Deficit Irrigation Treatments Research Articles

Effect of regulated deficit irrigation on the quality of raw and table olives

Fresh water scarcity is a major worldwide issue. There is a need to reduce water use whereas preserving the quality of food products. Regulated deficit irrigation (RDI) is a strategy to reduce fresh water consumption. The aim of this work was to study the effect of RDI on olives when applied before harvesting, without a rehydration period, on the quality of table olives. The experiment was performed in “La Hampa”, the experimental farm of IRNAS-CSIC at Coria del Río (Seville, Spain) during 2015 and 2016. Two deficit irrigation treatments were compared with a full irrigated control. Treatment 1 (T1) reduced irrigation from early September, about 2 weeks before harvest, until values of midday stem water potential were around −2 MPa. Treatment 2 (T2) reduced irrigation from mid-August, about 4 weeks before harvest, with a similar water stress level. The duration and level of water stress was described with the stress integral (SI). Fruit features were studied, before and after the industrial process to obtain Spanish-style table olives, in order to evaluate differences due to irrigation on raw olives and due to processing on table olives. Water stress conditions slightly changed olive characteristics, affecting size and composition. The industrial processing to table olives masked differences between irrigation treatments, though some features such as total polyphenols content (TPC) were still different. SI was significantly related with fruit weight, pit weight, equatorial diameter, linolenic acid and MUFAs content and (MUFA/PUFA)/SFA ratio.

Water stress for a long period before harvest and crop load effects on marketable yield and consumer acceptance of nectarine

Under water shortage growers may need to adjust horticultural practices to optimize yield and fruit quality. This study explores the reduction of crop load as a technique to mitigate water stress considering marketable yield and consumer acceptance as the most relevant traits. Commercial irrigation (CI) and deficit irrigation (DI) for a long period before harvest was applied to a late-maturing nectarine (‘Nectalady’) in 2011 and 2012. In both years, midday stem water potential (midday SWP) in CI trees was around −0.85 MPa while in DI trees the values ranged between −1.50 and −1.80 MPa. In the experiment, CI and DI were combined with three crop loads: low crop load (LCL, 85 fruits/tree) in 2011, and medium crop load (MCL, 150 fruits/tree) and commercial crop load (CCL, 230 fruits/tree) in 2012. Under CCL and MCL conditions, DI reduced marketable yield due to a significant reduction of the number of fruits that can be commercialize (fruit size higher than 65 mm). DI combined with LCL slightly reduced fruit size but not marketable yield. Reducing crop load by 60% (from 230 to 85 fruits/tree) maintained fruit size to the standard of marketable yield despite the water stress. Fruit thinning did not affect consumer acceptance of fruit, but it was slightly increased under DI in the first pick each year. The benefit of DI on consumer acceptance may have been observed because trees did not experienced midday SWP below −1.80 MPa for the extended period of water shortage (35 and 53 days in 2011 and 2012, respectively). For the levels of midday SWP experienced in this study (1.50 to −1.80 MPa), marketable yield was more sensitive to water stress than consumer acceptance. Consequently, growers do not need to worry about fruit quality, but crop load adjustments should be done to maintain marketable yield.

Determination of optimum irrigation and effect of deficit irrigation strategies on yield and disease rate of peanut irrigated with drip system in Eastern Mediterranean

This study aimed at examining the effects of different irrigation regimes (amount and frequency) on yield, water use, water productivity (WP), irrigation water productivity (IWP) and disease rate of drip irrigated peanut (Arachis hypogaea) during the 2014 and 2015 seasons in the Eastern Mediterranean region of Turkey. The treatments consisted of combinations of 3 irrigation frequencies (IF) (IF1: 25 mm; IF2: 50 mm; IF3: 75 mm of cumulative pan evaporation (CPE)), and 7 irrigation water levels (WL1 = 0.50, WL2 = 0.75, WL3 = 1.00 and WL4 = 1.25). WL1, WL2, WL3 and WL4 treatments received 50, 75, 100 and 125 of CPE. In addition, partial root drying (PRD) treatments WL5 = PRD50, WL6 = PRD75 and WL7 = PRD100 treatments were considered. They received 50, 75 and 100% of WL3 treatment from alternate laterals, respectively These 21 treatment combinations were arranged and analysed in a split-plot design with 4 replications. The main plots and subplots were established to irrigation frequencies (IF1, IF2 and IF3) and levels (WL1, WL2, WL3, WL4, WL5, WL6 and WL7). Both IF and WL were observed to have significantly influenced peanut yields at 1% level. In each of the experimental years, the largest and the smallest average peanut yields were acquired from the IF2WL4 and IF3WL1 treatments, respectively. Results indicated that peanut crops under PRD produced higher than those under deficit irrigation upon usage of the same volume of water amount. Significant linear relationships between irrigation – yield and evapotranspiration – yield were obtained during different irrigation frequencies in each season. The yield response factor (ky) was 0.58–0.65 in IF1, 0.65–0.70 in IF2 and 0.90–0.91 in IF3 plots in both years. Water stress raised the disease emergence in peanut markedly in the experimental years. The WP and IWP of PRD peanut were significantly greater than full irrigation and deficit irrigation (DI) treatments in both growing seasons, which demonstrated that limiting water did not reduce WP values. We conclude that DI treatments resulted in importantly lower WP (p ≤ 0.05) than PRD treatments in both years in spite of applying the same volume of water.

