Subsurface Drip System Research Articles

Soil Salinity and Quality of Sprinkler and Drip Irrigated Cool‐Season Turfgrasses

A 3‐yr study was conducted in New Mexico to investigate the effects of saline water on changes in quality, cover, and root zone salinity of seven cool‐season turfgrasses. Plots were irrigated using either sprinklers or subsurface drip with water of 0.6, 2.0, or 3.5 dS m−1. From March to November plots were rated monthly for quality, and green cover was determined using digital image analysis. Soil samples were collected at depths of 0 to 10, 10 to 20, and 50 to 60 cm in June and November and analyzed for electrical conductivity (EC), Na, and sodium adsorption ratio (SAR). Changes in soil EC, Na content, and SAR reflected seasonal changes in irrigation and natural precipitation and EC and Na values were highest (6.1 dS m−1 and 943 mg L−1, respectively) in June of 2006 on drip irrigated plots at depths of 0 to 10 cm. Electrical conductivity was higher in drip irrigated than sprinkler irrigated plots on four of the six sampling dates. Irrigation type and water quality did not affect EC and Na at soil depths of 50 to 60 cm. For four of the seven grasses tested, EC, Na, or SAR values showed a significant but weak relationship (0.18 < r2 < 0.27) with turf quality, indicating that more than one stressor affected visual ratings. With the exception of tall fescue [Festuca arundinacea (Schreb.)], cool‐season grasses could not be maintained at acceptable quality levels in the arid transitional climate when irrigated with saline water from either a sprinkler or a subsurface drip system.

Soil Type and Wetness Affect Tint of Peanut (Arachis hypogaea L.) Pod Shell

Abstract Peanut (Arachis hypogaea L.) is a globally important legume crop that is utilized fresh, roasted, or pressed for oil products. A substantial market exists for in-shell peanuts, and shell color is an important factor affecting price — consumers favor bright yellow. Field observations have indicated that the type of soil in which the peanut pods develop can affect shell color and tint. Field and greenhouse experiments in which plants were grown in sandy soil while pods were allowed to develop in various tested soils verified this primary observation: sandy soils resulted in bright-yellow shells, dark soils (such as peat) resulted in a darker shell color, while loess soils resulted in intermediate shell colors. Incubation of peanut pods in saturated soil solutions or filtered soil extracts inferred the existence of two opposing processes that may affect shell color: adherence of water-soluble soil components to the shell surface, and the washing-off of shell material from this surface. Overhead irrigation with a reduced amount of water or watering with a subsurface drip system concealed at a depth of 25 cm resulted in brighter shell colors than applying the normal amount of water by overhead irrigation. These data suggest that reducing soil wetness in the pod-development zone may increase shell brightness. Field experiments also indicating that final shell color is determined towards the end of pod development, suggesting that soil wetness in the pod-development zone should be controlled during at least the last 4 weeks of growth, to maintain a low level of wetness.

Effect of Subsurface Drip System in Nitrate Leaching

Fertigation enables the application of soluble fertilizers and other chemicals along with irrigation water, uniformly and more efficiently. Improved water efficiency under drip irrigation, by reducing percolation and evaporation losses, provides for environmentally safer fertilizer application through the irrigation water. The overall problem is to identify economically viable practices that offer a significant reduction of NO3-N losses through leaching, which also fit in the farming systems practiced under a particular soil type and set of climate conditions. An experiment was conducted at Precision Farming Development Centre, Water Technology Centre, Indian Agricultural Research Institute, New Delhi to study the leaching of nitrate from the root zone of potato under surface and subsurface drip irrigation system. The study consisted of 2 types of drip system (surface and surface drip) as main treatments and 3 levels of irrigation including 100% crop evapotranspiration, 80% of crop evapotranspiration and 60 % of crop evapotranspiration as sub-treatments. Direct correlation was found between the amount of irrigation water and nitrate leaching. Reduction of amount of irrigation water to the tune of 40% decreased the nitrate leaching from 30% to 10 per cent. It was observed that by changing the position of water source from surface to subsurface, the nitrate leaching decreased by 12-20%, and thus subsurface drip (10 cm depth of drip tape) was recommended in potato crop to get higher yield with minimum leaching of soil nitrate-nitrogen.

