Microirrigation Systems Research Articles

Dealing with Iron and Other Micro-Irrigation Plugging Problems

SL-265, an 8-page illustrated fact sheet by Tom Obreza, Ed Hanlon, and Mongi Zekri, describes problems with emitter plugging and discusses management strategies to overcome and correct causes of plugging in micro-irrigation systems. This publication focuses, in particular, on iron scaling, documenting recent successes in treating this common problem in Florida. Includes sources of further information. Published by the UF Department of Soil and Water Science, August 2008. SL 265/SS487: Dealing with Iron and Other Micro-Irrigation Plugging Problems (ufl.edu)

COMPARISON OF MICRO IRRIGATION SYSTEMS FOR OLIVE TREES

Micro-Irrigation Systems (MIS) apply water through small devices which deliver it onto the soil surface very near to the plant, which means in this context the use of bubbler, mini–sprinkler and trickle irrigation systems. From 2003 to 2006, 13 feddans of field research were established in sandy soil at Wadi EL Natrown On-Farm Irrigation Department Research Station operated by the Water Management and Irrigation System Research Institute, to evaluate the effect of MIS on olive trees. The experimental site was arranged in a split plots design. On 08-02-2003 olive trees (Olea europaea L, Calamata cv.) were planted in the center of an irrigated round base of 1 m diameter. The distance between the tree rows and the trees within the same row are 5ms. Each plot was divided into six replicates giving 18 experimental plots. All the micro irrigation systems were designed with the same control head components which consists of non- return valve, flow meter, venturi, air valve, pressure relief valve and 3 pressure gauges. Regarding the distributor units technical specifications and their placement: 1) For the trickle treatment 4 emitters (12 l/h) per each tree placed on one lateral line PE 16 mm diameter passing through the center of the tree round base; where each emitter is 30 cm distant from the next one; 2) For the bubbler treatment one bubbler per each tree (100 l/h) placed in the tree round base , 25 cm distance from the tree stem moving monthly in 180° clockwise to maintain good water distribution; 3) For the mini- sprinkler treatment one mini-sprinkler (70 l/h) per each tree with the same procedure as the bubbler. A comparison was made between the different systems taking into account the following points: olive trees morphology (plant height, stem diameter, shoots number/tree, leaves number/tree, shadow area and root distribution), number of fruits/tree, fruit weight, yield/tree, total yield per feddan, yield efficiency and both soil moisture content and soil salt distribution. Hydraulics characteristics for each type of MIS were also monitored. The results obtained show the usefulness of trickle irrigation system in olive trees growing where the trees height increased (cm) by 10 and 9.2%, stem diameter (mm) increased by 6 and 14%, shoots number per tree increased by 8 and 14%, leaves number per tree increased by 13 and 17%, shadow area (cm2) increased by 6 and 13% compared with bubbler and micro irrigation system respectively. Trickle irrigation systems demonstrate the highest values of sand soil moisture content which is about (18.19, 16.66 and 10.45% by weight) in the soil layers (00–30), (30-60) and (60-90) cm, respectively, whereas the bubbler irrigation systems were (16.66, 14.46 and 9.01% by weight) in the previous soil layers respectively, followed by mini-sprinkler irrigation systems treatment which were about (10.45, 9.01 and 6.58% by weight) in the same soil layers respectively. The olive trees root distribution under trickle irrigation showed more regularity than other types due to root distribution relative to the placement and the number of irrigation distributors. The net effect of trickle-irrigation was to increase water saving for producing one kilogram of olive fruits with 18 and 35 % less than with bubbler and mini-sprinkler respectively. The number of fruits increased under trickle irrigation by 16 to 24% while the olive tree yield (kg/tree) increased by 18 to 32% compared with bubbler and mini sprinkler irrigation system respectively. Trickle-irrigation can be recommended as an efficient irrigation system for olive trees in the irrigation areas of Wadi El Natrown in the west of the delta region.

