Pivot System Research Articles

Does efficient irrigation technology lead to reduced groundwater extraction? Empirical evidence

Encouraging the use of more efficient irrigation technology is often viewed as an effective, politically feasible method to reduce the consumptive use of water for agricultural production. Despite its pervasive recommendation, it is not clear that increasing irrigation efficiency will lead to water conservation in practice. In this paper, we evaluate the effect of a widespread conversion from traditional center pivot irrigation systems to higher efficiency dropped-nozzle center pivot systems that has occurred in western Kansas. State and national cost-share programs subsidized the conversion. On an average, the intended reduction in groundwater use did not occur; the shift to more efficient irrigation technology has increased groundwater extraction, in part due to shifting crop patterns.

Crop coefficient, water requirements, yield and water use efficiency of sugarcane growth in Brazil

A correct evaluation of water losses as evapotranspiration (ET) by crops is important for allocating irrigation water and improving water use efficiency. Field experiments were conducted throughout 2009/2010 (second ratoon) and 2010/2011 (third ratoon) in a sugarcane field of a commercial distillery located on the coastal area of Paraiba state, Brazil. The main objective of this study was to determine crop coefficient, water requirements and water use efficiency (WUE) of sugarcane grown in a tropical climate. The experimental design was by randomized block design with four irrigation treatments and three replications using two center pivots. Crop evapotranspiration (ET) was determined by field soil water balance and reference evapotranspiration (ETo) was obtained based on Penman–Monteith method (FAO/56), using data of air temperature, relative humidity, wind speed and solar radiation from Data Collection Platform, located next to the experimental site. The experimental area was cultivated with irrigation applied weekly by a center pivot system in addition to rainfall. The irrigation scheduling was based on four irrigation levels (T1=25%, T2=50%, T3=75% and T4=100% of ETo). Results showed that ET and WUE are strongly influenced by soil water availability. When averaged across two years, productivity increased according to increases in water level. Sugarcane ET ranged from 2.7 (rain-fed condition) to 4.2mm day−1 (100% ETo irrigation treatment)

TIPOLOGI GRAMATIKAL DAN SISTEM PIVOT BAHASA PAKPAK-DAIRI

This study aims to describe the grammatical typology and pivot system of the Pakpak-Dairi language (PDL). The data were analyzed using the distribution method with substitution and transformation techniques. The pivot testing was carried out on coordinate and subordinate constructions, adverbial clauses, and non-finite verbal clauses. The findings show that grammatically PDL belongs to the accusative language typology.The pivot testing shows that the deletion of a nominal phrase in PDL can be directly made if it functions as a subject or adverbial. If a nominal phrase functions as a predicate, the deletion cannot be directly made; one of the clauses must be made passive or topicalized first. Based on such a pattern, in can be concluded that PDL belongs to the accusative language typology with a pivot pattern of S/A.

Estimation of leaf area index in onion (Allium cepa L.) using an unmanned aerial vehicle

Leaf area index ( LAI ) is one of the most common indices in agronomy , being a parameter associated with physiological processes. Canopy cover and structure are related to LAI and they have effects on the interaction between crops and the environment. The aim was to evaluate a non-destructive method to measure canopy cover in an onion crop using an unmanned aerial vehicle (UAV). A field experiment was conducted in a commercial onion plot irrigated with a centre pivot system during the 2010 irrigation season. Several data sampling events were carried out in order to determine leaf area in eight experimental plots. In each one of these plots, aerial photographs were taken using a vertical take-off and landing (VTOL) quadrotor aircraft. Canopy cover ( CC ) was obtained by means of software developed for this study. The maximum value of LAI represents a CC of 56%, which is high for the characteristics of this crop. Three models were used to analyse the relationship between leaf area index and canopy cover. According to the results, a more linear relationship was found between both parameters during early growth stages than during more advanced stages. For the linear model, which best fitted all growth stages; the slope that relates CC with LAI was 2.877 with a coefficient of determination of 0.837. ► A non-destructive method was evaluated to measure canopy cover in an onion crop. ► Aerial digital photography from unmanned aerial vehicles was used. ► A software tool was developed to determine canopy cover. ► Relationship between canopy cover and leaf area index found using an automatic IR imaging system.

