ETc Irrigation Research Articles

Residual Effect of Irrigation Levels and Maize Genotypes on Performance of Succeeding Blackgram (Vigna mungo L.) in Maize-blackgram Sequence Cropping

Background: Maize is the third most important food crop in India. Conventionally it is a furrow irrigated crop and hence, it calls for an effective on-farm management of water in field through micro irrigation. Intensive agriculture practice like continuous monocropping without following the principles of crop rotation and sequence have resulted in several ecological complications. Hence, blackgram was introduced as a succeeding crop after drip irrigated maize. The aim of the study was to examine the residual effect of drip irrigation levels and maize genotypes and their interaction on succeeding crop i.e. blackgram. Methods: During summer 2018 and 2019, maize experiment was conducted with four irrigation levels (drip irrigation at 0.6, 0.8 and 1.0 ETc and furrow irrigation at 0.8 IW/CPE ratio) and four maize genotypes (NK-6240, Pinnacle, CP-818 and RCRMH-2). After maize, succeeding blackgram was taken up under rainfed condition of Dharwad during kharif 2018 and 2019. Result: Performance of blackgram was superior under residual effect of drip irrigation treatments over furrow irrigation method. Among the interactions, significantly higher yield, RWUE and net returns were recorded with residual effect of I1G4 treatment combination. However, it was on par with I1G2, I1G3, I1G1, I2G1, I2G2, I2G4, I3G2 and I3G3 treatment combinations.

English

For three years, the response of wheat grain yield to varying amounts of nitrogen fertilizer and different levels of irrigation was investigated. Three levels of irrigation (100, 75, and 50%ETc) and five nitrogen rates (0, 23, 46, 69, and 92 kg/ha) were used in a split plot design. Irrigation and nitrogen levels both had a considerable impact on wheat grain yield, but there was no interaction between the two. The three-year combined analysis result revealed that the maximum grain yield of wheat was recorded at 92 kg/ha nitrogen rate and 100%ETc irrigation treatment. The minimum was obtained from no application of nitrogen and 50%ETc irrigation treatment. The study revealed that the above ground biomass and grain yield of wheat increased with the increasing rates of nitrogen fertilizer and the full application of irrigation. The partial budget analysis revealed that an application of 100%ETc and 46 kg/ha nitrogen fertilizer gave the maximum marginal rate of return and optimum net benefits. Therefore, application of 100%ETc irrigation and 46 kg/ha nitrogen is recommended for optimum returns of irrigation and nitrogen fertilization of wheat in the study area. Key words: Nitrogen, Irrigation, Water use efficiency, partial budget, economic yield.

Evaluation of the Effect Mulching Practice Under Furrow Irrigation on Growth, Yield and Water Productivity of Head Cabbage at Adami Tulu Agricultural Research Center

The experiment was under taken among the amount of water and mulching practice at Adami Tulu Agricultural Research Center of experimental site for head cabbage production. With the objective of to investigate and evaluate the effect of furrow irrigation level and mulching on water productivity, yield and yield component of head cabbage. A field experiment was designed as a two factor factorial experiment (2*4) in RCBD, replicated three times. The two factors were irrigation water level and mulching material. Irrigation was applied to furrows using Parshal flume from furrows head ditch with similar inflow rate, but the amount of application of water varies. Results obtained revealed that Application of wheat straw mulch and plastic mulch significantly increased the growth and yield of cabbage. Straw mulch produced total yield of 9.68 ton/ha which was not significantly different with that obtained under White straw mulch (9.69ton/ha). Total yield harvested from black plastic mulch were 9.33ton/ha, which showed insignificant difference between the three mulching material. High yield of 16.60ton/ha was recorded from full irrigation that is 100%ETc and when half of irrigation water applied the yield were 9.4ton/ha which showed significant difference between the two irrigation level. Water productivity of 4.3kg/m³ and 3.8kg/m³ were produced under 50%ETc and 100%ETc or full irrigation water respectively. It was found that 50%ETc irrigation level saved 50% of water as compared to full irrigation and can irrigate additional land with the amount of water saved.

