W1128: Reducing Barriers to Adoption of Microirrigation

(Multistate Research Project)

Status: Inactive/Terminating

W1128: Reducing Barriers to Adoption of Microirrigation

Duration: 10/01/2004 to 09/30/2009

Administrative Advisor(s):

NIFA Reps:

Statement of Issues and Justification

Although microirrigation has proven to be an efficient irrigation method, it has been adopted on only a fraction of the land area appropriate for the technology. An irrigation survey conducted by Irrigation Journal in 2000 indicated there was 1.26 million hectares of microirrigation in the United States, reflecting 4.9% of the total irrigated land area. There are numerous barriers to adoption of microirrigation. However, the significance and/or magnitude of these barriers and the manner by which they combine and affect the decision making process are not well understood. The rules/reasons for adoption in one region may differ vastly from another, yet may have some commonality if fully explored. There have been few comprehensive studies of microirrigation adoption. In the proposed study, a different approach will be utilized to assess the significance of these barriers. It is often difficult to assess the true barrier to adoption of a technology from an individual that is currently not using that technology. It may be more appropriate to examine the adoption issues of those that have taken the step towards implementing microirrigation. The proposed multi-state survey, implemented on an incremental and appropriately modified basis can result in the formulation of a more general set of observed barriers. Once identified, these barriers can be addressed through a coordinated, multi-state effort with a cost-efficient use of manpower. The first objective of this study is to perform this comprehensive assessment of the different barriers to adoption of microirrigation. However, it is presently known that there are certain technical barriers in design, operation, and management that can be addressed through science. These barriers that form the basis of the remaining two objectives will be concurrently addressed during the barrier assessment phase.

One technical barrier to adoption lies in the design, layout, installation, and operational procedures for the microirrigation system. The effects of system design, lateral installation techniques, and placement on water application, crop performance, and quality continue to be issues that present uncertainty to the stakeholders (growers). The use of surface or subsurface drip irrigation varies by region and by crop, and is often based on perceived constraints of the vertical placement of the driplines. Areas of high-value crops tend to be associated with surface installations, while regions growing lower value crops can only economically consider multi-year SDI systems. In the Texas High Plains, soil water at planting is often limited, causing germination problems and these problems can be compounded by the cracking nature of many soils in the region (Evett et al.,1996, 2000). Cracks in the soil stop the movement of water from driplines to parts of the row that are on the other side of a crack. Efforts to examine and reduce these barriers to adoption should be increased. Similarly, some crops such as potato, are very sensitive water stress and dripline placement becomes a critical issue. Salinity buildup and nutrient distribution can also be negatively affected by system layout and dripline placement. Nonuniformity of water and nutrient application for some high value crops may justify the need for technologies that can vary their application spatially on a much smaller scale than presently considered. Research is needed to determine if system design, dripline placement, and system management can be structured in a manner to reduce these barriers. A more thorough understanding of water movement and redistribution as affected by system design, emitter discharge, soil parameters, and crop type can reduce some of these barriers. SDI installation techniques may distort emitter flow paths or alter emitter spacing (through stretching), or affect soil- hydraulic properties in the zone of installation. Surface drip irrigation systems can suffer from flowrate and uniformity distortions caused by increased temperatures. Preliminary evidence suggests uniformity problems may vary significantly by manufacturing techniques and perhaps the polymer used in dripline production. Research is needed to characterize these installation effects and to later develop techniques to minimize any negative aspects.

While great advances have been made during the last 30 years in system maintenance, filtration, and clogging prevention, clogging remains the number one cause of system failure worldwide. Clogging and maintenance problems often require localized applied research due to site specific conditions such as water source, climate, and system design. However, multistate collaboration can be used to coordinate research topics and approaches, as well as to summarize research findings into improved maintenance procedures. Long-term performance of microirrigation systems requires that individual emitters (dripper, microsprinklers, etc.) remain fully operational throughout the useful life of the system. During the past five years, SDI systems have been considered for use as a wastewater application system. This is an excellent method of applying wastewater due in-part to no wind drift, precision application, all contaminants are discharged below the soil surface, and minimal human contact with contaminated wastewater sources. Several drip irrigation products are available, some of which have been developed specifically for wastewater. However, this technology is still new, few field tests have been conducted, and system designers, consultants, and operators need more information for improved designs and long-term management.

Although filtration systems can remove the larger particulates that can clog emitters, dissolved chemical elements in the water and the conglomeration of smaller particles that pass through the filtration system can lead to clogging by means of chemical precipitates or enhanced biological growth. Clogging of emitters can be complete or partial and will lead to poor or undesirable system performance or complete system failure. Coordinated efforts are needed to identify and document common treatment and remediation procedures for various water quality and clogging issues. Additional research is needed to evaluate water treatment practices with wastewater sources that include assessment of filter systems, chemical water treatment, the effects of water treatment on emitter performance and soil microbiology, and the effects of emitter design on long-term performance, as well as other factors. Because wastewater can come from processing facilities, homes, municipal treatment plants, rural municipal lagoons, and livestock lagoons, the characteristics of these wastewater sources can vary widely in terms of chemistry, biological activity, and physical condition. These characteristics will influence filtration requirements, treatment practices, emitter performance, and soil quality. This collaborative research effort will allow researchers to evaluate treatment practices and performance assessments for different geographic locations, environmental conditions, soil characteristics, and water sources.

