Limited Irrigation Treatments Research Articles

Simulating Evapotranspiration and Yield Response of Selected Corn Varieties under Full and Limited Irrigation in the Texas High Plains Using DSSAT-CERES-Maize

Abstract. Water scarcity due to drought and groundwater depletion has led to increased interest in deficit irrigation strategies that reduce irrigation requirements while maintaining profitable yields. This has resulted in an increase in the number of modeling studies aimed at evaluating crop response to limited irrigation strategies. However, the ability of widely used crop simulation models to accurately represent responses to limited irrigation has not been thoroughly evaluated. The primary objective of this study was to determine the efficacy of DSSAT-CERES-Maize (ver. 4.6.1.0) to simulate leaf area index (LAI), crop evapotranspiration (ET), and yield response to full (100%) and limited (75% and 50%) irrigation regimes for two corn varieties. Comparisons of simulated and measured data from full and limited irrigation treatments of` two drought-tolerant corn hybrids (DuPont Pioneer AQUAmax P1151HR and Pioneer 33D49) grown in the Texas Panhandle in 2013 and 2014 were evaluated. Simulated in-season daily crop ET values for P1151HR grown in 2013 were also compared to those measured by precision large weighing lysimeters at Bushland, Texas. Additionally, a comparison of simulated and measured soil water content (SWC) within the root zone was performed for P1151HR grown in 2013. Simulated LAI for fully irrigated treatments approximated measured values reasonably well, although manipulation of plant genetic parameters failed to match measured LAI during the period between maximum LAI and the beginning of crop senescence in the 50% irrigation treatments. Similarly, simulated yield values approximated measured values for the fully irrigated treatments, while considerable overestimation of yield occurred in the limited irrigation treatments for both varieties. However, consistent overestimation of both LAI and yield for the limited irrigation treatments suggests a functional relationship between LAI and yield. Further, DSSAT overestimated crop ET by 16% for fully irrigated P1151HR and by 40% for limited irrigation treatments in 2013 as compared to measured lysimeter values. Corresponding underestimations of SWC were also observed in neutron probe measurements for both treatments. Overestimation of ET and yield and corresponding underestimation of SWC in limited irrigation treatments were mainly due to overestimation of LAI in those treatments, indicating a potential deficiency in the water stress algorithms. Additional comparisons of agronomic and lysimeter-based water balance data are needed to corroborate the findings of this study. Further investigations into the calculation of reference evapotranspiration (ETo), crop coefficients, and water stress functions in DSSAT are needed in order to provide suggestions for model improvement. Keywords: TCERES-Maize, Crop modeling, DSSAT, Evapotranspiration, Limited irrigation, Lysimeters, Maize, Semi-arid, Sprinkler irrigation, Weighing lysimeters.

Limited-irrigation improves water use efficiency and soil reservoir capacity through regulating root and canopy growth of winter wheat

The North China Plain (NCP) is a remarkable region with serious water shortages, especially during the winter wheat growing season. Developing water-saving irrigation is an important strategy to thoroughly resolving water scarcity in this region. Field experiments were conducted at Wuqiao Experiment Station of China Agricultural University, Hebei, China, in 2013–2014 and 2014–2015 using “Jimai22”, a winter wheat cultivar planted widely across China. The three irrigation regimes used were no-irrigation (no water applied after sowing), limited-irrigation (60mm of water applied at elongation), and sufficient-irrigation (a total of 180mm of water applied, with 60mm at regreening, elongation, and anthesis stages, respectively). Soil water storage, soil reservoir capacity, root length density, leaf expansion, water use efficiency (WUE), and grain yield of winter wheat were measured. The highest WUE was observed in the limited-irrigation treatment, achieving a relatively high grain yield. With increases in water (i.e., sufficient-irrigation), winter wheat grain yield increased, but water WUE decreased. Limited-irrigation hampered leaf expansion, which can reduce transpiration, and slightly reduced grain yield compared to the sufficient-irrigation treatment. Moreover, limited-irrigation stimulated roots to grow into deeper soil layers and thus enhanced the uptake of soil-stored water from the subsoil layer, developing a large soil reservoir capacity to store rain-water in summer. Overall, this study demonstrates that regulating soil water depletion moderately in the non-critical period and supplementary water in the critical period (through limited-irrigation, i.e., 60mm of water applied at elongation) in winter wheat results in high WUE with relatively high grain yield and enlarges soil reservoir capacity. Therefore, in years with typical climate conditions, irrigation of 60mm applied at elongation is the best irrigation scheme for efficient water use and relatively high yield in winter wheat in NCP.

