Water use efficiency

Water value as agriculture production may be overlooked, though it is an important factor to rational water allocations within a region. An analysis of cotton (Upland and Pima) lint yield, lint yieldconsumptive use ratio (LY:ET c ), water-use ef®ciency (WUE) and lint price for Arizona (AZ) and California (CA) during 1988±1999 is considered as part of an attempt to determine lint water value, or bene®t. It included determination of means and variability of cotton lint production, LY:ET c ratios and associated irrigation water values (IWVs) and compared these numbers with published estimates of WUE, forage hay water values and municipal water costs. Available rainfall, reference evapotranspiration (ET o ), lint yields and price data for counties in both states were used. Consumptive use was estimated using a four-stage crop coef®cient function veri®ed by literature values or County Advisor experience. As with dry matter production, cotton lint yields in interior valley regions of CA were weakly correlated with ET c and averaged 1.33 Mg/ha (Upland) and 1.08 Mg/ha (Pima). Cotton lint yields in desert regions of AZ and CA were not correlated with ET c . The greatest LY:ET c ratios (1.9±2.1 kg/ha-mm) were in the San Joaquin valley of CA, were similar to that from WUE type studies and resulted in gross IWVs ($3400±3800 US$/ha-m), with relatively moderate variability at a net irrigation water requirement (IWR) of approximately 720 mm. While this IWV is 2.5 times greater than water delivery prices below the California Delta, it is less than average municipal water costs of $4200 US$/ha-m for Los Angeles, San Francisco and Pheonix while the overall AZ/CA average cotton lint IWV is considerably less. However, cotton lint IWV is two to three times greater than that obtained for alfalfa and sudangrass hay crops in all regions. #

In the humid and sub-humid areas, agricultural production is largely rain fed and this needs to be urgently supplemented by irrigation practice if the country is to meet its food demand. A two years study was carried out at the experimental site of the Institute of Agricultural Technology and Biosystems Engineering, Johan Heinrich von Thünen Institute (vTI), Braunschweig, Germany to compare performance of maize crop for silage production using three different irrigation systems; rain fed, drip and rain-gun sprinkler. Growth parameters such as plant height, stem diameter were measured. The total yields of silage were obtained for all treatments at the harvesting. The experimental results reveal that total yields obtained from different treatments were 25.76, 24.23 and 9.30 Mg ha -1 in drip, rain-gun and rain fed irrigated maize, respectively. The results also showed that the water use efficiency reached 11.01 kg m -3 for drip irrigation in while it was 8.84 kg m -3 for rain-gun syste...

Biological nitrogen fixation (BNF) as a result of the legumes-rhizobia symbioses is the main source of nitrogen in organic farming systems. Lucerne (Medicago sativa L.), used as green manure or as forage legume, is important on arable farms under dry site conditions. In a field experiment on organically managed agricultural fields, we examined the impacts of the utilisation system (harvested = forage production versus mulched = green manure) and the crop composition (pure lucerne crops versus lucerne-grass mixtures) on yield, biological nitrogen fixation (BNF), soil inorganic N content, N balance and water consumption of autumn-cultivated lucerne crops. The study was conducted at the University of Natural Resources and Applied Life Sciences, Vienna, in eastern Austria-a region characterized by pannonian site conditions (9.8 8C mean annual temperature, 545 mm average total precipitation) and stockless farming systems. Our results indicate that the utilisation system and the crop composition had no marked influence on above-and below-ground dry matter (DM) and N yield, soil inorganic N contents, BNF, or water use efficiency of lucerne. The level of symbiotically fixed N 2 in harvested lucerne was 89-125 kg N ha À1 (27-33% Ndfa = nitrogen derived from atmosphere) in the first year and 161-175 kg N ha À1 (47-49% Ndfa) in the second year of the study. The high soil inorganic N supply in the first year increased the N uptake from soil by lucerne and led to a reduced BNF. Under the dry and unfavourable conditions in both study years, the nitrogen release from the legume mulch was retarded and BNF in mulched lucerne was not reduced. Assuming low gaseous N losses by mulching (15-30 kg N ha À1 ), the green manure system reached a positive N balance (+137 to +186 kg N ha À1 ) for the subsequent crops because abundant residues remained on the field. #

This study reports the seasonal assessment of energy balance components and carbon dioxides fluxes over a drip irrigated kiwifruit orchard, with a Leaf Area Index (LAI) of 3 at full canopy development. The most remarkable amount of energy partitioning throughout the whole season was due to latent heat flux that had values approximating to those of sensible heat flux (about

Growth and water uptake both decreases when tomato plants are irrigated with saline water. To determine the relative contribution of physiological traits to these decreases plant fresh and dry weight, leaf area, leaf water (c w) and osmotic (c P) potentials, gas exchange parameters, stomatal density, leaf chlorophyll and Na content were investigated in the tomato (Lycopersicon esculentum) cultivars, Daniela and Moneymaker. Plants were grown in greenhouse, in sand culture, and irrigated with a complete nutrient solution supplied with 0 (control), 35 and 70 mM NaCl over a period of 2 months. Salinity reduced plant dry weight, height and number of leaves even at 35 mM NaCl. Leaf c w and c P decreased with salinity but leaf turgor pressures were significantly higher in salinised than in control plants which suggests that bulk tissue turgor did not limit growth under the saline conditions tested. Increasing salinity in the irrigation solution led to both morphological changes [(reduction of plant leaf area and stomatal density) and physiological changes [reduction of stomatal conductance, transpiration, and net CO 2 assimilation (A CO 2)] Plant water uptake, measured as the difference between volume of nutrient solution supplied and drainage collected, was closely related to transpiration, stomatal conductance, and stomatal density. Chlorophyll content per unit of leaf area increased with salinity. Reduction of net A CO 2 with salinity was explained in higher degree by stomatal conductance and stomatal density than by Na accumulation in the leaves. Although plant water uptake was similar for the two cultivars, Daniela transported, per unit of water uptake, more Na to the leaves than did Moneymaker. However, Daniela reduced leaf area less than did Moneymaker. Water use efficiency, calculated either as the ratio between total plant dry matter and total plant water uptake, or as the ratio between net A CO 2 and transpiration, did not change under our saline growth conditions. The contribution of the observed salt-responses to reduction in shoot water loss, plant water uptake and salt loading, while keeping water use efficiency, is discussed in relation to salt tolerance. Because some of these salt-responses take a long time to develop, growing seedlings in seedbeds with saline media could be of interest to better tolerate further salty conditions in the field or greenhouse.

