Showing papers on "Water use published in 1991"

Nitrogen Fertility Influence on Water Stress and Yield of Winter Wheat

Abstract: Available soil water and N fertility are the primary factors limiting dryland winter wheat (Triticum aestivum L.) yields in the Central Great Plains. The objective of this field study was to determine how the level of N fertilization influences water use, water stress, and yield of dryland winter wheat grown in the area. The study was conducted during the 1988 and 1990 growing seasons on a Platner loam (fine, montmorillonitic, mesic Aridic Paleustoll) near Akron, CO. Nitrogen fertilizer was broadcast as NH 4 NO 3 at 0, 28, 56, 84, and 112 kg N ha −1 . Canopy temperatures were measured with an infrared thermometer and used to compute the crop water stress index (CWSI) (...)

Water Deficit Effects on Maize Yields Modeled under Current and “Greenhouse” Climates

Abstract: The availability of water imposes one of the major limits on rainfed maize (Zea mays L.) productivity. This analysis was undertaken in an attempt to quantify the effects of limited water on maize growth and yield by extending a simple, mechanistic model in which temperature regulates crop development and intercepted solar radiation is used to calculate crop biomass accumulation. A soil water budget was incorporated into the model by accounting for inputs from rainfall and irrigation, and water use by soil evaporation and crop transpiration. The response functions of leaf area development and crop gas exchange to the soil water budget were developed from experimental studies (...)

Water Use by No-Till Winter Wheat Influence of Seed Rate and Row Spacing

Abstract: Management practices are required in rainfed agriculture of western Canada to reduce early season water evaporation from soil relative to loss by transpiration. The objective of this study was to measure the effect of two seed rates and two row spacings on the pattern of water use and water use efficiency (WUE) of no-till winter wheat (Triticum aestivum L.). Nine field trials were conducted on Udic Haploboroll and Mollic Cryoboralf soils in Saskatchewan from 1987 to 1989 (...)

Effect of drought stress on residual transpiration and its relationship with water use of wheat.

Abstract: Increasing the water use efficiency (WUE) of wheat (Triticum spp.) has long been a goal in semiarid areas. Low rates of residual (cuticular) transpiration are thought to improve yield potential of wheat under dry conditions, although the linkage is tenuous. The objective of this work was to investigate the association of residual transpiration with water use, WUE, and leaf water status in hexaploid (T. aestivum L.) and tetraploid (T. turgidum L. var. durum) genotypes grown under two watering regimes in two glasshouse experiments. Single plants were grown in 0.1-m × 1-m (0.1-m × 0.5-m in exp. 2 low-stress treatment) PVC tubes filled with soil. The watering regimes consisted of weekly replenishment of water used (low stress), or addition of sufficient water to ensure plant survival (high stress). At anthesis, flag leaf residual transpiration (rate of water loss from excised leaves), stomatal conductance, relative water content (RWC), and osmotic potential (exp. 1 only) were measured. Water use was not corre...

Efficient Spatial Allocation of Irrigation Water

Abstract: In the presence of conveyance losses, the efficient quantity of water applied falls with distance from the water source, but the amount of water "sent" (including conveyance losses) actually increases with distance from the source, except toward the tail end of the inigation system. This implies that if marginal cost pricing were implemented, farmers at the middle and lower reaches of the system would have to pay more money for less water received. The model is illustrated and alternative financing schemes compared for an empirically derived demand function for imgation water. Despite massive public investments in irrigation infrastructure, ex post evaluations of irrigation projects in developed and developing countries indicate that actual benefits are substantially below projected levels. Considerable evidence suggests that these low benefits are largely the result of poor on-farm water use efficiencies and rent-seeking activities that result from water charges that are low and often unrelated to water use (Chaudhry, Repetto, Bowen and Young). For example, farmers near the system headworks are said to consume a disproportionate share of irrigation water, while tail farmers are left with scanty and unreliable residual supplies (Reidinger, Wade). Many governments, faced with increasing political pressure to conserve water and reduce fiscal deficits are considering higher water charges to decrease waste and increase cost recovery from project beneficiaries. There is also increased awareness that low water charges and loosely enforced water rationing guidelines lead to environmental damages and excessive mining of groundwater resources. In general, the problems of water allocation and low user charges contribute to derivative problems in achieving efficiency, equity, fiscal stability, and environmental sustainability.