One proposed advantage of microirrigation is that irrigation management (when and how much to apply) is primarily determined by patterns of consumptive water use (ET), and relatively independent of soil water storage characteristics. There are a number of good books and manuals that discuss general water management procedures for microirrigation (Burt et al., 1999; Dasberg and Or, 1999; Hanson et al., 1994; Schwankl et al., 1993; Van der Gulik, 1999). However, microirrigation generally requires a higher level of grower management than other systems such as sprinkler irrigation. Depending on the soil type, crop stage of development, and climatic conditions, microirrigation may require daily irrigation to avoid plant stress and yield reduction. Hence, producer uncertainty about the effectiveness and performance of the various types of irrigation scheduling procedures can be a further barrier to adoption of microirrigation. The accuracy of current ET models and alternative approaches for measuring ET are the subject of much current research (e.g., Snyder and Paw U, 1993) and other regional efforts (WCC-202). These efforts provide an important foundation for the proposed efforts in microirrigation management, but there is still significant uncertainty regarding the relative weight given to the soil-, plant-, and ET-based measurements that can be used for irrigation scheduling, as well as how these approaches affect crop response to irrigation, particularly crop yield and quality. In this proposal, a wide range of microirrigation scheduling procedures will be evaluated and analyzed with respect to real-time estimates of ET, across a range of crops and conditions. This requires a regional effort in order to obtain a wide range of soil and environmental conditions, and to compile all of the data into a common format for analysis. If this work is not done, there will continue to be uncertainty concerning whether different irrigation scheduling approaches can be considered equivalent or not. If all approaches approximate an ET approach, then water planners, and ultimately water rights can be uniformly defined in terms of ET. If, under certain soil or environmental conditions, irrigation need is substantially more or less than that predicted by ET, then ET would not be an appropriate basis for water planning or calculation of water rights. Most states involved in this objective are already evaluating ET and at least one other irrigation management method (plant based and/or soil based) for their respective crops. Thus, it will be feasible to compare scheduling methods across geographical, climatic, and soil conditions.

There are water quality and economic implications of nutrients and pesticides lost through leaching and surface runoff. Best management practices (BMPs) incorporating microirrigation technologies can, in many cases, reduce these losses below those occurring with other irrigation systems. Irrigation is essential for high yields and net returns for a myriad of high value crops sensitive to water stress. Many of these crops are typically grown on soils low in organic matter that are highly susceptible to nutrient and pesticide leaching under poor irrigation scheduling. Improved irrigation and nutrient management practices are important to minimize these leaching losses. Microirrigation offers a significant potential for improved water and nutrient application and use, but is not being fully utilized. In many cases where microirrigation is being used, its potential to reduce both nitrate leaching and the use of applied nutrients is not always fully realized. As the irrigation industry moves towards an increased integration with the information age using improved controls and sensors, microirrigation offers the best capability for delivering precise applications of both water and chemicals. Conversion to microirrigation raises growers concerns about the BMP required for optimal production. For the grower, the ultimate interests include the effect of microirrigation on crop yield, quality, and cost, as well as any off site environmental effects. With carefully managed microirrigation, water-use efficiency could increase, and nutrient and pesticide loads to the environment (especially to surface runoff and to groundwater) could decrease, hence improving water quantity and quality at the watershed level. In this proposal, guidelines will be developed for appropriate fertigation strategies, allowing effective nitrate distribution throughout the root zone, yet minimizing leaching below the root zone. The irrigation industry is facing increasing pressures to improve the efficiency of irrigation water use and to reduce environmental impacts such as rising groundwater, salinization, and groundwater pollution. Specifically, nitrate leaching to the groundwater from irrigated fields is a major problem in many areas worldwide. This leaching appears to be caused by a combination of excessive nitrate and water applications. Water and nutrient application redistribution is often nonuniform for microirrigation systems. This can be an advantage or disadvantage depending on the crop, soil and climate. System designs and operational strategies must be carefully considered when partial wetting of the soil surface or crop root zone occurs. Stakeholders (growers) need to know how much land area or root zone needs to be wetted to obtain optimum crop response.

Summarization and, ultimately, the generalization of microirrigation research results conducted in this multistate project will reduce a significant amount of grower uncertainty about using microirrigation. Microirrigation remains a relatively new technology with most of the research and development occurring since 1970. The proposed project will attempt to assess some of the barriers to adoption and to remove some of the important known technical barriers in the operation, design, and management of microirrigation systems. Identification and removal of these barriers will result in a greater adoption rate of microirrigation across the United States. The consequence of not conducting this research is that a continued fragmented approach to microirrigation adoption will be used by producers often with faulty information.