In large canal irrigation project areas, integrated management of surface and groundwater resources can improve water use efficiencies and agricultural productivity and also control water logging. Such integrated management requires an estimation of spatial distribution of recharge and ground water flow in the underlying aquifer. Recharge occurs both as percolation losses from fields and seepage losses from the water distribution network. Percolation losses are influenced by weather, soil properties, land use, and canal water and groundwater use. Seepage losses depend on the conditions of flow in the water distribution system. In large irrigation project areas all the factors influencing the recharge of groundwater vary spatially. In this study, a geographical information systems (GIS) is used to map the spatial distribution of recharge which then serves as input to a regional groundwater flow model for simulating the behavior of the underlying aquifer. The basis is that the project...

La evapotranspiración y necesidades de riego del arroz son un tema pendiente. Se ha determinado la evapotranspiración de un arroz tipo indica a partir de técnicas de covarianza de torbellinos. Se propone un método para la determinación del coeficiente de cultivo, Kc, a partir de información satelital. El coeficiente de cultivo a partir de la inundación alcanza valores máximos de 1.2-1.4 mientras el cultivo no cubre la totalidad de la superficie para mantenerse en valores cercanos a 1 durante la etapa de meseta. La estrategia de riego del agricultor puede tener influencia en los valores de Kc a lo largo del ciclo.

Photosynthetic capacity, leaf nitrogen content, and stomatal conductance decreased with increasing leaf age in the chaparral shrub, Lepechinia calycina, growing in its natural habitat. Efficiency of resource use for three resources that potentially limit photosynthesis did not, however, decrease with increasing leaf age. Light-use efficiency, given by the quantum yield of photosynthesis at low light intensities, was unaffected by leaf aging but decreased slightly through the winter and spring growing season. Water-use efficiency, the ratio of photosynthesis to transpiration at light saturation and with a constant water vapor concentration gradient, was not affected by leaf aging or seasonal change. Nitrogen-use efficiency, the ratio of photosynthesis at light saturation to leaf nitrogen content did not change with leaf age but was lower in the leaves with the highest specific weights. This ensemble of leaf-age effects is consistent with the hypothesis that aging represents resource redistribution and not uncontrolled deterioration.

Soil organic matter (SOM) is known to play a major role in soil fertility due to its influence on physical, chemical and biological properties of soil; and it is closely related to particle size distribution. The ratio of SOM (g kg À1 ) to clay + silt content (g kg À1 ) was evaluated as an indicator of soil quality for barley (Hordeum vulgare) grain yield, reflecting N availability and soil physical conditions to which crop development is sensitive. Thirty-eight sites in the semiarid Pampa region of Argentina with a wide range of SOM and texture were evaluated for malting barley yield during three growing seasons. In control plots, 51% of grain yield could be explained by this indicator. The threshold value between high and low N-fertilization response was 4.4. Better yield prediction to almost 68% was achieved by combining the SOM to clay + silt indicator with initial nitrate content of the soil at seeding. This combined indicator was also able to explain a high proportion of water use efficiency, particularly in the early growth stages. The ratio of SOM to clay + silt content provided a better tool for estimating grain yield than nutrient availability or SOM alone. #

Wheat (Triticum aestivum L.) is the most important cereal crop after rice in India. Optimum schedule of irrigation for wheat and its response to irrigation based on the ratio of irrigation water and cumulative pan evaporation (irrigation depth (IW):CPE at 1.2, 0.9 and 0.6) was studied in a field experiment during the winter seasons of 1989-1990 and 1990-1991. The site had a sandy loam (Typic Fluvaquent) soil and shallow water table, located in the humid tropical canal command area at the University Experimental Farm, Memari (2381 0 N, 8885 0 E and 21.34 m above mean sea level) in West Bengal, India. The yield of wheat, weekly and seasonal actual evapotranspiration (ETa) from water balance equation, crop coefficients (K c ), soil water stress coefficients (K s ), water extraction patterns, water use efficiency (WUE) and water application efficiency (A e ) were determined. Maximum profile water depletion and ETa of wheat occurred in the wetter moisture regime (1.2 IW:CPE). The average daily ETa varied from <1 mm per day in the early growing period to a maximum value of 2.72 mm per day at 9-14 weeks after sowing (WAS) under 1.2 IW:CPE when leaf area index (LAI) was >3. During crop development to mid season (4-14 WAS), 1.2 IW:CPE showed 9-15% increased ETa than 0.9 and 0.6 IW:CPE. The seasonal ETa of wheat with IW:CPE of 1.2 was 238.2 and 261.95 mm during 1989-1990 and 1990-1991, respectively. Maximum roots were concentrated in the top 150 mm layer (57% of root length density) and maximum root water extraction efficiency (U z ) was observed at 600-750 mm depth under the drier soil moisture regimes of 0.9 and 0.6 IW:CPE, respectively. The yield increased significantly with increasing levels of irrigation. IW:CPE ratio of 1.2 produced 13 and 21% more yield, and 8 and 14% improved WUE than 0.9 and 0.6 IW:CPE, respectively. Water application efficiency (A e ) was noticed higher (79.85%) under 0.6 IW:CPE irrigation regime. Precise information of K c , which is required for regional scale irrigation planning is lacking in developing countries. The estimated values of K c for wheat at four crop growth stages (initial, crop development, mid season and maturity) were 0.33, 0.82, 1.08 and Agricultural Water Management 59 (2003) 33-47 : S 0 3 7 8 -3 7 7 4 ( 0 2 ) 0 0 1 1 2 -9 0.64, respectively which were identical to those suggested by the FAO indicating need for generating these values at the local/regional level. The K s values of 0.6 IW:CPE decreased steeply and experienced more stress condition than 0.9 IW:CPE. #

