ETc Irrigation Research Articles

Response of Durum Wheat to Deficit Irrigation

Deficit irrigation trial has been conducted to see the response of durum wheat to the extent of deficit irrigation at Debre Zeit research center for three successive seasons from 2016 to 2018. Establishment irrigations were given for all plots after swing and irrigation water application events were monitored using long term meteorological data and soil moisture readings. Irrigation water application depths (amount of water applied) were calculated from cumulative crop evapotranspiration (ETc) values in a given period and plots were irrigated with depths that was replenish 100 %, 75%, and 50 % of the cumulative ETc as per the treatment to be applied. Measured amount of irrigation water applied to every plot measured by using 3 inch Parshall flume. Results indicated those grain yields significantly affected by deficit irrigation levels and furrow irrigation methods. The highest mean grain yield of 5.8 t/ha attained from 75% ETc irrigation level with alternate furrow irrigation method while the lowest mean yield of 3.989 t/ha was obtained from treatment irrigated with 50% ETc and conventional furrow irrigation method. Therefore, based on the current findings, the highest grain yield was obtained at 75% ETc with alternate furrow irrigation system while the highest WUE was recorded at irrigating 100% ETc with alternate furrow system.

Response of Malt Barley (<i>Hordeum distichum L.</i>) to Different Phosphorus Fertilizer Rates and Irrigation Levels Under Furrow Irrigation Methods in South Eastern Ethiopia

Nutrient availability to crops is a function of soil type, moisture condition, environment, crop type, and management and their interaction affects nutrient use efficiencies and crop growth conditions. The objective of this study was to determine the optimum P rate and deficit irrigation level, as well as to identify the interactive effect of nutrient and moisture levels on yield and yield quality malt barley under irrigation in Ormiya region Tiyo district. The experiment was conducted at small plot level for three consecutive years from 2020/21 to 2022/23 G.C. This experiment was conducted at Kulumsa Agricultural Research Center On-Station arranged by split-plot layout with RCBD design by three replications. Irrigation amounts (100%, 75% and 50%) were assigned the main plot and phosphorus fertilizer rates (0, 10, 20, 30 and 40 kg) corresponded to the subplot. The combined effect of irrigation levels and phosphorus fertilizer rate had a significant effect (p < 0.05) on malt barely grain yield, above-ground biomass, thousand kernel weight and water productivity but not on plant height, seeds per spike and protein content. The highest grain yield and above-ground biomass were 3.16 t/ha and 6.77 t/ha obtained from the application of 100% ETc with 30 kg of phosphorus fertilizer. The maximum water productivity (0.97 kg/m<sup>3</sup>) was observeat the application of 75% ETc with 30 kg of Phosphorus fertilizer while more profitable practice was found at 100% ETc with 30 kg of phosphorus application. The highest protein content (15.57%) was observed at the application of 50% deficit irrigation and the lowest (14.66%) was observed at 100% ETc irrigation application. Applying the optimum amount of irrigation with 30 Kg phosphorus fertilizer gives high grain and above biomass yield and is economically profitable in Tiyo district and agroecologies similar to Tiyo.

Quantitative Relationship of Plant Height and Leaf Area Index of Spring Maize under Different Water and Nitrogen Treatments Based on Effective Accumulated Temperature

To optimize the growth management of spring maize, it is essential to understand the dynamics of plant height and leaf area index (LAI) under controlled water and nitrogen supply. This study conducted two-year field experiments (2022–2023) in Karamay, Xinjiang. Three irrigation levels (75%, 100%, and 125% of Crop Evapotranspiration (ETc)) and four nitrogen application rates (0, 93, 186, and 279 kg N/ha) were set. A logistic growth model was fitted using accumulated effective temperature as the independent variable to analyze the growth and development characteristics of spring maize under various water and nitrogen conditions. The results demonstrated that the logistic models, based on relative effective accumulated temperature, had a determination coefficient (R2) of over 0.99 and a Normalized Root Mean Square Error (NRMSE) of less than 10%. Irrigation extended the rapid growth phase of plant height, whereas nitrogen application shortened the time to enter this rapid growth phase and prolonged its duration. Irrigation increased the maximum LAI growth rate and shortened and prolonged the rapid growth phase, while nitrogen extended the duration of the rapid growth phase for LAI. The W2N2 treatment, consisting of 100% ETc irrigation and 186 kg N/ha, was identified as the optimal drip irrigation water–nitrogen combination for spring maize in the study area. Under optimal water and nitrogen supply, both the maximum growth rate and the average growth rate during the rapid growth phase were higher, requiring accumulated effective temperatures of 825.16–845.74 °C·d and 856.68–890.00 °C·d, respectively, to reach these rates. The appropriate water and nitrogen supply significantly enhanced the synergistic promotion of growth and development in spring maize. This study provides a theoretical basis for the quantitative analysis of growth dynamics in summer maize using effective accumulated temperature.

