Reduce Irrigation Water Use Research Articles

DEFICIT IRRIGATION AND REFLECTIVE MULCH EFFECTS ON PEACH AND NECTARINE FRUIT QUALITY AND STORAGE ABILITY

The effects of deficit irrigation and reflective mulch were studied as possible means to reduce irrigation water use and improve peach fruit quality and storage ability. 'Royal Glory' peach and 'Caldesi 2000' nectarine trees were drip irrigated close to ETc (control) or with 50% of ETc (deficit) during the last three weeks before anticipated harvest of tree-ripe fruit. Reflective Extenday ® mulch was also applied on the tree row for almost a month before anticipated harvest at control or deficit irrigated trees. Fruit quality from the upper and lower parts of the tree was evaluated at harvest and after 2, 4 and 6 weeks at 2°C plus 1 day shelf life. Fruit quality included skin color, flesh firmness, specific conductivity and dry matter (DM), juice soluble solids content (SSC), acidity and total phenols (TP) and subjective evaluation of chilling injury (CI) symptoms (flesh leatheriness and browning). With storage time and in both cultivars, fruit skin only slightly changed, fruit flesh softened, specific conductivity, SSC, acidity and DM decreased and TP content and CI (mainly leatheriness) increased. With deficit irrigation or reflective mulch, the two cultivars behaved differently. Nectarines from deficit irrigated trees had improved quality but lower storage ability than fruit from control trees. Peaches from deficit irrigated trees had similar quality to control fruit except of higher SSC (mainly the fruit from the lower part of the canopy) and slightly higher Cl. Nectarines from reflective mulched trees had better skin color, harder flesh, higher acidity and DM, similar SSC and TP and higher leatheriness incidence than fruit from control trees. Peaches from reflective mulched trees had the most advanced maturity fruit at harvest compared to the other treatments, and higher quality fruit but also lower storage ability than control fruit. In short, fruit quality of both cultivars studied was improved due to deficit irrigation or reflective mulching but their storage ability was reduced from these treatments.

Comparison of energy of irrigation regimes in sugar beet production in a semi-arid region

This study analyzed the effect of three levels of drip irrigation in sugar beet ( Beta vulgaris L.) production in the Middle Anatolian region of Turkey. Two deficit irrigation treatments 75% and 50% of measured soil water depletion were compared with a full irrigation control treatment. In this paper, root yield, NEY (net energy yield), EEP (efficiency of energy production) and EWUE (energy water use efficiency) were investigated. Energy consumption of irrigation was found to be about 60% of total energy input in sugar beet production under full and deficit irrigation treatments. It was found that sugar beet had the highest EEP value (6.29) under the partial deficit irrigation (representing 75% of full irrigation). However, it was observed that full and severe deficit irrigation (representing 50% of full irrigation) treatments had a lower value. Results of this study indicated that the partial deficit drip irrigation technique can be applied in sugar beet production. In practice, deficit irrigation technique can reduce irrigation water use up to 25% compared to full irrigation technique. In addition, partial deficit drip irrigation technique may save 11.2% of total energy inputs, 16.1% of irrigation energy inputs, 21.2% of total fuel use and 25% of fuel use in irrigation.

Water conservation potential of smart irrigation controllers on St. Augustinegrass