Custos da irrigação e receita líquida do feijoeiro em um sistema pivô central sob variação do comprimento da tubulação de recalque e desnível topográfico

Neste trabalho, foi simulado o custo da irrigação de um sistema tipo pivô central com diferentes comprimentos da tubulação de recalque e desníveis topográficos na produção do feijoeiro comum, na região de Ilha Solteira -SP, bem como sua receita líquida. Considerou-se uma área irrigada pelo equipamento de 103,58 ha, sendo sua configuração a mais econômica possível para as variáveis consideradas. A participação da irrigação no custo de produção do feijoeiro variou de 14,8 a 21,5% entre as condições extremas, ou seja, do menor desnível topográfico (40 m) e comprimento da tubulação de recalque (2.000 m) ao maior desnível (80 m) e comprimento (3.000 m). Em todas as configurações do sistema de irrigação e com os preços praticados em agosto de 2008 ou com o preço histórico médio, seria viável a cultura do feijoeiro, proporcionando rendas líquidas de até R$ 3.959,64 ha-1 e até R$ 1.203,14 ha-1, respectivamente.

Real-Time Modelling and Optimisation for Water and Energy Efficient Surface Irrigation

The viability and sustainability of crop production is currently threatened by increasing water scarcity. Water scarcity problems can be addressed through improved water productivity and the options usually presumed in this context are efficient water use and conversion of surface irrigation to pressurised systems. By replacing furrow irrigation with drip or centre pivot systems, the water efficiency can be improved by up to 30% to 45%. However, the installation and application of pumps and pipes, and the associated fuels needed for these alternatives increase energy consumption. A balance between the improvement in water use and the potential increase in energy consumption is required. When surface water is used, pressurised irrigation systems increase energy consumption substantially, by between 65% to 75%, and produce greenhouse gas emissions around 1.75 times higher than that of gravity based irrigation systems so their use should be carefully planned keeping in view adverse impact of carbon emissions on the environment and threat of increasing energy prices. With gravity-fed surface irrigation methods, the energy consumption is assumed to be negligible. This study has shown that a novel real-time infiltration model REIP has enabled implementation of real-time optimisation and gravity fed surface irrigation with real-time optimisation has potential to bring significant improvements in irrigation performance along with substantial water savings of 2.92 ML/ha which is equivalent to that given by pressurised systems. The real-time optimisation and control thus offers a modern, environment friendly and water efficient system with close to zero increase in energy consumption and minimal greenhouse gas emissions.

Spatial variability for some properties of the wastewater irrigated soils

Composite surface soil samples (236 samples) were collected from three fodder farms irrigated for a long period with the treated sewage effluents or well water through a center pivot system. The soil of the 1st farm was loamy sand in texture while it was sandy loam for the other two farms, all were calcareous containing more than 10% of (CaCO3). The average values of EC for the 1st, 2nd and 3rd farms showed to be 3.48, 2.20 and 2.21dS m−1, respectively. The concentration of Zn was found to be 28.87mgkg−1 in the 1st farm, while it was 45.96 and 19.51mgkg−1 in the 2nd and 3rd farms, respectively. The Zn, Cu, Fe and Ni concentrations were higher in the farms irrigated with the treated sewage effluent than their concentrations in those irrigated with well water. The values were 28.87, 16.95, 4225, and 72.26mgkg−1 for Zn, Cu, Fe & Ni in 1st farm and 42.4, 60.5, 11215, and 180mgkg−1 for the 2nd farm. The Pb in the soil of the 1st, 2nd and 3rd farms reached 63.01, 37.10 and 27.69mgkg−1, respectively. It can be concluded that all soil properties except pH had high coefficients of variation, indicating strong variability over space. The data of geo-statistical analysis showed that only TDS and ESP in the 1st farm as well as OM in the 2nd farm had weak spatial dependency while other properties had moderate or strong spatial dependency. Moreover, the TDS and CaCO3 parameters of the 1st and 2nd farms had stronger nugget effects.

Use of digital photography from unmanned aerial vehicles for estimation of leaf area index in onion (Allium cepa L.)

Canopy cover and structure, which have considerable effects on the interaction between vegetation and the environment, especially in the case of crops, can be represented by a few parameters, which are based on the calculation of different vegetation indexes. One of the most common indexes in agronomy is the leaf area index, which is a parameter associated with agronomic, biologic, environmental, and physiologic processes. The aim of this study is to evaluate a non-destructive method to measure canopy cover in an onion crop by means of aerial digital photography from unmanned aerial vehicles, and to determine the relationship with leaf area index obtained by using an automated infrared imaging system. The field experiment was conducted in a 4.75ha commercial onion plot irrigated with a centre pivot system during the 2010 irrigation season. To determine the leaf area in the laboratory during crop development, data were sampled on three. At each sampling event, eight experimental plots of 1m2 were used. In each one of them, aerials photographies were taken by using a vertical take-off and landing quadracopter aircraft. Software for leaf area index calculation was developed to obtain canopy cover. Three models have been used to analyze the relationship between leaf area index and canopy cover. According to this, the model which best fits the relationship between leaf area index and canopy cover is the linear model. The relationship between both parameters was closer in the first stages than in more advanced stages.

