Furrow Length Research Articles

Effect of tillage on water advance and distribution under surge and continuous furrows irrigation methods for cotton in Egypt

AbstractA field experiment was carried out to assess the effect of tillage on water advance and water distribution in the root zone area (0.5 m) under continuous and surge flow irrigation in a cotton field. The experiment was conducted at the Agriculture Experimental Station, Assiut University, Assiut, Egypt. The location was classified as clay soil. The furrows with blocked ends were 76 cm long and 0.70 m wide with 0.0024 m m−1 of slope. To monitor the advance time, six points were established along the furrows at 9, 18, 27, 36, 45 and 76 m from the inlet. In order to study the water distribution along the furrows, soil moisture content was measured using the gravimetric method at 0–0.25 and 0.25–0.50 m depths at the beginning, middle and end of the furrows. A hand hoeing tillage system (HH) was compared with a weed control tillage system (WC) under continuous flow (CF) and surge flow irrigation (SF).Hand hoeing tillage decreased the water advance time compared to weed control tillage either under continuous or surge flow irrigation. Surge flow also decreased the advance time compared to continuous flow. The greatest effect on the advance time reduction resulted from the combined effect of surge flow with tillage (SFHH), which reduced the total supplied water by 22.4 and 25.7% during the first and second irrigation, respectively. The single effect of either tillage (CFHH) or surging (SFWC) also reduced the total amount of supplied water compared to continuous flow with weed control tillage (CFWC), but the reduction was less than that in the combined treatments. Due to tillage and surge effects, soil water was efficiently used and distributed uniformly along the furrow length. Combining surge irrigation and tillage could be an efficient method to use irrigation water efficiently and ensure uniform distribution of soil water. Copyright © 2006 John Wiley & Sons, Ltd.

Application efficiencies and furrow infiltration functions of irrigations in sugar cane in the Ord River Irrigation Area of North Western Australia and the scope for improvement

The introduction of irrigation in the Ord River Irrigation Area (ORIA) in the North West of Western Australia resulted in rising water tables in many parts of the ORIA. Commercial sugar cane production commenced in 1995 in the area, which exacerbated the problem caused by the longer growing and irrigation season and the large irrigation applications. Rising water tables are associated with deep drainage from paddocks and irrigation infrastructure. Improving the irrigation application efficiency (IAE) was identified as a manageable objective for sugar cane growers that is expected to reduce deep drainage. Existing irrigation practices were monitored and a surface irrigation model (SIRMOD) was used to simulate these irrigations. The lack of accurate infiltration parameters normally limits the extrapolation of SIRMOD simulation results to different irrigation scenarios. It was found that the infiltration into the Vertisols of the ORIA could be properly described by simple infiltration functions which were dependent on the soil moisture deficit (SMD) at irrigation as well as the shape of the irrigation furrow. The function described as Instantaneous Crack Fill (ICF) was appropriate for furrows with broad-based ‘U’-shaped furrows while a non-ICF described the infiltration behaviour of deeper ‘V’-shaped furrows. Summary tables were generated to illustrate the relationship between SMD, inflow rate, furrow length and irrigation duration for ‘U’-shape and ‘V’-shape furrows of Vertosols in the ORIA. From the tables it was determined that gains of up to 20% can be achieved in the IAE compared to the current situation.