Neuro-fuzzy approach in estimating Hazen–Williams friction coefficient for small-diameter polyethylene pipes

Low-pressurized multiple outlet pipelines are extensively used to uniformly distribute irrigation water under different types of low-volume micro-irrigation systems. Polyethylene (PE) is the main pipe material for smooth pipes in sub-main unit of a micro-irrigation system due to its flexibility and resistibility to the sun. For computing friction loss in PE pipes, many practicing engineers hesitate to use the generalized Darcy–Weisbach equation since the friction coefficient varies at each section of the lateral. Although its non-dimensional homogeneity and limitations in applicability, the empirical Hazen–Williams equation is still commonly preferred, because of its simplicity in practice. In the current hydraulic computations for friction loss, some typical fixed values for the Hazen–Williams coefficient ( C HW) in PE pipes are still recommended regardless of pipe diameter. Experimental works have confirmed that there is a strong dependence of the C HW on pipe diameter ( D), therefore a single value of the C HW cannot be used for all ranges of pipe diameters. The primary focus of this research is to investigate the accuracy of a fuzzy rule system approach to estimate the proper value of the C HW coefficient for different pipe diameters because of the imprecise, insufficient, ambiguous and uncertain data available. A neuro-fuzzy approach was developed to relate the input (flow rate and pipe diameter) and output ( C HW and friction loss) variables. The application of the proposed approach was performed using the measured data for friction losses available from the recent experimental analysis, hence its performance was tested using some statistic parameters for error estimation. The examination results indicated that through fuzzy rules and membership functions the proposed model can be successfully used to identify the proper values of C HW coefficient hence accurately estimate friction losses through smooth PE pipes.

MIRRIG: A decision support system for design and evaluation of microirrigation systems

The decision support system (DSS) MIRRIG has been developed to support the design of microirrigation systems and to advise farmers as a result of field evaluations. It is written in Visual Basic 6.0, runs in a Windows environment, and uses a database with information on emitters and pipes available in the market, as well as on crops, soils and the systems under design. MIRRIG is composed by design and simulation models and a multicriteria analysis model that ranks alternative design solutions based upon an integration of technical, economic and environmental criteria. User friendly windows are adopted for handling the databases and to manage the sub-models. The model allows creating and comparing a set of design alternatives relative to the pipe system and the emitters, either drip or microsprinkling emitters. For each alternative, the pipe system is sized and the irrigation system is simulated to produce performance, environmental and economic indicators. These include uniformity of water application, potential for contamination with agrochemicals due to water percolation, and installation and operation costs. Those indicators are used as attributes of the selected criteria. All alternatives are then compared and ranked through multicriteria analysis where the weights giving the relative importance of the adopted criteria are defined by the user. These procedures allow selecting the best design alternative and solving the complexities involved in the design of microirrigation systems. The model is available from the website www://ceer.isa.utl.pt/cms or by contacting cpedras@ualg.pt.

Multicriteria analysis for design of microirrigation systems. Application and sensitivity analysis

This paper presents a practical application of the DSS MIRRIG for the design of a microirrigation system for a citrus orchard in Algarve (Portugal). Several alternatives were considered using different emitter types (drippers, sprayers, pressure-compensating and non-pressure compensating emitters), different pipe sizes and layouts with and without pressure regulation valves, as well as different pressure head and discharge at the upstream end of the systems. This application is described and the ranking of alternative designs is analysed using the weights given by the farmer to the hydraulic, economic and environmental criteria. An analysis of impacts resulting from selecting different weights is presented aimed at understanding the sensitivity of the model in relation to those criteria. In addition, a sensitivity analysis is performed to test the robustness of the algorithms used for ranking with respect to changes in concordance and discordance threshold values, which show that the values selected by the model are those providing for a more clear ranking of design alternatives.