Drip fertigation and crop management in Bt cotton (Gossypium hirsutum)

A field experiment was conducted during the rainy season of 2014 and 2015 at Rahuri, Maharashtra, to study the effect of deficit irrigation, fertigation and planting techniques on growth, yield and quality parameters of Bt cotton (Gossypium hirsutum L.). Scheduling of irrigation at 1.0 ETc recorded significantly maximum growth, yield attributes and seed-cotton yield of Bt cotton, being at par with 0.8 ETc irrigation regime. Maximum and significantly higher seed-cotton yield was recorded in 1.0 ETc irrigation regime (3.3 t/ha), being at par with 0.8 ETc irrigation regime (3.1 t/ha) on pooled mean basis. Planting of Bt cotton at 90 cm × 90 cm was found superior to 150 cm × 60 cm in respect of growth, yield attributes and seed-cotton yield of Bt cotton. Planting of Bt cotton at 90 cm × 90 cm resulted in significantly higher seed-cotton yield (3.3 t/ha) than 150 cm × 60 cm planting (2.3 t/ha) on pooled mean basis. Fertigation of 100% GRDF up to 100 days + 20 kg MgSO4 /ha and 25 kg ZnSO4 /ha up to flowering at weekly interval + foliar spray of Fe (1.0 %) and B (0.5 %) at flowering and boll-development stages was found suitable for achieving the maximum growth, yield attributes and seed-cotton yield (3.1 t/ha) of Bt cotton. The maximum water use efficiency was obtained with 0.6 ETc irrigation regime (7.00 kg/ha-cm), followed by 0.8 ETc irrigation regime during both the years.

Effect of Tillage and Mulching on Growth and Yield Performance of Barley under Different Nitrogen and Irrigation Application Rates

Background: Integrated management of soil, water and nutrient resources is critical in improving animal feed production sustainably as it is highly resource demanding. Barley is considered as an excellent choice for animal feed owing to its rich nutritional composition, energy content, palatability, versatility and economic feasibility. Implementing sustainable crop management practices that improve soil health as well as enhance water and nitrogen availability is critical for improving crop productivity and ensuring improved animal feed production in these challenging environments. In arid regions with scarce water resources and less fertile soil, an interplay between water availability and nitrogen fertilization plays a significant role in enhancing barley production. Thus adoption of conservation agricultural practices coupled with optimized irrigation and fertilization regime is crucial in establishing sustainable animal feed production in the region. However, much insight is not delivered in the area of interactive effects of irrigation and fertilization with conservational agricultural practices on sustainable intensification of animal feed production in arid and semi-arid lands. The study investigated the interactive effect of tillage, mulching, irrigation and nitrogen application rates on growth and yield performance of barley under Kuwait’s environmental conditions. Methods: The study was conducted at KISR Station for Research and Innovation-KSRI (29.3156°N, 47.8403°E), Kuwait. The effect of tillage and mulching on the growth and yield performance of barley was evaluated under combinations of three different irrigation (100% ETc, 75% ETc and 50% ETc) and fertilization application rates (0 kg/ha, 50 kg/ha and 100 kg/ha). Split-split plot experimental design was employed with three replications to study the effect of different treatments on plant height, number of plants per square meter, spike length, number of spikes per square meter, biomass yield, grain weight, harvest index and residue yield. Result: Tillage, mulching, irrigation and fertilization application rates imposed a significant interaction effect on barley biomass and grain yield. Minimum tilled plots with mulching under 100% ETc irrigation and 100 kgN/ha recorded the highest biomass and residue yield. For grain yield, minimum as well as conventional tillage with mulching produced the highest value under 100% ETc irrigation and 50 kgN/ha. Highest plant height and number of spikes per square meter was noted in plots with minimum tillage and mulching under 100% ETc irrigation.