Water, nitrogen and yield losses for a nonhomogeneous furrow set

Water distribution can be nonuniform along the furrow length under surface irrigation. This “down field” nonuniformity is combined with “inter-row” non-uniformity which is a consequence of differences in infiltration characteristics across the plot. Global nonuniformity of application depth causes variation of yield, drainage and nitrogen leaching. In addition to that, due to year-to-year variability of climate, irrigation depths range significantly (from 0 to 360 mm/season). The objective of this paper is to study the impact of the nonuniformity of irrigation-water distribution within a furrow plot on yield, water and nitrogen losses when climate variation is taken into account. Six maize vegetation seasons on a Chromic Luvisol soil in the Sofia region with varying irrigation requirements are considered. Irrigation water is distributed in relative terms over the plot at different levels of nonuniformity (coefficient of variation Cv ranging from 13 to 66%) by the FURMOD model. Water and nitrogen cycle and crop growth are simulated then compared at 30 representative points in the set with various “climate-irrigation nonuniformity” combinations by the CERES-maize model. It was established that non-uniformity of irrigation is not important in wet vegetation periods. The drier the irrigation season, the higher the yield loss and risk to environment due to nonuniformity of irrigation water distribution. In moderate and dry irrigation seasons it causes yield losses of 2–14%, significant variation (30% < Cv < 200%) of drainage, nitrogen leaching and residual soil nitrate over the furrow set. Surface irrigation performances can be improved by reducing lateral nonuniformity of stream advance.

FURROW IRRIGATION MANAGEMENT WITH LIMITED WATER

Dwindling water supplies in the Great Plains are a major concern to the economics of the region. Watermanagement studies on limited irrigation usually focus attention on sprinkler irrigation for the delivery system. Furrowirrigation has more management factors that can influence water application including water advance and water distributionover the furrow length. This study compared water application strategies to reduce the amount of water delivered to cornduring the vegetative and late grain fill growth periods from 1998 to 2000. In addition to a full irrigation and late initiationof irrigation treatment, two water allocation treatments were imposed, which limited seasonal water applications to 150 and250 mm, respectively and rainfed treatment. Average grain yield over three years for late treatment was 0.2 Mg ha-1 or2% less than that of full treatment. Yields for the 150- and 250-mm treatments were 1.1 and 0.4 Mg ha-1 less than full.The reduction in gross water applied was 21%, 36%, and 51% for late, 250 mm, and 150 mm as compared to full. Soilwater was measured to a depth of 1.8 m at quarter points along the furrow to evaluate the distribution of the irrigation. Soilwater profiles tended to dry slightly during the season, but there was no statistical difference among the limited and fullirrigation treatments. Best management cropping practices were applied, including ridge tillage/planting, furrow packing,irrigation scheduling, and surge irrigation techniques to keep water in the soil profile and target water applications to criticalcrop growth stages.. These practices maximized the potential success of all irrigation treatments.

Field assessment of the water saving potential with furrow irrigation in Fergana, Aral Sea basin

The Aral Sea basin is a region that faces water scarcity due to aridity and man-made desertification. To reduce the disproportion between water demand and supply improved water management is required, particularly aimed at water saving and conservation in irrigated agriculture. One main issue is demand management by reducing the farm irrigation water demand by improved crop irrigation management since the modernization and rehabilitation of the conveyance and distribution systems are presently out of the scope in Uzbekistan. Under this perspective, the improvement of furrow irrigation systems, which are used on 98% of the irrigated lands, is a main issue. To assess the potential for improving the performance of furrow irrigation in the central part of the Fergana Valley, Uzbekistan, a set of evaluation experiments was carried out. Irrigation management alternatives included several furrow inflow rates (1.2–2.4 l/(s furrow)) and furrow lengths (130 and 400 m); comparing every-furrow irrigation with alternate-furrow irrigation. Results were evaluated through the application efficiency ( E a), the distribution uniformity (DU) and total applied irrigation depths. The best performances were obtained for alternate long furrows adopting the inflow rate of 1.8 l/(s furrow), which produced high E a and DU, superior to 80 and 83%, respectively, and led to seasonal water savings from 200 to 300 mm when compared with actual water use in every-furrow irrigation. Large water saving also resulted from reducing the irrigation cut-off times in every-furrow irrigation, corresponding 150–200 mm through the irrigation season. Also, improving the multi-tier reuse method when adjusting the cut-off times in agreement with the inflow rates produced high irrigation performances and water savings larger than 300 mm for the season. The field research provided information for alternative approaches to be further considered, such as surge-flow irrigation aiming at reducing advance times and tail-end runoff.