Scarcity and competition for water are matters of increasing concern, as are potential shortages of food. These issues intersect both within the agricultural sector and across all water using sectors. Irrigation is by far the largest user of water in most water-scarce countries, and is under pressure to reduce utilisation (to release water to other sectors, including the environment) and use water more productively to meet demands for food and fibre. The terminology for such intra-and inter-sectoral analysis must be unambiguous across sectors so that interventions and their impacts are properly understood. Such terminology, based on previous work and debate, is set out. Implications for a better understanding of the scope for improved productivity of water in agriculture are traced, and some examples are given using data from recent research submissions, demonstrating the benefits of precise water accounting.

Cassava or manioc (Manihot esculenta Crantz), a perennial shrub of the New World, currently is the sixth world food crop for more than 500 million people in tropical and sub-tropical Africa, Asia and Latin America. It is cultivated mainly by resource-limited small farmers for its starchy roots, which are used as human food either fresh when low in cyanogens or in many processed forms and products, mostly starch, flour, and for animal feed. Because of its inherent tolerance to stressful environments, where other food crops would fail, it is often considered a food-security source against famine, requiring minimal care. Under optimal environmental conditions, it compares favorably in production of energy with most other major staple food crops due to its high yield potential. Recent research at the Centro Internacional de Agricultura Tropical (CIAT) in Colombia has demonstrated the ability of cassava to assimilate carbon at very high rates under high levels of humidity, temperature and solar radiation, which correlates with productivity across all environments whether dry or humid. When grown on very poor soils under prolonged drought for more than 6 months, the crop reduce both its leaf canopy and transpiration water loss, but its attached leaves remain photosynthetically active, though at greatly reduced rates. The main physiological mechanism underlying such a remarkable tolerance to drought was rapid stomatal closure under both atmospheric and edaphic water stress, protecting the leaf against dehydration while the plant depletes available soil water slowly during long dry periods. This drought tolerance mechanism leads to high crop water use efficiency values. Although the cassava fine root system is sparse, compared to other crops, it can penetrate below 2 m soil, thus enabling the crop to exploit deep water if available. Leaves of cassava and wild Manihot possess elevated activities of the C4 enzyme PEP carboxylase but lack the leaf Kranz anatomy typical of C4 species, pointing to the need for further research on cultivated and wild Manihot to further improve its photosynthetic potential and yield, particularly under stressful environments. Moreover, a wide range in values of K m (CO2) for the C3 photosynthetic enzyme Rubisco was found among cassava cultivars indicating the possibility of selection for higher affinity to CO2, and consequently higher leaf photosynthesis. Several plant traits that may be of value in crop breeding and improvement have been identified, such as an extensive fine root system, long leaf life, strong root sink and high leaf photosynthesis. Selection of parental materials for tolerance to drought and infertile soils under representative field conditions have resulted in developing improved cultivars that have high yields in favorable environments while producing reasonable and stable yields under stress.

The effects of pre-anthesis water deficit and cycle length were examined in Papaver somniferum L., cultivated for alkaloid production, in two locations in southern Spain. The vegetative period was shortened by extending the photoperiod through supplemental lighting in the field, while water deficit in pre-anthesis was induced by avoiding irrigations and installing rain shelters. The treatments were: IN (irrigated-normal photoperiod), IL (irrigated-hastened flowering), DN (water deficit in pre-anthesisnormal photoperiod) and DL (water deficit in pre-anthesis and hastened flowering). The artificial photoperiod hastened the flowering by 15 and 21 days, for irrigated and deficit treatments respectively. Seasonal evapotranspiration (ET) ranged from 398 (DN) to 505 mm (IN). There was evidence of root water uptake deeper than 1.5 m. Stomatal conductance was reduced (16%) during water stress, and did not recover in post-anthesis after resuming irrigation. Head yields (capsule + seeds + 7 cm stem) ranged between 3.8 and 4.3 t ha −1 ; water deficit and short vegetative period both reduced the biomass accumulated, although the effect on yields in these treatments was counterbalanced by a higher harvest index. Early flowering had a detrimental effect on alkaloid concentration in the capsule. Alkaloids yield ranged between 27 and 37 kg ha −1 . Water use efficiency (WUE) ranged between 0.78 and 0.96 kg m −3 ET for yield and between 63.4 and 73.7 g m −3 ET for alkaloids. Water stress increased slightly the Water Use Efficiency. A shorter vegetative phase had no effect on WUE for biomass or yield, but decreased the WUE for alkaloids production.