Effects of Deficit Irrigation and Mulch Levels on Growth, Yield and Water Productivity of Onion (<i>Allium cepa</i> L.) at Werer, Middle Awash Valley, Ethiopia

Enhancing water productivity of irrigated crops through Agricultural water management is a vital option in water scarce areas, such as, Rift valley. Accordingly, a field experiment was conducted at Werer Agricultural Research Center to evaluate the effects of deficit irrigation and straw mulching levels on growth, yield and water productivity of onion (<i>Allium cepa</i> L.). The experiment was laid out in a randomized complete block design in factorial arrangement of three levels of irrigation (100, 80 and 60% of Crop Evapotranspiration and four levels of straw mulch (0, 3, 6 and 9ton wheat straw per ha) in three replications. The output of Cropwat model indicated that the highest seasonal water requirement of onion was 422.5 mm at 100% ETc while; the lowest was 253.5 mm at 60% ETc. The analysis of variance revealed that there was significant (p<0.05) difference in growth parameters and yield parameters were highly significant (p<0.01) influenced by the interaction effects of deficit irrigation and straw mulch levels. The highest marketable bulb yield (33.47 t/ha) was obtained from an experimental plot treated with combined application of 100% of ETc and 6 t/ha straw mulch, while the lowest (21.10 t/ha) was obtained from plots treated with 60% ETc irrigation level and no mulch treatment. Water productivity was also highly significant (p<0.01) influenced by the interaction effects of deficit irrigation and straw mulching levels; the highest (10.22 kg/m³) and the lowest (6.11 kg/m³) were recorded from the plots treated with 60% ETc and 9 t/ha straw mulch, and 100% ETc and no mulch treatments, respectively. Therefore, in terms of marketable bulb yield and water productivity, irrigating with 80% ETc with 6 t/ha straw mulch would be recommended for production of onion in the study area.

Investigation of the Response of onion (Allium Cepa L.) to continuous deficit irrigation as smart approaches to crop irrigation under Mediterranean conditions

Water is a crucial resource for food production and its scarcity associated with frequent droughts has increased the need for a more efficient use of it along with new irrigation management technologies. This study addressed onion crop responses to continuous deficit irrigation with trigging thresholds of readily available water content. The experiment was conducted on an experimental plot in open field in Morocco. Three water regimes were applied T1 control (100%), T2 (75%) and T3 (50%) of crop evapotranspiration ETc combined with two trigging thresholds (10% and 5%). This is a complete random block device with four repetitions. The measurements concerned the monitoring of vegetative, Eco physiological and yield parameters. The results obtained show that: (i) 100% ETc irrigation at a threshold of 5% of RAW recorded the maximum bulb diameter and weight, thus achieving the best marketable bulb yields. However, in terms of yields, this treatment is not significantly different from the other irrigation regimes with the exception of the irrigated treatment at 50% daily ETc and at a threshold of 10% RAW. The latter recorded the lowest values in terms of production parameters. (ii) For the ecophysiological parameters, significant effects of irrigation dose were observed for proline content, stomatal conductance and leaf temperature, and the effect of the trigging threshold was clearly observed for the moisture content of the leaves. (iii) Water restrictions have minimized the rate of premature run and population density of Thrips tabaci in the onion. (iv) Finally, the best agronomic efficiencies in the use of irrigation water were recorded in treatments with a water restriction of 50%.

Physiological behavior of olive (Olea europaea L.) varieties under different foliage nutrition and irrigation regimes in the hyper-arid zone

Olive (Olea europaea) is an emblematic tree in the Mediterranean regions that grows an integral part of the area. The Mediterranean vegetation often undergoes challenging periods of severe drought stress, which causes significant impairment to olive trees' growth and production performance. The practical study was designed to follow up the effect of three irrigation regimes (50%, 75% and 100% ETc) in combination with four doses (0, 2, 4 and 6 g/L) of Lithovit (CaCO3+MgCO3, micronized calcium carbonate) on growth performance, yield, and fruit quality of two olive (Picual and Manzanello) varieties during 2017 and 2018 growing seasons. Regardless Lithovit doses, irrigation regime 100% of ETc exhibited the highest values of leaf water content, leaf relative water content, total chlorophyll and N, P, K, Ca and Mg concentrations of both olive varieties compared to the other watering regimes. Interestingly, proline content in the fruit was enhanced with increasing water deficit (50% of ETc) and Lithovit dose (6 g/L). However, the highest yield and fruit oil content were obtained by the combination of 75% ETc irrigation level and Lithovit treatment at a rate of 4 g/L in both olive varieties. This study contributes to developing olive production technologies, thereby ensuring sustainable olive culture farming with high-quality yield in hyper-arid zones.