Influence of seed priming and water stress on selected physiological traits of borage

Abstract Borage is a valuable medicinal plant with various constituents in leaves, flowers and seeds. Hence, it is important to improve the performance of this medicinal plant under different environmental conditions. Thus, two field experiments were arranged as split-plots based on a RCB design with three replications in 2012 and 2013, to evaluate the effects of seed priming and different irrigation intervals on selected physiological properties of borage leaves. Irrigation intervals (irrigation after 60, 90, 120, 150 mm evaporation from Class A pans, respectively) and priming treatments (control, water, KNO3 and KH2PO4) were allocated to the main and sub plots, respectively. The chlorophyll content index was enhanced under limited irrigation treatments, mainly due to a decrease in leaf area index and intercepting more radiation. However, the membrane stability index was stable under different irrigation intervals. Decreased relative water content and leaf area index and increased leaf temperature under lower water availability led to some reductions in the grain yield of borage. All of the priming techniques, particularly hydro-priming, enhanced the seedling emergence rate, leaf area index and consequently grain yield per unit area. Therefore, seed hydro-priming can be used to improve the field performance of borage, particularly when sufficient water is available.

Berseem clover quality and basil essential oil yield in intercropping system under limited irrigation treatments with surfactant

The presented study is a comprehensive report on the qualitative configuration of crop quality, essential oil percentage and oil yield in berseem clover and basil under limited irrigation and additive intercropping systems using a nonionic surfactant. This experimental field study was conducted in the 2012–2014 growing seasons to identify the best combination of irrigation level, sowing pattern and water treatment for basil oil content and yield, and berseem clover with an acceptable forage quality for arid and semi-arid regions. The limited irrigation treatments comprised of full irrigation, I100 (100%), moderately limited, I75 (75%), and severely limited, I50 (50%). The planting systems of sole berseem clover and sole basil culture, along with the additive intercropping of berseem clover and 50% basil, were assigned to the plots under water treatment alone (control) and water with surfactant setups. Results show that, as the severity of drought stress increased (I50), dry matter digestibility of berseem clover in I50 with surfactant decreased moderately when compared to I50 irrigation alone. Crude protein, water-soluble carbohydrates and neutral detergent fiber percentages followed increasing trends in limited irrigation systems in water treatments both with and without surfactant. All forage quality traits of berseem clover were improved in the additive intercropping treatment (legume–basil mixture). Application of surfactant was favorable to a sole basil culture, enhancing the essential oil percentage as well as oil yield under a deficit irrigation treatment. The highest essential oil yield (11.45kgha−1) was achieved in the I75 with surfactant treatment. Additionally, the basil essential oil yield increased during sole cropping in comparison with the mixed cropping system. The water use efficiency in the intercropping system across surfactants in arid and semi-arid regions was improved during the warm season when soil water availability decreased due to the high temperature and low precipitation.

Surfactant and Limited Irrigation Effects on Forage and Seed Production and Water Use Efficiency in Alfalfa (Medicago Sativa L.)