Related, Current and Previous Work

This proposal represents the revision of a current USDA RRF multistate project, W-128 Microirrigation Technologies for Protection of Natural Resources and Optimum Production. The objectives of this project were to evaluate and refine microirrigation management strategies to promote natural resource protection and optimal crop production; to improve, modify, and evaluate microirrigation system design and components for natural resource protection and optimal crop production; to assess and develop decision criteria for adoption of microirrigation technologies, and to promote appropriate microirrigation technologies through formal and informal educational activities. The W-128 project was very productive during the last 5-year cycle and has accomplished many of the stated objectives. Perhaps, the least amount of progress was made in assessment of adoption criteria for microirrigation systems. Most of the work done for this objective was related to economic decision tools. KS developed an economic comparison tool for investment decisions related to center pivot sprinklers and SDI. This software tool has been updated twice and is available for free to growers (Lamm et al., 2002; Lamm et al., 2003). The current proposal seeks to refocus the effort in assessing adoption criteria by looking more at the economic, social and technical reasons for adoption and also through development of flowcharts and guidelines. These flowcharts and guidelines will represent a larger synthesis of regional information and can not only provide a better assessment of barriers, but also provide the basis for removing those barriers. The regional project W-128 continues to be active in developing new technologies and then transferring them. W-128 members organized special technical sessions and presented information in both the 2001 and 2002 Irrigation Association (IA) Technical Conference and Exposition in San Antonio, TX and New Orleans, LA, respectively. These presentations were published in the proceedings of these conferences. The sessions have been well received by IA and another session has been proposed for the fall of 2004. W-128 members have also been active in the revision of the 1986 book entitled Trickle Irrigation for Crop Production edited by Nakayama and Bucks (1986). This revision entitled Microirrigation for Crop Production should be completed in early 2004. During the last two years of the current project W-128 (2002-2003) there has been 148 publications and 60 presentations. There have been few comprehensive studies of microirrigation adoption. Wilson (2000) discussed some of the issues affecting adoption in the Southwest United States, Hawaii, and Israel but limited much of the discussion to intensively managed microirrigation. Kromm and White (1990) examined adoption of water-conserving technologies in the U.S. Great Plains but had very little focus on microirrigation. A recent study by Peterson and Bernardo (2003) indicated that some intensive economic studies conducted in the Great Plains from 1980-2000 failed to accurately predict the extent of irrigated land area, in part because of increased rates of irrigation technology adoption. A broader regional approach as proposed in this project may alleviate some of the shortcomings of these earlier studies. Clogging problems often have specific characteristics that are related to the water source and the region. Gilbert and Ford (1986) specifically listed three regions of the United States with distinctive differences in clogging issues. In the Southwestern United States, clogging was primarily associated with total suspended solids and water hardness. In the Southeastern United States, high biological activity associated with iron and sulfide laden waters was a concern. In Hawaii, the clogging issue was fine sand particles. Since 1986, microirrigation has expanded into additional U. S. locations and along with this expansion came new clogging issues and constraints. There have been few efforts to unify and summarize the results from these diverse regions primarily because microirrigation was a small evolving technology and because newly emerging regions did not have or could not allocate sufficient expertise to build on the earlier efforts. Some efforts to take a more scientific approach to the assessment and correction of clogging and maintenance issues were by Meyer (1985), Ford (1979), Pitts et al. (1990) and Kidder and Hanlon, (1997). Efforts are needed to reevaluate, summarize, and extend this information into newer regions. This process may be enhanced with the use of computerized decision tools and flow chart decision trees. Smajstrla et al. (1983) evaluated clogging of microirrigation emitters under field conditions in a Florida citrus orchard. They found that drip emitters clogged more frequently during low use periods and had more occurrences of clogging than microsprinklers on the same system. Most of the drip emitter clogging was associated with iron deposits and slimes or sludges formed as a result of iron bacteria. While this work identified the sources and extent of clogging, it did not address treatment or remediation. While several studies have been conducted on the hydraulic performance of drip irrigation products (Hills et al., 1989a; Hills et al., 1989b; Hills and El-Ebaby, 1990; Phene et al., 1992; Smajstrla and Clark, 1992; Boman and Parsons, 1993; Camp et al., 1993), most of those studies evaluated the effects of pressure changes and clogging on emitter discharge. A few earlier studies either modeled or directly evaluated the effects of water temperature on drip emitter and lateral performance (Clark and Huser, 2003; Parchomchuk, 1976; Peng et al., 1986). All of those studies indicated that emitter discharge rates change as influenced by water temperature. However, because product designs and plastics have changed, additional lab and field tests are still needed. A study of wastewater effluent application through four different dripline products was conducted by Hills and Brenes (2001). That study used secondary effluent from an activated sludge wastewater treatment plant. The water was filtered and treated with chlorine. However, livestock lagoon effluent has high levels of ammonia and other constituents that make continuous chlorination impractical. Trooien et al. (2000) evaluated livestock lagoon wastewater applications with five different drip irrigation laterals with emitter flow rates that ranged from 0.57 to 3.5 L/h. The two lower flow rate emitters (0.57 and 0.91 L/h) showed signs of clogging. They stated that the lower flow rate emitters (<0.91 L/h) may be risky for long-term use with wastewater. Hagedorn (2003) is evaluating the soil microbiological impacts associated with subsurface drip irrigation of septic tank-based effluent. Yost (2002) is measuring the long-term effects of domestic wastewater effluent application on soil quality and turfgrass growth. Trooien (2002) is evaluating filtration system design and requirements for use on lagoon systems and microirrigation. Some of the current microirrigation products have been modified and are promoted for use with wastewater sources. However, some of these products can cost twice as much or more than standard, non-treated drip products. Therefore, additional research is needed on the long-term hydraulic performance and required maintenance of these products with various wastewater sources and under varying operational and environmental conditions. DeTar et al. (1996) found on drip irrigated potatoes that dripline depths of 0.08 m (above the seed) and 0.46 m (below the seed) performed better than intermediate and greater depths. Zartman et al. (1992) examined dripline depths and emitter spacing on tuber yield and grade of Norgold Russet potato in Lubbock, Texas. Dripline depth or emitter spacing did not influence potato yield, but the proportion of misshaped tubers was greater when the dripline was buried at a 0.2 m depth than with shallower placement. Soil temperature was greater with the dripline at 0.2 m than at 0.1 m or 0.025 m. Shock et al., (2002) investigated the performance of Umatilla Russet under drip irrigation on a silt loam soil. The factors considered in the study were dripline placement (one dripline per row or one dripline per two rows) and four soil water potential levels for automatically starting irrigation (-15, -30, -45, and -60 kPa). They concluded that dripline placement had a significant effect on every variable except total marketable yield and bud-end fry color for which interactions of irrigation criteria with dripline number were significant. Dripline placement and irrigation criterion interacted to influence total yield, total marketable potatoes, and US No. 2 yield. Irrigation management has been a historically important issue in US agriculture, and members of W-128 have been actively involved in developing practical guidelines for microirrigation system design and management (e.g., Schwankl et al., 1993). Adoption of microirrigation technology can result in a significant improvement in irrigation system uniformity and efficiency over alternative systems, but under some conditions microirrigation may also require increased grower management effort, particularly with high frequency irrigation. One solution to this problem is to automate, or at least partially automate, irrigation management decisions, typically