Soilless cultivation is a method that permits the achievement of high yields, good control of plant growth and development, and is currently in practice all over the world. Several irrigation systems have been developed for containerized-crops (drip-irrigation and subirrigation). Irrigation system can significantly impact the effect of irrigation water salinity on crop performance. Comparing the subirrigation and drip-irrigation systems using saline and non-saline nutrient solutions can be useful for developing optimal management strategies in semiarid regions which are characterized by the shortage of good quality water. A greenhouse experiment was carried out during the spring-summer season to determine the influence two irrigation systems (drip and subirrigation) and two nutrient solution concentrations (2.0 and 4.1 dS m À1 ) on substrate electrical conductivity (EC e ), growth, yield, fruit quality (dry matter, carbohydrates, protein, Vitamin C), yield water use efficiency (WUE y ) and tissue mineral composition of zucchini squash (Cucurbita pepo L.). At the mid and at the end of the trial, plants grown with the subirrigation system resulted in a higher EC e in the upper and lower parts of the substrate in comparison to the drip-irrigation system, especially at an EC of 4.1 dS m À1 . At an EC of 2.0 dS m À1 , zucchini yield (total and marketable) was 13% lower with the subirrigation than with the drip-irrigation systems but offered several benefits: higher fruit quality (dry matter, glucose, fructose, starch and total carbohydrates content) and WUE y . The yield reduction with www.elsevier.com/locate/agwat Agricultural Water Management 82 (2006) 99-117 subirrigation was more pronounced at an EC 4.1 dS m À1 , where the zucchini production with subirrigation was lower by 36% than with drip-irrigation. Increasing salinity from 2.0 to 4.1 dS m À1 improved fruit quality (high content of dry matter, reduced sugars, starch, total carbohydrates, and Vitamin C) in both irrigation systems. The results indicate that the choice of the irrigation system appears to be of foremost importance especially when using low quality irrigation water. Unlike subirrigation, using drip-irrigation with saline solution (4.1 dS m À1 ) would be an attractive strategy in limiting yield reduction, taking advantage of the quality effect of saline water and improving the WUE y .

Scarcity of water is a severe environmental constraint to plant productivity. Drought-induced loss in crop yield probably exceeds losses from all other causes, since both the severity and duration of the stress are critical. Here, we have reviewed the effects of drought stress on the growth, phenology, water and nutrient relations, photosynthesis, assimilate partitioning, and respiration in plants. This article also describes the mechanism of drought resistance in plants on a morphological, physiological and molecular basis. Various management strategies have been proposed to cope with drought stress. Drought stress reduces leaf size, stem extension and root proliferation, disturbs plant water relations and reduces water-use efficiency. Plants display a variety of physiological and biochemical responses at cellular and whole-organism levels towards prevailing drought stress, thus making it a complex phenomenon. CO2 assimilation by leaves is reduced mainly by stomatal closure, membrane damage and disturbed activity of various enzymes, especially those of CO2 fixation and adenosine triphosphate synthesis. Enhanced metabolite flux through the photorespiratory pathway increases the oxidative load on the tissues as both processes generate reactive oxygen species. Injury caused by reactive oxygen species to biological macromolecules under drought stress is among the major deterrents to growth. Plants display a range of mechanisms to withstand drought stress. The major mechanisms include curtailed water loss by increased diffusive resistance, enhanced water uptake with prolific and deep root systems and its efficient use, and smaller and succulent leaves to reduce the transpirational loss. Among the nutrients, potassium ions help in osmotic adjustment; silicon increases root endodermal silicification and improves the cell water balance. Low-molecular-weight osmolytes, including glycinebetaine, proline and other amino acids, organic acids, and polyols, are crucial to sustain cellular functions under drought. Plant growth substances such as salicylic acid, auxins, gibberrellins, cytokinin and abscisic acid modulate the plant responses towards drought. Polyamines, citrulline and several enzymes act as antioxidants and reduce the adverse effects of water deficit. At molecular levels several drought-responsive genes and transcription factors have been identified, such as the dehydration-responsive element-binding gene, aquaporin, late embryogenesis abundant proteins and dehydrins. Plant drought tolerance can be managed by adopting strategies such as mass screening and breeding, marker-assisted selection and exogenous application of hormones and osmoprotectants to seed or growing plants, as well as engineering for drought resistance.

In many parts of the world, freshwater is already a scarce and overexploited natural resource, raising concerns about global food security and damage to freshwater ecosystems. This situation is expected to intensify with the FAO estimating that world food production must double by 2050. Food chains must therefore become much more efficient in terms of consumptive water use. For the small and geographically well-defined Australian mango industry, having an average annual production of 44,692 t of marketable fresh fruit, the average virtual water content (sum of green, blue and gray water) at orchard gate was 2298 l kg À1. However, due to wastage in the distribution and consumption stages of the product life cycle, the average virtual water content of 1 kg of Australian-grown fresh mango consumed by an Australian household was 5218 l. This latter figure compares to an Australian-equivalent water footprint of 217 l kg À1 , which is the volume of direct water use in Australia having an equivalent potential to contribute to water scarcity. Nationally, distribution and consumption waste in the food chain of Australian-grown fresh mango to Australian households represented an annual waste of 26.7 Gl of green water and 16.6 Gl of blue water. These findings suggest that interventions to reduce food chain waste will likely have as great or even greater impact on freshwater resource availability as other water use efficiency measures in agriculture and food production.

