Efficient Irrigation Practices Research Articles

THE USE OF SOIL MOISTURE PROBES FOR IMPROVED UNIFORMITY AND IRRIGATION CONTROL IN GREENHOUSES

There is wide variety of soil moisture sensors available for use in greenhouse production and research applications. Such sensors can play a valuable role in improving uniformity of substrate water content in greenhouses, as well as in automating irrigation based on plant water use. Quantification of spatial variability can be used to improve the design of irrigation systems to better match plant water use. The use of soil moisture sensors for irrigation control is promising, because it can greatly reduce temporal variability in substrate water content by watering based on actual crop water use. This not only results in better temporal uniformity, but can also greatly reduce water use. Understanding the spatial distribution of substrate water content and root water uptake within a container is important in determining the optimal sensor location within a container. At the same time, the properties of different sensors need to be considered when choosing the optimal sensor for a particular application. In small containers, it may be possible to measure most of the substrate with a single sensor, while in larger containers sensors ideally would be placed in that part of the substrate where most of the water uptake occurs. INTRODUCTION High quality irrigation water is becoming increasingly scarce in many areas of the world. Population growth, increased urbanization, and drought conditions can result in a decrease in the quantity of water available for irrigation, while salt water infiltration into fresh water aquifers can affect water quality in coastal areas. Efficient irrigation practices for agricultural production, including greenhouse production, will become increasingly important. Not only is greenhouse irrigation directly affected by the quality of the available irrigation water, greenhouse irrigation practices also can affect water quality. Soilless substrates generally have a low anion exchange capacity, and greenhouse growers typically use water-soluble fertilizers. This combination can result in leaching of water and dissolved nutrients, especially nitrate and phosphate. If this leachate is not collected and recycled, runoff from greenhouses can result in significant non-point source pollution (Lea-Cox et al., 2001). Increasingly strict environmental regulations put pressure on greenhouse growers to irrigate more efficiently in order to conserve water and reduce the risk of negative environmental impacts of their facilities. To improve irrigation practices, a detailed understanding of the spatial and temporal dynamics of the water in the root zone is required. Many commercial greenhouses use timers to turn irrigation on and off. Timers do not take into account that crop water use changes on a day-to-day basis, based on environmental conditions such as solar radiation, temperature, humidity, and air circulation. For example, daily water use of vinca (Catharanthus roseus) throughout a 40day period is shown in Figure 1, along with the daily light integral (DLI, total daily a mvanier@uga.edu b sburnett@maine.edu Proc. IS on High Technology for Greenhouse Systems GreenSys2009

Weighing Lysimeters for Developing Crop Coefficients and Efficient Irrigation Practices for Vegetable Crops

Large, precision weighing lysimeters are expensive but invaluable tools for measuring crop evapotranspiration and developing crop coefficients. Crop coefficients are used by both growers and researchers to estimate crop water use and accurately schedule irrigations. Two lysimeters of this type were installed in 2002 in central California to determine daily rates of crop and potential (grass) evapotranspiration and develop crop coefficients for better irrigation management of vegetable crops. From 2002 to 2006, the crop lysimeter was planted with broccoli, iceberg lettuce, bell pepper, and garlic. Basal crop coefficients, Kcb, defined as the ratio of crop to potential evapotranspiration when the soil surface is dry but transpiration in unlimited by soil water conditions, increased as a linear or quadratic function of the percentage of ground covered by vegetation. At midseason, when groundcover was greater than 70% to 90%, Kcb was ≈1.0 in broccoli, 0.95 in lettuce, and 1.1 in pepper, and Kcb of each remained the same until harvest. Garlic Kcb, in comparison, increased to 1.0 by the time the crop reached 80% ground cover, but with only 7% of additional coverage, Kcb continued to increase to 1.3, until irrigation was stopped to dry the crop for harvest. Three weeks after irrigation was cutoff, garlic Kcb declined rapidly to a value of 0.16 by harvest. Yields of each crop equaled or exceeded commercial averages for California with much less water in some cases than typically applied. The new crop coefficients will facilitate irrigation scheduling in the crops and help to achieve full yield potential without overirrigation.