Application of deficit irrigation in Phillyrea angustifolia for landscaping purposes

Phillyrea angustifolia is an evergreen shrub of interest for urban landscape design, as well as for use in revegetation projects in Mediterranean areas, which are characterized by an acute scarcity of water. The effect of different levels of water deficit on several physiological, ornamental and morphological parameters of Phillyrea angustifolia plants was studied to evaluate their adaptability to xerogarden and/or landscape conditions. Nursery grown plants were subjected to three irrigation treatments: a control (watered to container capacity) and two deficit irrigation treatments of 60 and 40% of the amount of water supplied in the control treatment (moderate and severe deficit irrigation). After 23 months, plant height was significantly inhibited by both water deficit treatments, although plant compactness (foliar area in relation to plant height) was not affected. Plants under severe deficit irrigation increased their root to shoot ratio and water use efficiency, which are positive aspects for hardening. Plants exposed to both deficit irrigation treatments exhibited slight dehydration throughout the experiment, especially in spring, as indicated by the lower leaf water potential and relative water content. The tolerance of P. angustifolia to drought was mainly related to adjust osmotic and regulated stomatal closure. It is concluded that both deficit irrigation treatments can be used successfully in P. angustifolia plant production to reduce water consumption while maintaining good overall quality. Moderate deficit irrigation is specially recommended for gardening purposes, since this treatment produced plants with of visual quality. Severe deficit irrigation is more suitable for landscaping purposes, as an effective nursery technique to produce plants better adapted to environmental stress during transplanting.

Irrigation Regime and Soil Conditioners Impact on Characteristics of Sandy Soil and Washington Navel Orange Trees

Due to limited water resources it has become needed to study the best ways to decrease irrigation water use, increasing the water use efficiency, improve tree growth and sustain citrus crop production under those circumstances. Afield experiment was conducted during 2015/2016 and 2016/2017 seasons at El-Nubaria city, Beheira Governorate to investigate the effect of irrigation regime (80% and 60% from full irrigation) and soil conditioners (hydrogel at rate of 50 and 100g/tree as synthetic water absorbing soil amendments or organic plant residues at rate of 3.5 and 6.5kg/tree as natural absorbing soil amendments) on some properties of sandy soil, growth, yield, quality and productivity of irrigation water (PIW) for Washington navel orange trees under drip irrigation system. The obtained results pointed out that: The application of soil conditioners led to enhancing the properties and microorganisms activities and macronutrients of sandy soil especially with the high rates. Whereas, the low values of soil field capacity (10.47%), wilting point (4.26%) and available water (6.21%) were recorded with full irrigation without conditioners while, the high values (11.31 to 12.28%), (4.35 to 4.68%), (6.78 to 7.62%) respectively under irrigation regime combined conditioners. Soil conditioners application combined with irrigation regime increased the available nitrogen (up to 22.76%, phosphours (up to 9.98%), potassium (up to 15.14%), organic matter (up to 41.79%, CEC (up to 16.53%) and salinity (up to 4.64%) while soil bulk density was decreased (up to 5.66%) compared to full irrigation without conditioners. Moderate irrigation plus organic plant residues at rate of 6.5 kg/tree (T5) or plus hydrogel at 100g/tree (T3) significantly increased the most growth parameters (canopy volume, number of shoots/branch and leaf area), fruit set and decrease the fruit drop. Lowest percentage of fruit splitting (6.58 and 5.87 %) coated with T3 and T5 compared to deficit irrigation treatments plus the lowest rate of hydrogel or organic plant residues (T8 and T9). The highest yield was obtained by T3 (78.6 kg/tree) and T5 (79. 6 kg/tree). Control treatment (T1) followed by T3 and T5 tended to improve the physical fruit quality meanwhile deficit irrigation treatments T8 and T9 increased the most of chemical fruit quality. PIW mean values of Washington navel orange with full irrigation without conditioners were low (2.75 kg m-3) while, irrigation regime at 80 % and 60% recorded high values (3.49 kg m-3 and 3.88 kg m-3, respectively). PIW was increased with the high rates of soil conditioners.

