable alternatives for saline drainage water management in areas such as California's San Joaquin Valley are needed. Previous work has demonstrated the short-term potential for reuse of saline drainage water for irrigation in this area. Results from our 6-year cyclic drainage reuse study, however, indicate that soil structural problems may occur which can greatly reduce stand establishment and crop yields in periodically salinized soils. To prevent these problems, we are evaluating the effectiveness of winter cover crop incorporation and gypsum applications relative to conventional fallows, for improving/maintaining soil physical properties and crop productivity in cyclically salinized soils. Six winter cover crop/fallow treatments have been imposed upon a rotation of tomatoes, tomatoes and cotton as summer crops. By monitoring water use, relevant soil physical and chemical properties as well as crop performance during the course of this 3-year rotation study, we are assessing the potential benefits and constraints of using winter cover crops in drainage water reuse systems.
J.P. Mitchell, D.M. May, and C. Shennan
76 POSTER SESSION 9 Water Stress, Water Utilization, & Water Management/Cross-Commodity
D.A. Devitt, R.L. Morris, and L.K. Fenstermaker
We investigated foliar damage to five landscape species sprinkler irrigated with either reuse water or one of five synthesized saline waters that contained elevated single salts mixed with Colorado River water, all having similar electrical conductivities. The experiment allowed us to compare the impact of elevated concentrations of Na, Mg, Ca, Cl, and SO4 on an index of visual damage (IVD), tissue ion concentrations, and spectral reflectance. Waters containing elevated concentrations of MgCl2 or NaCl caused greater foliar damage than did MgSO4, Na2SO4, CaSO4, or reuse water, as recorded in higher IVD values (p < 0.05). Privet and elm were damaged to a greater extent (higher IVD values) than were desert willow, guava and laurel (p < 0.05). Higher IVD values were recorded for all species irrigated with the MgCl2 waters, with mortality recorded in privet. Tissue nutrient concentrations were correlated with the IVD values. In the case of guava, 61% of the variability in the IVD could be accounted for based on N, P and K (P < 0.01). On a treatment basis, the single salts added to the municipal water showed little correlation with the IVD values, except in the case of MgCl2, where Mg was included in the regression equation (r 2 = 0.82, P < 0.01, IVD↑ as S04↓, Mg and P↑). Eleven different spectral indices separated based on treatment and/or species (P < 0.05). In elm, 70% of the variability in the IVD could be accounted for by including Red Edge, Normalized Difference Vegetation Index (NDVI) and Water Band Index (WBI)/NDVI. A mixed response was observed to a post 30-day irrigation rinse in an attempt to reduce IVD values. Based on our results, care should be given to monitoring not only the EC (and osmotic potential) but also the ionic composition when saline waters are blended with other water sources, with the aim of minimizing the concentration of Mg, Cl, and Na.
Larry R. Parsons*
Florida is one of the larger producers of reclaimed water in the U.S., and use of this water has increased greatly in the past ten years. The objective of this study is to compare changes in reclaimed water use by different entities over the past several years. From 1986 to 2002, total reuse treatment capacity and flow in Florida increased by 221% and 183%, respectively. In the 1980s, reclaimed water was considered to be an urban disposal problem, and cities encouraged use of this water by giving it away for no charge. Because it was free, agricultural irrigation became the largest user of reclaimed water in the mid-1990s and is still one of the larger users. From 1992 to 2002, overall agricultural land area irrigated with reclaimed water increased by 77%. Land area of edible crops irrigated with reclaimed water increased during that period but remained relatively constant around 6070 ha after 1996. Irrigation of other crops increased to 9800 ha. Golf course irrigation increased by 212% to 20,476 ha while residential irrigation increased around 8147% to 33,373 ha during this period. Total flow to ground water recharge and industrial uses increased by 125% and 424%, respectively. While agricultural irrigation is still a large user of this water, other uses such as golf course, residential, groundwater recharge, and industrial are becoming more important. Some cities are no longer willing to provide this water to agriculture for no charge as competition from other entities increases. Agriculture may have to pay for the water, use less water, or develop other water sources.
Constructed wetland biofilters have been widely used in recent years to provide secondary or tertiary water treatment, effectively reducing BOD, TSS, nitrate and ammonium, and some organic pollutants from municipal, industrial, and agricultural waste sources. The greenhouse and nursery industries, like all agricultural enterprises, have found themselves under increasing pressure to reduce or eliminate discharge of contaminated wastewater. In response, many greenhouse and nursery operators have installed, and are using, a variety of runoff containment and recirculating irrigation systems. While effective in reducing or eliminating wastewater discharge, these systems can become contaminated themselves and require treatment of the water before it can be reused in the irrigation system. Further, if the water should become contaminated and unusable, environmental discharge of this spent water from a recirculating irrigation system is perhaps even more problematic than simply allowing the excess irrigation water to be dumped in the first place. Potential contaminants in a recirculating irrigation system could include pesticide and other organic residues, excess fertilizer and non-fertilizer salts, and plant pathogens. The primary concern in greenhouse and nursery discharge wastewater is usually fertilizer salts, although pesticide and other organic chemical residues may also be of concern. Biological filtration using constructed wetlands may be a simple low-cost method for greenhouses and nurseries to treat these contaminants.
Responses to a 1993 survey showed that drip irrigation was used on 36,400 ha of commercial vegetables in the southeastern and mid-Atlantic United States. Florida led with 44% of total drip-irrigated vegetable area, followed by Georgia, North Carolina, and Pennsylvania, with about 10% each. Drip irrigation was used most commonly on tomato, pepper, and watermelon crops. The most-important benefits of drip irrigation were improved water and fertilizer delivery efficiencies compared to other irrigation systems, such as overhead sprinklers and subirrigation. Challenges with drip irrigation included high installation cost, emitter clogging problems, need for filtration, overirrigation problems, disposal of tubing, and lack of readily available expertise. Most drip irrigation was used with polyethylene mulch and most tubing was thin-wall disposable rather than thick-wall reusable. Eighty-one percent of the drip-irrigated vegetable acreage was fertigated with N and K. Survey responses indicated that drip irrigation use for vegetables is increasing.
Nathaniel Ferraro, Darrell Bosch, James Pease, and James S. Owen Jr.
Household, commercial, and environmental demands for fresh water are increasing. As fresh water sources become scarcer, innovative technologies and policies must be developed to address and manage water-related business risks. Practices to capture
Michael C. Shannon, Catherine M. Grieve, Scott M. Lesch, and John H. Draper
Research reported herein was funded by the California Department of Water Resources (DWR B-59922), Project Manager, Fawzi Karajeh. We thank M. McGiffen, Univ. Calif., Riverside, J.D. McCreight, USDA-ARS, Salinas, Calif., D.A. Dierig, USDA
Lawrence R. Parsons, Bahman Sheikh, Robert Holden, and David W. York
The purpose of this article is to discuss several aspects of reclaimed water that are of importance today. Emphasis is placed on water reuse in Florida and California because they are two of the largest producers of reclaimed water in the United