Alfalfa is one the most important forage resources in arid and semiarid regions of the world. To evaluate the response of alfalfa to limited irrigation and surfactant application, an experiment was conducted at Research Farm of College of Agriculture, University of Tehran, Iran, during 2013 and 2014 growing seasons. The experimental treatments were arranged as split plots based on a complete randomized block design with three replications. The limited irrigation treatments comprised of replenishment of 100%, 75% and 50% of weekly evaporation and plant water requirements assigned to the main plots. Water treatments of control (water alone) and water + surfactant, assigned to the subplots. The quantitative and physiological characteristics of alfalfa forage were recorded at 10% flowering stage. The seed yield of alfalfa was measured after the plants reached full physiological maturity stage. The result of the experiment showed that as the severity of limited irrigation increased, plant height, tiller number per plant, RWC, total forge yield and seed yield followed a decreasing trend. Across all the limited irrigation systems, surfactant application increased plant height, RWC, seed yield and total forge yield. As the severity of limited irrigation increased, water use efficiency (WUE) in forage yield followed a significant increasing trend. The highest forage (7500 kg/ha) and seed yield (820 kg/ha) under limited irrigation treatments were achieved at 75% weekly evaporation and plant water requirements + surfactant, while the highest irrigation water use efficiency for forage (1.5 kg/m3) and seed (0.16 kg/m3) production was observed in limited irrigation treatment of 50% weekly evaporation and plant water requirements + surfactant.

Surfactant effect on forage yield and water use efficiency for berseem clover and basil in intercropping and limited irrigation treatments

Quantifying crop response to irrigation is important for establishing effective irrigation management strategies. The present study was conducted to evaluate the response of berseem clover and basil to limited irrigation in an additive intercropping system using a surfactant. The experimental treatments were carried out in split–split plots based on a completely randomized block design with three replications. The limited irrigation treatments comprised of replenishment of I100 full irrigation, I75=25% limited and I50=50% limited weekly evaporation and plant water requirements which were assigned to the main plots. The planting systems of sole berseem clover and sole basil culture along with additive inter cropping of berseem clover+50% basil were assigned to the subplots. Water treatments of control (water alone) and water+surfactant were assigned to the sub-subplots. Results show that severely limited irrigation (I50) dramatically reduced the forage yield of berseem clover and basil by 19.5% compared with the control (I100). The severity of the adverse effects of limited irrigation stress decreased by the surfactant application in irrigation by water+surfactant (9.5% decrement compared to full irrigation). The highest irrigation water use efficiency (2.7kgm−3) was achieved in I50 treatment with an added surfactant. The highest total dry matter yield (berseem clover+basil dry matter) (9257.9kgha−1) was obtained from additive intercropping of berseem clover 100%+basil 50% while irrigated by water+surfactant.

Improving evapotranspiration simulations in the CERES-Maize model under limited irrigation

Limitations on water resources for agriculture in places such as Colorado, USA, have caused farmers to consider limited irrigation as an alternative to full irrigation practices, where the crop is intentionally stressed during specific growth stages in an effort to maximize yield per unit water consumed, or evapotranspiration (ET). While crop growth models such as CERES-Maize provide the ability to evaluate numerous management scenarios without the costs associated with multiyear field experiments, recent studies have shown that CERES-Maize performs well under full irrigation but overestimates ET of corn under limited irrigation management. The primary objective of this study was to improve CERES-Maize ET simulation under limited irrigation management while maintaining accuracy of other important model output responses. Field experiments with corn were performed in northern Colorado, USA from 2006 to 2010, where four replicates each of full (ET requirement supplied by irrigation throughout the season) and limited (no irrigation before the V12 growth stage unless necessary for emergence, then full irrigation afterwards) irrigation treatments were analyzed. The local sensitivity of model input parameters affecting ET was evaluated, prompting changes to the model code with a new dynamic crop coefficient (KCD) as a function of the crop leaf area index. The modified CERES-Maize model more accurately represented ET under full and limited irrigation, for example reducing late-season ET potential from a plant with reduced canopy and more closely matched FAO-56 crop coefficient curves under full irrigation. Using the limited irrigation data for evaluation, the modified model showed significant decreases in model error for seasonal cumulative ET (root mean square deviation RMSD from 80.9mm to 49.9mm) and water productivity (RMSD from 5.97kgha−1mm−1 to 2.86kgha−1mm−1) as compared to the original model. The modified model was subsequently applied to several hypothetical irrigation management strategies, indicating that reducing weekly vegetative stage water applications from 20mm to 2.5mm can increase simulated water productivity by over 15%. While these synthetic water production functions may not be feasible in a production field with natural climate variability, the modified ET model indicates promise for limited irrigation management increasing water productivity.