Water-Saving Irrigation Strategies in Potato Fields: Effects on Physiological Characteristics and Water Use in Arid Region

In this study, field experiments were conducted to investigate the effects of two water-saving practices—partial root-zone drying (PRD) and deficit irrigation (DI)—on potato growth and yield in comparison with full irrigation (FI). The required FI amount was applied to the potato plants to enable 100% crop evapotranspiration, and the plants received 70% and 50% of the irrigation amount of FI for DI (DI70 and DI50) and PRD (PRD70 and PRD50), respectively. The physiological characteristics of the potatoes during the 2014–2015 seasons indicated that the relative chlorophyll contents were not significantly higher for the DI and PRD treatments than for the FI treatment. The DI50 had the lowest net photosynthesis rate (p < 0.05) while DI50 and PRD50 had significantly lower stomatal conductance (gs) values in both years. Meanwhile, the values of the PRD treatments were lower than those of DI treatments based on the transpiration rates. The xylem (abscisic acid) based on PRD50 had an average increase of 0.38 mol/m2 s due to decreasing gs values compared with other water-saving irrigation treatments. However, the FI and DI treatments had increased fresh tuber yields compared with the yields of PRD treatments. Furthermore, the PRD70 and PRD50 treatments significantly reduced the water productivity (WP) values by 30.16% and 41.32%, respectively, relative to that of FI.

Water relations and quality changes throughout fruit development and shelf life of sweet cherry grown under regulated deficit irrigation

The performance of 'Prime Giant' sweet cherry trees under three different irrigation regimes was examined during two consecutive seasons, 2015–2016 and 2016–2017. The irrigation treatments evaluated were: (i) a control treatment (CTL) irrigated at 110% of crop evapotranspiration (ETcd) to maintain non-limiting soil water conditions, (ii) RDM a regulated deficit irrigation treatment which applied a mild water stress during preharvest (90% of ETcd.) and a medium stress during postharvest (65% of ETcd) and (iii) RDS a regulated deficit irrigation treatment which applied a severe water stress (55% of ETcd.) during postharvest.There were significant differences during postharvest in soil and plant water indicators such as soil matric potential, midday stem water potential and maximum daily branch shrinkage between CTL and regulated deficit irrigation treatments (RD). However, only midday stem water potential was able to distinguish between RDM and CTL during preharvest. Fruit quality parameters such as fruit size, color, soluble solids concentration (SSC) were periodically measured during fruit developing as well as fruit water potential and osmotic fruit water potential. In 2016, there were no differences in any parameter between treatments. However in 2017 both deficit treatments led to fruits with a higher SSC and darker color than CTL. There were no differences in fruit yield or number of fruits per tree among treatments in either year of the study. When fruit quality was assessed in 2016, the color of the pedicels of fruits from the deficit irrigation treatments were greener than those from CTL after 20 days of cold storage at 2 °C and 90% relative humidity (RH) but and after 5 days of shelf-life simulation (15 °C and 65% RH) the differences between treatments disappeared.

Assessing Soil and Water Assessment Tool Plant Stress Algorithms Using Full and Deficit Irrigation Treatments