using either weather-based (ET) or soil-based information (e.g., Dasberg and Or. 1999), or using a feedback control system based on canopy temperature (Evett et al., 1996, 2000). These methods have a sound theoretical basis, but growers have a number of site- and region-specific issues that also impact their irrigation decisions. For example, soil water reserves are a key factor in supplying water through the variable drought periods typically experienced by deep rooted crops in the Northeastern U. S. In theory, real-time soil-based information can be used to determine the need for irrigation in this situation, but practical application of this approach is limited because of soil spatial heterogeneity. Even where sustained irrigation is needed, there is evidence that ET and soil-based criteria must be combined for optimal performance (Shock et al., 2000), and the relative weight given to these criteria under different circumstances is not known. Another example of the limitations inherent in both ET and soil-based approaches to irrigation scheduling is the growing body of evidence that some crops respond positively to deficit irrigation, particularly as it relates to product quality and/or economic returns (e.g., Shackel et al., 2000). This represents a limitation because under deficit irrigation, plants use stored soil reserves, and the consequences of these reserves for plant stress will be dependant on the size of the root-zone, not just soil properties, as well as only being indirectly related to plant water demand. As an example, continuous irrigation at 50% ETc may have very little effect on a deeply rooted crop until late in the season (as reserves are depleted), whereas it may have a more immediate effect on a shallow rooted crop or a normally deep rooted crop on a shallow soil. Both of these effects will be more pronounced under high evaporative demand conditions than they will be under low evaporative demand conditions, and hence the importance of these issues will be region-specific. A CRIS search revealed 63 citations related to microirrigation scheduling that have occurred since 1995, many of these related to the efforts of W-128. For example, 'pepper and microirrigation' gave 13 citations, and all but one were connected to old S 264 or W 128 projects. For microirrigation of field corn, a CRIS search revealed 71 citations. The vast majority of these citations were related to research efforts being conducted in the member states of the USDA RRF regional project W 128. These efforts have concentrated on improving water and nutrient management of field corn through microirrigation, and on automation of irrigation scheduling using a canopy temperature based method (Evett et al., 1996, 2000). The appropriateness of ET based irrigation scheduling will be evaluated in the proposed work and some of the data sets developed in these earlier studies will be appropriate for analyses (e.g. Evett et al., 1996; 2000). A current multi-state regional project with some similarity to the proposed project is W-204, but those are concentrated on soil aspects and thus complement but do not duplicate the proposed efforts. The proposed work will be an enhancement to many of the previous and ongoing regional efforts by providing an analysis of ET based scheduling for more crops in more locations. Many of the barriers to adoption of microirrigation that are related to water and nutrient management are crop- or site-specific. For example, shallow rooted bell peppers are highly susceptible to water stress at the blossom period of growth (Bruce et al., 1980), and since microirrigation may not wet the entire root zone, the question arises whether the rootzone water availability needs of peppers can be adequately met during this period. Pecan water use has been estimated to be 131 cm for mature pecan trees grown in New Mexico's Mesilla Valley (Miyamoto, 1983), but the yields can alternate substantially (Conner and Worley, 2000), and it is not clear whether water and fertility management must also fluctuate to remain optimal. Recent research on water use rates under NY conditions has indicated that the calculated ETc for apple (from published values in CA and WA) on average overestimates apple water use by 20 30%. This is due to the differences in crop boundary layers that make ETc calculations overwhelmingly dependent on net radiation. All of these examples illustrate the degree of uncertainty that is involved with irrigation management in general, and because of its reliance on a higher frequency of wetting and a more limited wetted area, the consequences of these uncertainties are often perceived as more severe when using microirrigation. Sammis (1980) compared sprinkler, surface drip, subsurface drip, and furrow irrigation for the production of potato and lettuce in New Mexico. Subsurface drip irrigation with a -20 kPa irrigation criterion was among the most productive irrigation systems. Shae et al. (1999) studied four options for managing drip irrigation of potatoes in North Dakota. Automation of the irrigation based on a soil water potential irrigation criterion at -30kPa had relatively high water use efficiency. Smajstrla et al. (2000) compared automated controlled SDI irrigation with the conventional semi-closed seepage irrigation (sub irrigation) in Florida. The conventional irrigation system is under criticism because of surface runoff and nutrient contamination of adjoining waterways. The SDI system required more electrical energy but used 36% less water to obtain the same potato yield. Steyn et al. (2000) examined irrigation-scheduling options for drip-irrigated potatoes. A soil water balance irrigation scheduling technique produced higher yields than scheduling based on evapotranspiration or scheduling based on typical growers irrigation criteria. For sprinkler-irrigated potato, extensive work has been done on potato responses to N fertilizer and N losses, but relatively few studies have studied potato N fertilization and loss under microirrigation. Sprinkler irrigation at different irrigation criteria was compared to surface drip and buried drip irrigation (with a range of fertilization treatments) for potato yield and grade in Minnesota (Waddell et al., 2000). Less water was required using either drip irrigation system. Surface drip and SDI were among the most productive systems for total and marketable yield. Furthermore, microirrigation or sprinkler irrigation (at a relatively dry soil criteria) reduced nitrate leaching under potato compared to normal sprinkler irrigation (Waddell, et al., 1999). High N applications beyond the crop needs reduces crop quality and yield (Payero et al., 1990; Bowen and Frey, 2002). Generally, a review of research literature has shown that needed N should be applied 2/3 preplant and the remaining 1/3 during the growing season (Simone, 1998). The quality of soils, ground and surface water is specifically vulnerable in climatic regions where agricultural production is possible only by irrigation such as in California (USA). The regular application of nitrogen fertilizers accompanied by irrigation is likely responsible for the increase in nitrate concentrations of groundwater resources. To reduce the harmful effects of irrigated agriculture on its environment, practicing alternative irrigation water management practices is imminent. In this regard, microirrigation offers a large degree of control over water application, enabling accurate application of irrigation amounts according to crop water requirements. If managed properly, drip irrigation will reduce water losses by soil evaporation and drainage (Tanji and Hanson, 1990), and can achieve a salt load below the root zone equal to that of the applied irrigation water. Furthermore, fertilizers can be added to the irrigation water, thereby accurately placing plant nutrients near the plant roots, eliminating nutrient losses by leaching below the rooting zone towards the groundwater. Increasingly, recommended irrigation water and soil management practices tactically allocate both water and fertilizers, thereby maximizing their application efficiency and minimizing fertilizer losses through leaching towards the groundwater. For example, there has been the rise of new water and nutrient management techniques such as the simultaneous microirrigation and fertilization, or fertigation (Bar-Yosef, 1999), drip irrigation, regulated deficit irrigation (RDI) and band application of fertilizers. Although microirrigation methods have proven to be highly effective in achieving the desired crop yields, there is increasing evidence suggesting the need for the changing of scheduling and management of localized irrigation (drip/trickle), thereby satisfying the principles of sustainable agriculture in integrated crop production. As pointed out by van Noordwijk and van de Geijn (1996), this new agriculture will be directed at minimizing yield losses and crop quality, while keeping environmental side effects at acceptable levels. To date, limited research has been reported on nitrogen leaching by microirrigation. Some studies have investigated the distribution of fertilizer around the dripline (e.g. Clothier and Sauer, 1988; Mmoloawa and Or, 2000), but few studies have investigated the effect of fertigation/irrigation management on the spatial distribution and crop availability of supplied nitrogen (e.g. Somma et al., 1998).