Autonomous precision agriculture through integration of wireless underground sensor networks with center pivot irrigation systems

Precision agriculture (PA) refers to a series of practices and tools necessary to correctly evaluate farming needs. The accuracy and effectiveness of PA solutions are highly dependent on accurate and timely analysis of the soil conditions. In this paper, a proof-of-concept towards an autonomous precision irrigation system is provided through the integration of a center pivot (CP) irrigation system with wireless underground sensor networks (WUSNs). This Wireless Underground Sensor-Aided Center Pivot (WUSA-CP) system will provide autonomous irrigation management capabilities by monitoring the soil conditions in real time using wireless underground sensors. To this end, field experiments with a hydraulic drive and continuous-move center pivot irrigation system are conducted. The results are used to evaluate empirical channel models for soil-air communications. The experiment results show that the concept of WUSA-CP is feasible. Through the design of an underground antenna, communication ranges can be improved by up to 400% compared to conventional antenna designs. The results also highlight that the wireless communication channel between soil and air is significantly affected by many spatio-temporal aspects, such as the location and burial depth of the sensors, soil texture and physical properties, soil moisture, and the vegetation canopy height. To the best of our knowledge, this is the first work on the development of an autonomous precision irrigation system with WUSNs.

AN APPROPRIATE SUGAR-BEET HARVESTING MECHANIZATION FOR BIG-SCALE PROJECT

The aim of this research is to choose and evaluate the performance rate of three harvesting machines of sugar beet (lifting machine + topping machine, combined and self-propelled machines) appropriate with big scale projects with three different irrigation-systems (pivot, sprinkler and flood). The summarized results are: By using pivot irrigation-system, the maximum machine-performance rate of 3 fed/h ( 81 ton/h ) was obtained with forward speed of 6.5 km/h and 6-rows separated machines for topping and lifting of sugar beet. Meanwhile, the minimum machine-performance rate of 0.91 fed/h (24.30 ton/h) was obtained with forward speed of 3.5 km/h and 4-rows combined harvester of sugar beet. The maximum sugar-beet loss of 8 % was obtained with forward speed of 6.5 km/h, flood irrigation-system and combined harvesting-machine. Meanwhile, the minimum sugar-beet loss of 3.3 % was obtained with forward speed of 3.5 km/h, pivot system by using two machines for topping and lifting. The maximum lifting, loading and harvesting efficiencies of sugar-beet of 99.84, 97 and 96.7 % were obtained with forward speed of 3.5 km/h, pivot system by using two separated machines for topping and lifting. Meanwhile, the minimum sugar-beet lifting, loading and harvesting efficiencies of 99.6, 92.8 and 92 % was obtained with forward speed of 6.5 km/h, flood irrigation-system and combined harvesting-machine. The maximum sugar-beet yield of 27.2 ton/fed was obtained with forward speed of 3.5 km/h, pivot irrigation-system by using two machines for topping and lifting. Meanwhile, the minimum sugar-beet yield of 16 ton/fed was obtained with forward speed of 6.5 km/h, flood irrigation-system by using combined harvesting-machine. The minimum operation-costs were 17.75 L.E./ton (445.5 L.E./fed) by using 6-rows topping and lifting machines at forward speed of 3.5 km/h and pivot irrigation-system. Meanwhile, the maximum operation-costs and were 31.6 L.E./ton (780.9 L.E./fed) by using 4-rows combined harvester at forward speed of 3.5 km/h and flood irrigation-system.