Root system parameters determining water uptake of field crops

Abstract: The distribution of a crop rooting system can be defined by root length density (RD), root length (RL) per soil layer of depth Δz, sum of root length (SRL) in the soil profile (total root length) or rooting depth (z r . The combined influence of these root system parameters on water uptake is not well understood. In the present study, field data are evaluated and an attempt is made to relate a daily “maximum water uptake rate” (WUmax) per unit soil volume as measured in different soil layers of the profile to relevant parameters of the root system. We hypothesize that local uptake rate is at its maximum when neither soil nor root characteristics limit water flow to, and uptake by, roots. Leaf area index and the potential evapotranspiration rate (ET p ) are also important in determining WUmax, since these quantities influence transpiration and hence total crop water uptake rate. Field studies in Germany and in Western Australia showed that WUmax depends on RD. In general, there was a strong correlation between the maximum water uptake rate of a soil layer (LWUmax) normalized by ET p and RL normalized by SRL. The quantity LWUmax · ET was linearly related to (RL/SRL)1/2. The data show that the single root model will not predict the influence of RD on WUmax correctly under field conditions when water-extracting neighboring roots may cause non-steady-state conditions within the time span of sequential observations. Since the rooting depth z r was linearly related to (SRL)1/2, the relation: LWUmax · ET = f (RL1/2/z r ) holds. Furthermore it was found that the maximum “specific” uptake rate per cm root length URmax was inversely related to RD1/2 and to SRL1/2 or z r of the profile. Observed high specific uptake rates of shallow rooted crops might be explained not only by their lower RD-values but also by the additional effect of a low z r . The relations found in this paper are helpful for realistically describing the “sink term” of dynamic water uptake models. Growing plants extract water from the soil to meet transpiration needs. Rates of transpiration and of water uptake are set by evaporative demand and by plant and soil factors which influence capacity to meet that demand. These factors include crop canopy size and leaf characteristics, root system characteristics and hydraulic properties of the soil and the soil-root interface. Soil and root system properties vary with depth and all factors vary in time, so that parameters related to them require constant updating over a crop season. Dynamic simulation models describe water uptake by root systems under field conditions as a function of soil depth and time. Many of these simulation approaches are based on Gardner's (1960) single root model (Feddes 1981). These simulation procedures follow the assumption that water uptake is proportional to a difference in water potential between the bulk soil and the root surface or the plant interior, to the hydraulic conductivity of the soil-plant system and to the “effectiveness” of competing roots in water uptake. The effectiveness factor accounts more or less empirically for the influence of various root system parameters on water uptake such as percentage of “active” roots absorbing water, root surface permeability, root length density determining the distance between neighbouring roots, or total root length and depth of the root system. Such models however, will not always reflect correctly the influence of root system characteristics on water uptake since these assumptions have rarely been tested under field conditions. In many instances, there is better agreement between simulated and measured total water use of plants than between predicted and observed water depletion by roots within individual layers of the soil profile (Alaerts et al. 1985). Water uptake by an expanding root system as a function of depth and time has been studied under field conditions for several crops (listed in Herkelrath et al. 1977a; Feddes 1981; Hamblin 1985). They show that the dynamics of water uptake depend on root length density and the “availability” of soil water. However, the combined influence of root length density, total root length and rooting depth on the water uptake pattern has not been assessed. An evaluation of root system parameters with respect to soil water extraction should aid our understanding of how roots perform under field conditions and may assist our efforts to formulate the water uptake function of roots in dynamic simulation studies more realistically. The aim of the present investigation is to develop an approach that relates measured water uptake rates to relevant parameters of the root systems. This approach will be confined to situations where water uptake in a soil layer is not restricted by unfavorable soil conditions, such as in wet soil, by insufficient aeration and, in dry soil, by reduced water flow towards roots or by increased contact resistance (Herkelrath et al. 1977b). We will define a maximum water uptake rate WUmax that is neither soil-limited nor appreciably limited by the decreasing permeability of aging roots. This WUmax will be related to relevant root system parameters as they exist when WUmax is observed. Hence, water uptake by roots in a very wet, as well as in a dry soil, has been excluded from consideration.