  1. To identify and assess the significance of barriers to adoption of microirrigation.
  2. To reduce technical barriers associated with microirrigation system design, performance, and maintenance.
  3. To reduce existing water and nutrient management barriers associated with microirrigation.


Methods for Obj. 1 KS, TX, CO, ID, IA, LA, NY, UT, OH, CA, and AZ will jointly develop surveys, decision tools and flowcharts to identify and assess adoption barriers. KS and TX will conduct a pilot survey of microirrigation users. This survey requires information about soil type, cropping mix, topography, water availability, water quality, dripline diameter, emitter flowrate, emitter type, installation depth, system area, operation and maintenance schedules, irrigator perceptions of advantages and disadvantages and system location. A GIS structure will be used to pinpoint locales of particular technical and informational needs. The initial results will be shared at an annual project meeting. Refinement of the survey protocols will be made and ID, IA CO, OH, UT, NM, and LA will conduct surveys in their own region specific to their needs with the purpose of identifying a broader set of barriers. In NY and OH, a major barrier is the variability in soils and rainfall that affects the need (risk) for irrigation spatially and temporally. A risk-assessment worksheet for microirrigation needs will be developed to integrate precipitation, soil water reserves, crop water needs, and economics. OH will assess and model risk associated with alternative energy sources for pumping. KS, AZ, ID, IA, UT, and CA will work to develop a flowchart for adoption of microirrigation, which will be refined through annual meeting discussions. Efforts will be made to develop both computer- and paper-based tools. In most cases, Cooperative Extension personnel will take the lead on Objective 1, particularly with the survey aspects. Methods for Obj.2 A literature review will be conducted by KS, TX, CA and LA of clogging studies, issues, and treatment/remediation procedures. Information will be categorized into topics related to physical-, chemical- and biological-based clogging. This database, along with experiences and ongoing studies, will be used to develop a user-based water treatment and clogging remediation flowchart and computer-based decision tools. KS, TX, CA, and LA, addressing their own iron-clogging problems, will coordinate their approaches with the goal of developing more comprehensive generic prevention and maintenance tools. CA will evaluate the effectiveness of injecting phosphonic acid-based products and of aeration/reservoir settling techniques for preventing iron clogging problems. CA will determine performance of disc and screen filters used with organic contaminated water. Various concentrations of organic-contaminated water will be pumped through various mesh sizes, and clogging will be monitored by pressure transducers. In a field study, algal-laden pond water will be purified by disc filtration and used in surface microirrigation. Sufficient data will be gathered during these two studies to develop guidelines on organic particle removal via disc filtration. CA will evaluate paracetic acid pretreatment of secondary effluent for suitability as a disinfection agent for minimizing the clogging of torturous path emitters used in SDI. A mathematical model under development will be verified for various soil textures, emitter spacings and depths, and hydraulic and nutrient loading rates. KS, FL, and TX will evaluate the performance of various SDI products used to apply wastewater from livestock lagoons, on-site treatment systems, and other sources. Dripline flowrate will be monitored in the field as well as soil water contents at random locations along the dripline. Driplines will also be retrieved and tested in the lab to determine flowrate and extent of clogging. OH will focus on SDI performance with agricultural constructed wetlands, fed by harvested, subsurface drainage waters, as a water supply and treatment alternative. Installation and placement issues (dripline depths, irrigation uniformity) will be investigated by KS, CO, OR, TX, AZ, CA, OH, and USDA-ARS-CPRL. KS will evaluate the installation effects on flowrate and uniformity as affected by soil type and installation depth for three soil types for several commercial driplines. Similarly, the tolerances on emitter spacing and the aggregate number of emitters/30 m will be measured. After installation into the soil, the bulk flowrate and the number of emitters/30 m and the inside diameter will be compared to the pre-installation condition. KS and USDA-ARS-CPRL will investigate the effect of dripline depth on crop production. USDA-ARS-CPRL will examine the effect of permanent-bed dripline depth and dripline spacing for a corn-soybean rotation and develop tillage techniques that will increase off-season precipitation capture and fallow soil water storage to reduce irrigation required for crop germination. The approach will be to examine 3 dripline bed designs (0.76 m spacing with standard beds, 1.52 m spacing with standard beds, 1.52 m spacing with wide beds and rows planted within 10 cm of the dripline) and three dripline depths (0.15 m, 0.23 m, 0.30 m) at various irrigation levels. Criteria for evaluation will be germination rates, maturity, crop yield components, and water use parameters. Similarly, KS will evaluate the effect of 5 dripline depths (0.2, 0.3, 0.4, 0.5 and 0.6 m) on germination of corn and sunflower on a silt loam soil. Germination of seed will be assessed on 4-day increments after planting. Seed zone soil water will be measured gravimetrically in the crop row to a depth of 30 cm in increments of 10 cm. Modeling approaches, such as Hydrus, IID will be explored as a means of extending the results. CO will investigate the effect of dripline placement (0.1, 0.2, and 0.3m) on salt and nutrient movement. OR will evaluate the effectiveness of alternative dripline placement in potato in terms of crop yields, crop quality, and soil water dynamics. Three dripline/potato row placements will be examined (dripline installed 8 cm deep directly over the potato rows 91 cm apart; dripline installed 8 cm deep between double rows of potatoes 40 cm apart; and dripline installed at 8 cm depth but with the dripline offset 15-20 cm from the potato rows spaced 91 cm apart.) Trials will be automated to start irrigation at -20 or -30 kPa soil water potential using granular matrix sensors to monitor soil moisture content in the soil. AZ and KS will evaluate water emission discharge characteristics of various thin-walled drip irrigation tubing products with surface dripline placement when used with elevated water temperatures. Field tests will also be conducted to determine dripline water temperatures and emitter discharge rates under different conditions. CA will evaluate the potential to use site-specific microirrigation and variable-rate technology for fertigation. Controllable microsprinklers will be developed using latching valves to turn the water on and off and the coil will be wired to an output line of the microcontroller. These intelligent microsprinklers will later be tested in an almond orchard. OH will evaluate SDI and surface drip durability, efficiencies, and economics over a 4-year rotation of peppers, cabbage, sweet corn, and field corn on a silty clay soil. Methods for Obj. 3 Many microirrigation scheduling techniques are currently being used with varying levels of success. A key feature of this proposal is that all of the participating entities will collect, share, and together evaluate the weather data related to evaporative demand and ET and the applied irrigation water data for each experiment. This will allow a multi year, multi location comparison of how close an ET schedule comes to various alternative irrigation scheduling techniques. In order to accomplish this, a common data format will be established by CA, based on an Excel workbook, observing the following: 1) a daily time step and 2) two worksheets, one Raw Data one Notes, with notes containing any desired details (e.g., sources for the weather information and data on yield or some other measure of crop performance, and the raw data worksheet containing a treatment ID, date, rain, reference ET, crop coefficients and irrigation amounts). Individual crop coefficients and irrigation amounts will be specified for each treatment, including treatments that are not explicitly based on ET. CA will compile and summarize all of the data related to this portion of the objective. The compilation of all data into a single SAS format will allow interactive analysis of the data as well as hypothesis generation and testing as part of the annual meeting. NY will develop a risk assessment worksheet for drought stress for fruit growers in the Northeast to help them determine the relative need for irrigation, and if so, the amounts of water needed. Estimates of soil water reserves, crop water needs, and other factors (cover crop water use, etc.) will be made across a range of conditions. Previous results indicated that the use of grass reference ET and published crop coefficients for fruit crops from arid climates might give significant errors in humid climates. Refinements in crop coefficients will be sought to better predict the actual water use rates in wine grapes in the Northeast. CA will continue microirrigation trials in almonds, walnuts and prunes, and initiate a long-term study of regulated deficit irrigation (RDI) in almonds. In ongoing almond trials, a plant-based RDI regime is being compared to grower practice on two contrasting soil types. The RDI regime is managed to achieve mild to moderate stress (-1.4 to -1.8 MPa midday stem water potential, SWP) compared to full irrigation (-0.8 to -1.0 MPa SWP) during the hull split period. A new almond site will be established in the Sacramento region