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Water use in the United States increased from 1950 to 1980 and decreased from 1980 to 1985, on the basis of estimates compiled at 5-year intervals by the U.S. Geological Survey. Total withdrawals of freshwater and saline water during 1985 were 1,510 million cubic meters per day, a rate more than double that estimated for 1950 and 10 percent less than that estimated for 1980. For most categories, the rate of increase in water use declined from 1970 to 1975 and from 1975 to 1980. Withdrawals for thermoelectric-power generation and irrigation, the two largest categories of use, were 13 and 6 percent, respectively, less during 1985 than during 1980. The combined total for industrial, commercial, and mining water use during 1985 was 25 percent less than during 1980--the lowest combined estimate for these categories since the compilations began in 1950. The decrease in water use during 1985 compared to 1980 can be attributed to the following important factors:

  1. Streamflow generally was more plentiful during 1985 than during 1980 because of more rainfall; this reduced the dependence on ground water in many areas and the need to irrigate in some areas.

  2. The economic slowdown, improved plant efficiencies, depressed commodity prices, and new technologies that require less water decreased the requirements for industrial and irrigation water.

  3. Enhanced awareness by the general public to water resources and conservation programs in many States probably reduced water demands.

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Water conservation in a landscape is an important issue because periodic water shortages are common in many regions of the world. This increases the importance of specifying landscape plants that require less water and matching the plant to site microclimates. Our objectives were to establish water-use rates for three herbaceous landscape plants and to determine the level of water reduction these plants can tolerate while maintaining both visual and landscape quality. Water use rates were determined for Schizachyrium scoparium (Little bluestem), Hosta spp. (Hosta) and Festuca cinerea `Dwarf' (Dwarf blue fescue) in studies using pot lysimeters at the Univ. of Nebraska Horticulture Research Greenhouse facility. Each lysimeter was watered to saturation, allowed to drain to field capacity, and weighed. The lysimeters were weighed again 24 h later, and the process was repeated to determine daily evapotranspiration. Results indicated that hosta used less water than dwarf blue fescue and little bluestem. In a subsequent study to compare the relative effects of withholding irrigation among these species, seven groups of five replicates of each species were grown in 1 peat: 0.33 vermiculite: 0.66 soil: 1 sand (by volume) in 7.6-L containers. Each container was watered to saturation, allowed to drain for 24 h to reach field capacity, and allowed to dry down in 10-day increments. Results of the dry-down study indicated that little bluestem maintained the best visual quality for the longest duration of drought, followed by dwarf blue fescue and hosta in decreasing order of visual quality.

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The ongoing drought in the Intermountain West has brought a great deal of attention to water conservation over the past several years. During that time, turfgrass irrigation has been targeted as a source for large potential water savings. Some communities promote downsizing turfgrass areas as the best water conservation measure. In reality, turfgrass controls erosion, reduces evaporation from a site, and provides a safe surface for human activities. One alternative to elimination would be wider use of low water-use-grasses appropriate to the area. However, many questions arise regarding the choice of such grasses and their management. Our research addresses these questions. Plots have been established at Montana State University, Bozeman; Utah State University, Logan; and USDA-NRCS Plant Materials Center, Bridger, Mo. The grasses considered include 12 single species and 12 mixed species stands of `Cody' buffalograss, `Foothills' Canada bluegrass, `Bad River' blue grama, sheep fescue, sandberg bluegrass, muttongrass, and wheatgrasses `Sodar' streambank, `Road Crest' crested, `Rosana' western, and `Critana' thickspike with Kentucky bluegrass and tall fescue as controls. Line source irrigation allowed the plots to be evaluated at a number of levels of irrigation. Experimental measurements on the plots included growth response as determined by clipping yield and quality ratings, and species composition. Fescues and wheatgrasses retained their color, texture, and density throughout the growing season, regardless of moisture level. Warm-season grasses performed well in June, July, and August only, and worked poorly in mixtures as the green cool-season grasses could not mask the brown dormant leaves in cooler weather.

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Transpiration, respiration, dry weight gain, and water accumulation were measured to quantify the total carbon balance, total water utilization, carbohydrate cost for fruit growth, and water use efficiency in developing fruit of grapefruit (Citrus paradisi Macf). Rate of net carbon loss and net water loss (mg g-1FW hr-1) both decreased during fruit development. On a whole fruit basis, total carbon demand was reduced during the period of peak expansion, then increased rapidly during fruit maturation. In contrast, whole fruit rates of water loss and water utilization (loss plus accumulation) peaked at about 100 days after anthesis, then decreased toward fruit maturation. Carbohydrate cost for fruit growth was greatest (3.49 g sucrose g-1DW) at the early stage of fruit development (immediately following anthesis), whereas water use efficiency peaked (193 mg DM g-1 H2O) at the final stage of fruit development. The thickness of albedo and pectin content in fruit may contribute to the observed water conservation. Total estimated carbon cost of grapefruit development indicates approximately 120 g of sucrose would be necessary for production of a 450 g fruit (77 g DW) at 22 C.