Performance evaluation of evapotranspiration estimations in a model of soil water balance

AbstractSoil water content models have huge applications from an agronomic point of view and they are usually used as a sub‐model for weather and climate modelling. They are also useful tools for efficient water management irrigation practices. The aim of this investigation is to evaluate the performance of two different parameterizations of evapotranspiration when applied to a soil water balance model. Experimental data of a maize crop is used to evaluate model accuracy. The first methodology proposes a parallel resistance arrangement to represent the latent heat fluxes of the soil surface and the leaves in the canopy layer considering the leaf area index (LAI). The second methodology uses the parameterization proposed by the United Nations Food and Agriculture Organization (FAO), based on the crop coefficient (Kc) and the potential evapotranspiration obtained from the Penman–Monteith equation. The crop was divided into five plots with different irrigation systems according to their phenological stages. The model suitably predicts daily soil water content in five different irrigation systems. Predictions of soil water content using the LAI or Kc methodology tend to overestimate observations. In addition, the model has better predictions using the LAI methodology than the Kc methodology. The root mean square error and the determination coefficient were 0.059 and 0.92, respectively, with the LAI methodology and 0.063 and 0.87, respectively, using the Kc methodology. Copyright © 2010 Royal Meteorological Society

Growth and Water Use of Petunia as Affected by Substrate Water Content and Daily Light Integral

More efficient irrigation practices are needed in ornamental plant production to reduce the amount of water used for production as well as runoff of fertilizers and pesticides. The objective of this study was to determine how different substrate volumetric water contents (θ) affected petunia (Petunia ×hybrida) growth and to quantify the daily water use of the plants. A soil moisture sensor-controlled irrigation system was used to maintain θ within ≈0.02 m3·m−3 of the θ threshold values for irrigation, which ranged from 0.05 to 0.40 m3·m−3. Shoot dry weight increased as the θ threshold increased from 0.05 to 0.25 m3·m−3 and was correlated with the total amount of irrigation water applied over the 3-week course of the experiment. The daily water use of the petunias grown with a θ threshold of 0.40 m3·m−3 was 12 to 44 mL/plant and was positively correlated with both plant age and daily light integral. Lower θ thresholds resulted in a decrease in both leaf water (ψ) and osmotic potential (ψS). A decrease in turgor pressure (P) at lower θ was seen at 11, but not 20 days after the start of the treatments. There were no significant effects of θ on ψ, ψS, or P on fully rehydrated plants at the end of the study. Plants were able to survive and grow at all θs, although water at a θ less than 0.20 m3·m−3 is generally considered to be unavailable to the plants. Results show that it is possible to automatically irrigate plants with the use of soil moisture sensors, and this approach to irrigation may have applications in controlling the growth of ornamental plants.

Opportunities to reduce the vulnerability of dryland farmers in Central and West Asia and North Africa to climate change

The world's drylands will face not only increasing temperatures with climate change but more importantly also disruptions to their hydrological cycles resulting in less and more erratic rainfall that will exacerbate the already critical state of water scarcity and conflicts over water allocation. The rural poor in dry areas will suffer the most from these changes and will require a range of coping strategies to help them adapt to changing climates. Strategies will include changing of cropping systems and patterns, switching from cereal-based systems to cereal–legumes and diversifying production systems into higher value and greater water use efficient options. The latter include judicious use of water using supplementary irrigation systems, more efficient irrigation practices and the adaptation and adoption of existing and new water harvesting technologies. Scope for the application of conservation agriculture in dry areas is thought to be limited by low biomass production but current evidence suggests that even small amounts of residue retention can significantly decrease soil erosion losses. These options will be supplemented by the development of more drought and heat tolerant germplasm using traditional and participatory plant breeding methodologies and better predictions of extreme climatic events. The majority of drylands are occupied by rangelands with some 828 Mha in West Asia and North Africa alone. These vast areas provide environmental services such as the regulation of water quantity and quality, biodiversity and carbon sequestration. Rangelands have been neglected in the past partly because of problems of ownership, access and governmental policies that discourage investments in rangelands. The idea of payment for environmental services in rangelands is in its infancy but is discussed here as a potential option for better use and management of rangelands and as a safety net to reduce the vulnerability of rangeland inhabitants to climate change. In addition to the promising technological options to reduce vulnerability to climate change a brief discussion is included on the institutional and policy options needed to create a better enabling environment for increased adaptation and ecosystem resilience.