Scarcity of water is a severe environmental constraint to plant productivity. Drought-induced loss in crop yield probably exceeds losses from all other causes, since both the severity and duration of the stress are critical. Here, we have reviewed the effects of drought stress on the growth, phenology, water and nutrient relations, photosynthesis, assimilate partitioning, and respiration in plants. This article also describes the mechanism of drought resistance in plants on a morphological, physiological and molecular basis. Various management strategies have been proposed to cope with drought stress. Drought stress reduces leaf size, stem extension and root proliferation, disturbs plant water relations and reduces water-use efficiency. Plants display a variety of physiological and biochemical responses at cellular and whole-organism levels towards prevailing drought stress, thus making it a complex phenomenon. CO2 assimilation by leaves is reduced mainly by stomatal closure, membrane damage and disturbed activity of various enzymes, especially those of CO2 fixation and adenosine triphosphate synthesis. Enhanced metabolite flux through the photorespiratory pathway increases the oxidative load on the tissues as both processes generate reactive oxygen species. Injury caused by reactive oxygen species to biological macromolecules under drought stress is among the major deterrents to growth. Plants display a range of mechanisms to withstand drought stress. The major mechanisms include curtailed water loss by increased diffusive resistance, enhanced water uptake with prolific and deep root systems and its efficient use, and smaller and succulent leaves to reduce the transpirational loss. Among the nutrients, potassium ions help in osmotic adjustment; silicon increases root endodermal silicification and improves the cell water balance. Low-molecular-weight osmolytes, including glycinebetaine, proline and other amino acids, organic acids, and polyols, are crucial to sustain cellular functions under drought. Plant growth substances such as salicylic acid, auxins, gibberrellins, cytokinin and abscisic acid modulate the plant responses towards drought. Polyamines, citrulline and several enzymes act as antioxidants and reduce the adverse effects of water deficit. At molecular levels several drought-responsive genes and transcription factors have been identified, such as the dehydration-responsive element-binding gene, aquaporin, late embryogenesis abundant proteins and dehydrins. Plant drought tolerance can be managed by adopting strategies such as mass screening and breeding, marker-assisted selection and exogenous application of hormones and osmoprotectants to seed or growing plants, as well as engineering for drought resistance.

The water balance and growth of Eucalyptus grandis hybrid plantations in Brazil are presented based on 6 years of intensive catchment hydrology, physiological and forest growthsurveying, and modelling. The results show a balance between water supply by precipitation and output through evapotranspiration (considered as canopy interception, soil evaporation and trees transpiration) and runoff. The annual average precipitation was 1147 mm

A field study on cotton (Gossypium hirsutum L., cv.) was carried out from 2005 to 2008 in the Çukurova Region, Eastern Mediterranean, Turkey. Treatments were designated as I100 full irrigation; DI70, DI50 and DI00 which received 70, 50, and 0% of the irrigation water amount applied in the I100 treatment. The irrigation water amount to be applied to the plots

Soil erosion and moisture stress are the major problems for crop production and sustainable land management in Ethiopia. This study was conducted to determine whether incorporation of crop residues modifies the physical properties of the surface soil by increasing water infiltration and storage, decreasing evaporation rate, and improving soil tilth. The effect of maize (Zea mays L.) residues incorporated at a rate of 6 Mg ha -1 (with inorganic fertilizer (RF) and without (R)) were compared to applying inorganic fertilizer alone (F) and a control (C) on two soil types (a Mollic Andosol with sandy loam texture and a Dystric Nitosol with clayey texture) in the South Central Rift Valley of Ethiopia. After three (annual) residue incorporations, penetration resistance at the 10 cm depth of both soils and shear resistance at the 5 cm depth of the sandy loam soil were 22-52% lower in the RF and R treatments than in the C treatment. The macro-plus mesoporosity in the RF treatment of the sandy loam soil (0-7 cm depth) was 22% higher compared to that of the C treatment. Evaporative flux (0-20 cm depth) in the RF and R treatments of the sandy loam soil and in the R treatment of the clayey soil were lower compared to the C treatment by 39-57%. The results indicate that incorporating crop residues, especially in conjunction with the use of inorganic fertilizers, can improve rain water use efficiency and soil tilth. This will also have a direct effect in minimizing the rate of soil erosion in the area.

The effect of elevated CO2 concentrations (545 and 700 μmol mol−1) on gas exchange and stomatal response of four high Δ9-THC yielding varieties of Cannabis sativa (HPM, K2, MX and W1) was studied to assess their response to the rising atmospheric CO2 concentration. In general, elevated CO2 concentration (700 μmol mol−1) significantly (p < 0.05) stimulated net photosynthesis (P N), water use efficiency (WUE) and internal CO2 concentration (C i), and suppressed transpiration (E) and stomatal conductance (g s) as compared to the ambient CO2 concentration (390 μmol mol−1) in all the varieties whereas, the effect of 545 μmol mol−1 CO2 concentration was found insignificant (p < 0.05) on these parameters in most of the cases. No significant changes (p < 0.05) in the ratio of internal to the ambient CO2 concentration (C i/C a) was observed in these varieties under both the elevated CO2 concentrations (545 and 700 μmol mol−1). An average increase of about 48 %, 45 %, 44 % and 38 % in P N and, about 177 %, 157 %, 191 % and 182 % in WUE was observed due to elevated CO2 (700 μmol mol−1) as compared to ambient CO2 concentration in HPM, K2, MX and W1 varieties, respectively. The higher WUE under elevated CO2 conditions in Cannabis sativa, primarily because of decreased stomatal conductance and subsequently the transpiration rate, may enable this species to survive under expected harsh greenhouse effects including elevated CO2 concentration and drought conditions. The higher P N, WUE and nearly constant C i/C a ratio under elevated CO2 concentrations in this species reflect a close coordination between its stomatal and mesophyll functions.

Seshoka, J.; de Lange, W.; Faysse, N. 2004. The transformation of irrigation boards into water user associations in South Africa: Case Studies of the Lower Olifants, Great Letaba and Vaalharts Water User Associations. Working Paper 72. Colombo, Sri Lanka: International Water Management Institute. / water users' associations / case studies / irrigation water / farmers / river basins / water resource management / water quality / land ownership / financing / canals / dams / crops / water allocation / irrigation programs / South Africa / ISBN 92 9090 558 1

Barbados is almost wholly reliant on groundwater as its source of water largely due to replenishment during the wettest 1-3 months of the year. Annual renewable freshwater resources place it in the top 15 of the world's most water scarce countries. Acknowledging the scope of the problem, government officials have noted that the amount of water available for economic activity has become very limited and might therefore affect future development. Most of the proposed measures to date have focused on mains replacement and increased energy efficiency but little thought has been given to demand-side management. This study therefore attempts to provide a framework for managing the water resources in the island's single largest industry: tourism. It is conceptualised that a system of tradable permits would not only enhance the management of water resources, but should also reduce the cost of water resources to hotels.