The effects of nitrogen, light and water availability on tropic leaf movements in soybean (Glycine max)

Abstract: . Rapid, tropic leaf movements and photo-synthetic responses of the heliotropic plant, soybean, Glycine max cv. Cumberland, grown under two different nitrogen, three different light and two different water treatments were examined. Measurements of leaf orientation during midday periods outdoors, and tropic reorientation of leaflets in response to vertical illumination indoors, revealed a positive, linear relationship between leaf water potential and the cosine of the angle of incidence between the leaf and the direct beam of the excitation light. This relationship was altered by nitrogen availability, such that a lower cosine of incidence (lower leaf irradiance) for a given leaf water potential was measured for plants grown under low nitrogen compared to those grown under high nitrogen. Additionally, plants grown under low nitrogen and low water availability showed more rapid rates of leaf movement compared to plants receiving high levels of these resources. Light regime during growth had no effect on the relationship between the cosine of incidence and leaf water potential. Reduced water and nitrogen availabilities during growth resulted in lower photosaturated rates of photosynthesis and stomatal conductance, as well as alterations in the relationship between these parameters. Thus, higher values for the ratio of intercellular CO2/ambient CO2 were measured for low-N grown plants (higher nitrogen use efficiencies) and lower values of this ratio for water stressed plants (higher water use efficiencies). The results show that environmental growth conditions other than water availability have the potential to modify leaf orientation responses to vectorial light in heliotropic legumes such as soybean. This has implications for the potential of heliotropic movements to minimize environmental stress-induced damage to the photosynthetic apparatus, and to modulate leaf-level resource use efficiencies.

Growth, yield, nutrient uptake and water use of banana crops under drip and basin irrigation with N and K fertilization.

Abstract: Growth, productivity, nutrient uptake and water use of bananas under drip and basin systems of irrigation with different levels of N (100, 200 and 300 g plant −1 ) and K (100, 200 and 200 g K 2 O plant −1 ) fertilization were investigated at the Indian Institute of Horticultural Research, Bangalore, in plant and first ratoon crop cycles. Plants under drip irrigation had better growth, flowered earlier, accumulated more dry matter and nutrients and produced higher yield with increased water use efficiency compared with those under basin irrigation

Responses of tea (Camellia sinensis) to irrigation and fertilizer. II: Water use

Abstract: The water use of clonal tea (Clone 6/8) in a line-source irrigation × nitrogen experiment in the Southern Highlands of Tanzania was monitored with a neutron probe during 1987 and 1988 to a depth of 3 m and 1989 to a depth of 5 m. The results for 1989 were used to calibrate a single layer water balance model which was then used to estimate water use for the preceding 1986, 1987 and 1988 dry seasons. In the model evapotranspiration was reduced linearly when the soil water deficit exceeded a critical value of 60 mm. The model predicted water use well for unirrigated, partially irrigated and fully irrigated treatments. Total extractable water was 330 to 350 mm in the 5.5 m deep root zone and estimated annual water use in 1988/89 ranged from 800 mm for unirrigated to 1200 mm for fully irrigated plots, of which about 400 mm was used in the wet season from December to April. Water use efficiencies were between 1 to 4 kg of made tea ha−1 mm−1, increasing with improving water and nutrient status. The slope (b) of the relation between the relative yield loss and the relative reduction in water use was very steep (b = 1.3) reflecting the sensitivity of shoot growth and yield of this clone to water stress.

The influence of cyst nematodes and drought on potato growth. 2. Effects on plant water relations under semi-controlled conditions

Abstract: Potatoes were grown under a permanent rain shelter in mobile containers in soil with and without potato cyst nematodes (Globodera pallida). The plants were either subjected to an early drought stress period from planting until 43 days after planting, to a late drought stress period during tuber bulking or to a drought control. Leaf water potentials, stomatal diffusion resistances for water vapour, transpiration rates, dry matter accumulation and water use efficiencies of the plants were determined periodically. Both drought and nematodes decreased leaf water potential and increased stomatal resistance.

Conjunctive Water Use to Control Waterlogging and Salinization

Abstract: A conjunctive‐use model is developed to maximize water user's return under limited and dynamic water supply for long‐term conditions. Salt distribution in the crop root zone is modeled and its effect on crop yield is also taken into account in the model. The main objective of this conjunctive‐use study is to find the optimal ground‐water extraction for stabilizing the water table at specific depths below land surface, while at the same time supplementing the surface irrigation supply. Concepts of limited and stressed irrigation are used to maximize net return. A daily crop water stress index is used to quantify crop yield reduction due to water stress over the growing season of a crop. Yield reduction due to salinity is calculated from the weighted average salinities (electrical conductivity) of applied waters. Salt distribution and transport in crop root zone are modeled using the physical soil properties and mass balance.