A variety of technologies for reducing residential irrigation water use are available to homeowners. These “Smart Irrigation” technologies include evapotranspiration (ET)-based controllers and soil moisture sensor (SMS) controllers. The purpose of this research was to evaluate the effectiveness of these technologies, along with rain sensors, based on irrigation applied and turfgrass quality measurements on St. Augustinegrass ( Stenotaphrum secundatum (Walter) Kuntze). Testing was performed on two types of SMS controllers (LawnLogic LL1004 and Acclima Digital TDT RS500) at three soil moisture threshold settings. Mini-Clik rain sensors (RS) comprised six treatments at two rainfall thresholds (3 mm and 6 mm) and three different irrigation frequencies (1, 2, and 7 d/wk). Two ET controllers were also tested, the Toro Intelli-Sense controller and the Rain Bird ET Manager. A time-based treatment with 2 days of irrigation per week without any type of sensor (WOS) to bypass irrigation was established as a comparison. All irrigation controller programming represented settings that might be used in residential/commercial landscapes. Even though three of the four testing periods were relatively dry, all of the technologies tested managed to reduce water application compared to the WOS treatment, with most treatments also producing acceptable turf quality. Reductions in irrigation applied were as follows: 7–30% for RS-based treatments, 0–74% for SMS-based treatments, and 25–62% for ET-based treatments. The SMS treatments at low threshold settings resulted in high water savings, but reduced turf quality to unacceptable levels. The medium threshold setting (approximately field capacity) SMS-based treatment produced good turfgrass quality while reducing irrigation water use compared to WOS by 11–53%. ET controllers with comparable settings and good turf quality had −20% to 59% savings. Reducing the irrigation schedule (treatment DWRS) by 40% and using a rain sensor produced water savings between 36% and 53% similar to smart controllers. Proper installation and programming of each of the technologies was essential element to balancing water conservation and acceptable turf quality. Water savings with the SMS controllers could have been increased with a reduced time-based irrigation schedule. Efficiency settings of 100% (DWRS) and 95% (TORO) did not reduce turf quality below acceptable limits and resulted in substantial irrigation savings, indicating that efficiency values need not be low in well designed and maintained irrigation systems. For most conditions in Florida, the DWRS schedule (60% of schedule used for SMS treatments) can be used with either rain sensors or soil moisture sensors in bypass control mode as long as the irrigation system has good coverage and is in good repair.

Tomato nitrogen accumulation and fertilizer use efficiency on a sandy soil, as affected by nitrogen rate and irrigation scheduling

Tomato production systems in Florida are typically intensively managed with high inputs of fertilizer and irrigation and on sandy soils with low inherent water and nutrient retention capacities; potential nutrient leaching losses undermine the sustainability of such systems. The objectives of this 3-year field study were to evaluate the interaction between N-fertilizer rates and irrigation scheduling on crop N and P accumulation, N-fertilizer use efficiency (NUE) and NO 3–N leaching of tomato cultivated in a plastic mulched/drip irrigated production system in sandy soils. Experimental treatments were a factorial combination of three irrigation scheduling regimes and three N-rates (176, 220, and 330 kg ha −1). Irrigation treatments included were: (1) surface drip irrigation (SUR) both the irrigation and fertigation line placed underneath the plastic mulch; (2) subsurface drip irrigation (SDI) where the irrigation drip was placed 0.15 m below the fertigation line which was located on top of the bed; and (3) TIME (conventional control) with the irrigation and fertigation lines placed as in SUR and irrigation applied once a day. Except for the TIME treatment all irrigation treatments were soil moisture sensor (SMS)-based with irrigation occurring at 10% volumetric water content. Five irrigation windows were scheduled daily and events were bypassed if the soil water content exceeded the established threshold. The use of SMS-based irrigation systems significantly reduced irrigation water use, volume percolated, and nitrate leaching. Based on soil electrical conductivity (EC) readings, there was no interaction between irrigation and N-rate treatments on the movement of fertilizer solutes. Total plant N accumulation for SUR and SDI was 12–37% higher than TIME. Plant P accumulation was not affected by either irrigation or N-rate treatments. The nitrogen use efficiency for SUR and SDI was on the order of 37–45%, 56–61%, and 61–68% for 2005, 2006 and 2007, respectively and significantly higher than for the conventional control system (TIME). Moreover, at the intermediate N-rate SUR and SDI systems reduced NO 3–N leaching to 5 and 35 kg ha −1, while at the highest N-rate corresponding values were 7 and 56 kg N ha −1. Use of N application rates above 220 kg ha −1 did not result in fruit and/or shoot biomass nor N accumulation benefits, but substantially increased NO 3–N leaching for the control treatment, as detected by EC monitoring and by the lysimeters. It is concluded that appropriate use of SDI and/or sensor-based irrigation systems can sustain high yields while reducing irrigation application as well as reducing NO 3–N leaching in low water holding capacity soils.