Water strategy improves the inflorescence primordia formation of 'Arra 15' grapevine in the Brazilian semiarid region

Failure in irrigation management of grapevines grown in the Brazilian semiarid region can affect bud fertility. Adequate irrigation, considering both the development of bunches in the current cycle and the formation of fertile buds for subsequent cycles, can bring significant advances to viticulture. Therefore, the objective of this research was to investigate the effect of different irrigation levels during flowering on the formation of buds and potential bunches of 'Arra 15' grapevine and its relationship with metabolic processes. A field experiment was carried out in a commercial vineyard in Petrolina, Pernambuco, Brazil, during the 2021 and 2022 seasons. The experiment was designed in randomized blocks with four replications and five irrigation levels (70; 85; 100; 115 and 130% of crop evapotranspiration – ETc) during three production cycles. The variables fertile bud, vegetative bud, dead bud, potential fertility of the basal, median, and apical regions of the branches, number of potential bunches, reducing sugar, total soluble sugar, net photosynthesis, stomatal conductance, transpiration, and relative chlorophyll index were evaluated. The 115% ETc irrigation level improved the number of fertile buds and number of potential bunches. Irrigation level above 115% ETc increased gas exchange and relative chlorophyll index, while 70% ETc increased leaf sugar content. The most appropriate irrigation strategy is the application of 115% ETc during the flowering stage, for the increase of fertile buds and potential bunches of the next cycle, without influencing the vine metabolism. Total soluble sugars are a promising indicator of water deficit during flowering and as an indicator of vegetative bud formation for the next cycle.

Optimizing Nitrogen Fertilization for Barley Crop at Full and Deficit Irrigation in the Arid Region

Background: Nitrogen and water are two major limiting factors that affects the growth and yield of barley. Optimization of nitrogen application is crucial in enhancing barley yield and nitrogen use efficiency while minimizing the negative effects of its intense application on human health and the environment. However, the crop yield response to nitrogen application rates differ under different irrigation conditions owing to the complementary relationship between nitrogen and water. Therefore, it is vital to study the impact of different nitrogen application rates on improving barley growth and yield under full as well as deficit irrigation to select the best field management option, thereby enhancing sustainable agriculture. Methods: The present study investigated the impact of three nitrogen application rates [0 (control), 50 and 100 kgN/ha)] at two irrigation rates corresponding to 100% and 75% crop evapotranspiration (ETc) on the growth, yield and nitrogen use efficiency of barley. Stable isotopic technique was used to determine the nitrogen use efficiency. Result: The nitrogen application rate enacted a significant impact on plant height, number of plants/m2, number of spikes/m2, biomass yield and nitrogen use efficiency; whereas irrigation rates significantly affected the plant height, number of plants/m2, spike length, number of spikes/m2, biomass yield, grain and straw yield. In addition, a significant interaction between irrigation and nitrogen was observed for all the studied parameters except plant height, spike length, straw yield and total nitrogen uptake. The deficit irrigation 75% ETc with 50 kgN/ha presented the highest nitrogen use efficiency (37.56%), but the total biomass yield was reduced by 37% in comparison to 100% ETc irrigation. Thus irrigation and fertilization combination of 100% ETc with 50 kgN/ha was identified as the best irrigation and fertilization practice producing highest biomass yield, grain yield and straw yield in barley with a nitrogen use efficiency of 20.48%.

Increasing Water Use Efficiency of Irrigated Rice through Water Saving Techniques in Yobe Basin, North East, Nigeria

Increasing world population and dwindling water resources is exerting pressure to develop strategies for producing more food using less water.
 Aims: To investigate the effect of different irrigation schedules on grain yield and water use efficiency (WUE) of FARO 44 rice variety.
 Study Design: The research was laid out in a split plot arrangement. Twelve treatments replicated three time comprising of 3 irrigation intervals as main plot and 4 irrigation depth as sub plot.
 Place and Duration of Study: Gashua, Yobe State on the floodplains of river Yobe, Nigeria between March 2023 and July 2023.
 Methodology: Comprised of 3, 5 and 7 days irrigation intervals as main plot, with irrigation depth (amount) at 100% of crop water requirement (ETc), 85% of ETc, 70% of ETc and the farmers flooding practice as the sub plot treatments. Some growth, yield and components of the rice were determined. Reference evapotranspiration (ETo) and Crop evapotranspiration (ETc) were computed using Cropwat model. Crop and irrigation water use efficiencies were also calculated.
 Results: The 3 days irrigation interval produced the maximum growth parameters of rice along with both application of 100% of crop water requirement and the traditional flooding type of irrigation. The interaction of 3 days irrigation interval and 100%ETc and 85% of ETc significantly produced the highest grain yield (6484.85 kg ha-1.) 3 and 5 days irrigation interval with 100% and 85% of ETc irrigation depths significantly produced the highest water use efficiencies. A well fitted linear relationship (R2 = 0.834) existed between the irrigation scenarios and the rice grain yield.
 Conclusion: It can be concluded that irrigation frequency and amount can be reduced to arrive at highly acceptable yield in the study area. High rice yield can be maintained with 3 days irrigation interval and 85% of the crop water requirement and also improve its water use efficiency.