The combined application of cattle manure and inorganic fertilizer has been widely recommended in the context of integrated soil fertility management (ISFM) on smallholder farms in sub-Saharan Africa (SSA). However, the conditions under which this combination (hereafter ISFM) improves nutrient and water use efficiency and crop yields have not been systematically studied. Therefore, we undertook a meta-analysis of studies conducted in rain-fed maize production systems across SSA with the objective of (1) quantifying the magnitude of improvement in grain yield, rain use efficiency (RUE), agronomic efficiency of nitrogen (AEN) and phosphorus (AEP) due to ISFM; (2) determining conditions under which ISFM achieves greater yield response, RUE, AEN and AEP; and (3) compare yield responses to the substitutive and additive approaches of ISFM with sole application of cattle manure. Application of high rates of cattle manure in combination with high N fertilizer rates increased yield response only by 27.5%, but it achieved 47% lower AEN and 27% lower AEP relative to a combination of low manure and low N fertilizer rate. The substitutive approach of ISFM achieved 54% greater AEN and 16% greater AEP than the additive ISFM approach. Yield response and AEN also significantly varied with soil type. On most soil types, AEN was 2-195% lower under sole manure than under ISFM or sole fertilizer. We recommend application of moderate rates of cattle manure (5-10 t ha-1) combined with moderate doses of N fertilizer (\ 50 kg N ha-1) on responsive soils to

Chitosan (CHT) is a natural compound able to activate the plant own defence machinery against pathogen attacks and to reduce both transpiration and stomatal opening when applied as foliar spray. The data here reported show that CHT-induced antitranspirant activity in bean plants is mediated by ABA, whose level raised over threefold in treated leaves, 24 h after foliar spraying. This is thought to induce partial stomatal closure via a H 2 O 2 -mediated process, as confirmed by scanning electron microscopy (SEM) and histocytochemistry, and, in turn, a decrease of stomatal conductance to water vapor (G w ) and transpiration rate (E), assessed by gas exchange measurements. The relatively high internal CO 2 concentration (C i ) values, suggest the occurrence of a slight decrease in carboxylation efficiency after CHT treatment, which however did not prevail over stomatal limitations. The intrinsic water use efficiency (WUE i ) of CHT treated plants was not statistically different from controls and the maximal photochemical efficiency (F v /F m ) of PSII was not affected. Moreover, CHT determined a stimulation of the xanthophyll cycle towards deepoxidation state. On the whole, these results, besides confirming the effectiveness of CHT in reducing plant transpiration, prove that the mechanism underlying this activity differs from that showed by the commercial antitranspirant Vapor Gard ® (VP). In fact, the efficacy of the latter is based on the formation of a thin antitranspirant film over the leaf and not on the reduction of stomatal opening. Finally, suggestions for possible use of the two antitranspirants in different environmental conditions are discussed.

The production of dry matter and grain depends on the ability of crops to capture resources. On an annual basis, farming systems centred on single crops waste large proportions of key inputs including incoming solar radiation and rainfall. Intensive farming involving multiple crops per year could improve resource capture and productivity. Resource productivity is defined as the ratio between output (biomass or grain yield) and annual input of photosynthetically active radiation (PAR) or rainfall. This paper tested the hypotheses that (i) wheat-soybean (Triticum aestivum L. and Glycine max (L.) Merr., respectively) double cropping increases resource productivity in relation to single crops through improved capture and efficiency in the use of resources, and (ii) the link between radiation-(RUE) and water-use efficiency (WUE) previously established for sole crops remain when scaling up to double cropping.

Irrigation frequency is one of the most important factors in irrigation scheduling, and a proper irrigation frequency can establish moderate moist and oxygen conditions in the root zone throughout the crop growth period. This study was conducted to study the effect of scheduling irrigation on the water use efficiency and yield of cabbage. It was conducted on a cabbage farm within the Ho Municipality. The weights of harvested cabbage heads were recorded. Four raised beds were prepared with two replication labelled into various treatment (T1, T2, T3, and T4). Treatment 1 was irrigated every day, Treatment 2 irrigated three times in a week, Treatment 3 irrigated only once in a week and Treatment 4 was under control (No irrigation). Treatment 1 (T1) yielded the highest weight(kg) of cabbage head after harvesting and the lowest water use efficiency as compared to yields of treatment 2 and 3 with treatment 4 yielding the least in weight of cabbage heads. The relationship between yield and...

Efficient water delivery systems such as drip irrigation can contribute towards increasing crop yield potential, improving crop water and fertilizer use efficiency. However, critical management considerations such as subsurface drip irrigation are necessary to attain improved irrigation efficiencies and production benefits particularly under arid regions. The objective of this study was to determine the effect of two irrigation methods, surface and subsurface drip irrigation combined with four irrigation levels, 100, 80, 60 and 40% of crop evapotranspiration on yield and yield components of potato grown on sandy soil. The field experiments were conducted in the years 2008 and 2009. In terms of soil water availability to plants, subsurface drip provided more favorable growth conditions for plant growth and maintained higher soil water content at the root zone, which resulted in a significant higher potato yield compared to surface drip irrigation. The difference between the two irrigation methods on yield components was concentrated on the mean tuber weight per plant, while no significant difference was found on the tuber number per plant. Reducing the amounts of applied water significantly decreased total potato yield and its components. Under subsurface drip irrigation, reducing amounts of applied water to 80% ETc gave comparable yield and yield components to surface drip at full irrigation supply, indicating that 20% irrigation water can be saved without affecting the potato yield. At all irrigation levels, subsurface drip recorded higher water use efficiency (WUE) over surface drip. Maximum value was observed at 40% ETc. Fertilizer use efficiency (FUE) was also higher under subsurface drip and reduced significantly under both irrigation methods with increasing water deficit. These results suggested that subsurface drip offers the potential of better water management with respect to saving and distribution of water in the root zone and to obtain maximum yield accompanied by highest water and FUE.