Deficit Irrigation Optimization of Cotton with AquaCrop

Given the current pressures to reduce irrigation water use, it is important to optimize the use of water in irrigated agriculture. This work was aimed at determining the optimum level of applied irrigation water (AIW) for cotton (Gossypium hirsutum L.) production in southern Spain under several climatic and agricultural policy scenarios. To generate the yield response to variations in AIW, we used the FAO crop water productivity (WP) model, AquaCrop. Model calibration and validation using four experiments conducted in the region showed that AquaCrop adequately simulated the yield response to AIW. The model was then used to determine the yield–AIW functions for different scenarios, assuming the best deficit irrigation (DI) strategy. An economic optimization procedure showed that maximum profits occurred at AIW values between 540 and 740 mm, depending on the climatic scenario. However, profits stayed close to the maximum (above 95%) for AIW levels exceeding 300–350 mm, indicating that under DI, AIW may be reduced significantly with little impact on profits. A sensitivity analysis suggested that increasing the price of water above the current level will have only a limited impact on optimum AIW, and that the current Common Agricultural Policy (CAP) of the European Union does not encourage water conservation in cotton irrigation. We conclude that AquaCrop is a useful tool to assist managers for making decisions in cotton irrigation under water supply restrictions.

Cotton Subsurface Drip and Overhead Irrigation Efficiency, Maturity, Yield, and Quality

Subsurface drip (SSD) is used as a water‐efficient alternative to overhead irrigation in many crops. This study compared soil water, water use, crop maturity, lint yield, and fiber quality of cotton (Gossypium hirsutum L.) grown with SSD to cotton grown with overhead irrigation. Three experiments were conducted at two Georgia locations in 2004 and 2005. Treatments consisted of overhead irrigated, nonirrigated, SSD matched to overhead irrigation rates (SSD Matched), and SSD based on soil water (SSD Fed). Cotton maturity was affected by irrigation treatment as nonirrigated cotton matured earliest, whereas overhead irrigated cotton matured latest. Subsurface drip irrigated cotton produced similar or higher lint yields than overhead irrigated cotton. Subsurface drip provided adequate soil water and irrigation amounts were 4.4, 8.2, and 0.5 cm less than overhead irrigation at the three locations. Water use efficiency (WUE) of cotton SSD irrigated was 23 and 15% higher than overhead‐irrigated cotton in two experiments. Irrigation method did not substantially affect fiber quality; however, micronaire was higher in cotton from the SSD Fed treatment than cotton in the Overhead treatment in two locations. We conclude that SSD irrigation provides the same positive effects as overhead irrigation in cotton production while reducing irrigation water use and may allow for improved irrigation efficiency.

Simulated Crop Yields Response to Irrigation Water and Economic Analysis: Increasing Irrigated Water Use Efficiency in the Indian Punjab

The Indian Punjab has been heralded for its technical achievements but increasingly criticized for leveraging its success on the environment. Irrigation has been one of the main pillars of the Punjab's Green Revolution. The availability of water has pushed rice and wheat productivity to new heights. Cheap water policies have enabled farmers to exploit groundwater. Water tables are shrinking in some areas, while water logging poses a major problem in other parts of the Indian Punjab. This article investigates the potential for reducing irrigation water use through policies that align irrigation water prices with their true social cost. This includes charging Punjabi farmers for irrigation water and introducing alternative, more water efficient crops. Results indicate that alternative crops, cotton (Gossypium hirsutum L.) and soybean [Glycine max (L.) Merr.], would enter cropping patterns provided that irrigation water prices moved to about 25% of the price charged by municipal water authorities. Shifting cropping patterns toward more water‐efficient enterprises would decrease irrigation water use on a typical paddy by nearly 66%. Future policy considerations are required to offset the declines in producer welfare that would accompany the irrigation water pricing.