Effect of Deficit Irrigation on Wheat (Triticum aestivum L.) Yield and Water Use Efficiency in the Semi-Arid Region of Awash Basin, Ethiopia

Crop production is largely limited by water availability in arid and semi-arid regions of Ethiopia. Changing climate conditions and declining water resources demand appropriate approaches to improve crop yield and water use efficiency through a reduced and more reliable water supply. A field experiment was conducted to evaluate the effect of limited irrigation water use on bread wheat production and water use efficiency under the semi-arid climate conditions of Awash basin of Ethiopia. Five irrigation levels, that is, full irrigation (100% ETc/control), 85% ETc, 70% ETc, 55% ETc, and 40% ETc, were evaluated using a randomized complete block design (RCBD) with four replicates. Statistical analysis has shown a significant effect of irrigation levels on wheat grain yield, water use efficiency, economic profit, wheat grain quality, and aboveground biomass. The highest grain yield (5,085 kg ha−1) was obtained from 100% ETc irrigation application (i.e. 417.2 mm of water), and the lowest grain yield was obtained from 40% ETc (i.e. 223.7 mm of water) application. A deficit level of 85% ETc resulted in a yield that was comparable to that of full irrigation. Compared to other treatments, the 70% ETc application produced the highest water use efficiency (1.42 kg m−3). Using the saved water obtained from 70% ETc deficit irrigation application, 23.4% more wheat could be produced on 1.38 ha of land, resulting in the highest profit (US$2,563.9) and higher MRR (137%). The yield response factor and crop-water production function indicated that maintaining irrigation at optimal levels can prevent potential yield reductions. Consequently, a 70% ETc deficit irrigation application was found to be optimal for increasing wheat grain yield, water use efficiency, and economic benefits from irrigated wheat production. These results suggest that deficit irrigation for wheat under semi-arid climatic conditions is a viable irrigation management option for enhancing water use efficiency.

Maximizing irrigation water use and crop productivity under mulching with geotextile for lettuce plants (Lactuca sativa L. var. capitata)

One of the fields that will be negatively impacted by climate change is agriculture, particularly in developing countries. Most crops are affected when grown under limited water supplies as it produces low productivity, especially during the late growing stage. For this reason, it is important to improve irrigation efficiency and crop yield. Two successive seasons were conducted during 2021 and 2022 to test the action of mulching types on iceberg lettuce plants (Lactuca sativa L. var. capitata) with irrigation stress. In the sandy loam soil conditions of the El Sharkia Governorate in Belbeis, Egypt, iceberg lettuce plants were grown with different types of mulching (no mulching, white geotextile sheet, and black plastic sheet) under varying levels of water (100, 80, and 60% of ETc, or evapotranspiration). Results showed that mulching the soil surface with plastic and geotextile produced the highest data of soil moisture content inside the root zoon. In conclusion, compared to the control (no mulching), all mulching types treatments result in a significant increase in yield parameters. In this study, however, mulching with white geotextile sheets and requiring 100% ETc irrigation proved to be the statistically most effective treatment, while 80% ETc combined with white geotextile sheet get values were statistically equal to the results with the control (100% ETc without mulching). It is possible to achieve results similar yield to the control or better, while saving an amount of irrigation water of up to 20% by using ETo 80 % combined with mulching with white geotextile sheet without any negative effect on the plant. However, it can be recommended to use geotextile compared to black plastic, as plastic requires more time to degrade, which will be harmful to the environment.

Nitrogen reduction combined with ETc irrigation maintained summer maize yield and increased water and nitrogen use efficiency.