Core Ideas SWAT simulated corn LAI and yield of full irrigation matched measured data well. Stress algorithms adjusted corn LAI and yield unsatisfactory for limited irrigation. Stress algorithms only consider dominant stress factors such as water and temperature. Stress algorithms only adjust LAI and biomass rather than crop growth parameters. Long‐term measured field data are needed to develop new stress algorithms. ABSTRACTDecreased groundwater levels of the Ogallala Aquifer have increased interest in simulating crop responses to deficit irrigation strategies to evaluate the sustainable irrigation management for profitable crop production. However, the ability of widely used simulation models to accurately represent crop responses to deficit irrigation is not thoroughly evaluated. Therefore, the objective of this research was to evaluate the efficacy of the plant stress algorithms in Soil and Water Assessment Tool (SWAT) to simulate corn (Zea mays L.) responses to deficit irrigation treatments. Results showed simulated corn leaf area index (LAI), biomass, and yield under full irrigation scenarios matched measured data reasonably well at two study sites. However, clear reductions in model performance statistics for corn LAI simulations were found under the deficit irrigation scenarios for both sites (Nash‐Sutcliffe efficiency [NSE] <0.49; percent bias [PBIAS] >14%). Additionally, considerable overestimation of yield occurred in the deficit irrigation scenarios for both sites (PBIAS >30% in most years). The unsatisfactory results from simulations of both LAI and yield under the deficit irrigation scenarios suggested potential deficiencies of the plant stress algorithms in SWAT. Two apparent limitations of the plant stress algorithms were (i) the equation for computing actual plant growth factor using a singular stress factor, determined by the maximum value of four plant stress factors of water, temperature, nitrogen, and phosphorus, and (ii) the computed actual plant growth factor only adjusting potential daily accumulations of LAI rather than modifying the shape of the LAI development by adjusting related parameters.

Vegetative and reproductive response of ‘Prime Giant’ sweet cherry trees to regulated deficit irrigation

The agronomic response of sweet cherry (Prunus avium L.) ‘Prime Giant’ to a 4 year-long experiment involving deficit irrigation strategies in a Mediterranean climate was studied in a commercial orchard located in the southeast of Spain (Jumilla, Spain). Four drip irrigation treatments were imposed: (i) control treatment (CTL), irrigated without restrictions at 110% of seasonal crop evapotranspiration (ETc); (ii) sustained deficit irrigation (SDI) treatment irrigated at 85% ETc during pre-harvest and post-harvest periods and at 100% ETc during floral differentiation; (iii) regulated deficit irrigation (RDI) treatment irrigated at 100% ETc during pre-harvest and floral differentiation and at 55% ETc during post-harvest, and (iv) farmer treatment (FRM), irrigated according to the farmer’s normal practice. The crop’s response to the different irrigation treatments was analyzed in relation to tree water status. Soil water deficit reduced tree midday stem water potential (Ψstem), stomatal conductance (gs) and net photosynthesis (Pn). Branch maximum daily shrinkage (MDS) responded rapidly to irrigation changes during pre-harvest and post-harvest. The lowest Ψstem values were reached by SDI during pre-harvest and by RDI and FRM during post-harvest. RDI did not lead to Ψstem water potentials falling to below the threshold of −1.6 MPa in any season, although, FRM caused, Ψstem to fall below −1.8 MPa in 2017.RDI reduced vegetative growth and did not cause significant lower yields or fruit quality. However, with SDI there was a trend towards smaller fruits and a slightly higher soluble solid content. Post-harvest deficit irrigation increased water productivity without penalizing fruit yield or the quality parameters studied, and allowed water savings of 39% compared to CTL at a time when other fruit tree species require more water. Moreover, RDI and SDI led to significantly less cracking incidence and a lower cracking index, which could extend fruit shelf life.

Evaluation of mobile 3D light detection and ranging based canopy mapping system for tree fruit crops

In this study, 3D light detection and ranging (LiDAR) and an inertial measurement unit (IMU) were integrated on a ground vehicle for mapping tree fruit crops. A custom interface was developed in robot operating system for synchronous communication with hardware modules and for continuous field data collection. Point cloud data processing methods were developed for reconstruction and estimation of canopy parameters including height, voxel grid and convex hull methods-based volume and gap fractions in the canopy. The system was tested in apple tree and grapevine canopies. Overall, the mobile 3D LiDAR mapping system provided realistic representation of the canopy compared to the manual methods. For apple trees, the manual canopy volume measurements were strongly correlated to volume derived from the mobile 3D LiDAR mapping system (Convex hull: r = 0.81, Voxel grid: r = 0.51). The voxel grid method adequately considered gaps in the canopy during volume estimation and performed better than the convex hull method. The system was also evaluated for estimating canopy growth in grapevines with different rates of subsurface irrigation treatments. Deficit irrigation treatments did not show any significant effect on the canopy growth due to a high moisture content in the soil, resulting from high winter snowpack prior to that particular season. Nonetheless, the 3D LiDAR mapping system was able to aid in visualization of the temporal changes in canopy growth during the growing season. Change in vine canopy volume for the treatments followed a similar trend to the area ratio estimated from normalized differential vegetation index images derived from small unmanned aerial system based multispectral imagery. Overall, the 3D LiDAR based canopy mapping system and pertinent data mining algorithms can be the useful tool to the growers in rapid assessment of perennial fruit crop canopies for real-time management decision making.