Straightforward guidelines for deficit irrigation (DI) can help in increasing crop water productivity in agriculture. To elaborate such guidelines, crop models assist in assessing the conjunctive effect of different environmental stresses on crop yield. We use the AquaCrop model to simulate crop development for long series of historical climate data. Subsequently we carry out a frequency analysis on the simulated intermediate biomass levels at the start of the critical growth stage, during which irrigation will be applied. From the start of the critical growth stage onwards, we simulate dry weather conditions and derive optimal frequencies (time interval of a fixed net application depth) of irrigation to avoid drought stress during the sensitive growth stages and to guarantee maximum water productivity. By summarizing these results in easy readable charts, they become appropriate for policy, extension and farmer level use. We illustrate the procedure to derive DI schedules with an example of quinoa in Bolivia. If applied to other crops and regions, the presented methodology can be an illustrative decision support tool for sustainable agriculture based on DI.

This study was conducted to determine the influence of irrigation regimes on yield of two tomato cultivars – TY-DANA and GS12. Experimental treatments were three irrigation intervals (2, 4, and 6 days), and three irrigation quantities (50%, 75%, and 100% of pan evaporation [Ep]). The total yield increased with increasing amount of irrigation water for both cultivars. The total yield increased about 10% and 17% for 100% of Ep treatment compared with 50% Ep treatment for TY-DANA and GS12 cultivars, respectively. The 100% Ep treatment showed the lowest irrigation water use efficiency (IWUE) (16.7 and 10.4 kg m−3), while 50% Ep showed the maximum IWUE (23.9 and 17 kg m−3) for TY-DANA and GS12 cultivars, respectively. The average fruit weight for 100% Ep treatment was usually higher than the other treatments. Generally, yield decreased using 50% Ep, however, the benefits of increasing IWUE and saving around 50% of irrigation water will help to grow crops in more areas and in managing the limited water resources in arid environments.

Studies were carried out to optimize the use of water and nutrients by the crop with three moisture regimes [0.9, 1.2 and 1.5 irrigation water:cumulative pan evaporation (IW:CPE) ratios], two variables of organic mulch (control and sugarcane trash at 7 t/ha) and three levels of nitrogen (0, 100 and 200 kg/ha). Soil moisture regimes maintained at 1.2 IW:CPE ratio significantly increased the crop growth and herb and essential oil yields as compared with that of 0.9 IW:CPE ratio. The increase in herb yield due to 1.5 and 1.2 IW:CPE ratios was recorded to be 28.5% and 19%, respectively, over the irrigation given at 0.9 IW:CPE ratio, with the corresponding increase in essential oil yield to the extent of 23.5% and 15.5%. Interaction effect of moisture regimes and nitrogen rates indicated that increasing levels of irrigation at the highest level of N (200 kg/ha) improved essential oil yield of the crop. Application of N at 200 kg/ha in the mulched plots significantly enhanced the N uptake by the crop and essential oil yield over the control and 100 kg N/ha applied in the mulched/or unmulched plots and 200 kg N/ha applied in the unmulched plots. Application of organic mulch and nitrogen at 200 kg/ha improved the water use efficiency (WUE) in menthol mint crop. Higher moisture regimes maintained up to 1.2 IW:CPE ratio increased the WUE. The quality of essential oil in terms of its major constituent, menthol, improved slightly with 1.2 IW:CPE ratio as compared to 0.9 and 1.5 IW:CPE ratios at first and second harvests of the crop.

Touriga Franca grapevines were grown in Open-Top Chamber (OTC) and in outside plot (Exterior) for 3 years (2004-2006) to investigate the impact of these structures on climatic conditions and, consequently, on physiological and yield attributes. In general, CO 2 assimilation, stomatal conductance, carbohydrate concentration, maximum bulk modulus of elasticity, palisade parenchyma thickness, leaf mass per unit area and values of red/far-red ratio transmitted by leaves were lower, whereas intrinsic water use efficiency, SPAD-readings and osmotic potential at full turgor were higher in OTC leaves. However, OTC did not affect leaf water potential, maximum PSII photochemical efficiency, stomatal density and soluble proteins concentration. Also, there were no significant differences in C, P, Ca and Fe between treatments. Meanwhile, N and Mg were higher, whereas K concentration was lower in OTC leaves. The environmental conditions inside OTC provided a significant reduction in yield and Ravaz index of 2004, mainly due to a decrease in clusters weight. Regarding the vegetative growth parameters, OTC did not influence the pruning weight, but in 2006 the weight/shoot was significantly lower in OTC vines. In conclusion, the use OTC facility to study the impact of CO 2 enrichment was very expedite, but the extrapolation of results to the open-field environment must be prudent due to the OTC effect.

We examined the extent to which farmers have improved food production in recent years with low cost, locally available and environmentally sensitive practices and technologies. We analysed by survey during 1999-2000 208 projects in 52 developing countries, in which 8.98 million farmers have adopted these practices and technologies on 28.92 million hectares, representing 3.0% of the 960 million hectares of arable and permanent crops in Africa, Asia and Latin America. We found improvements in food production occurring through one or more of four mechanisms: (i) intensification of a single component of farm system; (ii) addition of a new productive element to a farm system; (iii) better use of water and land, so increasing cropping intensity; (iv) improvements in per hectare yields of staples through introduction of new regenerative elements into farm systems and new locally appropriate crop varieties and animal breeds. The 89 projects with reliable yield data show an average per project increase in per hectare food production of 93%. The weighted average increases across these projects were 37% per farm and 48% per hectare. In the 80 projects with small (<5 ha) farms where cereals were the main staples, the 4.42 million farms on 3.58 million hectares increased household food production by 1.71 t per year. We report on the practices and technologies that have led to these increases: increased water use efficiency, improvements to soil health and fertility, and pest control with minimal or zero-pesticide use. This research reveals promising advances in the adoption of practices and technologies that are likely to be more sustainable, with substantial benefits for the rural poor. With further explicit support, particularly through national policy reforms and better markets, these improvements in food security could spread to much larger numbers of farmers and rural people in the coming decades.