High rainfall and excessive urea application are counterproductive to summer maize growth requirements and lower grain yield and water/nitrogen (N) use efficiency. The objective of this study was to determine whether ETc irrigation based on summer maize demand and reduced nitrogen rate in the Huang Huai Hai Plain increased water and nitrogen use efficiency without sacrificing yield. To achieve this, we conducted an experiment with four irrigation levels [ambient rainfall (I0) and 50% (I1), 75% (I2), and 100% (I3) of actual crop evapotranspiration (ETc)] and four nitrogen rates [no nitrogen fertilizer (N0), recommended nitrogen rate of urea (NU), recommended nitrogen rate of blending controlled-release urea with conventional urea fertilizer (BCRF) (NC), and reduced nitrogen rate of BCRF (NR)] in 2016-2018. The results show that reduced irrigation and nitrogen rate reduced Fv/Fm, 13C-photosynthate, and nitrogen accumulation both in the kernel and plant. I3NC and I3NU accumulated higher 13C-photosynthate, nitrogen, and dry matter. However, 13C-photosynthate and nitrogen distribution to the kernel was decreased from I2 to I3 and was higher in BCRF than in urea. I2NC and I2NR promoted their distribution to the kernel, resulting in a higher harvest index. Compared with I3NU, I2NR increased root length density by 32.8% on average, maintaining considerable leaf Fv/Fm and obtaining similar kernel number and kernel weight. The higher root length density of I2NR of 40-60 cm promoted 13C-photosynthate and nitrogen distribution to the kernel and increased the harvest index. As a result, the water use efficiency (WUE) and nitrogen agronomic use efficiency (NAUE) in I2NR increased by 20.5%-31.9% and 11.0%-38.0% than that in I3NU, respectively. Therefore, 75%ETc deficit irrigation and BCRF fertilizer with 80% nitrogen rate improved root length density, maintained leaf Fv/Fm in the milking stage, promoted 13C-photosynthate, and distributed nitrogen to the kernel, ultimately providing a higher WUE and NAUE without significantly reducing grain yield.

Optimization of Water Management for Green Pepper Production in a Water-Limiting Tropical Savanna Agroecological Zone Based on Crop Water Productivity

This study aimed to determine the optimum levels of irrigation regime and irrigation schedule based on crop water productivity for the sustainable production of green pepper in a water-limiting tropical savannah agroecological zone. The study was conducted at the Hydro Farm of MotorKing Company Limited in the Tamale Metropolis, Northern Region, Ghana. The experimental design was a 2 × 3 factorial experiment laid out in a randomized complete block and replicated five times. Irrigation schedule at two levels (one-time daily application and split daily application at 60% morning and 40% evening) and irrigation regime at three levels (100% ETc, 80% ETc, and 60% ETc) were the factors. The “Yolo Wonder” variety of green pepper was the test crop. The crop was planted at a planting distance of 0.3 m within rows and 0.5 m between rows. Treatments were applied using a drip irrigation system. Crop water requirements (ETc) of green pepper were estimated using the CROPWAT model. Crop yield and water applied under each treatment were determined. Crop yield was measured at harvest as the total weight of fruits per hectare. Crop water productivity was determined under each treatment as crop yield per unit of water consumed. Data analysis was done in Genstat (12th edition). Analysis of variance (ANOVA) and Duncan’s multiple range test at 5% level of significance were employed to separate differences in treatment means. The results suggest that both irrigation regime and irrigation schedule have significant influence on the yield and crop water productivity of green pepper. Irrigating at 60% ETc and split irrigation (60% morning and 40% evening) gave significantly higher yields and crop water productivity compared to the other levels of the factors. This study demonstrated that irrigation schedule and irrigation regime are important factors to consider in the optimization of water management for green pepper; however, further research is needed to identify the optimal levels of these factors and the most effective irrigation strategies for the crop in different environments.

Effects of Different Irrigation Levels and Fertilizer Rates on Yield, Yield Components and Water Productivity of Onion at Adami Tulu Agricultural Research Center

Today’s agriculture sector faces a complex series of challenges to cope with the demands for sustainable management and production, which entails an increase in food production to ensure food security while using less water per unit of output and reducing nitrogen (N) fertilizer losses through leaching. The experiment was conducted at Adami Tulu Agricultural Research Center on-station to study the effect of different irrigation levels and N-fertilizer rates on plant height, bulb yield, bulb diameter, and bulb height and water productivity of onion. The treatments of the experiment had factorial combinations of three levels of watering and four N-fertilizer amounts. Results indicated that the highest plant height (53.07 cm), bulb height (6.13 cm), bulb diameter (6.21 cm), marketable bulb yield (241.39 qt/ha) and total bulb yield (252.89 qt/ha) were obtained from full irrigation and fully N-fertilized compared to the deficit conditions. The highest water productivity was recorded from 60% ETc irrigation level and 150 Kg/ha N-fertilizer application rate, but the reduction in water productivity with 80% ETc and 150 Kg/ha N-fertilizer application rate was not significant. Hence, if water is not limiting factor, 100% ETc irrigation level and 150 Kg/ha N-fertilizer could be suggested to apply. But if water becomes 232 limiting factor, 80% ETc irrigation level with 150 Kg/ha N-fertilizer would be more appropriate for growing onion in the study area. Therefore these can be used as one package of onion production technology and all growers better to apply.