English

Water is a vital resource to sustain civilizations and pecuniary development and most importantly agriculture. Agriculture is the main contributor to the Ethiopian economy. The field experiment was conducted at Werer Agricultural Research center to evaluate the effects of drip and furrow irrigation under different irrigation levels on maize water use efficiency. The experiment was laid out in an RCBD split-plot arrangement where drip and furrow irrigations were assigned as the main plot and irrigation levels (100, 85, 70, and 55% of ETc) were assigned in the subplot arrangement with three blocks. The highest seasonal water requirement of maize was 701.7 mm at 100% ETc under conventional furrow irrigation which is considered as control while the lowest was 321.6 mm at 55% ETc under alternative furrow irrigation. The interaction effects of irrigation systems and irrigation levels have shown a highly significant (p&lt;0.01) effect on water use efficiency. The highest (2.38 kg/m3) and the lowest (0.60kg/m3) water use efficiency were recorded from the plots treated with drip irrigation at 100% ETc and conventional furrow irrigation at 100% ETc treatments, respectively. In terms of water use efficiency and economic prominence, irrigating with a drip irrigation system with 100% ETc can be recommended for the production of maize in the study area. Key words: Agriculture, efficiency, irrigation, main plot, split plot.

Shifts in the phenolic composition and aromatic profiles of Cabernet Sauvignon (Vitis vinifera L.) wines are driven by different irrigation amounts in a hot climate

Wine final color, taste and aroma are closely related to the accumulation of secondary metabolites that may be affected by deficit irrigation applied in viticulture. A two-year study was conducted to assess the different fractions of crop evapotranspiration (ETc) irrigation replacement on wine composition, addressing the analysis of flavonoids and volatiles under context of global warming. Irrigating with 100% ETc (full grapevine demand) enhanced wine hue, antioxidant capacity, and some aromas; however, it came with a diminution of flavonoids and a less stable flavonoid profile. Replacing 25 and 50% ETc in wine grape improved wine color intensity, concentration of flavonoids, and shifted the aromatic profiles. These treatments increased some terpenes and esters which may enhance the desirable aromas for Cabernet Sauvignon, and decreased C6 alcohols related to unpleasant ones. Therefore, despite the warming trends in Mediterranean climates, 100% ETc irrigation would be not advisable to improve or maintain wine quality, and 50% ETc was sufficient.

Effect of Drip Lateral Spacing and Water Levels on Yield and Water Use Efficiency of Onion ( allium cepa l. ) Under Awash Melkassa Climatic Condition

Water being scarce resources, irrigation water is the most limiting factor for vegetable production in the central rift valley of Ethiopia. Drip irrigation technique together with deficit irrigation application improves crop yield and water use efficiency. Hence, the objective of this study was to enhance onion production and WUE through the application of drip irrigation technology and deficit irrigation application. Field experiment was conducted at Melkassa agricultural research center during the cool cropping season of 2019/2020 to investigate the effects of drip lateral spacing and irrigation levels on onion yield, water use efficiency and net return. Two levels of drip lateral spacing viz., lateral placed in every row and between two rows, and three levels of deficit irrigation viz., 80% ETc, 70% ETc and 55% ETc, and one-full irrigation (100% ETc). The treatments were arranged in split plot with three replications. Data were analyzed using statistical package appropriate to split plot with the help of SAS software. The result showed that onion yield, yield parameters and water use efficiency was affected by the effects of drip lateral spacing and irrigation water levels but not affected by their interaction effect. Onion bulb yield decreased with increased levels of water deficit. In contrast, both water use efficiency and irrigation water use efficiency increased with increase in water deficit level. Maximum onion bulb yield of 41.43 t ha-1 were obtained from lateral spacing in every row and full irrigation application level of 100% ETc and has no a significant difference with every row lateral spacing, and 85% and 70% ETc irrigation application levels. The highest water use efficiency of 13.33 Kgm-3 was recorded from every row drip lateral spacing and irrigation application of 70% ETc. Therefore, onion could be irrigated every row drip lateral spacing with 70% ETc application to increase water use efficiency without a significant total bulb yield reduction.