where this RDI regime will be compared to a full ET regime. In walnuts, full ET-based irrigation is being compared to two levels of plant-based RDI. In prune, a single, plant-based RDI regime will be demonstrated on 10 grower sites throughout the state, and at three of these sites, system uniformity will be documented and water meters to measure applied water have been installed. More detailed studies will be performed to determine a sampling and storage protocol that allows rapid collection of field samples with SWP measurement made subsequently. USDA-ARS-WMR will determine water use of peaches and several vegetable crops using large weighing lysimeters. Accurate crop coefficients will be calculated under SDI. Crop water use will be related to plant development, ETp and grass ETr. Crop response (stress, growth, yield, quality) and soil water response to varying amounts of irrigation water (0.75 - 1.50 Etc) will be compared for surface drip, subsurface drip, and surface irrigation. NM will develop a pecan crop simulation model by modification of an existing irrigation scheduling model. The model will estimate daily ET, biomass accumulation and allocation to tree components, water and nitrogen balance in the root zone, and nitrate leaching based on readily available daily weather data and heat units. A crop coefficient will be developed from measurements of reference ET using a standard climate station and ET determined using two one propeller eddy correlation systems. A second method will be used that uses the surface-renewal analysis (SR) using structure functions to determine H. FL will evaluate citrus production, levels of tree stress (SWP) for microsprinkler systems that cover approximately 25, 50, 75, and 100% of the land area. Results will be compared to microsprinkler- and drip-irrigated tests with other crops in other states to develop common principles or guidelines for partial wetting. ID, IA, CO, UT, and OR will continue work with soil based sensors and data loggers, comparing the soil based irrigation schedule to ET-based methods. ID will compare plant-, soil-, and ET-based microirrigation scheduling techniques for turf, street trees vineyards and orchards to determine if a modified ET approach is adequate for these crops. CO will compare soil- and ET-based scheduling procedures for cantaloupe, watermelon, and onion through crop yield and quality criteria. IA will evaluate three scheduling methods for bell peppers on three soil types: 1) replacement of daily pan ET; 2) calculated ET water budgets; and 3) soil moisture potential measurements. Criteria for evaluation will be yield, fruit quality, and water use efficiency. OR will evaluate the use of soil-based sensors for scheduling irrigation of potatoes with three alternative system layouts (See Obj. 2). Crop yield, crop quality, and water applications will be compared for the different placements and scheduling techniques. UT will compare conventional (grower tradition) and soil- and ET-based irrigation scheduling methods for onion production. PR, VI, FL and LA will investigate the use of tensiometers for scheduling of fruits, ornamental plants, and vegetables. PR will irrigate orange trees when tensiometers reach treatment levels of 10 15 cb and 35 45 cb as compared to a rainfed check. Growth and development consisting of canopy volume, trunk circumference, earliness, and fruit weight and number will be analyzed to determine the effect of water depletion on citrus. Yam production will be examined with and without plasticulture and microirrigation for 3 soil water levels. VI will compare ET and tensiometer approaches in determining water requirements of tomato, banana and plantain. Irrigation at 40, 60 and 80% ET will be compared to 20, 40, and 60 kPa tensiometer thresholds. FL will evaluate scheduling methods for ornamental plants produced in plastic containers. The ET based method will be compared with TDR and tensiometer soil water measurements. Water use efficiency, plant growth, and container-media moisture changes will be studied. LA will investigate irrigation scheduling based on soil tensiometers (30, 45, 60 cm) compared with an ET approach for small fruits and vegetables using evaluation criteria of water and nutrient efficiency, plant growth, and yield. KS, NM, OH and USDA-ARS-CPRL will continue to research SDI of field corn. Several existing data sets in KS will be obtained, analyzed and summarized under this objective. The effect of full-season ET based scheduling will be evaluated by comparing several fractions of ET replacement in terms of corn yield, measured water use, irrigation amounts, and water use efficiencies. Similar evaluations will be made for scheduling procedures that incorporate limits on daily irrigation amounts, compare dripline depths, compare irrigation frequencies, or compare treatments where irrigation is withheld during specific growth stages. These 5 datasets can be useful in determining whether ET based scheduling is appropriate for field corn on the deep silt loam soils. In NM, corn will be grown under SDI with four ET replacement rates (0.50, 0.75, 1.00, and 1.25 x ET) with two rates of nitrogen (150 and 250 kg /ha). These data will be compared with earlier and current studies from KS to develop some generic guidelines and protocols for the combined management of irrigation and nitrogen for corn. USDA-ARS-CPRL will evaluate soil water-based irrigation scheduling in a SDI study for a corn-soybean rotation (see Obj. 2). Soil water content will be measured using neutron thermalization. Irrigations will be scheduled weekly to replenish soil water to field capacity in the root zone. Canopy temperatures will be measured using infrared thermometers and irrigations scheduled using the time-temperature threshold method will be predicted. Weather data will be used to schedule irrigations using a dual crop coefficient based on corn and soybean water used measured on large weighing lysimeters. The experiment will include four irrigation levels: dryland (after germination), 33%, 66%, and 100% of soil water replenishment to field capacity. Criteria for evaluation will include crop yield components and water use parameters. Several states (CA, OR, IA, and FL) will be conducting a literature review addressing water and nutrient management with microirrigation as related to application timing and distribution to reduce leaching losses. OR will quantify the effects of drip irrigtaion versus sprinkler irrigation on potato yield, quality, nitrogen requirements, and N leaching losses. Grids of soil moisture sensors will monitor the pattern of water movement in the soil profile under sprinkler and drip irrigation. Nitrate leaching patterns would be determined through soil analyses and with wick lysimeters. OR will include evaluation of environmental differences in potato canopies, soil temperature, and water use patterns and efficiency under sprinkler and drip irrigation systems. Soil and air temperature and air relative humidity would be monitored in sprinkler and drip-irrigated fields. IA will conduct an evaluation of 3 methods of N application to a bell pepper crop: 1) the traditional grower method of 168 kg/ha with 112 kg applied preplant and the remaining applied through the trickle system in weekly increments beginning at the fruit blossom stage of growth; 2) a preplant N application based on previous cropping history and sidedress N based on the PSNT; and 3) a preplant N application based on previous cropping history and sidedress N based on leaf petiole sap NO3-N value. Yield and fruit quality as measured by fruit size, lobe number, and pericarp thickness will be determined. Cost and return will be determined for each method. Cooperating states will include some measure (leaf or soil) prior to sidedress N application. Data will be pooled to determine if a plant/soil test can be used to predict the need or reduce the amount for additional N. FL will use multi-level groundwater samplers to determine the amounts of soluble inorganic N, and soluble ortho P in the shallow groundwater beneath grower/cooperator strawberry production fields to assess off-site discharge during rainfall and overhead irrigation events. BMPs to be evaluated for grower adoption include conversion to drip irrigation, optimum fertilization rates including pre-plant and fertigation systems, improvement of plant establishment and freeze protection irrigation efficiency through redesign of in-place irrigation systems, and use of tissue testing to better track actual crop-nutrient contents. A pre- and post-study survey will be used to determine base-level practices and to gauge BMP adoption. Also included is the assessment of costs associated with various implemented and projected nutrient reduction scenarios. CA will conduct modeling of fertigation scenarios using the computer simulation model, HYDRUS-2D, to simulate the transient two-dimensional movement of water and multiple solutes in soil. In addition, the models allow for specification of root water and nitrate uptake affecting the spatial distribution of water and nitrate availability between irrigation cycles. The soil hydraulic properties required for the simulation model will be determined for different soil types. Spatial patterns of water content and nitrate concentration will be determined for different fertigation strategies including different injection durations and different injection times relative to the irrigation event time. USDA-ARS-WMR will explore management practices that minimize the vertical water movement per unit of water (microirrigation application) for a range of soil types. Field trials using a range of preceding soil water contents, emitter flowrates, and frequency will be compared with water distributions predicted by a soil water flow model (HYDRUS-2D) to determine if the model can be used to optimize management practices to minimize deep percolation.