Effect of drip irrigation regimes on growth, yield and economics of maize (Zea mays) genotypes

A field experiment was conducted during summer 2018 and 2019 to study the performance of maize (Zea mays L.) genotypes under drip and furrow irrigation regimes at the Main Agriculture Research Station, University of Agricultural Sciences, Dharwad, Karnataka. The experiment was laid out in strip plot design with 3 replications. Treatments included 4 irrigation levels (drip irrigation at 0.6 ETc, 0.8 ETc and 1.0 ETc and furrow irrigation at 0.8 IW/CPE ratio) and 4 maize genotypes. The data indicated that, furrow irrigation at 0.8 IW/CPE ratio and drip irrigation at 1.0 ETc recorded significantly higher and on par growth and yield parameters, grain yield (75.8 q/ha and 71.4 q/ha, respectively) and economic returns. Drip irrigation at 1.0 ETc consumed 28.6% less water but recorded significantly higher water productivity over furrow irrigation. Among the genotypes, NK-6240 found superior over rest of the genotypes. The combination of furrow irrigation with NK-6240 recorded significantly higher growth and yield attributes as well as grain yield and economics over rest of the combinations. However, this treatment remained statistically non-significant with drip irrigation at 1.0 ETc with NK-6240 and furrow irrigation with CP-818.

Combined Impact of Irrigation, Potassium Fertilizer, and Thinning Treatments on Yield, Skin Separation, and Physicochemical Properties of Date Palm Fruits.

Orchard cultural practices, i.e., irrigation, fertilizer, and fruit thinning, are crucially encompassed to enhance fruit yield and quality. Appropriate irrigation and fertilizer inputs improve plant growth and fruit quality, but their overuse leads to the degradation of the ecosystem and water quality, and other biological concerns. Potassium fertilizer improves fruit sugar and flavor and accelerates fruit ripening. Bunch thinning also significantly reduces the crop burden and improves the physicochemical characteristics of the fruit. Therefore, the present study aims to appraise the combined impact of irrigation, sulfate of potash (SOP) fertilizer, and fruit bunch thinning practices on fruit yield and quality of date palm cv. Sukary under the agro-climatic condition of the Al-Qassim (Buraydah) region, Kingdom of Saudi Arabia. To achieve these objectives, four irrigation levels (80, 100, 120, and 140% of crop evapotranspiration (ETc), three SOP fertilizer doses (2.5, 5, and 7.5 kg palm-1), and three fruit bunch thinning levels (8, 10, and 12 bunches palm-1) were applied. The effects of these factors were determined on fruit bunch traits, physicochemical fruit characteristics, fruit texture profile, fruit color parameters, fruit skin separation disorder, fruit grading, and yield attributes. The findings of the present study showed that the lowest (80% ETc) and highest (140% ETc) irrigation water levels, lowest SOP fertilizer dose (2.5 kg palm-1), and retaining the highest number of fruit bunch per tree (12 bunches) had a negative effect on most yield and quality attributes of date palm cv. Sukary. However, maintaining the date palm water requirement at 100 and 120% ETc, applying SOP fertilizer doses at 5 and 7.5 kg palm-1, and retaining 8-10 fruit bunches per palm had significantly positive effects on the fruit yield and quality characteristics. Therefore, it is concluded that applying 100% ETc irrigation water combined with a 5 kg palm-1 SOP fertilizer dose and maintaining 8-10 fruit bunches per palm is more equitable than other treatment combinations.