Caracterização do enraizamento da beterraba sacarina (Beta vulgaris L.) num solo de aluvião

Knowledge of plant rooting patterns and their evolution during the crop season is important for the apropriate soil water and nutrients management. The implementation of efficient irrigation practices – such as the irrigation management in real time for a certain area – needs information on meteorological, soil and crop parameters: such as crop growth stage, crop coefficients, paths of rooting depth, crop sensitivity to water stress, allowable soil water deficit, etc. Also, the characteristics of irrigation events should also be known, normally irrigation amount, opportunity, and evaluation. The objective of the present study is to evaluate a sugar beet crop growth including root growth pattern, on an Alluvial soil, under irrigation to give the crop the optimum water amount for maximum growth. The minirizotron method was used for monitoring root growth during crop season. Later on, trenches were opened for directly observing and measuring root development and pattern, up to 50 cm depth. Beet root depth and weight were evaluated at several points – growing stage from 0 to 69 days after seeding (DAS), yield formation from 69 to 166 DAS, and ripening from 166 to 196 DAS - and crop growth indices were also determined: leaf area index (LAI), and the duration of crop growing stages. Finally, biomass and grain production were evaluated. Data obtained showed that: 1) Maximum values for biomass and LAI were observed at 96 to 111 days, the values decreasing afterwards, while leaf senescence and rapid root growth occurred; and 2) Mass and depth of the beet root was observed to increase throughout the crop cicle, but faster between 96 and 111 DAS, reaching 2000 g and 40 cm respectively at 196 DAS. Images obtained with the minirizotron showed that fine beet roots had grown down to 90 cm depth.

A low-cost microprocessor and infrared sensor system for automating water infiltration measurements

Understanding the nature of soil infiltration properties is important for a number of applications, including planning efficient irrigation and erosion control practices, evaluating effectiveness of linings for sanitary landfills and waste lagoons, and landscape design and management. A common method for measuring infiltration is with the use of cylinder infiltrometers. This method can be very labor intensive and time-consuming, thus limiting its practicality. We describe the construction of an inexpensive system that can be readily adapted to single- and dual-ring infiltrometers to provide automated measurements on the scale of seconds to days. The system is comprised of an infrared distance-measuring sensor and microcontroller that can be programmed to collect water level measurements at various time intervals. Data are logged by the system in the field and can be downloaded for processing and analysis. This system is not only inexpensive, but also small, lightweight and versatile, and can be readily adapted to collect additional parameters.

Predicting Soil Salinity under Various Strategies in Irrigation Systems

This paper presents a model to estimate the soil salinity for different on-farm management strategies under irrigated conditions. It is based on research in the Manicoba irrigation scheme in northeast Brazil, where upward flow from the shallow water table is the main cause of soil salinization. The model calculates soil water and salt balances for the topsoil. It is calibrated for the topsoil of abandoned plots and for the root zone (0.9 m) of mango trees. Simulating the effect of different management scenarios on soil salinity may help to organize the switch from intensive surface irrigation to more efficient irrigation practices.

Rivers of Life: the challenge of restoring health to freshwater ecosystems

The world is moving into a period of widespread water stress and competition, with enormous implications for food security, the health of the aquatic environment, and social and political stability. In the second half of the 20th Century water demand more than tripled, the major factor being irrigation for food production. Over the same period, the number of large dams worldwide climbed from 5,000 to 45,000-bringing about a major alteration of river hydrology and ecosystem function. Rivers have been disconnected from portions of their channels, their floodplains, their deltas, and from the seas into which they empty. The resulting loss of aquatic habitat has put freshwater life in grave jeopardy. In the 21st Century it will be possible to satisfy the needs of 8-9 billion people while protecting the health of aquatic ecosystems, but only with a fundamental shift in the way society uses, manages and values freshwater. It will likely require a doubling of water productivity over the next 25 years--including more efficient irrigation practices and greater recycling of wastewater. To guide policy, nations need to systematically determine their freshwater ecosystem flow requirements in a way that perhaps only South Africa is attempting so far. Underpinning all these measures is the need for a guiding water ethic that states that enough water should be provided for all living things before some get more than enough.