Assessing AquaCrop model to simulate soil water contents under semi arid climate of Central Tunisia

The objective of the present study was to preliminary calibrate and validate AquaCrop model based on crop conservative parameters from the literature for plant growth and water stress thresholds. In addition, physical soil characteristics, root growth, duration of plant stages and atmospheric demands were introduced according to field measurements. Based on this preliminary calibration, simulated water contents were compared to a measured data set of water contents retrieved from deficit and full irrigation treatments on a potato cropped field during an experimental year of 2015. Statistical indexes were computed and finally this performance in simulating water contents were validated under independent measurements carried out during an experiments campaign on the same field on 2014. Moreover, the paper presents the experimental protocol followed for soil characterization, considered as a milestone component for this soil water contents prediction. Results showed, that under the followed preliminary calibration, the model was able to simulate water contents (0v). In general, values of Root Mean Square Error were lower than 0.03 cm3.cm-3 representing the magnitude of error of the time domain reflectometry probe. Moreover values of Nash coffecients were close to 1 confirming the goodness of fit between measured and estimated water contents. Once assessed, the model could be used to study effects of different irrigation strategies on dynamic of water contents aiming to increase water use efficiency.

Response of(Vitis vinifera L.)cv. Fantasy Seedless to water deficit treatments: Phenolic compounds and physiological activities

This paper describes an investigation on the effects of deficit irrigation treatments on phenolic compounds and physiological activities of Fantasy Seedless table grape variety. Research was conducted in Viticultural Research Institute of Manisa, located in Aegean Region of Turkey, during two consecutive years (2016–2017). Three irrigation treatments were assayed; namely full irrigation (T-F), deficit irrigations (T-35 and T-65). In T-F, soil water deficit in the 90 cm within the one week intervals was completed to the field capacity. T-35 and T-65 treatments received 35% and 65% of water applied to T-F. Sub-surface drip irrigation system was used in the research and soil water content was measured by MobiCheck probe while vine water status was monitored through midday leaf water potential before the irrigations. Results showed that water deficit treatments (T-35 and T-65) affected berry composition particularly individual phenolics [Gallic acid, (+)(−) Catechine, (−)-Epigallocatechin gallate, (−)-Epicatechin gallate, Caftaric acid, Chlorogenic acid, Caffeic acid, p-Coumeric acid, Ferulic acid, Sinapic acid, Trans-Resveratrol, Myricetin, Quercetin hydrate, Kaempferol, Oenin Chloride, Delphinidin Chloride, Cyanidin Chloride, Malvidin Chloride] differently. The highest Catechine content in the samples was obtained from T-65, T-35 and T-F treatments, respectively. Furthermore it was determined that DI treatments did not change the Myricetin and Quercetin hydrate contents in 2017. On the other hand minimum Ψmdvalue was observed from the T-35 treatment in both years. Last of all, our findings show a strong relationship between the amount of water and berry composition values especially individual phenolics which are benefical to health.