Using AquaCrop as a Decision-Support Tool for Small-Scale Irrigation Systems Was Dictated by the Institutional and Market Incentives in Ethiopia

The threat of water scarcity in sub-Saharan Africa is exacerbated by the expanding agricultural water needs, increasing climate variability and inappropriate land use. It calls for technological and institutional innovations to improve water productivity, while sustaining the resources base. This study was undertaken to examine the effect of deficit and supplementary irrigation for staggered production of potato driven by market opportunities at different periods in northeastern Ethiopia. We used potato (Solanum tuberosum) to demonstrate AQUACrop as a tool for improving water productivity during Belg (short) and Meher (long) rainfall seasons. A field experiment was undertaken using supplementary irrigation at different levels of potato crop water satisfaction (50% ETc, 75% ETc, 100% ETc and rainfed conditions) during the Belg (February–May 2020) and Meher (July–October 2020) seasons. Upon proper calibration of AquaCrop for the local potato variety (Belete), long-term simulations revealed that the mean net irrigation requirements were 249 mm during Belg season while the probability of applying supplementary irrigation during Meher was &amp;lt;10% when the effective precipitation was greater than the crop water requirement (ETc) in more than 75% of the years. Although there was significantly higher potato tuber yield from the 100% ETc than that from the 75% ETc, the latter had higher water supply efficiency than the former. Long-term simulations further revealed that the number of rainfall days was more important than the amount of rainfall during the growing period. We engaged water users' associations to employ the recommendation and enforce supplementary irrigation as predicted by the model and we present farmers' response and reasons for resistance toward water saving approaches. Hence, we concluded that 50% ETc and 75% ETc irrigation levels can still be recommended upon proper scheduling to address long dry spells, especially during the middle growth stages in the face of irrigation conflict. However, the institutional settings and market incentives associated with it are the major drivers of adopting improved irrigation water management practices.

Partial Wetting of Root Zone to Enhance Furrow Irrigation Indices, Yield Responses and Economic Return Of Soybean الترطيب الجزئى لمنطقة الجذور لتحسين مؤشرات الرى بالخطوط واستجابة المحصول والعائد الاقتصادي لفول الصويا

This study was carried out in a private farm located in Gharbiya Governorate, the Nile Delta, Egypt. The study aimed to assess how far the alternative furrow application and deficit irrigation may improve irrigation indices and water productivity of Soybean. Two techniques of alternation were applied. The first is Standing Alternate furrow Irrigation (SAI), the second is Reciprocal Alternate furrow Irrigation (RAI). The two techniques were compared with Conventional furrow Irrigation (CI), at which, all furrows are conventionally irrigated per each irrigation (Control). Results revealed that irrigation requirements under both of (SAI) and (RAI) techniques s are significantly less than that with (CI). Surface runoff increased as the level of application increased. The significant difference was found only between (RAI) with the level of 50 % Etc. and the treatment of (CI) with the level of 100% Etc. The highest value of (Ea) was achieved with (RAI) and 75% ETc irrigation level while the lowest value was found with (CI) and 100% ETc irrigation level. The lowest values of actual ET were found (RAI) and 50% ETc irrigation level. Also, results indicated that produced yield of soybean varied significantly (P<0.05) and influenced by both irrigation techniques and application levels. Yield of soybean was depressed by about 12% under (SAI) with 50% ETc, compared with the treatment of (CI) and 100% ETc. It could be concluded that, the (RAI) and 75% ETc irrigation level is efficient management for soybean production without the risk of reduced grain yield under the experiment conditions.