Effect of deficit irrigation and soil fertility management on wheat production and water productivity in the Upper Blue Nile Basin, Ethiopia

In the Ethiopian Upper Blue Nile Basin, like in other regions in the world, agricultural productivity is declining due to water scarcity owing to longer dry seasons coupled with soil acidity−induced fertility problems. Wheat is one of the major food security crops in Ethiopia but its productivity is reduced due to water scarcity, especially during the irrigation season. Addressing these problems might be essential to increase productivity. This study explores the effect of deficit irrigation (DI) combined with lime, manure and inorganic fertilizer on wheat production and water productivity (WP) in the Koga irrigation scheme, Ethiopia. Four levels of DI strategies (100% ETc or 0% deficit as a control, 80%, 60% and 50% ETc) were applied for two irrigated seasons. Five levels of soil fertility management were applied for four consecutive cropping seasons: (i) 0.86 t ha−1 lime combined with 3 t ha−1 manure and full dose urea and NPS−B (hereafter referred to as inorganic fertilizer) (L3); (ii) 1.15 t ha−1 lime combined with 3 t ha−1 manure and full-dose inorganic fertilizer (L2); (iii) 1.43 t ha−1 lime combined with 3 t ha−1 manure and full dose inorganic fertilizer (L1); (iv) 3 t ha−1 manure combined with full dose inorganic fertilizer (M); and (v) full dose inorganic fertilizer alone (C). The grain yield and biomass data were collected at harvest from a sample area of 2 m × 3 m from each plot with three replicates. The effect of DI and liming, as well as manuring on average grain yield and biomass, were highly significant. Under all irrigation scenarios, higher grain yield and biomass were found at L1, L2, L3 and M (in that order), compared with C. The highest WP was obtained at 50% ETc irrigation dose, compared with 60%, 80% and 100% ETc (in that order). Yet, the lowest WP was found at C under all irrigation scenarios compared with L1, L2, L3 and M. The WP increased when the amount of water supply decreased and liming doses increased. The application of full dose lime and manure combined with 50% ETc DI resulted in comparable grain yield, biomass and WP as 100% ETc full irrigation at L3 and M. It could be concluded that liming and manuring could be used to mitigate the yield penalty effect of DI in the study area. In scenarios where farmers have to pay for water, profitability rises as the irrigation water supply reduces. Thus, under such conditions, a 50% ETc irrigation scenario is more profitable than scenarios with 60%, 80% and 100% ETc irrigation.

Water consumption, soil nitrate-nitrogen residue and fruit yield of drip-irrigated greenhouse tomato under various irrigation levels and fertilization practices

The excessive irrigation and chemical fertilizer application in the greenhouse can lead to resources waste, environmental pollution and instable or even reduced fruit yields. A four-season experiment was conducted with three irrigation levels (W1, 100%ETc; W2, 75%ETc; W3, 50%ETc, where ETc was the crop evapotranspiration) and five fertilization practices (CC, chicken manure and chemical fertilizer; SO, only soluble organic fertilizer; SC, only soluble chemical fertilizer; SOSC, soluble organic and chemical fertilizer; CK, a control with no fertilizer) to explore their integrated effects on the growth, water consumption, soil nitrate-nitrogen residue and fruit yield of drip-fertigated greenhouse tomato. The results showed that the root shoot ratio in autumn (3.21 ×10−2) was greater than that in spring (2.05 ×10−2). Fruit dry matter had the most significantly positive relationship with fruit yield in both autumn and spring seasons; however, leaf dry matter, stem dry matter and leaf SPAD had significantly positive relationship with fruit dry matter only in autumn. The average fruit yield over the four growing seasons was 70.68, 67.16 and 62.66 t ha−1 under W1, W2 and W3, respectively. The SOSC increased plant height, dry matter, leaf SPAD and fruit yield of tomato and reduced soil nitrate-nitrogen residue (0–60 cm), while both SO and SOSC obtained greater root shoot ratio. Both SC and SOSC showed greater water consumption at the seedling stage, blooming and setting stage than CC; however, the water consumption at the harvest stage under both SO and SOSC was greater than that under SC. Under W1, plant overgrowth occurred under SC, resulting in lower fruit yield. The difference in fruit yield between CC and SC reduced with the increasing water stress. Overall, the combination of soluble organic and chemical fertilizer along with 100%ETc irrigation (W1SOSC) was more conducive to promoting tomato yield (73.40 t ha−1) and reducing soil nitrate-nitrogen residue , while the combination of soluble organic and chemical fertilizers along with 75%ETc irrigation (W2SOSC) had the potential of achieving water-saving greenhouse tomato production in arid and semiarid regions.