Integrated Irrigated Crop–Livestock Systems in Dry Climates

Arid and semiarid landscapes are often fragile and, thus, vulnerable to both natural weather extremes and human activities. Climate change and increasing demands for food to meet needs of a growing global population will place greater stress on these environments. Cropping and livestock systems have generally succeeded in these regions to the extent that the environment could be altered through water development and irrigation. Water sources for irrigation, including surface and groundwater, are declining in quality and quantity. Improvements in irrigation use efficiency now exceed 95% but often have led to increased water use, instead of water savings, as more systems have been installed. Also, as groundwater becomes scarce, more energy is required to extract water from greater depths. Increasing demands for alternative water uses and depletion of historic water sources make many irrigated systems in dry climates nonsustainable. The Texas High Plains exemplifies these challenges, where agriculture depends heavily on irrigation at nonsustainable rates of water extraction from the Ogallala aquifer. Today, agriculture uses about 95% of total water withdrawn from the aquifer. Crop rotations and integrating crop and livestock systems could reduce irrigation water use and diversify income compared with a monoculture. This region was historically a grazing land ecosystem offering opportunities for pastoral systems and benefits from diversification. Long‐term comparisons of two irrigated systems [a cotton (Gossypium hirsutumL.) monoculture and an integrated cotton–forage–beef cattle system] in the Texas High Plains have demonstrated water savings of about 25% achieved through integration, while remaining economically viable and diversifying income sources. Additional benefits included reduced soil erosion, lower chemical inputs including a 40% reduction in N fertilizer, improved soil microbial and enzymatic activities, enhanced C sequestration, and greater rainfall infiltration than the monoculture system. Greater annual crop yields can shift short‐term profitability to the monoculture system, but long‐term sustainability is likely to depend on environmental benefits and water savings achieved by integrated systems. Challenges include existing large investments in local infrastructure focused on monoculture systems, producer adoption of alternative strategies, enhanced knowledge and management skill required, and a need for more research. Dryland agriculture will increase with remaining water diverted to other uses including livestock, municipalities, manufacturing, and energy generation. Technological advances can increase water savings but can also decrease system resilience with dependence on nonsustainable external buffers. Regional resource and economic stability will likely depend more on internal resilience of appropriately integrated plant and animal agricultural systems.

Deficit irrigation for reducing agricultural water use

At present and more so in the future, irrigated agriculture will take place under water scarcity. Insufficient water supply for irrigation will be the norm rather than the exception, and irrigation management will shift from emphasizing production per unit area towards maximizing the production per unit of water consumed, the water productivity. To cope with scarce supplies, deficit irrigation, defined as the application of water below full crop-water requirements (evapotranspiration), is an important tool to achieve the goal of reducing irrigation water use. While deficit irrigation is widely practised over millions of hectares for a number of reasons - from inadequate network design to excessive irrigation expansion relative to catchment supplies - it has not received sufficient attention in research. Its use in reducing water consumption for biomass production, and for irrigation of annual and perennial crops is reviewed here. There is potential for improving water productivity in many field crops and there is sufficient information for defining the best deficit irrigation strategy for many situations. One conclusion is that the level of irrigation supply under deficit irrigation should be relatively high in most cases, one that permits achieving 60-100% of full evapotranspiration. Several cases on the successful use of regulated deficit irrigation (RDI) in fruit trees and vines are reviewed, showing that RDI not only increases water productivity, but also farmers' profits. Research linking the physiological basis of these responses to the design of RDI strategies is likely to have a significant impact in increasing its adoption in water-limited areas.

Assessing impacts of surge-flow irrigation on water saving and productivity of cotton

To improve water saving and conservation in irrigated agriculture, a range of field evaluation experiments was carried out with various furrow irrigation treatments in cotton fields to estimate the possibilities of improving furrow irrigation performances under conditions of Central Fergana Valley, Uzbekistan. The research consisted in comparing surge and continuous-flow in long furrows and adopting alternate-furrow irrigation. The best results were achieved with surge-flow irrigation applied to alternate furrows. Field data allowed the calibration of a surface irrigation model that was used to identify alternative management issues. Results identified the need to better adjust inflow rates to soil infiltration conditions, cut-off times to the soil water deficits and improving irrigation scheduling. The best irrigation water productivity (0.61 kg m −3) was achieved with surge-flow on alternate furrows, which reduced irrigation water use by 44% (390 mm) and led to high application efficiency, near 85%. Results demonstrated the possibility for applying deficit irrigation in this region.