Estimation of maize evapotranspiration and yield under different deficit irrigation on a sandy farmland in Northwest China

A field experiment was conducted on a sandy farmland in Northwest China to estimate on the response of maize evapotranspiration and yield to deficit irrigation. The five irrigation treatments consisted of specific combinations of full irrigation and limited irrigation in different crop growing phases (I, from elongation phase to heading; II, from heading phase to milk; III, from milk phase to physiological maturity) were designed. And for estimation of maize evapotranspiration, reference crop evapotranspiration (ET0), basal crop coefficient (Kcb), soil evaporation coefficient (Ke), and water stress coefficient (Ks) in different treatments were calculated. Results showed that; 1) the crop actual evapotranspiration (ETc) for treatments SII (deficit irrigation in phase I), ISI (deficit irrigation in phase II), IIS (deficit irrigation in phase III), SIS (deficit irrigation both in phase I and III), and III (full irrigation) were 570, 604, 579, 542, and 607 mm, respectively. (2) The phase II was the most sensitive phase to water deficit, with reductions in leaf area index (LAI), biomass, yield, irrigation water productivity (IWP), and harvest index (HI). In this phase, the effect of water stress on Ke and Ks was slight, and the evapotranspiration has no obvious difference between full irrigation and limited irrigation. (3) Deficit irrigation in phase I can slow down the crop development in early phase, and can also reduce maize biomass and yield. In this phase, water stress obviously reduced Ke and Ks, and the evapotranspiration in limited irrigation treatments were obviously lower than full irrigation treatment in this phase. (4) However, deficit irrigation in phase III has no significant effect on height and leaf area of maize, and did not also significantly reduce maize biomass and yield. In this phase, the evapotranspiration in limited irrigation treatments were also obviously lower than full irrigation treatment. It can be concluded that it was possible to reduce water consumption and maintain the maize yield by adopting deficit irrigations from milk to physiological maturity, then from elongation to heading, but not from heading to milk in this sandy farmland regions. Key words: Evapotranspiration, deficit irrigation, sandy farmland, maize.

Global sensitivity and uncertainty analysis of a dynamic agroecosystem model under different irrigation treatments

Savings in consumptive use through limited or deficit irrigation in agriculture has become an increasingly viable source of additional water for places with high population growth such as the Colorado Front Range, USA. Crop models provide a mechanism to evaluate various management methods without performing costly and time-consuming experiments, e.g., field studies investigating irrigation scheduling and timing effects on crop growth. Few studies have focused on CERES-Maize crop model parameterization with respect to water-stressed conditions, and the model has previously been shown to overestimate evapotranspiration (ET) for limited irrigation treatments (stress during vegetative stage). It is therefore desirable to quantify the effects of CERES-Maize input parameters on model output responses typically used for calibration and/or important in limited irrigation management, including vegetative growth, crop yield, and ET. A sensitivity analysis (SA) utilizing the Morris one-at-a-time screening and Sobol’ variance-based methods was performed on CERES-Maize v4.5 input parameters affecting water balance and crop growth including soil hydraulic properties, phenological growth properties, and radiation use efficiency. CERES-Maize output responses of interest for the SA included anthesis date, maturity date, leaf number per stem, maximum leaf area index, yield, and cumulative ET. The SA study utilized five years of multi-replicate field management data (both full and limited irrigation treatments) for each combination of random input parameters. Results comparing the Morris mean and the Sobol’ total sensitivity index showed very high correlation between the two, indicating that in this study the computationally cheaper Morris method could have been used as an effective indicator of input parameter sensitivity. For the full irrigation treatment, CERES-Maize output responses were mostly sensitive to crop cultivar parameters. For the limited irrigation treatment, CERES-Maize leaf area index, yield, and ET output responses were highly influenced by soil lower limit and drained upper limit input parameters, which define water holding capacity. There was also a greater amount of interaction between input parameters for the limited irrigation treatment than for full irrigation. An uncertainty analysis was also conducted using model outputs from the Sobol’ SA method. In some cases, cumulative ET had higher values for limited irrigation than for full irrigation, further indicating the need to evaluate model processes governing ET under water stress. A new methodology for systematic calibration of CERES-Maize, based on the Morris and Sobol’ sensitivity indices for the two irrigation treatments, is proposed for future model evaluation as sensitivity differences between treatments indicates that existing CERES-Maize calibration procedures (typically based on non-stressed crops) may need to be reconsidered in cases of water stress.