Dynamics and modeling of soil water under subsurface drip irrigated onion

Subsurface drip irrigation provides water to the plants around the root zone while maintaining a dry soil surface. A problem associated with the subsurface drip irrigation is the formation of cavity at the soil surface above the water emission points. This can be resolved through matching dripper flow rates to the soil hydraulic properties. Such a matching can be obtained either by the field experiments supplemented by modeling. Simulation model (Hydrus-2D) was used and tested in onion crop ( Allium cepa L.) irrigated through subsurface drip system during 2002–2003, 2003–2004 and 2004–2005. Onion was transplanted at a plant to plant and row to row spacing of 10 cm × 15 cm with 3 irrigation levels and 6 depths of placement of drip lateral. The specific objective of this study was to assess the effect of depth of placement of drip laterals on crop yield and application of Hydrus-2D model for the simulation of soil water. In sandy loam soils, it was observed that operating pressures of up to 1.0 kg cm −2 did not lead to the formation of cavity above the subsurface dripper having drippers of 2.0 l h −1 discharge at depths up to 30 cm. Wetted soil area of 60 cm wide and up to a depth of 30 cm had more than 18% soil water content, which was conducive for good growth of crop resulting in higher onion yields when drip laterals were placed either on soil surface or placed up to depths of 15 cm. In deeper placement of drip lateral (20 and 30 cm below surface), adequate soil water was found at 30, 45 and 60 cm soil depth. Maximum drainage occurred when drip lateral was placed at 30 cm depth. Maximum onion yield was recorded at 10 cm depth of drip lateral (25.7 t ha −1). The application of Hydrus-2D confirmed the movement of soil water at 20 and 30 cm depth of placement of drip laterals. The model performance in simulating soil water was evaluated by comparing the measured and predicted values using three parameters namely, AE, RMSE and model efficiency. Distribution of soil water under field experiment and by model simulation at different growth stages agreed closely and the differences were statistically insignificant. The use of Hydrus-2D enabled corroborating the conclusions derived from the field experimentation made on soil water distribution at different depths of placement of drip laterals. This model helped in designing the subsurface drip system for efficient use of water with minimum drainage.

Effect of subsurface drip irrigation on onion yield

Subsurface drip system is the latest method of irrigation. The design of subsurface drip system involves consideration of structure and texture of soil, and crop’s root development pattern. A 3-year experiment was conducted on onion (Allium Cepa L., cv. Creole Red) in a sandy loam soil from October to May in 2002–2003, 2003–2004 and 2004–2005 to study the effect of depth of placement of drip lateral and different levels of irrigation on yield. Tests for uniformity of water application through the system were carried out in December of each year. Three different irrigation levels of 60, 80 and 100% of the crop evapotranspiration and six placement depths of the drip laterals (surface (0), 5, 10, 15, 20 and 30 cm) were maintained in the study. Onion yield was significantly affected by the placement depth of the drip lateral. Maximum yield (25.7 t ha−1) was obtained by applying the 60.7 cm of irrigation water and by placing the drip lateral at 10 cm soil depth. Maximum irrigation water use efficiency (IWUE) (0.55 t ha−1 cm−1) was obtained by placing the drip lateral at 10 cm depth. The greater vertical movement of water in the sandy-loam soil took place because of the predominant role of gravity rather than that of the capillary forces. Therefore, placement of drip lateral at shallow depths is recommended in onion crop to get higher yield.

Drip irrigation provides the salinity control needed for profitable irrigation of tomatoes in the San Joaquin Valley

Despite nearly 30 years of research supporting the need for subsurface drainage-water disposal facilities, the lack of these facilities continues to plague agriculture on the San Joaquin Valley's west side. One option for coping with the resulting soil salinity and shallow water-table problems is to convert from furrow or sprinkle irrigation to drip irrigation. Commercial field studies showed that subsurface drip systems can be highly profitable for growing processing tomatoes in the San Joaquin Valley, provided that the leaching fraction can achieve adequate salinity control in the root zone. Computer simulations of water and salt movement showed localized leaching fractions of about 25% under subsurface drip irrigation, when water applications equaled the potential crop evapotranspiration. This research suggests that subsurface drip irrigation can be successfully used in commercial fields without increasing root-zone soil salinity, potentially eliminating the need for subsurface drainage-water disposal facilities.