FURROW IRRIGATION SYSTEM DESIGN FOR CLAY SOILS IN ARID REGIONS

This article presents an accurate and simplified method for designing a furrow irrigation system that would be useful in arid regions with clay soils. Field experiments were conducted at a site in Egypt where cotton is grown in clay soils. The site is usually irrigated every 10 days and follows a three-turn crop rotation. Several parameters were measured including furrow geometry, slope, width, length, infiltration characteristics, advance time, cut-off time, depletion time, and recession time. A volume balance model was applied to simulate water flow in the furrow system, and the results were compared to those obtained from the field measurements. This study shows that a volume balance model can be satisfactorily applied to clay soils, and the length of the furrow and its inlet inflow are the main factors affecting application efficiency. Further, this study indicates that in order to obtain high application efficiencies, furrow inflow rates must increase with longer furrow lengths.

Simulation of continuous and surge flow irrigation under short field conditions

This paper describes the simulation results for continuous and surge flow irrigation under short field conditions by the computer model SIRMOD III in order to evaluate the performance and applicability of the model for short furrows and to investigate the viability of the two-point method for calculating infiltration parameters under continuous and surge flow irrigation in short fields. These specific field conditions are found on farms smaller than 1 ha and with a furrow length of 70 m. To evaluate the model a series of experiments has been carried out in two locations in Egypt and in one site in the Netherlands. The experiments in Egypt were conducted on a field with clay soil situated at the Agriculture Experimental Station, Assiut University, and on a sandy soil field located at the Assiut University Experimental Station for Desert Land, El-Wadi El-Assuity, Assiut. The experiments in the Netherlands were carried out at the Tunnel Experimental Setting of the Irrigation and Water Engineering Group of Wageningen University. The tunnel was covered as a greenhouse to protect the investigations against the external weather conditions, especially rainfall. Two soil types were available inside the tunnel, namely sandy clay and sandy clay loam. All the experiments were carried out in furrows with a blocked end and their length and width were 70 and 0.70 m, respectively. Measured field data were used to evaluate the computer model SIRMOD III. The results of the evaluation indicated that the model can accurately simulate continuous and surge flow irrigation under short field conditions for the measured infiltration parameters. These field data are very important for a good simulation of the advance time and consequently the infiltration. The two-point method can be successfully used to obtain the infiltration parameters for continuous and surge flow irrigation under short field conditions and for different soil types. Copyright © 2005 John Wiley & Sons, Ltd.

Surge flow irrigation under short field conditions in Egypt

AbstractSeveral studies carried out in long furrows have shown that surge flow irrigation offers the potential of increasing the efficiency of irrigation. The effects of surge flow in short fields, such as in Egypt, are still not well known, however.To investigate the effect of surge flow irrigation in short fields a series of experiments have been carried out at two different locations in Egypt. The first location with a clay soil was situated at the Agriculture Experimental Station, Assiut University, Assiut. The second location with a sandy soil was situated at the Assiut University Experimental Station for Desert Land, El‐Wadi El‐Assuity, Assiut. The blocked end furrow lengths and widths were 70 and 0.70 m respectively. Three discharges were selected for each soil type, namely 0.46, 0.74 and 0.90 l s−1 for clay soil and 0.73, 1.0 and 1.4 l s−1 for sandy soil. For each discharge two cycle times were investigated, namely 16 and 24 minutes. For each cycle time three cycle ratios were chosen, 1/4, 1/2 and 3/4 for the 16‐minute and 1/3, 1/2, and 2/3 for the 24‐minute cycle time. The water content was measured at three locations, namely at the beginning, middle and end of the furrow. In each location three points were measured in a vertical line at a depth of 0–0.1, 0.1–0.3 and 0.3–0.7 m.The results show that surge flow irrigation leads to a more uniform water distribution along the furrows than continuous flow. This uniformity is more pronounced in clay soil than in sandy soil. Surge flow irrigation decreases the advance time in comparison to continuous flow. The reduction in advance time was more pronounced with the discharges of 0.74 and 1.0 l s−1 in clay and sandy soil respectively. The 24‐minute cycle time is better than the 16‐minute cycle time. The reduction in advance time with a cycle time of 24 minutes is due to the effect of the off‐time. Different cycle ratios can be used but the 1/3 cycle ratio may be the best. In conclusion, surge flow irrigation under the short field conditions as prevailing in Egypt decreases the advance time, increases uniformity and efficiency by decreasing deep percolation and reduces applied water volume by 15–35%. Copyright © 2004 John Wiley &amp; Sons, Ltd.