Modeling of Full and Limited Irrigation Scenarios for Corn in a Semiarid Environment

Population growth in urbanizing areas such as the Front Range of Colorado has led to increased pressure to transfer water from agriculture to municipalities. In some cases, farmers may remain agriculturally productive while practicing limited or deficit irrigation, where substantial yields may be obtained with reduced water applications during non-water-sensitive growth stages, and crop evapotranspiration (ET) savings could then be leased by municipalities or other entities as desired. Site-specific crop simulation models have the potential to accurately predict yield and ET trends resulting from differences in irrigation management. The objective of this study was to statistically determine the ability of the CERES-Maize model to accurately differentiate between full and limited irrigation treatments in northeastern Colorado in terms of evapotranspiration (ET), crop growth, yield, water use efficiency (WUE), and irrigation use efficiency (IUE). Field experiments with corn were performed near Fort Collins, Colorado, from 2006 to 2008, where four replicates each of full (100% of ET requirement for an entire season) and limited (100% of ET during reproductive stage only) irrigation treatments were evaluated. Observations of soil profile water content, leaf area index, leaf number, and grain yield were used to calibrate (2007) and evaluate (2006 and 2008) the model. Additionally, ET and water use efficiency (WUE) were calculated from a field water balance and compared to model estimates. Over the three years evaluated, CERES-Maize agreed with observed trends in anthesis date, seasonal cumulative ET (Nash-Sutcliffe efficiency ENS = 0.966 for full irrigation and 0.835 for limited irrigation), leaf number in 2007 (ENS = 0.949 for full irrigation and 0.900 for limited irrigation), leaf area index in 2008 (ENS = 0.896 for full irrigation and 0.666 for limited irrigation), and yield (relative error RE = 4.1% for full irrigation and -3.4% for limited irrigation). Simulation of late-season leaf area index in limited irrigation was underestimated, indicating model overestimation of water stress. Simulated cumulative ET trends were similar to observed values, although CERES-Maize showed some tendency to underpredict for full irrigation (RE = -7.2% over all years) and overpredict for limited irrigation (RE = 12.7% over all years). Limited irrigation observations showed a significant increase in WUE over full irrigation in two of the three years; however, the model was unable to replicate these results due to underestimation of ET differences between treatments. While CERES-Maize generally agreed with observed trends for full and limited irrigation scenarios, simulation results show that the model could benefit from a more robust water stress algorithm that can accurately reproduce plant responses such as those observed in this study.