Soil water in relation to irrigation, water uptake and potato yield in a humid climate

Efficiently controlling soil water content with irrigation is essential for water conservation and often improves potato yield. Volumetric soil water content ( θ v) in relation to irrigation, plant uptake, and yield in potato hills and replicated plots was studied to evaluate four water management options. Measurements of θ v using a hammer driven probe were used to derive a θ v index representing the relative θ v status of replicated plots positioned along a hill slope. Time series for θ v were determined using time domain reflectometry (TDR) probes at 5 and 15 cm depths at the center, shoulder, and furrow locations in potato hills. Sap flow was determined using flow collars in replicated field plots for four treatments: un-irrigated, sprinkler, surface drip, and sub-surface drip irrigation (40 cm depth). Irrigated yields were high/low as the θ v index was low/high suggesting θ v excess was a production problem in the wetter portions of the study area. The diurnal pattern of sap flow was reflected in the θ v fluctuation it induces at hill locations with appreciable uptake. Hill locations with higher plant uptake were drier as was the case for the 5 cm (dry) depth relative to the 15 cm (wet) depth and for locations in the hill (dry) relative to the furrow (wet). The surface drip system had the lowest water use requirement because it delivers water directly to the hill locations where uptake is greatest. The sub-surface drip system wetted the hill gradually (1–2 days). Measurement of the θ v index prior to experimental establishment could improve future experimental design for treatment comparisons.

Management of Irrigation for Vegetables: Past, Present, and Future

Vegetables are grown throughout the U.S. on various soil types and in various climates. Irrigation is essential to supplement rainfall in all areas to minimize plant water stress. In the U.S., irrigated vegetable production accounts for about 1.9 million ha or 7.5% of the irrigated area. California, Florida, Idaho, Washington, Texas, Nebraska, Oregon, Wisconsin, and Arizona account for 80% of the U.S. production of irrigated vegetables. In the U.S., surface and subsurface (seepage) irrigation systems were used initially and are currently used on 45% of all irrigated crops with a water use efficiency of 33%. Sprinkler or overhead irrigation systems were developed in the 1940s and are currently used extensively throughout the vegetable industry. Sprinkler systems are used on 50% of the irrigated crop land and have a water use efficiency of 75%. In the late 1960s, microirrigation (drip or trickle) systems were developed and have slowly replaced many of the sprinkler and some of the seepage systems. Microirrigation is currently used on 5% of irrigated crops. This highly efficient water system (90% to 95%) is widely used on high value vegetables, particularly polyethylene-mulched tomato (Lycopersicon esculentum), pepper (Capsicum annuum), eggplant (Solanum melongena), strawberry (Fragaria ×ananassa), and cucurbits. Some advantages of drip irrigation over sprinkler include reduced water use, ability to apply fertilizer with the irrigation, precise water distribution, reduced foliar diseases, and the ability to electronically schedule irrigation on large areas with relatively smaller pumps. Drip systems also can be used as subsurface drip systems placed at a depth of 60 to 90 cm. These systems are managed to control the water table, similar to that accomplished with subsurface irrigation systems, but with much greater water use efficiency. Future irrigation concerns include continued availability of water for agriculture, management of nutrients to minimize leaching, and continued development of cultural practices that maximize crop production and water use efficiency.

Lycopene, carbohydrates, ascorbic acid and yield components of diploid and triploid watermelon cultivars are affected by de®cit irrigation

SummaryMany vegetable production regions in the southwestern US are strictly regulated on water use. In addition, demand for high quality and nutritious vegetables has increased. This study was performed to explore the effects of de®cit irrigation on yield, fruit quality, lycopene content, vitamin C and sugar composition of red-¯eshed diploid and triploid watermelon (Citrullus lanatus (Thunb) Matsum & Nakai) cultivars. Irrigation treatments were 1.0, 0.75 and 0.5 evapotranspiration (ET) rates. Cultivars used were `Summer Flavor 710', `RWM 8036', `Allsweet', `Sugarlee', and `SWD 7302' (diploids) and `Summer Sweet 5244', `SWT 8706', `Sugar Time', and `Tri X Sunrise' (triploids). Total water applied through a subsurface drip system was 395, 298 and 173.mm, for the 1.0, 0.75 and 0.50 ET rates, respectively. Total yields were highest at 1.0 ET (53.9 t ha±1) compared with 0.5 ET (26.8.tha±1). Triploids had a 34% higher total yield and fewer culls (2%) compared with diploid cultivars (25%). Highest yields were obtained for `Tri X Sunrise', `SWT 8706', and `SWD 7302'. `Sugar Time' had the highest soluble solids content (13.4%) of all cultivars (range 9.7±11.0%). Triploid cultivars had ®rmer ¯esh compared to diploids (12.0 v 9.9..N). Lycopene content increased slightly with maturity (55.8 to 60.2.mgg±1 fw), and was signi®cantly higher at 0.75 ET and 1.0 ET. Lycopene content averaged over all treatments was 60±66.mgg±1 fw for triploids and 45 to 80.mgg±1 fw for diploid fruits. Overall, lycopene and vitamin C content did not decrease with de®cit irrigation at 0.75 ET. There was genetic variability for lycopene, vitamin C, and sugar composition, primarily fructose, among diploids and triploids.