NUMERICAL MODELING FOR SOIL WATER MOVEMENT UNDER DEFICIT IRRIGATION AND PARTIAL ROOT ZONE DRYING

The successful water management is considered one of the best solutions for the problem of water shortage. The first step in successful water management is to estimate the water requirements for crops accurately and monitoring the residual water content in soil during the growth season, but that cost a lot of everts and money. Others most important techniques for water saving are deficit irrigation (DI), partial root zone drying (PRD) and the integration between them. So, the aim of this study is to simulate the water flow in soil by Hydraus-1D as an easy and a cheap method. Also, studying the applied full irrigation (FI), two levels of sustainable deficit irrigation (DI) applied 75% of total crop evapotranspiration (ETc) (DI75%)and applied 50% of ETc (DI50%), partial root zone drying (PRD) and the integration between DI and PRD on eggplant yield and water productivity efficiency (WP). The experimental work was carried out during the summer seasons of 2017 and 2018 at the experimental farm of Faculty of Agriculture (Moshtohor), Benha University. The soil water content (θ) was measured several times during the growth season by using soil moisture sensor (ML3-Theta-Probe) at depths of 10, 30 and 50 cm. In addition, a numerical modeling was used for predicting the soil water content and comparing the output of model with the actual measured soil water content. The results of the numerical model showed that, the simulated and measured θ values were very close to each other. Moreover, the soil water content under subsurface drip irrigation (SSDI) at a depth of 10 cm were higher by 15.44 % than the corresponding ones under surface drip irrigation (SDI), while at depths of 30 and 50 cm, the values of θ under SDI were higher by 7.16 % and 11.41 % than the corresponding ones under SSDI, respectively. PRD technique with full irrigation (FIPRD) treatment increase the yield and WP by average values about 7.5 % and 16.25 % than that obtained without PRD, respectively under SDI and SSDI. In addition, the PRD technique associated with deficit irrigation treatments resulted in lower fluctuation in the water contents in the vertical distribution than that obtained by the corresponding treatments without PRD technique. While, the using DI decreased the yield and increase WP by different percentage. DI75% decrease the yield by average value 14.9 % than that obtained at FI and increase WP by 29.1 % under SDI and SSDI. DI50% significantly decreased the yield by average value 36.25 % and increase significantly the WP by 59.1 % than the corresponding values at FI. The statistical analysis showed that, there were no significant differences among the FIPRD, FI and DI75+PRD. The SDI resulted in increasing in yield by 4.11 % but not significant than that obtained by SSDI, and SSDI increased WP by 7.15 % than that achieved under the SDI, however the differences between these values were not significant.

Response of Drought-Tolerant Corn to Varying Irrigation Levels in the Texas High Plains

Abstract.Corn ( L.) for grain continues to be an important crop for livestock feed in the Texas High Plains (THP) region despite lackluster prices. It offers greater crop water productivity compared with other crops grown in the region but also has a relatively high water requirement, which must be met by irrigation. The sole water resource in the region is the Ogallala Aquifer, which is declining because withdrawals exceed recharge, and this is of major concern. Producers are interested in the performance of drought-tolerant (DT) corn, but data on DT crop production functions are limited. From 2015 to 2017, studies of DT corn response to different irrigation treatments were conducted in the THP at Bushland, Texas. Results showed that grain yields, seasonal evapotranspiration (ETc), and crop water use efficiency (WUE) varied significantly between seasons and among different DT hybrids. Comparisons between a mid-season (MS) and an early-maturing (EM) hybrid showed: (1) at the severe deficit irrigation treatment level, grain yields were low, but the EM hybrid produced 400% more grain; (2) at the moderate deficit irrigation treatment level, grain yields and ETc were similar; and (3) at the full irrigation treatment level, the EM hybrid required 75 mm less water, but it produced 24% less grain. Non-hail damaged MS DT corn produced grain yields that were numerically greater than conventional corn grown in the THP in an optimal year. However, during drought seasons, DT hybrid response was not improved over conventional hybrids under severe deficit irrigation. This study demonstrated that MS DT corn hybrid P1151AM, irrigated at a level that fully met evapotranspiration demand, resulted in grain yield and WUE levels that were near the upper limits for corn produced in the THP. Further research is needed to determine the constancy of response among different DT hybrids under favorable and drought conditions. Keywords: Center pivot, Deficit irrigation, Early-maturing corn, Hail damage, Mid-season corn, Variable-rate irrigation, Water use efficiency.

Sesame Yield Response to Deficit Irrigation and Water Application Techniques in Irrigated Agriculture, Ethiopia

The study was conducted at Werer Agricultural Research Center, Addis Ababa, for two years, 2013 and 2015, during main seasons and for three years, 2012/13, 2013/14, and 2014/15, during the cool period cropping season (November to February) as in the local cropping calendar. The study was aimed at identifying optimum soil moisture stress for sesame and thereby determining appropriate water-saving irrigation methods and also productivity under limited water resource conditions. Nine treatments with three levels of irrigation water percentage based on evapotranspiration of the crop (ETc) (100% ETc, 75% ETc, and 50% ETc) and three types of furrow irrigation methods (alternate furrow, fixed furrow, and conventional furrow) were used. The study design was randomized complete block design (RCBD) with three replications. The yield of sesame had significant (p<0.05) variation among treatments due to deficit irrigation levels and application methods for sesame planted in main seasons. The highest mean yield of 937.50 kg/ha and 2797.6 kg/ha was obtained from the treatment of 50% ETc with alternate and conventional furrow application methods in 2013 and 2015, respectively. The combined mean yield of two years (2013–2015) showed different levels of deficit irrigation, and irrigation methods had a significant effect (p<0.05) on main season planted sesame. Hence, the highest mean yield of 1846.7 kg/ha was obtained from the application of 50% ETc with the conventional furrow application method. In the cool planting season, the highest mean yield of 528.55 kg/ha, 1432.3 kg/ha, and 1562.5 kg/ha was obtained from treatments of 50% ETc, 75% ETc, and 100% ETc with the conventional furrow application method in 2012/13, 2013/14, and 2014/15, respectively. Moreover, during the same period over years, combined analysis showed that the highest mean yield of 1053 kg/ha was obtained from application of 100% ETc with the conventional furrow application method. Thus, it is concluded that a deficit irrigation treatment of 50% ETc with the conventional furrow application method for main season and application of 100% ETc with the conventional furrow application method for cool planting season are best practices of water-saving strategies for irrigated agriculture system.