Quantifying the impacts of soil water stress on the winter wheat growth in an arid region, Xinjiang

Wheat growth in response to soil water deficit play an important role in yield stability. A field experiment was conducted for winter wheat (Triticum aestivum L.) during the period of 2002-2005 to evaluate the effects of limited irrigation on winter wheat growth. 80%, 70%, 60%, 50% and 40% of field capacity was applied at different stages of crop growth. Photosynthetic charac- teristics of winter wheat, such as photosynthesis rate, transpiration rate, stomatal conductance, photosynthetically active radiation, and soil water content, root and shoot dry mass accumulation were measured, and the root water uptake and water balance in different layer were calculated. Based on the theory of unsaturated dynamic, a one-dimensional numerical model was developed to simulate the effect of soil water movement on winter wheat growth using Hydrus-1 D. The soil water content of stratified soil in the experimental plot was calculated under deficit irrigation. The results showed that, in different growing periods, evapotranspiration, grain yield, biomass, root water up- take, water use efficiency, and photosynthetic characteristics depended on the controlled ranges of soil water content. Grain yield response to irrigation varied considerably due to differences in soil moisture contents and irrigation scheduling between seasons. Evapotranspiration was largest in the high soil moisture treatment, and so was the biomass, but this treatment did not produce the highest grain yield and root water uptake was relatively low. Maximum depth of root water uptake is from the upper 80 cm in soil profile in jointing stage and dropped rapidly upper 40 cm after heading stage, and the velocity of root water uptake in latter stage was less than that in middle stage. The effect of limited irrigation treatment on photosynthesis was complex owing to microclimate. But root water uptake increased linearly with harvest yield and improvement in the latter gave better root water uptake under limited irrigation conditions. Appropriately controlled soil water contents can improve the root water uptake and grain yield. Consistently high values of root water uptake and grain yield were produced under conditions of mild water deficit at the seedling and start of regrowth to stem-elongation stages, in addition to a further soil water depletion at the physiological maturity to harvest stage. We suggest that periods of mild soil water depletion in the early vegeta- tive growth period together with severe soil water depletion in the maturity stage of winter wheat is an optimum for limited irrigation regime in this oasis. Considerable potential for further improve- ment in agricultural water use efficiency in the arid zone depends on effective conservation of moisture and efficient use of the limited water.

Agronomic response of maize to limited levels of water under furrow irrigation in southern Spain

The yield response to limited irrigation is a major concern where water resources are limited. The objective of the work was to know the agronomic response of 12 maize hybrids cultivars under full and limited irrigation levels. Full irrigation consisted in 5 to 7 furrow irrigations events (90 mm) applying a total depth of 450-630 mm. In the limited irrigation treatment, three irrigations (90 mm) were applied, beginning 2-3 weeks before silking and ending 3-5 weeks after it. Results indicated a mean yield loss of 17% due to limited irrigation. The main effect of limited irrigation was a reduction of the ears per plant and 1,000 kernel weight. Maize yield decreased as season length was reduced. The main effect of season length reduction was a reduction of kernels per ear. Limited or regulated deficit irrigation is one way of maximizing productivity of total applied water (PAW); thus, the limited irrigation treatment reached a higher PAW value (2.66 kg/cubic m) than full irrigation (1.90 kg/cubic m). In both irrigation levels, PAW was higher as the growth cycle increased. It can be concluded that, in the conditions of Southern Spain, reduced irrigation provided larger yields when applied to long cycle cultivars (FAO 700-800), with increased PAW values.

CROP ROTATIONS WITH FULL AND LIMITED IRRIGATION AND DRYLAND MANAGEMENT

ABSTRACT Irrigated cropping systems need to maximize the economic value of both rainfall and irrigation water, especially in areas of declining groundwater. This study compared water management systems in a winter wheat (Triticum aestivum, L.)-corn {Zea mays, L.)-soybean (Glycine max, L.) (W-C-S) and continuous corn (CC) rotation in west central Nebraska for dryland, limited irrigation (150 mm/yr), and full irrigation. Crop yield, evapotranspiration, and soil water storage were determined from field studies conducted at North Platte, Nebraska, on a Cozad silt loam (Fluventic HaplustoU) soil. Dryland com used 21.5% more evapotranspiration (ET) in the W-C-S rotation compare to CC. ET for the limited and full irrigation com was 4.6% and 4.9% more for the W-C-S rotation compared to the CC and was statistically significant at the P > 0.08 level. Water use efficiency, defined by the slope of the linear relationship between grain yield and ET (3Y 3ET-^), was the same for com in the W-C-S and CC rotations. Com grain yield response to irrigation and ET was more than the yield response of winter wheat and soybean. The W-C-S rotation increased com grain yields in two out of three years at this location for dryland management and increased the seasonal ET of corn compared to continuous corn. Full irrigation management did not consistently increase winter wheat and soybean grain yields above the limited irrigation treatments. Soil water storage for the full irrigation management was greatly reduced compared to dryland and limited irrigation management for both rotations.