Role of Sociodemographic Characteristics in Projections of Water Use

Abstract: The effects of demographic and other socioeconomic variables (other than total population size) on differentials in per capita residential water use have received insufficient attention in water resource planning and water-use projection efforts. This analysis uses secondary and primary data from a study completed in Texas to examine the magnitude and nature of the effects of such factors on per capita residential water use, and to evaluate the effects of the inclusion of such variables on the accuracy of projections of water use. Using regression and standard projection-simulation techniques, the results suggest that demographic and socioeconomic variables, such as the age of the householder, racial or ethnic status, and household composition, markedly affect water use, and are often of relatively greater importance than economic, climatic, or other physical factors in explaining per capita water use. The analysis also suggests that the inclusion of these variables in water-use projection models could substantially increase the accuracy of the models in projecting aggregate levels of water use.

Soil–plant–water relations of oilseed rape ( Brassica napus and B. campestris )

Abstract: Chinoli (Brassica campestris subsp. oleifera × subsp. chinensis), Marnoo and Apetalous (B. napus), with contrasting morphological characters, were compared over four seasons in Tasmania in 1985/86 and 1986/87. The total water use estimated from a depth of 70 cm increased in proportion to irrigations. Before irrigation all the crops had a similar pattern of moisture extraction but differences between the lines, and due to irrigations, emerged after the irrigation treatments. The genotypic differences were clearer in the winter sowing of 1986/87, when the growing season was longer. Apetalous, when unirrigated, extracted a greater amount of water from the lower, wetter regions of the soil profile, particularly in the longer winter sowing when its water use was the same as in the treatment receiving one irrigation. With consistently higher stomatal conductance, Apetalous used more water than chinoli or Marnoo. It also maintained a higher turgor at lower osmotic potentials, suggesting a greater degree of drought tolerance than found in the short duration chinoli which, although it had a lower water use, also gave lower seed yields.

Water use by shrubs as affected energy exchange with building walls

Abstract: Abstract Landscape plants in urban areas are routinely grown next to buildings which are sources of sensible heat and radiation. An experimental study was conducted to explore how building walls affect water use by adjacent landscape plants. Instantaneous rates of sap flow were measured using heat-balance, stem-flow gauges attached to wax leaf ligustrum shrubs growing adjacent to all four walls of a building shell. For comparison, sap flow was also measured on shrubs grown away from the influence of the building. Peak flow in plants adjacent to each wall occurred when direct beam irradiance on the wall and wall temperature were at their maxima. Peak flow was highest in plants adjacent to east and west walls, and lowest in plants adjacent to the north wall. Longwave radiation emitted by the walls appeared to be a major factor affecting flow while reflected radiation from walls was of secondary importance because of the low albedo of the walls. Cumulative flow was greatest in the shrubs grown away from the influence of the building, probably due to the absence of any shading by walls during the day, and to wind speeds that were higher than those adjacent to the building.

Hygiene, skin infections and types of water supply in Venda, South Africa.

Abstract: The impact of the installation of a system to supply chlorinated drinking water in Venda, South Africa, on water quality, water use and health status was evaluated by means of questionnaires, examination for skin infections, and microbiological analysis of water samples. Although the water collection journey became shorter in comparison with use of traditional water supplies such as boreholes and unprotected springs, water use per caput showed no increase. The improved water supply showed no contamination with coliforms even after storage. Borehole water exhibited low coliform counts at the source, but after storage a 10- to 15-fold increase took place. Water samples from unprotected springs exhibited high coliform counts, which declined during storage. The prevalence of infectious skin diseases (27·5%) and diarrhoea (3·7%) among pre-schoolchildren showed no correlation with the quality of drinking water or the use of water per caput . Although the prevalence of infectious skin diseases did exhibit a negative correlation with the frequency of washing, no significant health benefit of the improved water supply could be demonstrated in this limited study.