Integrating water harvesting and gravity-fed micro-irrigation system for efficient water management in terraced land for growing vegetables

Enhancing and sustaining the productivity of hill agriculture in North-West Himalayan Region (NWHR) is a major challenge as it is practised under ecologically fragile environments which include altitudinal, climatic and topographical variations. The present study envisaged the scope for water resources development and its utilization in crop production through gravity-fed micro-irrigation enhancing water use in the terrace land of NW Himalaya. The water was harvested from a distantly located ultra low discharge water source to the lined tank and the micro-irrigation system (MIS) was integrated such that it could be operated by gravity. The system performance was found satisfactory as the flow rate variation, Christiansen uniformity coefficient and distribution uniformity were 26.5%, 86.3% and 87.5%, respectively. The system saved 41.1% and 33.3% irrigation water as compared to check basin irrigation in case of vegetable pea and French bean, respectively. The water use efficiency of the system was significantly higher than check basin irrigation. Economic indicators such as Net Present Value, Benefit Cost Ratio, Internal Rate of Return and payback period were used to evaluate the gravity-fed MIS and were INR 160,523 (1$ = 40.50 INR), 1.78, 12.2% and 3.38 years, respectively. It is recommended that the gravity-fed MIS must be integrated with the water harvesting system to effectively and economically utilize the water in vegetable cultivation in terraced land of the hill farming system.

Definition of a SCADA system for a microirrigation network with effluents

A supervisory control and data acquisition (SCADA) system has been developed to monitor and control microirrigation system performance. The microirrigation system had four types of filtration units and, placed after each one of them, twenty-four irrigation laterals using urban effluents. The SCADA system activated the irrigation system and the backwashing filter procedure. It also monitored pressure and flow at the filtration units and irrigation laterals to assess clogging problems and measure the consumed water volume in filter backwashing. The system was also prepared for remote access via Internet.

Methods and technologies to improve efficiency of water use

The competition for existing freshwater supplies will require a paradigmatic shift from maximizing productivity per unit of land area to maximizing productivity per unit of water consumed. This shift will, in turn, demand broad systems approaches that physically and biologically optimize irrigation relative to water delivery and application schemes, rainfall, critical growth stages, soil fertility, location, and weather. Water can be conserved at a watershed or regional level for other uses only if evaporation, transpiration, or both are reduced and unrecoverable losses to unusable sinks are minimized (e.g., salty groundwater or oceans). Agricultural advances will include implementation of crop location strategies, conversion to crops with higher economic value or productivity per unit of water consumed, and adoption of alternate drought‐tolerant crops. Emerging computerized GPS‐based precision irrigation technologies for self‐propelled sprinklers and microirrigation systems will enable growers to apply water and agrochemicals more precisely and site specifically to match soil and plant status and needs as provided by wireless sensor networks. Agriculturalists will need to exercise flexibility in managing the rate, frequency, and duration of water supplies to successfully allocate limited water and other inputs to crops. The most effective means to conserve water appears to be through carefully managed deficit irrigation strategies that are supported by advanced irrigation system and flexible, state‐of‐the‐art water delivery systems. Nonagricultural water users will need to exercise patience as tools reflecting the paradigmatic shift are actualized. Both groups will need to cooperate and compromise as they practice more conservative approaches to freshwater consumption.

Studying the feasibility of using microirrigation systems for vegetable production in a canal command area

AbstractField investigations were carried out for 3 years with the aim of studying the feasibility of using microsprinkler and drip irrigation systems for vegetable production in a canal command area. These systems were compared with the existing flood irrigation method for onion production with four irrigation levels, viz. 0.60, 0.80, 1.00 and 1.20 of irrigation water to cumulative pan evaporation ratio (IW/CPE). Microsprinkler and drip irrigation systems were also compared with fertigation rate of 100 (50:25:25 NPK), 150 (75:37.5:37.5 NPK) and 200 (100: 50: 50 NPK) kg ha−1. Microirrigation systems resulted in higher onion yield and greater profitability than surface irrigation at each irrigation schedule. However, microsprinklers indicated better economics than a drip irrigation system. Microsprinkler, drip and surface irrigation system with 1.20 IW/CPE of irrigation produced maximum crop yields of 34.34, 33.10 and 22.57 t ha−1, respectively. Increased crop yield with microsprinkler and drip irrigation is the factor behind higher profitability than existing surface irrigation. Reduction in nutrient application by 25% in fertigation from the dose of flood irrigation did not reduce yield and net returns significantly. But net return was significantly higher in microsprinkler (Rs 67 334 ha−1) than drip (Rs 59 930 ha−1) fertigation. The overall results of the present study favoured microsprinkler over existing irrigation methods for onion production in a canal command area with higher profit under limited available surface water. Copyright © 2008 John Wiley & Sons, Ltd.