Enhancement of Depleted Loam Soil as Well as Cucumber Productivity Utilizing Biochar Under Water Stress

ABSTRACTBiochar has recently received increased attention because it improves poor soil fertility. However, its potentiality to enhance soil physical properties under water stress conditions not yet deeply investigated. Hence, extensive field investigations were carried out to study the effects of biochar addition (BA) with deficit irrigation (DI) on soil bulk density (BD), porosity percentage (P%), soil moisture content (SMC%), soil hydraulic conductivity (K), cucumber yield and water use efficiency (WUE) during two consecutive seasons (2016 and 2017). The biochar treatments were B0 (0 ton ha−1), B1 (10 ton ha−1and B2 (20 ton ha−1), while the DI treatments were 1.0 (W1), 0.60 (W2) and 0.40 (W3) of the reference evapotranspiration (ET0). The parameters were measured at soil depths of 0–10 (d1), 10–20 (d2) and 20–30 cm (d3) for measurement periods of before sowing (P1), mid-season (P2) and after harvest (P3). The results showed that the B2W1 combination gave the highest yield (57 and 45.2 t ha−1), WUE (10.94 and 11.27 kg m−3), SMC (39.2 and 40.1%) in both seasons, respectively. The B2W3 had the highest porosity (47.5 and 46.1%) values at the d1. Meanwhile, the lowest soil BD values of 1.1 and 1.05 g cm−3 were obtained by the B2W1 at d1 for 2.16 and 2017, respectively. Statistically, most of the parameters studied under B2W2 and B0W1 had non-significant differences between them. Hence, the addition of biochar with DI could be an integrated approach to address the drought stress, while enhancing soil and plant properties.

Physiological response of red pepper to different irrigation regimes under drip irrigation in the Mediterranean region of Turkey

A study was conducted to analyse the physiological response of red pepper (Capsicum annuum L.) to different irrigation regimes by means of periodical measurements of leaf water potential (LWP) and stomatal resistance (rs) and crop water stress index (CWSI) at midday during 2010 and 2011 seasons in the Mediterranean region of Turkey. The treatments consisted of full irrigation (FI), deficit irrigation (DI-75, DI-50), partial root zone drying (PRD-A, PRD-F, A: alternative, F: fixed). The greatest yield was obtained from the FI treatment followed by DI-75, PRD-A, DI-50 and PRD-F treatments resulted in the smallest yield. The FI irrigation treatment had less stomatal resistance (17.4 s cm−1 in 2010 and 16.4 s cm−1 in 2011) and CWSI (0.25 in 2010 and 0.27 in 2011) in comparison with deficit irrigation treatments. Red pepper performed best at FI with a corresponding leaf water potential of -0.65 to -0.53 MPa for experimental years. There were large differences among treatments in LWP, CWSI and rs, indicating that crop responded differently to different soil water levels. Significant relationship between stomatal resistance, water use and yield were obtained. The results also revealed significant dependency among CWSI, rs and LWP were found.