Irrigation Rate and Fungicide Effects on Peanut Kernel Damage, Yield, and Net Return

Abstract Field studies from 2002 through 2004 examined effects of irrigation rate and fungicide on peanut kernel damage, yield and net return in Gaines County, TX. Irrigation rates, the main plots of a split-plot design, were applied with a center pivot system planted in concentric circles, and represented a base irrigation rate (B)(ca. 75% of evapotranspiration), B + 33%, and B − 33%. Azoxystrobin or metalaxyl were applied to the subplots at 60 and 90 days after planting and there was a no-fungicide control. Irrigation rate had no effect on percent damaged kernels from harvested pods. Plots with B + 33% irrigation rate had higher pod yields (P < 0.05) than B or B − 33% irrigation rates in 2002 and 2003, but had similar yields to the B rate in 2004, a relatively wet growing season. Irrigation rate did not result in an overall difference in net return in any year. Plots treated with azoxystrobin had higher peanut grades and lower percent damaged kernels in all 3 yr than no-fungicide and metalaxyl treated plots. Azoxystrobin treated plots had higher yield and net return than metalaxyl treated and no-fungicide treated plots in 2 of 3 yr. Rhizoctonia spp. was the primary fungal pathogen isolated from peanut pods. Use of azoxystrobin resulted in an average net return of $170/ha. Azoxystrobin effects on yield were additive to water status across the entire spectrum of irrigation rates during the combined three years. Peanut producers from this region who want to maximize yield by increasing irrigation rate should use azoxystrobin if there is any history of Rhizoctonia pod rot.

Analysis of water application costs with a centre pivot system for irrigation of crops in Spain

The aim of this study was to present a methodology to analyse the main factors that influence annual water application costs in centre pivot irrigation systems and to determine the most cost-effective centre pivot design, given the variables of machine length, lateral pipe diameter, sprinkler type (LEPA and fixed and rotating spray plate sprinklers (FSPS and RSPS)), system capacity, application efficiency, and water and energy costs for the irrigation of crops such as maize under conditions in Spain. Annual water application costs were calculated as the sum of the investment (Ca), energy (Ce), water (Cw), and equipment maintenance costs (Cm). Parameters used to assess the influences on pivot design were system capacity Sc = 1.25 L s−1 ha−1; application efficiency Ea = 80% for FSPS, Ea = 85% for RSPS, and Ea = 90% for LEPA; water price Pw = 0.06 € m−3 (0.081 US dollars); energy price Ene = 0.10 € kWh−1 (0.135 US dollars); net annual crop irrigation water requirement Nn = 7,000 m3 ha−1 year−1; and net daily peak crop water requirement Nnmax = 7.63 mm d−1 for maize. Results indicate that for plots smaller than 30 ha, the recommended pipeline diameter is 127.0 mm (5 in); for 30–40 ha, 168.3 mm (6 5/8 in); for 40–75 ha, 219.1 mm (8 5/8 in); and for 75–100 ha, 254.0 mm (10 in). A multidiameter pipe solution only slightly reduced water application costs in most cases studied. It was also determined that water costs and irrigation efficiency have a major influence on the total annual cost of water application; however, system capacity and energy price did not strongly affect total cost. For this reason, water application uniformity is very important and can be accomplished using a proper nozzle package and regular maintenance. The paper helps farmers determine the most cost-effective centre pivot design and management.

Optimal design of center pivot systems with water supplied from wells

Irrigation is one of the sectors in which energy consumption is increasing, mainly due to modernized systems designed to conserve water through the use of pressurized water distribution. Energy is one of the principle costs in irrigation. In this study, a new methodology is developed to determine the minimum total water application cost (investment+operation costs) in center pivot systems withdrawing water from wells. The proposed methodology optimizes the characteristic and efficiency curves for the pump as well as the types and diameters of pipes for pumping and distribution. In addition, the method accounts for hydrological variables (dynamic water table level and temporal variation), soil variables (infiltration parameters, surface storage capacity, surface impermeability), hydraulic variables (head losses in pipes, flow demand) and economic variables (energy costs, pump and pipe costs). In order to facilitate the technology transfer to managers and technicians, free software (DOP, “Diseño Optimo de Pivotes,” or Optimal Pivot Design) has been developed using MATLAB™. Results show that the best options are timing irrigation to avoid periods of high energy costs as well as increasing pumping power and pipe size, with a greater system capacity (1.5Ls−1ha−1), and shorter operation time (18hday−1). The minimum water application cost is obtained in all case studies in this paper for center pivot systems irrigating 75ha, with lateral pipes of 254mm (10in.).