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Due to increasing consumption of water in landscapes and concern over conservation of water resources, this study was conducted to determine the effect of fertilizer source on water consumption of turf and ornamentals and to compare total water use (WU) of st. augustinegrass and ornamentals. The experiment was performed in a climate-controlled greenhouse at the G.C. Horn Turfgrass Field Laboratory at the University of Florida in Gainesville. `Floratam' st. augustinegrass (Stenotaphrum secundatum Walt. Kuntze) was compared to a mix of common Florida ornamentals including canna (Canna generalis L.H. Bailey), nandina (Nandina domestica Thunb.), ligustrum (Ligustrum japonicum Thunb.), and allamanda (Allamanda cathartica L.). All plants were grown in 300-L plastic pots in Arredondo fine sand. There were three fertilizer treatments [quick-release fertilizers (QRF) 16–4–8 and 15–0–15, and slow-release fertilizer (SRF) 8–4–12] applied at 4.9 g N/m2 every 60 days. Water was applied as needed to maintain turgor and turfgrass pots were mowed weekly. Experimental design was a randomized complete block design with four replications. Visual quality ratings and time domain reflectometry (TDR) data were collected weekly. Both turf and ornamentals consumed less water and had higher water use efficiency (WUE) when treated with SRF. Ornamentals consumed from 11% to 83% more water than turf, depending on season. These results may have implications in future research on irrigation management to verify WUE between turf and ornamentals in an urban landscape.

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Landscape water consumption has become a prime target for water conservation and regulation. Imposing water restrictions during landscape establishment is detrimental to plants that have not developed sufficient root systems to compensate for transpirational water losses. Generally, municipalities regulate irrigation frequency but not application rate. Application frequency affects establishment rates of shade trees, but the effects on shrub establishment are not well documented. This study evaluated three irrigation frequencies during establishment of Ilex cornuta `Burfordii Nana' and Viburnum odoratissimumin a landscape. To simulate maximum stress, both species were transplanted into field plots in an open-sided, clear polyethylene covered shelter. Each species was irrigated either every 2, 4, or 7 days, and received 9 L of water per plant per event. Predawn, midday, and dusk water potentials were recorded at 28-day intervals and cumulative stress intervals calculated. Water potentials were taken the day prior to irrigation (maximum stress day) and the day of irrigation (minimum stress). Growth indices were also recorded. As days after transplant (DAT) increased, significant declines in cumulative water stress of Ilexwere found among treatments on the day of maximum stress. The 7-day treatment declined at a faster rate than the other treatments tested. No differences were found for Viburnum. No significant differences were found on the day of irrigation as DAT increased. Differences in canopy size were not significant among treatments for either species.

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Arizona's golf and sod industry generates $280 M year-1 in revenue and surpasses the vegetable, cotton and dairy industries. Despite the economic worth of turf, a need still exists to conserve the limited supply of potable water in this harsh Sonoran Desert environment. Mandatory water conservation programs have been developed for many sectors of the Arizona economy. To meet this challenge, the turfgrass industry and government bodies have begun to contribute to the development of research programs which reduce turfgrass water requirements and dependence upon potable water. Current research includes a) determining the minimum water requirements of higher quality turf under conditions of high temperatures and vapor pressure deficits; b) the turfgrass potential of grasses with lower water requirements than bermudagrass; c) the development of a statewide weather station network to predict daily turfgrass water use; and d) determine management strategies for turfgrass irrigated with wastewater effluent. The overall goal of these programs is to produce high quality and functional turf with 20 to 50 percent less water.

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The use of microirrigation in Florida citrus production has increased rapidly in recent years. Most new groves are now being developed with microspray or drip irrigation. Many existing sprinkler and seepage (subirrigation) systems have also been converted to micro irrigation. Although water management districts have encouraged the use of micro irrigation for water conservation, research results which solved problems with the practical implementation of this technology and which demonstrated economic incentives are primarily responsible for its popularity in Florida citrus production. Research programs have (1) developed management techniques to eliminate emitter clogging, (2) demonstrated the effective use of microspray systems for freeze protection, (3) increased young tree growth with respect to conventional irrigation methods, (4) demonstrated the cost-effectiveness of microirrigation, and (5) developed management techniques for efficient use of water and nutrients in fruit production.

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The use of microirrigation in Florida citrus production has increased rapidly in recent years. Most new groves are now being developed with microspray or drip irrigation. Many existing sprinkler and seepage (subirrigation) systems have also been converted to micro irrigation. Although water management districts have encouraged the use of micro irrigation for water conservation, research results which solved problems with the practical implementation of this technology and which demonstrated economic incentives are primarily responsible for its popularity in Florida citrus production. Research programs have (1) developed management techniques to eliminate emitter clogging, (2) demonstrated the effective use of microspray systems for freeze protection, (3) increased young tree growth with respect to conventional irrigation methods, (4) demonstrated the cost-effectiveness of microirrigation, and (5) developed management techniques for efficient use of water and nutrients in fruit production.

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A closed, insulated, pallet production system (CIPPS) has been designed to meet current challenges: 1) Elimination of production related pollution. 2) Reduction and conservation of resources. 3) Improvement of working conditions. 4) Alternatives to pesticides. 5) Prevention of temperature extremes and rapid temperature fluctuations in the plant environment. Biological feasibility of CIPPS was established in research on pathogen epidemiology, water and fertilize efficiency, plant growth and development in CIPPS. Water and fertilizer ion movement-removal in the closed system was plant-driven in response to growth and transpiration; water and fertilizer use in CIPS was 10% of that applied to open containers. Growth of 28 plant species ranging from herbaceous annuals to woody perennials was greater in CIPPS than in control, individual containers. Phytophthora cinnamomi did not spread from inoculated to noninoculated plants within CIPPS. Inoculation with nonpathogenic bacteria increased plant growth (gfw) in CIPPS but not in open plant containers.

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