Deficit irrigation: a viable option for sustainable confection sunflower (Helianthus annuus L.) production in the semi-arid US

With water resources becoming more limited in arid and semi-arid regions, water-saving strategies are needed to reduce agricultural water use. A furrow-irrigated field experiment was conducted during 3 years (2010–2012) in the western US to evaluate the response of confection sunflower to deficit irrigation. Treatments were full irrigation (FI, irrigation as scheduled by farmers), two deficit irrigation strategies (R1, started irrigation when miniature floral heads appeared; and R4, started irrigation when floral heads began to open), and rainfed (CK) as control. Results showed that growth and yield of confection sunflower were significantly affected by treatments. The FI and deficit irrigation treatments (R1 and R4) led to significantly higher leaf area index (LAI), aboveground biomass, head diameter, and yield compared with the CK treatment. Relative to FI, deficit irrigation decreased sunflower LAI, head diameter, and aboveground biomass. Average yield was 6% and 15% less in R1 and R4 treatments, respectively, compared with the FI treatment. There was no significant difference in yield between FI and R1, except during extremely dry years, suggesting that the R1 strategy may maintain yield while reducing one irrigation event. Based on the growth and yield of sunflower, an irrigation for crop establishment and then resuming of irrigation at the R1 stage could be considered as a water-saving strategy for surface-irrigated confection sunflower grown in water-scarce regions.

Broadcast woody biochar provides limited benefits to deficit irrigation maize in Colorado

Biochar soil amendments have been widely promoted for their ability to improve soil fertility in degraded tropical soils, and irrigation and fertilizer use efficiency in fertile temperate agricultural systems. Here, we evaluate if a woody biochar can produce both agronomic and environmental benefits in deficit irrigation systems by ameliorating water stress, improving crop N uptake and mitigating greenhouse gas emissions. To evaluate these responses, we established a maize field trial in northern Colorado under deficit irrigation treatments with a woody biochar amendment. Irrigation treatments included recommended irrigation (Full), recommended irrigation except during non-essential growth phases (Limited) and 50% of recommended irrigation (Drought). We measured crop biomass, grain yield, grain N uptake, mineral N availability, soil water content, soil field capacity, soil C sequestration and N2O emissions. Drought treatments reduced both grain and biomass yield while Limited irrigation showed no significant yield reduction relative to Full irrigation. Biochar amendments did not provide any yield improvements. Biochar also did not alter mineral N availability within the soil profile or grain N uptake. Biochar amendments increased gravimetric soil water content by 9.7% over the field season and increased water retention by 7.4%. However, these increases failed to alleviate the water stress coefficient, an index of how much the water content has dropped below the maximum soil water depletion acceptable between irrigation applications, which was correlated with yield. Biochar sequestered C primarily as coarse biochar particles with significant losses, likely a result of erosion. Across irrigation treatments biochar treatments trended towards a lower mean cumulative N2O emissions over the growing season, but such effect was not significant due to high spatial variability in N2O fluxes. Both biochar amendments and Limited irrigation treatments did not significantly impact yield-scaled cumulative N2O emissions or irrigation water-use efficiency. This research highlights the importance of targeting the deficit irrigation treatment timing and amount to maximize biochar’s improved water retention in order to reduce crop water stress. It also confirms the diminished biochar N2O emission reductions in the field relative to most lab incubations due to drier field conditions and crop N uptake.

Modeling Deficit Irrigation of Maize with the DayCent Model

Core Ideas A new version of the DayCent model was capable of simulating the responses in maize‐dominated agroecosystems under water‐deficit conditions. The accuracy of DayCent‐simulated GLAI, biomass, SWC, and yield was similar to that observed with more complex models. There was no significant difference in the major output variables when the stress coefficient, Ks, was calculated by the FAO method or the original DayCent method. A promising solution to help close the gap between water demand and supply in semiarid regions is deficit irrigation strategies that use less water but aim to increase crop yield per unit of water applied. Dynamic models can be used to assess the impacts of deficit irrigation and to support decision‐making. In this study, we evaluated the capability of a new version of the DayCent agroecosystem model to model crop growth, yield, and water use in response to water‐deficit conditions resulting from different deficit irrigation strategies employed in three field experiments with maize (Zea mays L.) in eastern Colorado. Overall, the DayCent model with improved algorithms for plant canopy development provided accurate estimates of green leaf area index (GLAI) for full and deficit irrigation treatments, though the method tended to overpredict the GLAI during the late vegetative growth period in the deficit irrigation treatments. Simulated soil water content (SWC), biomass, and grain yields compared well with the field measurements. We tested the drought stress coefficient (Ks) method in the FAO Irrigation and Drainage Paper No. 56 as an alternative to the original DayCent method for estimating drought stress. There were only marginal differences between the two Ks methods in predicting the major output variables in DayCent, but the FAO method is simpler and easier to parameterize. Overall, the DayCent model can simulate the responses in agroecosystems with maize under water deficit conditions and could be used as a guide for applying deficit irrigation strategies for water savings.