Calibration and Evaluation of the FAO AquaCrop Model for Canola (Brassica napus) under Varied Moistube Irrigation Regimes

The AquaCrop model was calibrated and validated for canola (Brassica napus) under Moistube irrigation (MTI) and various water regimes [(i) 100%, (ii) 75%, and (iii) 55% of crop water requirement (ETc)] over two seasons, 2019 and 2020. The normalised root mean square (nRMSE), Model Efficiency (EF), R2, and the Willmot’s index of agreement (d) statistics were used to evaluate the model’s efficiency in simulating biomass (B), canopy cover (CC), yield (Y), and harvest index (HI). The calibration results indicated the model simulated with accuracy the CC (under 100% ETcR2 = 0.99, EF = 0.92, nRMSE = 6.4%, d = 0.98) and 75% ETc (R2 = 0.99, EF = 0.92, nRMSE = 10.3%, d = 0.98). The model simulated CC well for validation for 100% ETc (R2 = 0.97, EF = 0.93, nRMSE = 22.5%, d = 0.98) and 75% ETc (R2 = 0.84, EF = 0.45, nRMSE = 59.2%, d = 0.86) irrigation regimes. Final biomass simulations were reasonably good under 100% ETc, 75% ETc, and 55% ETc irrigation regimes (R2 &gt; 0.90, d &gt; 0.65). The study showed the usefulness of AquaCrop for assessing yield response of canola to full and deficit irrigation scenarios under MTI.

Effects of Various Quantities of Three Irrigation Water Types on Yield and Fruit Quality of ‘Succary’ Date Palm

A field experiment was conducted on date palm trees (Phoenix dactylifera ‘Succary’) cultivated on sandy loam soil from 2017 to 2018. This study investigated the effects of providing water of three different qualities, namely freshwater (FR) and two saline water sources: reclaimed wastewater (RW) and well-water (WE) applied through three irrigation levels representing 50% (I50), 100% (I100), and 150% (I150) of crop evapotranspiration (ETc), on the soil water and salt distribution patterns, yield, water productivity (WP), and fruit quality of the ′Succary′ date palm. The electrical conductivity (ECw) of FR, RW, and WE were 0.18, 2.06, and 3.94 dS m−1, respectively. Results showed that WE applied by the I150 treatment had the highest soil water content, followed by RW used in the I100 irrigation level and FR with I50, whereas the soil salt content was high for WE applied in the I50 level and low for FR applied by the I150 treatment. Deficit irrigation (I50) of date palms with either RW or WE reduced date yields on average 86 kg per tree, whereas the yield increased under over-irrigation (I150) with FR to 123.25 kg per tree. High WP values were observed in the I50 treatments with FR, RW, or WE (on average 1.82, 1.68, and 1.67 kg m−3, respectively), whereas the I150 treatment with each of the three water types showed the lowest WP values. Fruit weight and size were the lowest in the full irrigation (I100) with WE, whereas the I150 treatment with RW showed the highest values. There were no significant differences in either total soluble solids (TSS) or acidity values when the irrigation level decreased from 100% to 50% ETc. Compared with both I50 and I100 treatments, reduced values of both TSS and acidity were observed in the I150 treatment when ECw decreased from 3.94 to 0.18 dS m−1,. Fruit moisture content decreased with the application of saline irrigation water (i.e., RW or WE). Total sugar and non-reducing sugar contents in fruits were found to be decreased in the combination of RW and I150, whereas the 50% ETc irrigation level caused an increment in both parameters. These results suggest that the application of deficit irrigation to date palm trees grown in arid regions, either with FR or without it, can sufficiently maximize WP and improve the quality of fruits but negatively affects yield, especially when saline water is applied. The use of saline water for irrigation may negatively affect plants because of salt accumulation in the soil in the long run.

The Effect of Irrigation Rate on the Water Relations of Young Citrus Trees in High-Density Planting