Growth and Production of Young Peach Trees Irrigated by Furrow, Microjet, Surface Drip, or Subsurface Drip Systems

A 3-year study was conducted in central California to compare the effects of furrow, microjet, surface drip, and sub surface drip irrigation on vegetative growth and early production of newly planted `Crimson Lady' peach [Prunus persica (L.) Batsch] trees. Furrow treatments were irrigated every 7, 14, or 21 days; microjet treatments were irrigated every 2-3, 7, or 14 days; and surface and subsurface drip (with one, two, or three buried laterals per row) treatments were irrigated when accumulated crop evapotranspiration reached 2.5 mm. The overall performance showed that trees irrigated by surface and subsurface drip were significantly larger, produced higher yields, and had higher water use efficiency than trees irrigated by microjets. In fact, more than twice as much water had to be applied to trees with microjets than to trees with drip systems in order to achieve the same amount of vegetative growth and yield. Yield and water use efficiency were also higher under surface and subsurface drip irrigation than under furrow irrigation, although tree size was similar among the treatments. Little difference was found between trees irrigated by surface and subsurface drip, except that trees irrigated with only one subsurface drip lateral were less vigorous, but not less productive, than trees irrigated by one surface drip lateral, or by two or three subsurface drip laterals. Within furrow and microjet treatments, irrigation frequency had little effect on tree development and performance with the exception that furrow irrigation every 3 weeks produced smaller trees than furrow irrigation every 1 or 2 weeks.

MICROIRRIGATION OF ALMONDS

A large scale field trial was conducted at the Nickels Soils Laboratory in the Sacramento Valley of California to evaluate three microirrigation systems; Surface Drip, Subsurface Drip (SDI) and Micro-jet on four cultivars of almonds, ’Nonpareil’, ’Butte’, ’Carmel’ and ‘Monterey’ (Prunus dulcis [Mill.] D.A.Webb.). Ten years of evaluation has shown that high commercial yields (2500 kg/ha) of high quality almonds can be produced using all three types of microirrigation. Micro-jet irrigated trees tended to outyield drip irrigated trees by about 10% in some years for some cultivars. No consistent yield differences were found. Tree growth under SDI, as measured by trunk size, was comparable to surface drip irrigation but slightly smaller than micro-jet irrigated trees when equal amounts of irrigation water were applied. Root development was more extensive under micro-jet irrigated trees compared to both single hose drip systems. No significant root intrusion was found in trifluralin impregnated SDI emitters but standard SDI emitters were plugged by almond root growth after five years of field operation. Minor root pinching was evident on the buried flexible supply hoses in both SDI and surface drip systems. Micro-jet irrigation increased system maintenance and resulted in higher herbicide use to control vegetation on the orchard floor.

Yield, Quality, and Water Use Efficiency of Muskmelon Are Affected by Irrigation and Transplanting Versus Direct Seeding

Restrictions on pumping water from underground aquifers are limiting vegetable production in Southwest Texas. To determine yield, quality, and water use efficiency (WUE) of muskmelon (Cucumis melo L. group Cantalupensis, `Caravelle'), six irrigation systems with varying input levels and their interactions with stand establishment (containerized transplants vs. direct seeding) were examined. Irrigation systems were: 1) pre-irrigated followed by dryland conditions; 2) furrow/no mulch; 3) furrow/mulch (40-μm-thick black polyethylene); 4) surface drip (0 cm depth)/mulch; 5) subsurface drip (10-cm depth)/mulch; and 6) subsurface drip (30-cm depth)/mulch. Field experiments were conducted on a silty clay loam soil during four seasons (1995-98). In 1995, marketable fruit yields were greater for subsurface drip systems at 30-cm depth than for furrow systems, with or without plastic mulch. Transplants grown with surface drip irrigation produced 75% greater yield in the 9-count fruit class size during early harvest than did those grown with subsurface drip (10- or 30-cm depth), but total yield was unaffected by drip tape depth placement. In 1996, the driest season of these studies, direct-seeded plants had higher total yields than did transplants; yield was greatest for direct-seeded plants on subsurface drip placed at 10- or 30-cm soil depth, and for transplants on subsurface drip at 10-cm depth. Soluble solids content was minimally affected by irrigation method, but was higher in fruit from transplants than in those from direct-seeded plants in 3 years. Across all seasons, the average water applied for drip systems was 53% lower than that for conventional furrow systems, and WUE was 2.3-fold as great.