Water requirements and single and dual crop coefficients of sugarcane grown in a tropical region, Brazil

A field experiment was conducted throughout 2009/2010 in a sugarcane field of a commercial distillery located on the coastal area of Paraiba state, Brazil. The objectives were to determine sugarcane water requirements and to test the single and dual crop coefficients by comparing the calculated values of ET with measured ones. Crop evapotranspiration was determined by field water balance, reference evapotranspiration (ETo) by the Penman-Monteith approach, while single and dual crop coefficients were computed through the standard FAO-56 methodology. The experimental area was cultivated with irrigation applied weekly by a centre pivot system in addition to rainfall and the irrigation scheduling was based on 100% ETo. Three statistical tests, mean bias difference (MBD), normalized root mean square difference (NRMSD) and regression analysis, were used to evaluate the performance of single and dual crop coefficients. Results showed that there was a notable symmetry between ET measured and ET calculated by Kc dual. The ET values, calculated from Kc single, underestimated those obtained from soil water balance measurements by 36%.

Uniformity of distribution of water and water depth applied in central pivot system in function of the relative position of the lateral line

An irrigation system should enable the efficient management of applied water. For this it is necessary to evaluate the performance of the system in operation. This study aimed to evaluate the uniformity of distribution, consumption of electricity and water depth applied by a center pivot irrigation system in function of the relative position of the lateral line. It was tested three positions of lines collecting water: incline of 3.45%, level and slope of 11.78%. The experimental design was completely randomized design with three repetitions at each position tested. It was applied the analysis of variance followed by Tukey test. The average coefficient of uniformity of Heermann & Hein was 90.02%, describing the uniformity of water distribution as very good. The mean weighted depth of irrigation applied was 5.84 mm, varying in each test significantly (5%) between the positions of slope versus incline and level. It was concluded that the position of the lateral line significantly influenced the uniformity of distribution, water applied and energy consumption.

Using radiation thermography and thermometry to evaluate crop water stress in soybean and cotton

Abstract The use of digital infrared thermography and thermometry to investigate early crop water stress offers a producer improved management tools to avoid yield declines or to deal with variability in crop water status. This study used canopy temperature data to investigate whether an empirical crop water stress index could be used to monitor spatial and temporal crop water stress. Different irrigation treatment amounts (100%, 67%, 33%, and 0% of full replenishment of soil water to field capacity to a depth of 1.5 m) were applied by a center pivot system to soybean ( Glycine max L.) in 2004 and 2005, and to cotton ( Gossypium hirsutum L.) in 2007 and 2008. Canopy temperature data from infrared thermography were used to benchmark the relationship between an empirical crop water stress index (CWSI e ) and leaf water potential ( Ψ L ) across a block of eight treatment plots (of two replications). There was a significant negative linear correlation between midday Ψ L measurements and the CWSI e after soil water differences due to irrigation treatments were well established and during the absence of heavy rainfall. Average seasonal CWSI e values calculated for each plot from temperature measurements made by infrared thermometer thermocouples mounted on a center pivot lateral were inversely related to crop water use with r 2 values >0.89 and 0.55 for soybean and cotton, respectively. There was also a significant inverse relationship between the CWSI e and soybean yields in 2004 ( r 2 = 0.88) and 2005 ( r 2 = 0.83), and cotton in 2007 ( r 2 = 0.78). The correlations were not significant in 2008 for cotton. Contour plots of the CWSI e may be used as maps to indicate the spatial variability of within-field crop water stress. These maps may be useful for irrigation scheduling or identifying areas within a field where water stress may impact crop water use and yield.

Agronomic and economic evaluation of various furrow irrigation strategies for corn production under limited water supply

It is commonly known that furrow irrigation is a less efficient method of irrigation than a sprinkler center pivot system, but many fields9 irregular shapes prevent the use of center pivot irrigation. Restricted water allocations of surface and subsurface water are forcing farmers to implement irrigation strategies that will reduce water application on furrow-irrigated fields. The study site was located in south central Nebraska. The objective of this study was to evaluate two irrigation scheduling scenarios: (1) the every-furrow irrigation method with 50% (0.5), 70% (0.7), and 90% (0.9) field capacity (FC) treatments and (2) the every-furrow (EF) irrigation method compared to the every-other-furrow (EOF) method with both using the 75% field capacity (0.75 FC) treatment effects on corn (Zea mays L.) yield, net economic return, and residual soil nitrate-nitrogen. The experimental design was a randomized complete block with three replications. Grain yield showed no significant difference in both years for all irrigation treatments. Irrigation water application with the 0.5 FC strategy reduced the amount of applied water by approximately 70% and 200% compared to 0.7 FC and 0.9 FC, respectively, in both years. The water savings with the EOF method over the EF method was 23%. The economic return with 0.5 FC was 6% to 13% and 36% to 69% over 0.7 and 0.9 FC irrigation treatments, respectively. The 0.5 FC strategy showed no significant reduction in nitrate-nitrogen loss over 0.7 FC and 0.9 FC, while the EOF method reduced soil nitrate-nitrogen loss by 11% to 26% over the EF irrigation method in both years. The average economic return over two years with the 0.5 FC strategy was 9.5% and 52.5% over 0.7 FC and 0.9 FC irrigation treatments, respectively, while the average economic return with the EOF method over the EF method was 9.5%. Findings demonstrated that economic and environmental benefits of using 0.5 FC or the EOF method is much superior to other furrow irrigation strategies, especially in areas with limited water resources where less efficient irrigation methods may lead to significant water loss.