Nutrient leaching losses from undisturbed soil cores following applications of piggery wastewater

Land disposal of wastewater from intensive livestock industries can result in large amounts of nutrients and salts being applied to soils. When irrigated at rates to meet crop phosphorus (P) requirements, nitrogen (N), calcium (Ca), magnesium (Mg), potassium (K), sodium (Na), chloride (Cl), and sulfate (SO4) applied in the wastewater often exceed crop demands, and are susceptible to leaching. Leaching of surface-applied piggery wastewater was investigated using large undisturbed soil cores (30 cm i.d. by 60 or 75 cm long) from 2 piggery wastewater disposal areas (Site 1, Vertosol; Site 2, Sodosol) in south-east Queensland. About 3% of the total wastewater P applied to the Vertosol, and about 10% of that applied to the sodosol, was leached. The magnitude of these losses was consistent with the chemical properties of each soil, and the availability of P sorption sites (i.e. hydrous Fe oxides). The major forms of P in the leachate included both molybdate reactive P (MRP) and unreactive P (UP, includes dissolved organic P, soluble organic P, particulate P, and non-reactive P). Phosphorus leached from the Vertosol was largely (≈80%) as UP because the MRP was sorbed by the soil colloids. Much of the P leached from the sodosol was present as MRP (≈70%) because the wastewater applied to this soil also contained about 70% MRP, and this soil had only a limited ability to sorb MRP. Losses of nitrogen (N) were found to be of a major environmental concern. Both wastewater samples contained very high levels of N, with ammonium (NH4-N) making up about 80% of the total Kjeldahl N (TKN) and organic N about 20%. Negligible amounts of applied NH4-N were detected either sorbed by the soil or in the leachate because it was converted to nitrate (NO3-N) within the soil core. This NO3-N was highly mobile, and was readily leached from the soil cores. Nitrogen represented the major limitation to the long-term use of land for disposal of piggery wastewater. For land disposal to be an effective management option, N applied in piggery wastewater may need to be limited to about 200 kg/ha.year. Significant amounts of Ca, Mg, K, and Na applied in the wastewater were leached from the soil cores. It is recommended that more attention be placed on the impact of N (TKN, NH4-N, and NO3-N), Ca, Mg, K, and Na on the receiving soil and water environments rather than focussing primarily on wastewater P. Management strategies should be developed for disposal sites to minimise leaching losses by maximising nutrient removal from the soil solution through crop uptake, reaction with the soil colloids, and efficient irrigation practices. nitrogen, phosphorus, cations, nitrification, piggery wastewater.

Effects of agricultural activities on water pollution with nitrates and pesticides in the Central Valley of Chile

The objectives of this study are, first, to describe the present use of fertilisers between the Regions III and VIII of Chile, identifying the associated environmental impacts and their relationship with the predominant agricultural practices and climatic characteristics. Secondly, to simulate the transport of nitrates and pesticides in a dairy and breeding farm of the Central Valley of Chile, employing EPIC (USDA/ARS) in order to determine the importance of these contamination processes. In the North area of Chile, agricultural production generates soil and groundwater salinization problems due to low average rainfall and the use of highly efficient irrigation practices. In the Central zone, nitrate contamination due to agricultural diffuse pollution is evident; this is especially valid for groundwater contamination with nitrates. The South Central area suffers from eutrophication due to an increase in the nutrient levels in surface water. The simulation indicates that the dairy farm in the Central Valley of Chile has a soil loss of 5.02 tons/ha/year or of 14.67 tons/ha/year, based on MUSS or USLE estimates, respectively. It is important to point out that loss of NO3 and pesticides estimated by MUSS and USLE do not exceed maximum allowable standards.

Effects of agricultural activities on water pollution with nitrates and pesticides in the Central Valley of Chile

The objectives of this study are, first, to describe the present use of fertilisers between the Regions III and VIII of Chile, identifying the associated environmental impacts and their relationship with the predominant agricultural practices and climatic characteristics. Secondly, to simulate the transport of nitrates and pesticides in a dairy and breeding farm of the Central Valley of Chile, employing EPIC (USDA/ARS) in order to determine the importance of these contamination processes. In the North area of Chile, agricultural production generates soil and groundwater salinization problems due to low average rainfall and the use of highly efficient irrigation practices. In the Central zone, nitrate contamination due to agricultural diffuse pollution is evident; this is especially valid for groundwater contamination with nitrates. The South Central area suffers from eutrophication due to an increase in the nutrient levels in surface water. The simulation indicates that the dairy farm in the Central Valley of Chile has a soil loss of 5.02 tons/ha/year or of 14.67 tons/ha/year, based on MUSS or USLE estimates, respectively. It is important to point out that loss of NO3 and pesticides estimated by MUSS and USLE do not exceed maximum allowable standards.