Effect of Partial Root Drying and Deficit Irrigation on Yield and Water Use Efficiency of Tomato Grown Under Greenhouse

Water conservation strategies are becoming increasingly important as a result of the shortage of water and climate change. The purpose of this study is to address water-saving irrigation strategies by evaluating the effect of partial root drying irrigation (PRD) and Deficit Irrigation (DI) practice on the yield and water use efficiency of tomatoes (Shivam variety). The treatments were partial root drying (PRD) at 75% and 50% crop evapotranspiration, ETc (PRD25 and PRD50, respectively), and deficit irrigation (DI) at 75% and 50% of ETc (DI25 and DI50, respectively). The PRD practice requires wetting one half of the root zone and keeping the other half dry, consequently using less amount of irrigation water that was applied. In the successive irrigations, the wet and dry sides were alternated. Over a growing season after transplanting, the highest fruit yield was obtained under FULL irrigation (225 t ha-1). In comparison to deficit irrigation that received the same quantity of water, the PRD treatments produced an increased yield of 5–10%. PRD and DI irrigation improved WUE considerably, and that was 30.35% and 25.71% respectively higher than FI. Results suggest that PRD treatment may be an option in a water shortage.

Variety specific irrigation of almonds during hull split, effects on yield and quality

Regulated deficit irrigation (RDI) during hull-split can reduce water applied in almond orchards. Strategies for imposing RDI in almond orchards with multiple varieties with different hull-split schedules have not been extensively developed. Commonly, irrigation system design requires the same irrigation schedule for all varieties in the orchard. A 2-year study evaluated the impacts of two different regulated deficit irrigation strategies in an almond orchard with Butte, Aldrich, and Nonpareil varieties in the Sacramento Valley of California, USA. The two strategies were (1) RDI in all varieties during Nonpareil hull-split timing and (2) RDI according to variety-specific hull-split timing. The two levels of irrigation were 50 % and 75 % of potential crop evapotranspiration (ETc) replacement during the hull-split period. Results show that the kernel thickness of the Aldrich almonds increased under 75 % ETc irrigation replacement during the Aldrich hull-split period compared to 75 % ETc and 50 % ETc irrigation replacement during the Nonpareil hull-split period. In the Butte almonds, 75 % ETc and 50 % ETc irrigation replacement during variety-specific hull-split reduced the fraction of sealed shells of the Butte variety compared to 75 % ETc and 50 % ETc irrigation replacement during the Nonpareil hull-split period. This study demonstrated that an irrigation system design that allows for the independent irrigation scheduling of each variety can change the almond physical quality in the Butte and Aldrich varieties. RDI according to variety-specific hull-split did not result in significant marketable kernel yield improvements after two years of imposing the irrigation strategies. More research should be conducted for different orchard designs, varieties, and climates.

Maize response to coupled irrigation and nitrogen fertilization under center pivot, subsurface drip and surface (furrow) irrigation: Soil-water dynamics and crop evapotranspiration

Determination of crop evapotranspiration (ETc) and root zone soil-water dynamics/distribution coupled with nitrogen (N) management strategies is important for effective management of agricultural fields for enhancing production efficiency. However, limited data and knowledge exist that sufficiently inform how soil-water dynamics and ETc response may vary with coupled irrigation levels and different N application timings under different irrigation methods. Extensive field experiments were conducted in 2016 and 2017 under center pivot (CP), subsurface drip irrigation (SDI), and furrow irrigation (FI) at full irrigation treatment (FIT), 80% FIT, 60% FIT, and rainfed treatment (RFT) with N application timing treatments of traditional N (TN), non-traditional-1 (NT-1), and non-traditional-2 (NT-2) to quantify and compare seasonal maize (Zea mays L.) grain yield, soil-water dynamics, ETc, and ETc vs. seasonal irrigation and total water supply relationships. Soil-water status and plant water extraction exhibited substantial differences between the irrigation levels and N management and with the irrigation methods. Irrigation method significantly (p < 0.05) influenced ETc. CP had significantly higher ETc than SDI; and SDI had significantly higher ETc than FI. The NT-1 and NT-2 treatments had significantly higher ETc than TN. ETc was greatly influenced by the water availability more than N timing applications. The slope of maize ETc exhibited inter-annual and intra-annual variation between N treatments, irrigation methods, and years. CP had higher slope than FI and SDI and FI had higher slope than SDI under traditional and NT N management in both years (except NT-2 at SDI in 2017). These important findings can provide guidance to improve maize production efficiency by considering the coupled irrigation and N management strategies under different irrigation methods.