Determining Operating Inlet Pressure Head Incorporating Uniformity Parameters for Multioutlet Plastic Pipelines

An important objective of a microirrigation system is to determine the proper operating inlet pressure head, ensuring the desired level of water application uniformity as well as the allowable pressure head variation along the multioutlet pipeline. This paper offers, simple, direct, but sufficiently accurate, relationships incorporating different microirrigation uniformity parameters, such as Christiansen uniformity coefficient, coefficient of variation of emitter discharge, and allowable pressure head variation, to determine the operating inlet pressure head (i.e., pressure head and outflow profiles) for multioutlet plastic pipelines. In this analysis some mathematical expressions were deduced to relate three uniformity parameters; then the operating inlet pressure head is simply reformulated by taking into account a multiplying factor α to the required average outlet pressure head, in terms of three uniformity parameters. Resulting, the influence of different uniform pipe slopes on the water application uniformity and the operating inlet pressure head for various emitter discharge exponents, was evaluated. In addition, to cover various design combinations an extensive comparison between the proposed equations and those of the previous studies was also presented. Examination of the results from this research indicated that, the performance of the proposed technique is sufficient in comparison to those of the recent analytical and numerical procedures.

Fator de atrito em tubos de polietileno de pequenos diâmetros

On this paper, the results of an experimental study on the hydraulic friction loss for small-diameter polyethylene pipes are reported. The experiment was carried out using a range of Reynolds number between 6000 to 72000, obtained by varying discharge at 20oC water temperature, with internal pipe diameters of 10.0 mm, 12.9 mm, 16.1 mm, 17.4 mm and 19.7 mm. According to the analysis results and experimental conditions, the friction factor (f) of the Darcy-Weisbach equation can be estimated with c = 0.300 and m = 0.25. The Blasius equation ( c = 0.316 and m = 0.25) gives an overestimate of friction loss, although this fact is non-restrictive for micro-irrigation system designs. The analysis shows that both the Blasius and the adjusted equation parameters allow for accurate friction factor estimates, characterized by low mean error (5.1%).

Water balance and crop coefficient estimation of a citrus orchard in Uruguay

The actual evapotranspiration (ETc) of mature "Valencia" orange trees (Citrus sinensis (L.) Osb.), drip-irrigated and non-irrigated, was calculated using the water balance method, over three years. Annual ETc was 24% higher from irrigated trees that from non irrigated trees (767 and 620 mm/year, respectively). Maximum monthly average ETc was 3.3 mm/day or 80 L/tree/day (trees were spaced at 6 x 4 m). Generally ETc rate was reduced in January, the month of maximum atmospheric demand, compared with December, even under fully irrigated trees. The average annual value of the crop coefficient (Kc) for irrigated trees was 0.69. Monthly Kc values also showed a clear seasonal trend, with minimum values in summer (0.60), intermediate values in autumn and spring (0.77 and 0.80, respectively) and maximum values in winter (0.87). These values provide a useful base for the design and operation of microirrigation systems, for mature citrus trees in Uruguay.

Analysis of relationships among different parameters of irrigation uniformity in fully-compensated micro-irrigation system

Analysis of relationships among different parameters of irrigation uniformity in fully-compensated micro-irrigation system

Climate change impacts on irrigation water requirements in the Guadalquivir river basin in Spain

Irrigated production in the Guadalquivir river basin in Spain has grown significantly over the last decade. As a consequence, water resources are under severe pressure, with an increasing deficit between available supplies and water demand. To conserve supplies, the water authority has reduced the volume of water assigned to each irrigation district. Major infrastructural investments have also been made to improve irrigation efficiency, including the adoption of high technology micro-irrigation systems. Within a context of increasing water scarcity, climate change threatens to exacerbate the current supply-demand imbalance. In this study, the impacts of climate change on irrigation water demand have been modelled and mapped. Using a combination of crop and geographic information systems, maps showing the predicted spatial impacts of changes in agroclimate (climate variables that determine the irrigation requirements) and irrigation need have been produced. The maps highlight a significant predicted increase in aridity and irrigation need. Modelling of irrigation water requirements shows a typical increase of between 15 and 20% in seasonal irrigation need by the 2050s, depending on location and cropping pattern, coupled with changes in seasonal timing of demand.