Managing subsurface drip irrigation in the presence of shallow ground water

A 3-year project compared the operation of a subsurface drip irrigation (SDI) and a furrow irrigation system in the presence of shallow saline ground water. We evaluated five types of drip irrigation tubing installed at a depth of 0.4 m with lateral spacings of 1.6 and 2 m on 2.4 ha plots of both cotton and tomato. Approximately 40% of the cotton water requirement and 10% of the tomato water requirement were obtained from shallow (<2 m) saline (5 dS/m) ground water. Yields of the drip-irrigated cotton improved during the 3-year study, while that of the furrow-irrigated cotton remained constant. Tomato yields were greater under drip than under furrow in both the years in which tomatoes were grown. Salt accumulation in the soil profile was managed through rainfall and pre-plant irrigation. Both drip tape and hard hose drip tubing are suitable for use in our subsurface drip system. Maximum shallow ground water use for cotton was obtained when the crop was irrigated only after a leaf water potential (LWP) of −1.4 MPa was reached. Drip irrigation was controlled automatically with a maximum application frequency of twice daily. Furrow irrigation was controlled by the calendar.

SUBSURFACE DRIP DISPERSAL OF RESIDENTIAL EFFLUENT: II. SOIL HYDRAULIC CHARACTERISTICS

Changes in soil water retention, pore size distribution, and saturated hydraulic conductivity due to wastewaterapplication by subsurface drip systems were investigated at two sites in Texas. Undisturbed soil core samples were collectedfrom different locations and depths around drip emitters and from outside the drip fields. Core samples were used to determinehydraulic conductivity and soil water retention. Application of wastewater resulted in increased soil water retention,decreased volume of pores with large radii, and a decrease in saturated hydraulic conductivity. The major influence ofwastewater application on soil hydraulic properties occurred slightly below the drip emitter. This decrease in hydraulicconductivity reflected the decrease in volume of large soil pores compared to that of small pores. Application of treated effluenthad more influence on soil hydraulic properties in the transect along the drip lateral than in a transect perpendicular to thedrip lateral emitter.

SUBSURFACE DRIP DISPERSAL OF RESIDENTIAL EFFLUENT: I. SOIL CHEMICAL CHARACTERISTICS

Changes in soil chemical characteristics due to wastewater application by subsurface drip systems were investigated at four sites in Texas. Soil samples were collected from different locations and depths around drip emitters and from outside the drip fields. These soil samples were analyzed for phosphorus (P), total nitrogen (TN), sodium (Na), calcium (Ca), magnesium (Mg), soluble sulfate (SO4), potassium (K), salt content (EC), and total organic carbon (TOC). Application of wastewater resulted in a significant increase in soil Na where concentration of Na in the applied effluent was high and Na concentration in the original soil was low. Concentration of P was significantly increased in the vicinity of the emitter and near the soil surface where the drip line was installed at a shallow depth. There were no drastic changes in TN, Ca, Mg, K, and TOC concentration or in EC values in the soil profile.

Attenuation of microorganisms in the soil during drip irrigation with waste stabilization pond effluent

Waste stabilization ponds (WSP) are one of the most appropriate wastewater treatment methods to reduce nematode and faecal coliforms. However, there is still a risk of contamination of crops and soil irrigated with this kind of effluent. The purpose of this work was to examine the fate of microorganisms (faecal coliforms, F+, and somatic coliphages and helminth eggs), from WSP effluent used for irrigation of a vineyard orchard, under onsurface (ODI) and subsurface drip (SDI) systems. The field is located near the City of Arad (Israel). The soil and water samples were taken during the irrigation periods of two consecutive years (1997 and1998). During the first year the vineyard was irrigated with a low quality effluent from WSP (sedimentation and maturation ponds only) and during the second year a high quality effluent (sedimentation, anaerobic, and a series of aerobic ponds and a final reservoir) was used. The results showed a substantial elimination of microorganisms in the soil, decreasing negative impacts, and minimising environmental and health risks.