Tillage and irrigation effects on root growth, soil water depletion and yield of wheat following rice

Abstract: The effects of deep tillage and no-tillage on soil physical properties and wheat yield following rice were compared with conventional tillage at three irrigation rates (irrigation water:open pan evaporation ratios of 0·6, 0·9 and 1·2) in 1982–85 at the experimental station of the Punjab Agricultural University, Ludhiana. Deep tillage decreased soil bulk density and penetrometer resistance, and increased depth of rooting, profile water use and wheat yield. No-tillage adversely affected all these variables. The tillage effects varied with amount and distribution of rain during the cropping season.

Progress in reducing water use and wastewater loads in the U.S. paper industry

Abstract: Les resultats d'une enquete du National Council for Air and Stream Improvement montrent que l'industrie papetiere des USA a reduit de facon significative sa consommation d'eau et sa charge polluante depuis 1975.

Water Relations of Hibiscus following Pruning or Chemical Growth Regulation

Abstract: Growth of potted hibiscus (Hibiscus rosa-sinensis L.) was limited either by pruning or by a soil drench of ' uniconazole at 3.0 mg a.i. per pot. Both treatments changed the water use of hibiscus. Five days after treatment with uniconazole, plants showed reduced water use, an effect that became more pronounced with time. Water use of pruned plants was reduced immediately after pruning, but soon returned to the level of the control due to the rapid regeneration of leaf area. Pruned or chemically treated plants used 6% and 33% less water, respectively, than the control. Chemically treated plants had a smaller leaf area, and individual leaves had lower stomatal density, con- ductance, and transpiration rate than control plants. Under well-watered conditions, the sap flow rate in the main trunk of control or pruned plants was 120 to 160 g·h -l ·m -2 , nearly three times higher than the 40 to 70 g·h -1 Control of growth has long been an important factor in the management of trees and shrubs near power lines, during nur- sery production, and in the urban environment. Control tradi- tionally has been accomplished by mechanical pruning, but recently the use of growth-regula ting chemicals has gained ac- ceptance (Watson, 1987). The effects of these practices on tree or shrub water use will become increasingly important as water resources become more limited or expensive. Both pruning and chemical growth retardants can reduce water use as a result of a reduction in the leaf area. In the former, leaf area is physically removed, while in the latter, the physi- ology of leaf and/or shoot growth is changed (Barrett and Nell, 1981; Sachs et al., 1975; Sterrett, 1988). There are also many reports that plants treated with chemical growth retardants ex- hibit a reduction in water use not related to changes in leaf area (Barrett and Nell, 1981; Mishra and Pradhan, 1972; Swietlik and Miller, 1983). The available evidence suggests that the re- duced water use is due to the inhibition of stomatal opening (Orton and Mansfield, 1976) or to anatomical changes in water transport or related tissues (Gao et al., 1988; Wang and Gregg, 1989). The objective of this study was to quantify the effect of two plant growth-regulation methods, pruning and the growth-reg- ulating chemical uniconazole, on water use of hibiscus during well-watered and dry conditions. Transpiration rates, conduct- ance, water potential, and capacitance of individual leaves, liq- uid flow conductance in the main trunk or stem, and capacitance of the plant top were measured to further the understanding of how these two methods of growth regulation affect the water relations of hibiscus.

Ontogeny and Water Use of No-Tillage Sorghum Cultivars on Dryland

Abstract: Grain sorghum [Sorghum bicolor (L.) Moench] yields are strongly influenced by soil water content at planting and use of that water during the growing season. Sorghum on Pullman soils (fine, mixed, thermic Torrertic Paleustolls), however, usually does not use water from as deep in the soil as other crops, thus possibly not attaining its full yield potential. This study was conducted from 1986 to 1989 to determine whether eight sorghum hybrid cultivars grown under no-tillage conditions on a dryland Pullman clay loam at Bushland, TX, differed with respect to water use depth, growth, yield, yield components, total water use, and water use efficiency (...)

Water Reductions From Residential Audits

Abstract: The water reductions resulting from Contra Costa Water District's 1989 residential audit program are measured using a multivariate regression model. The model explains metered residential water use as a function of both conservation and other household variables. The principle conclusions drawn are that (1) installation of low-flow showerheads reduced indoor water use by 9.7 percent or 7.8 gallons per capita day, (2) the outdoor segment of the audit reduced irrigation needs by 18.7 percent, and (3) irrigation timers are being used inefficiently.