Assessment of emitter discharge in microirrigation system as affected by polluted water

A drip irrigation system has the advantage of maintaining high water content near the plant root. However, its performance depends on water quality as it may induce the emitter clogging. In the Tohaku National Irrigation Project, in western Japan, mist spray emitters are widely used for irrigation in the field and greenhouses for vegetable and orchard crops. Seven emitters of different types were evaluated for the variation in their discharge rate without filter. The statistical analysis of mean discharge ratio and the coefficient of variation of the performance of emitters along a lateral line in the field indicated that the mist spray emitters had the best performance for irrigation in Tohaku area, particularly the new emitters or 1-year old emitters. The results suggest that after using the emitter line for two irrigation seasons it should either be replaced in the third season or washed carefully if further used.

Pressure-driven modeling for performance analysis of irrigation systems operating on demand

Assessing the performance of irrigation systems is required both to improve management activities and to identify appropriate modernization and/or rehabilitation measures. In pressurized irrigation systems, pressure and discharge variations cause low service performances and negatively impact farm sprinkler or micro-irrigation systems. Several models exist to simulate pressurized irrigation systems and assess the respective performance when a steady state approach may be assumed. However, when the variation in flow regimes and discharges at hydrants is pressure-driven, i.e., when the networks are not equipped with adequate flow limiters and pressure regulators at the hydrants, or when the pressure is insufficient at the hydrants, the flow rate delivered is a function of the available pressure and that approach does not apply. To allow the performance analysis of these systems, the FLUCS model has been developed and tested. It simulates flow in the pipe systems using a simplified solution of the characteristic equations of flow. The respective governing equations are described, as well as the boundary and initial conditions. The performance analysis adopted bases upon the computation of the relative pressure deficits at every hydrant within a given number of configurations of hydrants operating simultaneously. These configurations are randomly generated in a much larger number than the number of hydrants. This approach allows identifying which hydrants do not satisfy the preset pressure and discharge conditions and the areas where pipe sizes may be undersized, thus contributing to pressure deficits. This approach may be used for the analysis of performance of pressurized systems under operation or under design, including to assess the impact of different types of flow regulators and flow limiters. The model was tested with data collected in the Capitanata irrigation system (Southern Italy). Results demonstrate the ability of the model to reproduce the conditions observed at selected hydrants.

Economics, adoption determinants, and impacts of micro-irrigation technologies: empirical results from India

Micro-irrigation technologies are promoted for various reasons in India. Despite the reported significant economic advantages, and the concerted support of the government and NGOs, the current micro-irrigation area in India remains an insignificant proportion of its potential. This paper analyzes: (1) the economics of alternative micro-irrigation technologies, (2) the determinants of adoption, (3) the poverty outreach of the different micro-irrigation systems, and (4) the sustainability implications of micro-irrigation adoption. In line with the findings of other studies, this study indicates that micro-irrigation technologies result in a significant productivity and economic gains. The most important determinants of micro-irrigation adoption include access to groundwater, cropping pattern, availability of cash, and level of education, the social status and poverty status of the farmer. Contrary to the expectations, the majority of the current adopters of low-cost micro-irrigation systems are the better-off farmers. The study indicates that the impact of micro-irrigation systems on the sustainability of groundwater resources depends upon the magnitude of the overall productivity gain following the shift from traditional irrigation method to micro-irrigation system, the pattern of use of the saved water, and the type and potential number of adopters.