Comparison between surge irrigation and conventional furrow irrigation for covered black tobacco cultivation in a Ferralsol soil

Over 51,000 ha of low yield tobacco were harvested in the year 2000/2001 in Cuba. Since the Union of Tobacco Enterprises plans to increase this area to 72,000 ha of tobacco in 2005, where most of these new areas will be irrigated with surface irrigation, then the introduction of new irrigation technologies is an important premise to achieve high yield productions. Because of this, some field evaluations of furrow irrigation with continuous and intermittent flow applications were carried out on a plot belonging to the "Cítricos Ciego de Avila" enterprise, in the Ceballos municipality of the Ciego de Avila province, Cuba. The objective of these field evaluations was to compare the hydraulic behavior of different water management strategies of furrow irrigation for the cultivation of black tobacco in a Ferralsol soil, using a surface irrigation simulation model. The intermittent application of water considerably reduced the infiltration capacity of the soil. Likewise, the influence of soil water content and furrow wetted perimeter on infiltration parameters was corroborated. The surge flow furrow irrigation with variable time cycles increased the application efficiency by more than six fold, and the water volume was reduced by more than 80% compared to continuous irrigation. The largest rises in distribution uniformity and reductions in percolation losses were obtained with a furrow length of 200 m and a discharge of 1 L s-1, respectively.

Bemisia tabaci

<i>Bemisia tabaci</i>

Alternative techniques improve irrigation and nutrient management on dairies

Many of the dairies in California's Central Valley use a water flush system for manure handling; the manure water is eventually mixed with freshwater and applied to cropland during irrigation. Good performance during irrigation applications is important due to the nutrients in the manure water. This project evaluated alternative management techniques (furrow torpedoes, surge irrigation and shortening furrow lengths) for improving irrigation practices on dairies. All three techniques reduced the amount of water required for irrigation. The project also investigated the impact of changing the timing of manurewater additions to the fresh irrigation water. Delaying the addition of manure water until the advancing fresh irrigation water had reached approximately 80% of the distance down the field improved nutrient-application uniformity and reduced nutrient applications.

Morphological distinction of molecular types in Ammonia – towards a taxonomic revision of the world’s most commonly misidentified foraminifera