Irrigation Effects in Oklahoma and Texas

Groundwater contamination is a serious water quality problem since 50% of the population derives drinking water from groundwater sources. Severe water quality problems have resulted from deep percolation under irrigated areas, carrying high salt loads and increased nitrate concentrations to groundwater aquifers. This review looks at studies that have dealt with the effect of deep percolation from irrigation on groundwater quality. Recommendations are developed to minimize the undesirable effects of groundwater contamination by irrigated agriculture. Major among the conclusions is that improved and/or more efficient irrigation and fertilizer management practices are required to minimize the adverse impact of irrigated agriculture on the quality of underlying groundwater. When water and nutrient application and use efficiencies are improved, deep percolation is decreased and less downward movement of pollutants occurs. Structural improvements in irrigation systems are a necessary aid to achieving the desired level of management.

A NEW CHALLENGE FOR WESTERN WATER SUPPLIES1

ABSTRACT: In many of the limited water resource areas of the western United States most water supplies have been put to beneficial uses. Energy, a fast expanding high‐priority water use, is making challenging demands for these limited supplies. Can water supplies be stretched, supplemented, or redirected so that present uses can be maintained and energy water needs satisfied? The Bureau of Reclamation is investigating innovative methods of water management, reregulation, and use to meet these demands. Related programs under study include potentials for: development of additional hydroelectric power, installation of low‐head turbines in western water courses, utilization of pumped storage and underground storage, use of geo‐thermal heat, extension of water supplies through more efficient irrigation systems and practices, and weather modification.

IRRIGATION DEVELOPMENT IN THE USSR DURING THE 10TH FIVE-YEAR PLAN (1976–1980)

Irrigation development in the 10th Five-Year Plan is a continuation of long-term Soviet efforts to improve agriculture in arid regions by supplementation of natural moisture supplies. Major emphasis is on expanding irrigation in Central Asia, the Ukraine, the North Caucasus and along the lower Volga. Serious problems continue to plague this economic sector: organizational inadequacies, an inefficient technology, and widespread secondary soil salinization. Serious efforts are being made to alleviate these difficulties in the 10th Five-Year Plan. The most critical future obstacle to expansion of irrigation may be a shortage of surface flow, necessitating more efficient irrigation practices, greater use of ground water, and ultimately large-scale interbasin river diversions.

Land and Water Use Impacts on Ground‐Water Quality in Las Vegas Valleya

ABSTRACTMarked changes in the occurrence and quality of near‐surface ground water in Las Vegas Valley, Nevada result from urban and industrial land and water use practices. In‐valley recharge has increased tenfold in the period 1943 to 1973 and now amounts to about 40,000 acre‐feet/year (49.3 million m3). Ground‐water flows leaving the Valley have increased from 250 acre‐feet/year to about 12,000 acre‐feet/year.Twenty to 400 tritium units (T.U.) in shallow ground water confirm widespread addition of recent recharge. Trend‐surface analysis of recent water‐quality data for depth intervals or “slices” of 0 to 50, 51 to 100, and 101 to 300 feet (0 to 15.2 m, 15.5 to 39.5 m, 30.8 to 91.4 m) revealed that natural trends below a depth of 50 feet are explainable in terms of broad hydrogeologic conditions. From 0 to 50 feet quality is highly irregular and markedly more influenced by land and water use practices and waste disposal in particular. Chloride, TDS, and nitrate are particularly diagnostic of return flows as is spring development and (or) a rising water table resulting from increased recharge and low vertical permeability. Statistical tests on water‐quality data for the period 1912 to 1968 yielded generally insignificant change with time. However, the extreme paucity of the data base makes any conclusion questionable.More efficient irrigation practices could reduce the present irrigation water demand by 15,000 acre‐feet/year and reduce return flows by 11,000 acre‐feet/year. Return flows by the year 2000 could easily amount to 75,000 acre‐feet/year or about three times the total water budget of the Valley prior to urbanization. Therefore, groundwater problems are likely to worsen and, if present monitoring practices prevail, go unnoticed.