Measurement of Progress and Results


  • Identification of barriers through surveys on a state-by-state basis, and on a regional basis.
  • Publication of survey findings in a regional report format or other appropriate publication.
  • Development of a water treatment and remediation template / flowchart to assist users and designers of microirrigation systems.
  • Manuals and other publications outlining and describing grower guidelines for design, management, and maintenance of general use and wastewater microirrigation systems.
  • Project-wide synthesis of research results related to microirrigation design and placement issues.
  • Additional Outputs (6 through 12). 6. Improved research protocols and reporting procedures for studies that address hydraulic characteristics of microirrigation components. 7. Multi-year, multi-location comparison of soil-, plant and ET-based irrigation scheduling procedures for microirrigation. 8. Comprehensive descriptions and criteria for using various irrigation scheduling techniques as affected by crop, soil type, climate and region. 9. Identification of problematic irrigation scheduling issues for microirrigation. 10. Improved handbooks and guides for water and nutrient management of fruits and vegetables. 11. Identification of effective BMPs for crop production. 12. Improved criteria and models for prediction of soil water movement and prevention of leaching under microirrigation.

Outcomes or Projected Impacts

  • Targeted information delivery will be improved due to better understanding of regional barriers to adoption.
  • Microirrigation adoption by producers will be increased in response to more widely available, easier to use information.
  • System purchasers and users will be more aware of proper system design, placement, installation, operation, and maintenance requirements.
  • Improved microirrigation components will become available from industry and growers will select the most appropriate components for their end-use.
  • The potential life of microirrigation systems will be increased with sustained performance for a variety of water sources including fresh, recycled and waste waters.
  • Additional Outcomes/Impacts (6-9). 6. Uncertainty related to microirrigation scheduling will be reduced thorough better understanding of the scheduling procedures including their strengths and weaknesses. 7. In humid regions, fruit growers will be able to better predict the needs for irrigation and improve their irrigation scheduling. 8. Proper selection of microirrigation scheduling and nutrient management procedures will optimize crop production in terms of crop yield and quality, water and nutrient input costs, and costs to the environment. 9. Improved understanding of soil water movement will lead to improved, easier to use models that will benefit both the scientific research community and the growers through environmentally-friendly crop production.