In this study, morphometric analysis has been performed on 178 Ammonia specimens belonging to 12 different molecular types, plus non-sequenced type specimens of Ammonia beccarii and A. tepida. Molecular type distinction is based on phylogenetic analysis of 267 partial LSU rDNA sequences, obtained from 202 living Ammonia specimens, sampled in 30 localities from 17 countries bordering the Pacific Ocean, Atlantic Ocean, Mediterranean Sea, Caribbean Sea and North Sea. Restriction fragment length polymorphism (analysis was carried out for another seven specimens. Morphometric analysis was based on measurements or assessments of 37 external test characters in spiral, umbilical, profile and close-up Scanning Electron Microscopic views. Cluster analysis, canonical variates analysis, and detrended correspondence analysis, performed on the morphological data set, suggest that each molecular type can be distinguished morphologically and can be regarded as a separate species. Primary types of A. tepida and topotypes of A. beccarii are shown to be morphologically separate from any of the molecular types so far recognised. We are aware of at least 9 more distinctive morphotypes that have not yet been sequenced, and thus we infer that the total number of genetically distinct and morphologically separable living species of Ammonia worldwide is likely to exceed 25–30. At this stage not all molecular types can be unequivocally assigned to formally described species. Several genetically-based species can be distinguished by the presence of one distinct character, but most are discriminated on the basis of a combination of many different characters. Morphological characters (e.g. test shape, chamber shape, porosity, prolocular diameter, folium shape, radial furrow length, umbilical diameter) are shown to be slightly more valuable in separating the molecular types than surficial ornament (beads, pustules, bosses, secondary calcite). One highly distinctive group (2–3 species – beccarii, batava, ? inflata) is readily discriminated on the basis of its large test size, strongly beaded and grooved ornament, and the presence of fissures along the sutures on the spiral side. The results of this study imply that the widespread practice of recognising only one, two or three species of Recent Ammonia worldwide should be abandoned. The most commonly used name, Ammonia beccarii, should be restricted to a large, compressed, highly ornamented species, so far not recognised beyond its type locality in the Adriatic Sea. Other commonly used names, such as A. parkinsoniana and A. tepida, apply to species with far more restricted distributions than the literature would suggest.

Demonstration of characteristic skin surface contours of extramammary Paget's disease and parapsoriasis en plaque by image analysis of negative impression replicas

The surface contours of lesional skin of certain skin diseases, such as parapsoriasis en plaque (PEP) and extramammary Paget's disease (EMPD), in which there is a massive infiltration by non-epidermal cells, looks somewhat different from that of the adjacent normal skin, needless to state that they are apparently different from that of ordinary chronic inflammatory dermatoses where we found acanthotic epidermis accompanied by hyperkeratosis. We attempted to objectively characterize these unique skin surface changes qualitatively and quantitatively using non-invasive methods. Negative impression replicas were taken from the lesional skin of patients with EMPD or PEP as well as from the adjacent uninvolved skin. The findings were confirmed histologically. The replicas were examined by using computerized image analysis. Several parameters were analyzed that correlate with the changes in the anisotropy of the skin furrows (VC1), average skin roughness (KSD), average length of skin furrows (LEN), and number of skin furrows (NUM). There were significant decreases in KSD and NUM in EMPD, indicating a smoother skin surface in the lesional skin than in the adjacent normal skin. In contrast, the PEP lesion had an increase in VC1 and LEN and a decrease in NUM, which suggests larger skin ridges in the lesional skin than in the uninvolved skin. Thus the unique skin surface of the cutaneous disorders accompanied by epidermal invasion by non-epidermal cells, such as EMPD and PEP, was characterized both qualitatively and quantitatively using computerized image analysis of negative impression replicas.

Effects of site preparation on runoff, erosion, and nutrient losses from Pinus plantations established on the coastal lowlands of south-east Queensland, Australia

Site preparation practices used during establishment of second rotation Pinus plantations on the coastal lowlands of south-east Queensland became more conservative during the 1990s. Traditionally, site preparation included stick raking of residue into windrows, followed by burning. Areas subject to periodic saturation were then cultivated to form continuous high mounds, while better drained sites were contour strip cultivated. These practices were replaced by retention of residue biomass on hillslopes. Similarly, intensive site disturbance was increasingly replaced by tillage of the immediate planting zone only and, as far as possible, avoidance of continuous furrows, major drainage structures, and high mounding works. In the study reported here, simulated rainfall and overland flows were used to assess the impacts of the earlier, less-conservative site preparation practices on hillslope soil loss, nutrient loss, and the potential for off-site nutrient movement.Where residue from clearfell harvesting of the first rotation was not removed, runoff, erosion, and nutrient loss were negligible. Harvesting tended to distribute residue widely across hillslopes, and, together with naturally occurring understorey biomass, it formed a largely continuous groundcover. Highest concentrations of sediment in overland flow were recorded for hillslopes in the newly stick-raked condition. Sediment concentrations in overland flows applied to properly designed and constructed high mounds were low, even for large flows simulating relatively long furrow lengths. However, sediment in rainfall-induced runoff from mounded areas was observed to be nutrient enriched, indicating potential for an off-site nutrient pollution risk, at least prior to establishment of grass cover along furrows. Nutrient enrichment was correlated with enrichment of finer size classes of sediment in runoff.The work reported in this paper vindicated the move away from traditional residue removal and site preparation practices to an approach based on residue retention, minimum site disturbance, and, wherever possible, ‘spot’ rather than continuous mounding/cultivation.