The availability and proper irrigation scheduling of water are some of the most significant limitations on citrus production in Florida. The proper volume of citrus water demand is vital in evaluating sustainable irrigation approaches. The current study aims to determine the amount of irrigation required to grow citrus trees at higher planting densities without detrimental impacts on trees’ water relation parameters. The study was conducted between November 2017 and September 2020 on young sweet orange (Citrus sinensis) trees budded on the ‘US-897’ (Cleopatra mandarin x Flying Dragon trifoliate orange) citrus rootstock transplanted in sandy soil at the Southwest Florida Research and Education Center (SWFREC) demonstration grove, near Immokalee, Florida. The experiment contained six planting densities, including 447, 598, and 745 trees per ha replicated four times, and 512, 717, and 897 trees per ha replicated six times. Each density treatment was irrigated at 62% or 100% during the first 15 months between 2017 and 2019 or one of the four irrigation rates (26.5, 40.5, 53, or 81%) based on the calculated crop water supplied (ETc) during the last 17 months of 2019–2020. Tree water relations, including soil moisture, stem water potential, and water supplied, were collected periodically. In addition, soil salinity was determined. During the first year (2018), a higher irrigation rate (100% ETc) represented higher soil water contents; however, the soil water content for the lower irrigation rate (62% ETc) did not represent biological stress. One emitter per tree regardless of planting density supported stem water potential (Ψstem) values between −0.80 and −0.79 MPa for lower and full irrigation rates, respectively. However, when treatments were adjusted from April 2019 through September 2020, the results substantially changed. The higher irrigation rate (81% ETc) represented higher soil water contents during the remainder of the study, the lower irrigation rate (26.5% ETc) represents biological stress as a result of stem water potential (Ψstem) values between −1.05 and −0.91 MPa for lower and higher irrigation rates, respectively. Besides this, increasing the irrigation rate from 26.5% to 81%ETc decreased the soil salinity by 33%. Although increasing the planting density from 717 to 897 trees per hectare reduced the water supplied on average by 37% when one irrigation emitter was used to irrigate two trees instead of one, applying an 81% ETc irrigation rate in citrus is more efficient and could be managed in commercial groves.

Development of A Spatial Decision System for Irrigation Management

Spatial decision system provides a framework for integrating database management systems, analytical models, and graphics to improve the decision-making process from a farm-scale to a regional level. In this study, a graphical user interface for irrigation management has been developed with the support of a geographical information system (GIS) customization using Visual Basic for Application (VBA). Inverse distance weighted (IDW) method is employed to interpolate spatial inputs through an embedded environment provided by the GIS for customization with VBA technique. The developed Interface was used to analyze, simulate, handle, and integrate the irrigation management's spatial data. It can be used effectively from a farm-scale to a regional level and temporal data with interpolation techniques to generate thematic maps of rainfall, effective rainfall, reference evapotranspiration (ETo), crop evapotranspiration (ETc) using weather, crop, and soil data. The tool allows visualization of the spatial distribution of water requirements in the specified region and facilitates the localization of any discrepancies in water management, indicating whether interventions are required. Finally, interface was applied to estimate spatial irrigation water requirement to provide output, i.e., spatial maps of rainfall, effective rainfall, daily ETo, daily ETc, and net irrigation requirement (NIR). ETo was higher at Bhopal, Tikamgarh and Jhansi and lowered at Raisen and Sagar. The generated NIR map shows that the area nearby Khurai station has a higher irrigation requirement. On the other hand, the area covered by Begumganj, Sironj, Tikamgarh, and Banda has lower irrigation requirements. This information may help irrigation management's decision-making from a farm-scale to a regional level in the Betwa River Basin, India.

Influence of kaolin application on most important fruit and leaf characteristics of two apple cultivars under sustained deficit irrigation