Operational performance of the mechanized and semi-mechanized potato harvest

Potato is an important crop plant throughout the world. Harvesting is a fundamental step in its production system. Maybe, it is the most complex and expensive operation. Thus, the objective of this work was to compare the cost of the mechanized and semi-mechanized harvest, the operational capacity and the production losses during the potato harvest process. The work was accomplished in a commercial farming, cultivated under pivot system, in the municipal district of Perdizes - MG, Brazil. A completely randomized design with two treatments was used: mechanized and semi-mechanized harvest. The mechanized harvest used a self-propelled harvester. In the semi-automated harvest, a digger mounted on tractor was used and the potato was manually harvested. It was concluded that the cost of mechanized harvest was 49.03% lower than the cost of semi-mechanized harvest. On average, the harvester had a work for 23 workers in manual harvest. Mechanized harvest showed losses of 2.35% of potato yield, while the semi-mechanized harvest showed losses of 6.32%.

Cost of irrigation and profit of bean in a center pivot system with water pumped by diesel engine under variation of length pressurized pipe and topographic levels

En este trabajo se estimo el costo de un sistema de riego con pivote central con bombeo por un motor diesel e realizados en diferentes longitudes de la tuberia de recalque y desnivel de la topografia en la produccion de frijol en la region de Ilha Solteira – SP, y sus ingresos netos. Se considero un area de riego de 103,58 hectareas, y la configuracion del sistema mas economico posible para las variables consideradas. La cuota de riego en el costo de produccion de granos vario desde 26,6 hasta 37,6% entre los extremos, es decir, la pendiente mas baja (40 m) y la longitud de la tuberia de recalque (2000 m) hasta la brecha mas grande (80 m) y longitud (3000 m). Teniendo en cuenta los precios en agosto de 2008 todos los ajustes del sistema de riego por gasoleo puedem ser viable y atractiva, proporcionando ingresos netos de hasta R$ 3,283.37 ha -1 . Para el precio promedio historico (en el periodo de agosto de 2001 a 2008), en las configuraciones despues de una longitud de 3000 metros de tuberias, la cosecha de frijol de riego se convierte en inviable, y las perdidas ascienden R$ 332.10 ha -1 .

Microbial Transport from Dairying under Two Spray‐Irrigation Systems in Canterbury, New Zealand

Transport through the soil and vadose zone to groundwater of Escherichia coli, fecal coliforms, and Campylobacter spp. from pasturing of dairy cows was studied on two working dairy farms under a traveling irrigator and a center pivot system. Leachate was collected from 1.5 m depth using a large linear lysimeter over a period of 4 yr after rainfall or irrigation applied using a traveling irrigator. There was little transport of fecal coliforms or Campylobacter from irrigation applications of 55 mm. There was some transport of fecal coliforms at applications of 80 mm (corresponding to irrigation plus heavy rainfall) but no detectable Campylobacter. When fresh cow pats were placed on half of the lysimeter plots with an 80-mm water application, there was transport of fecal coliforms and Campylobacter, but levels of Campylobacter were low (<or=4 MPN L(-1)). Groundwater at the farm with center pivot spray irrigation was monitored monthly from September 2001 to June 2007, with 60% of samples being collected from downgradient wells. Escherichia coli were detected in 5.4 and 2.8% of samples from upgradient and downgradient wells, respectively, at concentrations of >or=1 cfu 100 mL(-1). Campylobacter was detected in 0.7% of samples over the study period, with equal percentages from up- and downgradient wells. The results indicate minimal impact of dairying at these sites on microbial quality of groundwater as a result of spray irrigation using traveling irrigators at rates of approximately 55 mm every 2 wk or center pivot irrigators at 18 mm every 3 to 4 d.