Optimal Furrow Design. II: Explicit Calculation of Design Variables

The furrow irrigation system design problem (at minimum cost) is significantly simplified by analytically solving it. For a specified furrow length, a simple algebraic equation is derived to directly calculate the appropriate inflow rate (and cutoff time) so that the minimum cost of the furrow system is obtained. The proposed equation is independent of the water and labor cost coefficients. Comparison tests indicated that the optimum inflow rate values obtained analytically were in close agreement to the optimum values obtained using the outcome of the zero-inertia numerical model. The method is extended for furrow design considering the furrow length also as a design variable. The optimum number of distribution lines and widthwise furrow sets are easily determined by a simple calculation procedure.

Analysis and Design of Furrow Irrigation Systems

Application efficiency is the primary criterion for furrow irrigation system design and management. In this study, the application efficiency function of a furrow irrigation system is analyzed. The application efficiency function is unimodal with respect to inlet flow rate and furrow length. Optimality conditions are derived for the cases in which application efficiency is a function of either furrow length or flow rate. Simple and sufficiently accurate equations and design and management rules are developed.

Programa computacional para dimensionamento e avaliação de sistemas de irrigação por sulco

Este trabalho apresenta o aplicativo denominado DimSulco, desenvolvido em linguagem Visual Basic 5, em ambiente Windows 95, que objetiva facilitar ao usuário o dimensionamento e a avaliação de sistemas de irrigação por sulco, a partir do conhecimento prévio de parâmetros básicos de projeto. O DimSulco foi estruturado em cinco módulos: I - Irrigação sem déficit hídrico e comprimento do sulco definido; II - Irrigação sem déficit hídrico e comprimento do sulco indefinido; III - Irrigação com déficit hídrico e comprimento do sulco definido; IV - Irrigação com déficit hídrico e comprimento do sulco indefinido e V - Sistema de reutilização de água. Os módulos I e III foram divididos em dois submódulos, que permitem o dimensionamento e a avaliação do sistema com e sem vazão reduzida. Os módulos II e IV foram divididos em quatro submódulos, contemplando as seguintes opções: a) sem vazão reduzida e tempo de avanço (Ta) igual a ¼ do tempo de oportunidade de infiltração da lâmina requerida no final da parcela (To); b) com vazão reduzida e Ta igual a ¼ de To; c) sem vazão reduzida e Ta igual a To e d) com vazão reduzida e Ta igual a To. O módulo V dimensiona sistemas de reutilização da água a partir de um dimensionamento prévio efetuado em qualquer um dos módulos anteriores, definindo os elementos básicos de cada setor e recalculando os índices de desempenho. Para ilustrar a execução do programa, utilizou-se um exemplo de dimensionamento de um sistema de irrigação por sulco.