Nitrogen Sources for Organic Vegetable Crops

Fertilization is the most expensive cultural practice for the increasing numbers of organic vegetable growers in the United States. Nitrogen (N) is the most important and costly nutrient to manage, and cost-effective N management practices are needed for efficient organic vegetable production. There is a wide array of organic N sources available, but they vary in cost, N content, and N availability. Compost and cover crops are commonly used sources of N for vegetables because they are relatively inexpensive and offer additional nutrients or soil improvement qualities in addition to N. Studies have shown that compost quality factors that affect N mineralization vary by source and among different batches from the same source. Compost carbon to N ratio should be equal to or less than 20:1 to assure net short-term mineralization. Cover crops also vary in N content and mineralization rate after incorporation. Leguminous cover crops decompose and release N more rapidly than grass or cereal cover crops at the preheading stage typically incorporated. Even the most efficient N-supplying composts, cover crops, or other organic N sources do not release appreciable N to a subsequent crop beyond 6 to 8 weeks from incorporation, and this burst of early N may not synchronize with N requirements for many vegetable crops. Other potential organic fertilizer N sources have been evaluated for vegetables, and they vary in N cost and N mineralization rate. Materials evaluated include seabird guano, liquid fish, feather meal, corn meal (Zea mays), blood meal, and liquid soybean meal (Glycine max) among others. Of those evaluated, feather meal, seabird guano, and liquid fish stand out as more economical organic sources of available N. Organic sources generally lack uniformity and are bulky, unstable, and inconsistent as a group, and this contributes to additional hidden management costs for organic growers. Liquid organic N sources for use in microirrigation systems may have additional disadvantages caused by loss of valuable nutrient N that is removed by filters.

Evaluation of urea–ammonium–nitrate fertigation with drip irrigation using numerical modeling

Microirrigation with fertigation provides an effective and cost-efficient way to supply water and nutrients to crops. However, less-than-optimum management of microirrigation systems may cause inefficient water and nutrient use, thereby diminishing expected yield benefits and contributing to ground water pollution if water and nitrogen applications are excessive. The quality of soils, ground, and surface waters is specifically vulnerable in climatic regions where agricultural production occurs mostly by irrigation such as in California. Robust guidelines for managing microirrigation systems are needed so that the principles of sustainable agriculture are satisfied. The main objective of this research was to use an adapted version of the HYDRUS-2D computer model to develop irrigation and fertigation management tools that maximize production, yet minimize adverse environmental effects. This software package can simulate the transient two-dimensional or axi-symmetrical three-dimensional movement of water and nutrients in soils. In addition, the model allows for specification of root water and nitrate uptake, affecting the spatial distribution of water and nitrate availability between irrigation cycles. Recently, we analyzed four different microirrigation systems in combination with five different fertigation strategies for various soil types using a nitrate-only fertilizer, clearly demonstrating the effect of fertigation strategy on the nitrate distribution in the soil profile and on nitrate leaching. In the present study, the HYDRUS-2D model was used to model the distribution of soil nitrogen and nitrate leaching using a urea–ammonium–nitrate fertilizer, commonly used for fertigation under drip irrigation. In addition, the distribution of phosphorus and potassium was modeled. Model simulations are presented for surface drip and subsurface drip tape, each associated with a typical crop in California.

ANALYSIS AND DESIGN OF A MICROIRRIGATION LATERAL

Micro-irrigation systems are methods of applying water, nutrients and chemicals directly to the plant root area at a controllable rate, which allows maximum results and minimum use of water and energy. For these reasons, microirrigation systems are developed in arid countries with insuffi ciency water resources. It has expanded to many countries engaging in modern agricultural practices due to relatively high agricultural outputs and low energy expenses. For micro-irrigation to be profi table, system design’s must be based on precise calculations and rigorous management. The precision with which micro-irrigation lateral and network’s are designed is of fundamental importance to system operation, the uniformity of distribution of water and fertilizer, and the consumption of energy. The computation model presented in this paper is based on equations of mass and energy conservation within an elemental control volume on the lateral. Considering the variation of the out-fl ow regime leads to an algebraic, coupled and non-linear equation system whose resolution is based on the numeric methods to a defective analytic approach. In this work, the control volume method was selected due to its simplicity. A program of computation has been developed for this and applied to a lateral for the fi rst time. Results from this simple model are precise and are similar to those from other validated models. Precision design increase effi ciency of water and fertilizer distribution. This method can be applied to the design of micro-irrigation lateral’s or network’s.