(214) Adult Pear Response to Integrated Nitrogen Fertigation and Drip Irrigation System

Responses of adult pear to the integrated N fertigation and drip irrigation system have not been documented in Oregon. A field trial was conducted on adult pear at the Mid-Columbia Agricultural Research and Extension Center, Hood River, Ore., in 2005. Two N and water management systems (integrated N fertigation and drip irrigation system; and broadcast application of dry N fertilizer to the soil surface and microsprinkler irrigation system) were compared on pear cultivars of Bartlett and Golden Russet Bosc, and rootstocks of OH×F97 and OH×F87. The responses of these cultivars and rootstocks to the integrated N fertigation and drip irrigation system were similar. The integrated N fertigation and drip irrigation system consumed 1450 m3·ha-1 of irrigation water during the entire season from May to September, reducing irrigation water use by 73% compared with 5297 m3·ha-1 under the current system—broadcast application of dry N fertilizer to the soil surface and microsprinkler irrigation system averaged over the four cultivar and rootstock combinations. The fruit yield was statistically similar for the integrated N fertigation and drip irrigation system and the broadcast application of dry N fertilizer and microsprinkler irrigation system on the average of the four cultivars and rootstocks. Differences in fruit size and color were negligible between the two N and irrigation management systems. Overall, our results suggest that adopting the integrated N fertigation and drip irrigation system does not cause significant reduction in yield or quality of adult pear; the integrated N fertigation and drip irrigation system could be a profitable and environmentally sound management alternative for pear production.

Towards a better understanding of crop water requirement in orchards: a case study from the Goulburn Valley

Responses of fruit trees to reduced irrigation in micro-irrigated peach and apple orchards in the Goulburn Valley, Victoria were investigated during the 2000–01 season. Field experiments examined the effects of applying 2 irrigation levels on soil water content, crop water relations, vegetative growth, yield, yield components and fruit quality. Irrigation regimes were 50% and 100% of current management practice where inputs are scheduled from pan evaporation and locally derived crop coefficients. Water was applied to only one side of the tree rootzone in the 50% treatment (0.5I) while the current management practice treatment (1.0I), received water on both sides of the tree. Over the season, the irrigation inputs for peach and apple equated to a crop coefficient of 0.93 and 0.87, respectively. Orchard water use (ETpeach and ETapple) was predicted using reference crop evapotranspiration (ET0) and published crop coefficients (Kc) with adjustment for the fraction of shade cast by the trees on the orchard floor at solar noon (effective canopy cover, ECC). Throughout the season, ECC measured as midday tree canopy radiation interception, remained low for both peach and apple (<35%). ETpeach and ETapple were substantially lower than current water scheduling practices (1.0I treatments). For the 0.5I apple regime, irrigation closely matched ETapple suggesting that these trees were adequately irrigated. This was supported by no detrimental effects on crop production, vegetative growth, and fruit quality measures of the 0.5I irrigation regime. However, in the peach orchard the 0.5I regime reduced fruit volume suggesting that these trees may have been water stressed. Based on ECC, we calculated the full crop water requirement Kc for the peach and apple orchards to be 0.42 and 0.37, respectively. In summary, for the apple orchard, our 0.5I treatment was close to predicted full crop water requirement (ETapple). But for the peach orchard, the ETpeach was greater, albeit slightly, than our 0.5I regime. Taken overall, these results demonstrate that better matching of water application to the evaporative surface of the orchard canopies (i.e. ECC) can substantially reduce irrigation water use in Goulburn Valley orchards. It is also apparent that ECC in these orchards where row spacing is typically 4–5 m can be relatively low.

Integrating Cotton and Beef Production to Reduce Water Withdrawal from the Ogallala Aquifer in the Southern High Plains