Deep Ripping and Blocked Furrow Effects on Lower 1/3 Furrow Irrigation Infiltration

Methods of primary tillage between annual crops of corn or sorghum on the Southern High Plains commonly includes disking followed by chiseling or occasional deeper loosening by ripping (subsoiling) or moldboard plowing. On slowly permeable clay loams, irrigation water infiltration on the upper 2/3 of graded furrow lengths is usually adequate to wet the rooting depth of about 1.2 m (4 ft). However, reduced infiltration opportunity time on the lower 1/3 can cause inadequate wetting and reduce grain yield unless excessive furrow runoff is allowed. This study was conducted during 1995-1996 on the Southern High Plains at Bushland, Texas, to evaluate the effects of deep ripping the lower 1/3 on irrigation infiltration, soil water storage and distribution, and grain yield along the furrow. Rip treatments were tilled 0.3 m deep and the remainder of the study area was chiseled 0.15 m deep. Treatments included ripping with furrow ends blocked to prevent runoff, ripping with open-end furrows, chiseling with blocked furrow ends, and chiseling with open-end furrows. With blocked-end furrows, irrigation was cut off after about 2 h ponding on the more rapidly advancing furrows to allow water to reach ends of slower furrows. Open-end furrows received 6 to 8 h of runoff during the infiltration phase. Deep ripping increased infiltration during infiltrometer tests in the lower 1/3 furrow interval by 26% to 29% immediately after primary tillage. However, subsequent furrow traffic and soil consolidation from irrigation and rainfall reduced this tillage effect on infiltration to where net irrigation, evapotranspiration, and grain yield were not significantly affected on a field average basis for the complete crop season. Furrow blocking with earlier irrigation cut-off reduced gross application by about 24% and net application by 17% to 20% while the related reduction in grain yield was only 13% in 1995. In 1996, furrow blocking reduced net irrigation by 11% and grain yield by only 3%. Growing season water use efficiency was not significantly affected by any treatment.

Surge irrigation studies in maize (i) crop response for geometry and on-off timings

Field experiments were carried out from December 1994 to March 1995 at Tamil Nadu Agricultural University to study the impact of maize planting geometry and on-off timings under cost free surge irrigation as compared to continuous flow and basin furrow method of farmers. The quantum of flow was 1.5 lps per furrow and the length of furrow was 150m. The single row planting geometry with higher volume of water consumption influenced the plant height, root volume in surge and continuous flow under two on-off timings of 10 and 15 minutes but not for 20 minutes. Farmers' method recorded increased plant height among the irrigation methods. There is reduction in plant height in sector 5 irrespective of planting geometry, irrigation methods and on-off timings. Single row planting geometry recorded increased cob length as compared to double row planting except on-off timings of 20 minutes. Single row recorded lower yield. Among the sectors, there was a progressive decrease from sector one to four and significant decrease in Sector 5 due to penultimate depression and increase in the last sector due to stagnation. Water saving under single row geometry was ranging from 15-22 per cent.

Forecasting and optimizing furrow irrigation management decision variables

Furrow irrigation can be better managed if the management decision variables (irrigation time and amount; inflow rate and cutoff) can be determined ahead of time. In this study, these decision variables were forecast and optimized using 1 day ahead grass reference crop evapotranspiration (ET0) forecasts, based on the ARMA (1,1) time-series model, with a seasonal furrow irrigation model for both homogeneous and heterogeneous infiltration conditions. Heterogeneity in infiltration characteristics was restricted to variations along the furrow length as opposed to variations between furrows. The results obtained were compared with their counterparts using the observed ET0 for the same period during the 1992 cropping season. Seasonal performance (application efficiency, inflow, runoff and deep percolation volumes) and economic return to water (yield benefits minus seasonal water related and labor costs) were affected by infiltration conditions, while irrigation requirement and bean yield were unchanged. In a given infiltration case, seasonal performance, irrigation schedules, bean yield and economic return to water were comparable (lower than 4% difference) for the two ET0 conditions. For each ET0 condition, individual irrigation events resulted in different irrigation designs (inflow rate and cutoff time) except inflow rates with heterogeneous infiltration. Differences in inflow volume were less than 2% and 5%, respectively, for homogeneous infiltration and heterogeneous infiltration. For the conditions studied, furrow irrigation management decision variables can be forecast and optimized to better manage the irrigation system, because irrigation performance was the same for both (forecast and observed) ET0 cases.