Water is one of the most important inputs for economic development. As the demand increases, so too does the importance of water. This is clearly the case in Egypt, where rainfall is rare and the governmentally enforced quota for withdrawal from the Nile River has not changed since 1959. The water demand has multiplied as a result of population growth, agricultural expansion, as well as industrial development and a rise in the standard of living. In this paper, a vision for the future water status in Egypt is presented. This vision is based on a perception of the current status of the available water resources. The water uses, the water use efficiency, the institutional and legislative frameworks of water management, and the strategies and policies to rationalize water use and to augment water supply are discussed. The local, regional and international governing and controlling factors of water utilization and management in Egypt are also analyzed and discussed. Three future water scenarios for year 2020, each reflecting alternate programs to develop the water systems and to rationalize the water uses, are presented. All scenarios showed that Egypt will suffer considerable water shortages in the near future. Recommendations to help overcome anticipated water challenges and to optimize the available opportunities are provided.

Salt-induced changes in growth, photosynthetic pigments, various gas exchange characteristics, relative membrane permeability (RMP), relative water content (RWC) and ion accumulation were examined in a greenhouse experiment on eight sunflower (Helianthus annuus L.) cultivars. Sunflower cultivars, namely Hysun-33, Hysun-38, M-3260, S-278, Alstar-Rm, Nstt-160, Mehran-II and Brocar were subjected to non-stress (0 mM NaCl) or salt stress (150 mM NaCl) in sand culture. On the basis of percent reduction in shoot biomass, cvs. Hysun-38 and Nstt-160 were found to be salt tolerant, cvs. Hysun-33, M-3260, S-278 and Mehran-II moderately tolerant and Alstar-Rm and Brocar salt sensitive. Salt stress markedly reduced growth, different gas exchange characteristics such as photosynthetic rate (A), water-use efficiency (WUE) calculated as A/E, transpiration rate (E), internal CO 2 concentration (C i ) and stomatal conductance (g s ) in all cultivars. The effect of 150 mM NaCl stress was non-significant on chlorophyll a and b contents, chlorophyll a/b ratio, RWC, RMP and leaf and root Cl -, K ? and P contents; however, salt stress markedly enhanced C i /C a ratio, free proline content and leaf and root Na ? concentrations in all sunflower cultivars. Of all cultivars, cv. Hysun-38 was higher in gas exchange characteristics, RWC and proline contents as compared with the other cultivars. Overall, none of the earlier-mentioned physiological attributes except leaf K ? /Na ? ratio was found to be effective in discriminating the eight sunflower cultivars as the response of each cultivar to salt stress appraised using various physiological attributes was cultivar-specific.

Now is an ideal time to reflect, to take stock of where the Australian water industry is at, to scan the trends, disruptions and innovation opportunities that lie ahead, to imagine what the water industry could look like in the next 20 to 30 years, and to work out what it would take to realise that vision. As the weight of history, the push of the present and the pull of the future unfold, there is a need to take control, innovate, advocate and consciously head in the desired direction to ensure that the collective vision of the future water industry is fulfilled. The Water Services Association of Australia (WSAA), the peak industry body that represents over 70 public and privately, owned water or water related organisations, commissioned the Institute to research and write this discussion paper on the trends and potential disruptions to Australia’s urban water futures.

"The increasing awareness of the accelerating rate of depletion of water resources is resulting in the high level of demand for water-efficient buildings. Currently towards 35% of human water use is unsustainable, drawing on diminishing groundwater and reducing the flows of major rivers: this percentage is likely to increase if climate change worsens especially "Global Warming", populations increase, groundwater becomes progressively depleted and supplies become polluted and unsanitary .

The Red Sea region is one of the potential touristic zones facing water shortage in Egypt, although its touristic and economic development strategies are primarily based on water availability. The Red Sea region has no surface water sources, low rainfall seasons on highlands and high-saline coastal ground water aquifers. The sustainable use of water implies resource conservation, environmental friendliness, technological appropriateness, economic viability, and social acceptability of development issues. Innovation includes the adaptation of traditional know-how to the current day challenges, the adaptation of the externally available technologies to the prevailing physical and social conditions .

The design, construction and operation of buildings have a tremendous impact on our environment and our natural resources. Green operation practices reduce resource use and pollution while increasing the value derived from each resource used. The building operation practices are large consumers of water. Many important decisions regarding a water-efficient building can be made during the operation phase. Some of these important decisions are using potable water efficient techniques, depending on waste water treatment methods and utilizing non-potable water applications. Water-efficient practices should be selected based on design and construction requirements, adaptation with climatic conditions and achievement of water-saving, durability and suitable initial costs .

In this thesis, studying different water-efficient techniques which can be used in the Egyptian Red Sea region. First, categorizing all discused techniques based on type of water used (potable or non-potable water). Then, analysis of water consumption in all indoor functional sectors of the selected resort case studies along the Red Sea coast. Finally, concluding a rating categorization for the different water-efficient techniques which can be used during a resort operation. It also defines the related decisions made by architects to choose the suitable water-efficient techniques during design process or after the construction of a resort in the Red Sea region."