BackgroundApple is one of the oldest and most valuable fruits. Water restriction is one of the major problems in the production of this fruit in some planting areas.MethodsEffects of kaolin spray treatments were studied on two early apple cultivars of Golab and Shafi-Abadi under sustained deficit irrigation (SDI) in Alborz province, Iran during 2017 and 2018. Irrigation treatments were 100%, 85%, and 70% ETc and kaolin application were concentrations of 0, 3 and 6% in 2017 and 0, 1.5 and 3% in 2018.ResultsResults showed that 85% ETc treatment compared to other irrigation treatments improved apple tree crown volume in 2017. Deficit irrigation treatments significantly reduced fruit weight in both years. Application with 6% kaolin resulted in 33.3% increase in apple fruit weight compared to non-kaolin treatment at 100% ETc irrigation in the first year. Severe deficit irrigation (70% ETc) significantly reduced apple fruit length in both years, but 6% kaolin increased fruit length in both apple cultivars in 2017. Severe deficit irrigation treatment increased the firmness of apple fruit compared to control and mild deficit irrigation (85% ETc) in the first year of experiment. There was no significant difference between irrigation treatments for apple fruit firmness in the second year of experiment. Kaolin treatments of 1.5% and 3% at full irrigation increased the soluble solids content of apple fruit by 36.6% and 44.1% in 2018, respectively. Deficit irrigation treatments significantly increased leaf proline content compared to control in both years. In the first year, kaolin treatments increased leaf proline but in the second year, leaf proline was not significant. Deficit irrigation treatment of 70% ETc and 6% kaolin had the highest amount of glycine betaine content, malondialdehyde and hydrogen peroxide in apple leaf in the first year of experiment.ConclusionsSevere deficit irrigation stress (70% ETc) increased the activity of nonenzymatic defense systems of apple trees. Kaolin as a drought stress reducing agent can be recommended in apple orchards of Golab and Shafi-Abadi cultivars as an effective and inexpensive method to improve tolerance to drought stress conditions.

Effect of deficit irrigation on physiology, plant growth, and fruit yield of cucumber cultivars

Increased water scarcity necessitates the implementation of water-conserving irrigation management practices to sustain crop production,especially in water-limited areas. A two-year field study was conducted during 2019 and 2020 to evaluate the effect of deficit irrigation on physiology, plant growth, and yield of cucumber cultivars. The experiment was conducted in a split-plot design with four irrigation levels (100% ETc (crop evapotranspiration), 80% ETc, 60% ETc, and 40% ETc) as main plot factor and two cultivars (Poinsett 76 and Marketmore 76) as subplot factor with three replications. Results showed that stomatal conductance (gs), transpiration rate (E), photosynthesis rate (Pn), intercellular CO2 concentration (Ci), and leaf area were significantly lower in 60% ETc and 40% ETc compared to 100% ETc while stomatal limitations, intrinsic water use efficiency (WUEi), and relative leaf temperature were significantly higher in 60% ETc and 40% ETc compared to 100% ETc. The observed values of these aforementioned parameters were comparable between 100% ETc and 80% ETc. A decrease in leaf area, as well as a decrease in Pn, resulted in a decline in overall photosynthesis per plant in 60% ETc and 40% ETc compared to 100% ETc. As a consequence of this, plant dry biomass and total fruit yield were significantly lower in 60% ETc and 40% ETc compared to 100% ETc. However, photosynthesis per plant was comparable between 100% ETc and 80% ETc due to comparable Pn and leaf area between them. Because of comparable photosynthesis per plant, plant dry biomass and fruit yield were comparable between 100% ETc and 80% ETc. Marketmore 76 had significantly higher gs, E, Pn, Ci, and leaf area and it had significantly lower stomatal limitations, WUEi, and relative leaf temperature than Poinsett 76. Vegetative dry biomass and total above-ground dry biomass were higher in Marketmore 76 but fruit yield was higher in Poinsett 76. These results suggest that 80% ETc irrigation level and Poinsett 76 cultivar can be recommended for successful cucumber production without causing a significant decline in fruit yield in water-limited Southern High Plains of United States.

Effect of Furrow Irrigation Techniques and Deficit Irrigation Levels on Yield and Water Productivity of Onion (&amp;lt;i&amp;gt;Allium cepa l.&amp;lt;/i&amp;gt;) at Werer, Middle Awash Valley, Ethiopia

Deficit irrigation is one of the techniques used to enhance water productivity without significant yield loss in semiarid areas. A field experiment was conducted at Werer, Middle Awash Valley during the dry season of the 2017/18, 2018/19 and 2019/20 for three consecutive years to investigate the effects of deficit irrigation levels and furrow irrigation methods on onion yield and water productivity. Split plot design with three replications, in which the irrigation methods (Conventional, Fixed and Alternate Furrow) were assigned to the main plot and the three deficit levels (100% ETc, 75% ETc and 50% ETc), were in the sub-plot. Results indicate that marketable onion bulb yield and water productivity were highly affected by the interaction effect of furrow irrigation methods and irrigation levels (p<0.05). The highest bulb yield (17580.43 kg ha^-) and water productivity (11.79 kg/m³) were obtained from conventional furrow irrigation method with100% ETc and alternate furrow irrigation with 50% ETc respectively. Considering water saved and maximum yield, Onion irrigated by AFI 100% ETC resulted in 15% yield reduction with up to 50% irrigation water saving as compared to CFI 100% ETc. The present study suggests that, under water limiting conditions, adopting alternate furrow irrigation with 100% ETc can be an alternative to increase water productivity without significant yield reduction.