Soil water variability under subsurface drip and furrow irrigation

Non-uniformities in soil hydraulic properties and infiltration rates are considered to be major reasons for the inefficiencies of some surface irrigation systems. These non-uniformities may cause non-uniformities in soil water contents and could potentially affect plant growth. To investigate whether the non-uniformities in soil water contents can be overcome by well-managed irrigation systems, fields with clay loam soils and planted to cotton were irrigated with a continuous-flow, a surge flow, and a subsurface drip system. Measurements of water contents in each field were taken throughout the growing season at several depths. The water contents measured within the top 0–0.9 m in the three irrigations systems were evaluated in terms of their spatial and temporal variabilities. The analyses indicated that on this soil, use of the surge flow system did not lead to increased spatial uniformities of soil water contents compared with the continuous-flow system. Use of the subsurface drip system resulted in very non-uniform soil water contents above the depth of the emitters. Variability in water contents below the emitter depth was comparable to the surface irrigation systems.

Potato Growth Uniformity as Affected by Subsurface Drip and Seepage Irrigation

Growth and production uniformity of potato (Solanum tuberosum L.) as influenced by conventional seepage irrigation and by subsurface drip irrigation was evaluated in field studies during two seasons in plots 16 rows (18.3 m) wide and 183 m long. Seepage irrigation water was supplied through ditches located on each side of each plot. Drip irrigation water was distributed through buried tubes placed under the beds 6.1 m apart extending the length of the rows. Water application throughout the plots was accomplished more rapidly with the subsurface drip system and water use during the two seasons was 33% less than with the conventional seepage system. Tuber yield during the first season was similar with the two irrigation systems. During the second season, plant growth, tuber development, and tuber yield were sampled on alternate rows beginning on each outside bed, at each end of each plot, and in the middle of the plots. Irrigation method and bed location among the 16 beds had little influence of potato growth and development. With water flow from north to south, plant growth, and tuber yield were significantly higher from potatoes growing at the north end, lowest in the plot center, and intermediate from potatoes growing at the south end. These data indicate that potato production with the two irrigation systems was similar.

Managing irrigation and drainage systems in arid areas in the presence of shallow groundwater: case studies

Two field studies were conducted on the west side of the San Joaquin Valley of California to demonstrate the potential for integrated management of irrigation and drainage systems. The first study used a modified cotton crop coefficient to calculate the irrigation schedule controlling the operation of a subsurface drip system irrigating cotton in an area with saline groundwater at a depth of 1.5 m. Use of the coefficient resulted in 40% of the crop water requirement coming from the groundwater without a loss in lint yield. The second study evaluated the impact of the installation of controls on a subsurface drainage system installed on a 65 hectare field. As a result of the drainage controls, 140 mm less water was applied to the tomato crop without a yield loss. A smaller relative weight of tomatoes classified as limited use, was found in the areas with the water table closest to the soil surface.

Methods and Economics of Drainage Reduction through Improved Irrigation

Drainage reduction through improved irrigation is needed for addressing the problem of drainage water disposal in the San Joaquin Valley in California. Options for improving irrigation include improved management of existing systems (irrigation scheduling, duration of water applications), upgrading traditional surface irrigation systems (reduced field length, increased unit flow rate, surge irrigation, furrow compaction, tailwater recovery), and converting to pressurized irrigation systems (hand-move and linear-move sprinklers, low-energy precision application (LEPA) machines and rip irrigation). The most effective upgrade of surface irrigation systems for reducing subsurface drainage is a reduced field length coupled with reduced irrigation times. Increased furrow flow rates resulted in little change in drainage in some cases. Surge irrigation offers an opportunity of reducing subsurface drainage by only about 1/3. Converting to pressurized irrigation methods can substantially reduce subsurface drainage, but may be uneconomical in some cases. Analyses of large-scale field comparisons of irrigation methods revealed that generalizing about the best irrigation method is difficult. Economic analyses of these comparisons showed a well-managed furrow system to be more profitable than a subsurface drip system in one case, but a subsurface drip system to be more profitable compared to a marginally managed furrow system in another case. The analyses also revealed that disposal costs of subsurface drainage water may need to be much higher than projected costs to economically justify converting from furrow irrigation to irrigation systems with high capital costs.