(2005): Develop pilot survey instrument in cooperation with extension personnel. Progress reports on buried and surface positioned tubing flow rates, filter performance, and treatment practices with wastewater (Year 1). Obtain dripline products and filters for lab tests, field tests and analyses. Develop and finalize protocols for evaluation of subsurface dripline and filter installations. Conduct studies on effect of dripline depth and dripline placement (Year 1). Conduct mitigation of iron clogging field tests. Agreement and standardization of data requirements and format guidelines for evaluation of ET scheduling procedures (MS Excel format). Conduct studies on nitrogen dynamics and efficiency (Year 1). Conduct studies on micro-environmental differences in potato (Year 1).

(2006): Extension personnel will conduct pilot survey in Kansas and Texas . Progress report on buried and surface positioned tubing flow rates, filter performance, and treatment practices with wastewater (Year 2). Publish applicable data. Construct and test standardized lab testing apparatus for dripline products. Conduct study on subsurface installation issues. Progress report on effect of dripline depth and placement on crop production issues (Year 2). Progress report on iron clogging mitigation strategies (Year 2). Compilation and analysis of ET Scheduling data from earlier W-128 projects. Progress report on nitrogen dynamics, and micro-environmental differences (Year 1). Conduct studies on nitrogen dynamics and efficiency (Year 2). Conduct studies on micro-environmental differences in potato (Year 2).

(2007): Revise and modify survey and survey additional states. Final report on buried and surface positioned tubing flow rates with wastewater (Year 3). Initiate further research on filter performance and water treatment practices. Conduct lab tests on the different dripline products. Final report on study of subsurface installation issues. Complete study on effect of dripline depth and placement on crop production issues. Complete field studies of iron clogging mitigation strategies. Develop preliminary descriptions/guidelines for use of various irrigation scheduling procedures and identification of specific conditions where certain methods are inadequate. Progress report on nitrogen dynamics, and micro-environmental differences (Year 2). Conduct studies on nitrogen dynamics and efficiency (Year 3). Conduct studies on micro-environmental differences in potato. (Year 3)

(2008): Compile and summarize survey results and recommendations. Develop draft guidelines for design and management of SDI wastewater systems. Continue research on filter performance and water treatment practices. Continue lab tests on the different drip line products. Final report on study on effect of dripline depth and placement on crop production issues. Final report on the effects of drip tape placement in potato. Draft handbook of maintenance of microirrigation systems. Finalize descriptions/guidelines for use of various irrigation scheduling procedures and identify specific conditions where certain methods are inadequate. Progress report on nitrogen dynamics, pesticide effectiveness, and micro-environmental differences (Year 3) Final report on nitrogen dynamics and efficiency Final report on micro-environmental differences in potato

(2009): Finalize guidelines for design and management of SDI wastewater systems Completion of handbook on maintenance of microirrigation systems. Summarize guidelines for treatment and filtration into final report Finalize management guidelines for microirrigation of potato. Ascess the progress of project at removing barriers and identify areas needing further research.

Projected Participation

View Appendix E: Participation

Outreach Plan

A broad mix of traditional and non-traditional educational mediums will be used in outreach. This will include but will not be limited to field days, tours, demonstration sites, college class seminars, targeted training sessions (e.g. NRCS staff, Consultants), regional, national, and international conferences, newsletters, newspaper and popular press articles, audio and video tapes, slide sets, factsheets, extension bulletins, research publications, refereed journal articles and Internet-based educational material. Project members from Cooperative Extension and Research scientists will jointly work in this area.

Some of the proposed mediums have unique aspects that will be discussed here.

Project members will propose to coordinate, develop, moderate, and present a technical session at a national or international conference during the third year of the project. Possible conferences would include, but not be limited to the Irrigation Association, the American Society for Agricultural Engineers (ASAE), Agronomy and Soil Science Society (ASA), and the American Society of Horticultural Science (ASHS).

Project members believe that the multidimensional range of disciplines and educational mediums will provide high credibility and increased acceptance of the research by producers. Educating producers is a critical part of the successful implementation of this technology. However, educating consultants who are often largely responsible for data interpretation is of equal importance. The Project will conduct targeted training sessions for consultants and staff from Cooperative Extension, USDA-NRCS, other state and local agencies.

The Internet can help broaden the availability of information developed in this project and also provides a method of interaction between author and clientele for feedback and clarifications. Project members agree to work towards improving microirrigation technology transfer through Internet-based educational material. A dedicated Internet site will be maintained at Oregon State University.


The organization and implementation of the project will be in accordance with the "Manual for Cooperative Regional Research." The Regional Technical Committee will consist of representatives from each cooperating Agricultural Experiment Station and federal agency cooperating in this project. The representative(s) will be appointed by their respective Experiment Station or Research Director. The above will constitute the voting membership of the technical committee. The Regional Technical Committee will be responsible for the planning and execution of the research project. It will be responsible for coordinating research activities of each cooperating Experiment Station and federal agency and for the developing of appropriate research methods and procedures. A Director from the Agricultural Experiment Stations of the Western Region appointed by the Agricultural Experiment Station Directors of the Western Region will serve as Administrative Advisor and an ex-officio (non-voting) member of the technical committee. A representative of the Cooperative State Research Service will serve as an ex-officio (non-voting) member of the technical committee. An executive committee, consisting of a chair, vice-chair, and secretary will be elected from the voting members of the technical committee. The executive committee will serve one year in each elected office with the provision that the vice-chair will ascend to chair, and the secretary to vice-chair. A secretary will be elected each year. The executive committee will have the authority to act on behalf of the technical committee. The chair, with the approval of the Administrative Advisor, will notify technical committee members of the time and place of meetings, prepare the agenda, and preside at meetings of the technical committee and executive committee. The chair will also be responsible for naming appointments to subcommittees for specific assignments. The chair will be responsible for annual and final reports. In the absence of the chair, the vice-chair will perform these duties. The secretary will record and distribute the minutes of the meetings.

Literature Cited

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