Agriculture in the Texas High Plains depends heavily on irrigation with water withdrawn from the Ogallala aquifer at nonsustainable rates. Our hypothesis was that integrating crop and livestock systems would reduce irrigation water use, maintain profitability, and diversify income compared with a cotton (Gossypium hirsutum L.) monoculture. Thus, from 1998 to 2002, two large‐scale systems, with three replications in a randomized block design, compared water use, productivity, and economics of (i) a cotton (var ‘Paymaster 2326RR’) monoculture with terminated wheat (Triticum aestivum L.) and (ii) an integrated three‐paddock system that included cotton in a two‐paddock rotation with grazed wheat and rye (Secale cereale L.) and the perennial ‘WW‐B. Dahl’ old world bluestem [Bothriochloa bladhii (Retz) S.T. Blake] for grazing and seed production. All paddocks were irrigated by subsurface drip. Angus crossbred beef steers (Bos taurus L.; initial body weight = 249 kg; standard deviation = 26 kg) grazed from January to mid‐July. During the 4 yr of this experiment following the establishment year, cotton lint yield was 1036 and 1062 kg ha−1 for the cotton monoculture and the integrated system, respectively. Bluestem seed yield averaged 24 kg pure live seed ha−1. Steers gained 153 kg on pasture and 0.82 kg d−1. Per hectare, the integrated system used 23% less (P < 0.001) irrigation water, 40% less N fertilizer, and fewer other chemical inputs than the cotton monoculture. Profitability was about 90% greater for the integrated system at described conditions. Integrated production systems that are less dependent on irrigation and chemical inputs appear possible while improving profitability.

Effect of Tillage and Preplant Irrigation on Sorghum Production

Reducing irrigation water requirements with furrow irrigation systems is important in the Southern High Plains. Growing grain sorghum, without a preplant irrigation, can potentially reduce irrigation water use and increase crop water use efficiency (WUE), defined as yield/ET. ET includes irrigation, rainfall, and soil water depletion during the crop season. A four-year study was conducted at Bushland, Texas where three tillage methods were evaluated for their effect on off-season soil water storage, furrow irrigation water intake, grain yield, and WUE; both with and without preplant irrigation. Treatments receiving a preplant (PP) irrigation averaged 483 mm (19 in.) of irrigation intake compared with only 280 mm (11 in.) for the treatments without a preplant irrigation (No-PP). This was a 70% increase in irrigation intake for the PP treatment with only a 10% increase in grain yield. The extra pumping cost for the PP irrigation was about $10.00/ha ($4/acre) more than the value of the increased grain yield. Tillage method did not affect over-winter soil water storage and only slightly affected irrigation intake, grain yield, and WUE. Only about 25% of the PP irrigation water intake was recovered in soil water storage. Irrigation intake is defined as the amount applied through graded furrows minus the tailwater runoff. Although the No-PP soil profile averaged 204 mm (8 in.) of soil water in storage (82% of field capacity) to 1.8 m (6 ft) deep, the lack of late April or early May precipitation in two of the four years resulted in a relatively dry seedbed at planting time. Thus, the No-PP irrigation treatment planting was delayed from May until occurrence of early June rainfall. The later planting dates (June 14 and 22) reduced grain yield up to 10%, however, WUE was increased up to 20% by avoiding the preplant irrigation.

FURROW INFLOW AND INHLTRATION VARIABILITY IMPACTS ON IRRIGATION MANAGEMENT

ABSTRACT Furrow-to-furrow infiltration variability causes non-uniform water absorption rates, furrow stream advance rates, and runoff rates from the furrow tail end. Unevenly set inflow rates to furrows compound these latter two non-uniformities. In order for an irrigator to ensure adequate water advance on a desired portion of furrows, the average inflow rate must be increased. To ensure adequate water application to a desired portion of the furrows, the application time must be extended. Thus, inflow and infiltration variability result in excess water application and reduced irrigation water use efficiency. Models, based on Gaussian distributions of inflow and infiltration, are presented which relate excess furrow irrigation applications to these variabilities.

Within-row irrigation saves water on croplands

Excessive water use and soil erosion from furrow irrigation are two of the most serious management problems on irrigated silt loam soils in southern Idaho, U.S.A. These problems are especially serious on croplands planted to dry beans. In conventional bean production, fields are irrigated before planting to wet the entire soil surface. It is not unusual for farmers to apply as much as 30 cm of water over the entire field during a single preplanting irrigation. Results from this study showed that planting beans in the bottom of pre-irrigated furrows without soaking completely between the furrows reduced preplanting water application by 60%. The continuing within-row treatments reduced irrigation water use by 42% compared to conventional irrigation practices. Total bean yields on the preplanting, within-row treatments were not significantly different from the conventional treatments.