Simulated deficit irrigation and climate change effects on sunflower production in Eastern Colorado with CSM-CROPGRO-Sunflower in RZWQM2

Sunflower (Helianthus annuus L.) has been used as an alternative summer crop in the traditional wheat (Triticum aestivum L.)-fallow rotation in the Great Plains of the USA. However, few studies have been conducted to quantify sunflower productivity and water productivity (WP) under semi-arid conditions and projected climate change. Experiments were conducted in 2008, 2010, and 2011 on sunflowers under deficit irrigation to meet a fraction of crop evapotranspiration (ETc) as estimated by FAO-56 in eastern Colorado. The field data was used to calibrate and validate the CSM-CROPGRO-Sunflower model that is incorporated in the Root Zone Water Qualify Model (RZWQM2). The calibrated model was then used to simulate sunflower production under projected climate conditions with four Representative Concentration Pathways (RCP) scenarios (2.6, 4.5, 6.0, and 8.5) and four irrigation levels (100%, 60%, 40% ETc and rainfed) in the late 21st century. The results showed that the model was able to adequately simulate sunflower biomass, yield, and soil water storage under the different irrigation treatments in all three years. The corresponding relative root mean square deviation (RRMSD) values were between 0.05 and 0.15 for the simulations of soil water storage, yield, and biomass. Under future climate change conditions, the model simulated greater impact of irrigation treatments than RCP scenarios on sunflower production. For example, yield was 3251.3, 2638.85 and 1937.17 kg ha−1 with 100%, 60% and 40% ETc irrigation under baseline (1992–2013) and was 2932.47, 2360.53 and 1810.65 kg ha−1 with these irrigation treatments under RCP8.5 (2070–2091). Simulation results also showed that scheduling irrigations based on 60% of ETc was the best choice for sunflower WP in eastern Colorado. Climate change did not affect sunflower biomass, yield, and WP. There was an increasing trend of irrigation amount was simulated from the baseline to RCP8.5 scenario to maintain a certain percent of ETc due to high temperature projected. For instance, the irrigation amount for 100%, 60% and 40% of ETc irrigation treatment was 16.4%, 17.3%, and 20.0% higher under RCP8.5 than those under baseline conditions with CO2 fertilization. Finally, our results demonstrated that RZWQM2 can be used to effectively schedule sunflower irrigations based on crop evapotranspiration requirement.

Performance of cabbage at different irrigation levels under drip and microsprinkler irrigation systems*

AbstractField experiments were conducted for 3 years to investigate an appropriate irrigation management strategy that would lead to increased cabbage productivity along with saving in irrigation water. Cabbage was grown with microsprinkler and drip irrigation methods with four irrigation levels based on crop evapotranspiration (ETc) as 0.8 ETc, 0.9 ETc, 1 ETc, and 1.1 ETc. It was found that cabbage crop performed better with the microsprinkler system than the drip system. All the growth‐ and yield‐contributing characters in the microsprinkler irrigation method were significantly superior over drip irrigation. The maximum yield of cabbage was obtained by the microsprinkler method (37 t ha−1) with irrigation scheduling at 1 ETc followed by 0.9 ETc (35.5 t ha−1). However, highest water use efficiency (114 kg ha−1 mm−1) was obtained in drip irrigation with 0.9 ETc irrigation level, and the highest net income per mm of water (Rs 622) was obtained in drip irrigation with 1 ETc irrigation level. Microsprinkling gave 7.30% more yield of cabbage than the drip method, whereas the drip method saved 32% more water than the microsprinkler method. It is therefore recommended to adopt the microsprinkler irrigation method to obtain a potential yield of cabbage. However, when water is a limiting factor, it is recommended to grow cabbage with the drip irrigation method.