Management of Sorghum Under Limited Irrigation1

AbstractGrain sorghum [Sorghum blcolor(L.) Moench] is produced with furrow irrigation across much of the semiarid West. Rising energy costs and declining water supplies in some regions have caused many farmers to irrigate with less water than required for maximum yield. Irrigation needs could be reduced if rainfall were used effectively on irrigated land. Research was done at the Texas Agric. Exp. Stn.. Etter, TX from 1979 to 1982 to compare different systems for limited irrigation of sorghum while attempting to maximize the use of rainfall. The study was conducted on graded furrows (0.3% slope) on a fine, mixed, mesic Torrertic Paleustoll (Sherm silty clay loam soil). The irrigation treatments were: 0, 2.5, 3.8, 5.1, and 10.1 (full irrigation) cm applied at each irrigation. The treatment receiving 2.5 cm was irrigated only in every third furrow and the treatment receiving 3.8 cm was irrigated in alternate furrows. All limited irrigation treatments contained furrow dams spaced 3 m apart. Total water applied varied with years due to rainfall. The seeding rate was varied down the row on plots that received 2.5, 3.8, and 5.1 cm per irrigation. Variable seeding rate was compared with uniform seeding on the 3.8 cm water treatment. Every third row was left blank on the 2.5 cm water treatment. Limited irrigation reduced runoff compared to full irrigation. Water advanced further down the field in alternate than in every furrow irrigation. The dams of non‐irrigated furrows were left in better condition to retain water from precipitation than in the irrigated furrows. The irrigation water use efficiency of 3.8 cm applied to alternate furrows was higher than 5.1 cm applied to every furrow with no change in yield. The yield and water use efficiencies from plots with uniform seeding rate were equal to those from variable seeding rate plots

Time and Frequency of Irrigation Effects on Sunflower Production and Water Use

AbstractSunflower (Helianthus annuus L.) production has greatly increased in the U. S. in recent years, with some being produced under irrigation in the Southern Great Plains. However, because of limited water supplies in the Southern Great Plains, sunflower usually is not fully irrigated. The objective of this study was to determine the influence of limited irrigation on sunflower growth, seed yield and quality, oil percent and quality, and water use and use efficiency. Treatments providing one or two irrigations at readily identifiable growth stages were compared with treatments providing no, adequate, and full irrigation. Sunflower irrigated before flowering averaged 17 cm taller than those not irrigated between emergence and flowering. Seed yields averaged highest (2.49 t/ha) with full irrigation, but in individual years, differences between full irrigation and other treatments were not always significant. Usually, the highest seed yield resulted from flowering or late flowering irrigations. These irrigations usually also resulted in the highest seed test weight and weight/seed. Oil percent averaged highest (48.8%) for the emergence plus late flowering irrigation treatment and lowest (43.4%) with the emergence plus budding treatment. Irrigation treatments significantly affected linoleic and oleic acid concentrations of the oil, but the maximum difference among treatments was only four and five percentage units for linoleic and oleic acids, respectively.Total water use increased with increased number of irrigations, but yield increases were not proportional to water use, especially for the adequate and full irrigation treatments. With these treatments, water‐use efficiency was less than for limited irrigation treatments that provided adequate water from flowering to late flowering.