Full Water Requirement Research Articles

Humic acid application on soil stability indices and enzyme activity at different bell pepper water requirements

Use of organic materials helps in reducing the consumption of chemical fertilizers, contributing to the sustainability of agricultural ecosystems. Humic acid can improve soil structure, especially in soils with low clay content, aiding in water retention and enhancing water absorption by plants. This characteristic has led to the attention of humic acid application in drought stress, particularly in arid soil regions. The present study aimed to investigate the simultaneous effects of humic acid and plant water requirements on the physical and biological properties of soil under bell pepper cultivation. The factorial experiment was conducted in a completely randomized block design with three levels of humic acid: 0 (HA0), 2 (HA2), and 4 (HA4) g/Kg of soil and four levels of plant water requirements: 60 (L60), 80 (L80), 100 (L100), and 120 % (L120), with four replications under greenhouse conditions. Bell pepper seedlings were transferred to 10 Kg pots after applying humic acid treatments and after the establishing of seedlings, plant water requirement treatments were applied for 80 days. During this period, plants were maintained at a temperature of 25 degrees Celsius during the day, 18 degrees Celsius at night, and a relative humidity of 75%, with a carbon dioxide concentration of 80 milligrams per liter. The results of this study showed that treatments L80HA4, L100HA4, and L120HA4 had the most significant impact on improving soil physical properties, such as normal stability index, total soil stability index, mean weight diameter of soil particles, soil particle stability, geometric mean diameter of soil particles, and reduction in soil particle destruction percentage. The highest values of wet and dry weight diameter of soil particles were observed in treatment L100HA4, which were 42.92%, 74%, and 67.01% higher, respectively, compared to the control (L60HA0). In contrast, the highest percentage of soil particle destruction was observed in treatment L60HA0, showing a 32.90% increase compared to treatment L100HA4. Furthermore, the best performance of bell pepper yield was observed in treatments L80HA4, L100H4, and L120HA4, although the differences between treatments were not statistically significant. The application of humic acid, in addition to improving bell pepper yield, increased water use efficiency and reduced water use. The lowest yield (3283 Kg/ha) and the lowest water consumption (3584 cubic meters/ha) were observed in treatments L60HA0 and L60HA4, respectively. Additionally, the results showed that the highest water use efficiency observed in L80HA4 treatment (7.45 Kg/m³), while the lowest was in L60HA0 treatment (0.80 Kg/m³). Moreover, humic acid significantly influenced the activity of soil enzymes, including soil phosphatase and urease. With more application of humic acid, soil moisture retention, microbial biomass carbon, urease, phosphatases activities increased. However, in treatments with full water requirements and 20 percent more than plant water requirements, enzyme activities decreased.

Foliar Spray with Selenium to Mitigate the Impact of Water Stress on Chemical, Enzymatic, and Hormonal Parameters of Garlic Allium sativum L.

The current research explored the beneficial role of selenium (Se) in alleviating the negative impacts of water stress on the chemical, enzymatic, and hormonal parameters of garlic plants via manipulating chemo-physiological mechanisms. A field experiment was executed at the research station of the Faculty of Agriculture, University of Kufa, Iraq in September 2022 using a randomized complete block design with three replicates based on a strip-plot system. Three water levels (100%, 80%, and 60%) were set up in the whole plots while foliar application of selenium (Se) with three concentrations (0, 10, and 20) mg.L-1 were assigned to the subplots. Our findings revealed a significant increase in the leaf content of free proline acid, sulfur, and ABA, as well as an increase in the activity of the antioxidant enzymes SOD and CAT when reducing irrigation levels from (100% to 60%) of the water requirement. While there was a significant decline in the plant hormones GA3 and IAA content in garlic leaves @ (60%) level of irrigation. The plants treated with foliar selenium @ (20 mg.L-1) enhanced most of the studied characteristics of garlic plants grown at different water levels. Moreover’ the full water requirement in combination with foliar Se @ (20 mg.L-1) provided the highest values of GA3 and IAA which were both comparable to the interaction treatment of water level @ (80%) and foliar Se @ (20 mg.L-1).

Decision-support system for precision regulated deficit irrigation management for wine grapes

Deficit irrigation is often used in the wine grape industry to balance grape yield for optimizing fruit quality for winemaking. Regulated deficit irrigation (RDI) is an irrigation management strategy which applies less water than the full water requirement in some growing phases (e.g. from fruit set to veraison). This study focused on developing a decision-support system for managing precision RDI in vineyards. The system consists of a soil moisture prediction model and an RDI scheduling model developed based on artificial neural networks (ANN). Initial soil moisture, weather variables, crop coefficient, and irrigation amount were used as inputs to the soil moisture prediction model. The output from this prediction model provides an indicator of future water status in soil and vines. Initial soil moisture, weather variables, crop coefficient and desired soil moisture target were used as inputs to the RDI scheduling model for regulating the amount of water applied to achieve a desired soil moisture target which is connected to the grapevine water stress target. Field data were collected weekly during the 2017 to 2021 growing seasons. Data from the first four seasons (2017–2020) was used to train the models, and the 2021 data was used to test the system’s performance. Validation test results showed that the soil moisture prediction model could predict the soil moisture in the following week with an R2 of 0.9325 and RMSE of 0.8609 % m3·m−3, and the RDI scheduling model could estimate the weekly irrigation water amount for maintaining a target soil moisture with an R2 of 0.9413 and RMSE of 8.8518 L per drip irrigation emitter. The results demonstrated that this system was capable of predicting the following-week soil moisture changes and creating an adequate weekly drip irrigation plan for controlling the soil moisture at desired levels. This system could potentially be a useful practical tool for managing RDI in vineyards with the aim of achieving the production goal of balanced yield and optimized fruit quality.

Effect of different managements with drip irrigation (tape)

Conventional irrigation methods to new methods have been altered with respect to reduction of water resources and climate change. Considering the corn cultivation development, applying modern irrigation methods namely drip irrigation with the aim of improving the efficiency of water consumption as well as the zone under cultivation has been investigated. In this research, the performance of corn (SC 704) in various managements of drip irrigation (by strip method) both in single-row and double-row planting patterns was considered with a variety of densities. This test was carried out on random complete blocks in the form of a 3-repetitive Split Design in Isfahan-Iran during the years 2018–2019. Four irrigation levels containing: 80, 100 and 120% of full water requirement with drip irrigation (strip) and 100% of water requirement with normal drip irrigation were utilized. The results indicated that applying the aforementioned drip tapes and different surface treatments with soil and water monitoring, the water consumption of corn seasonal irrigation can be saved by 81, 71, 61, 52 and 36% compared to normal drip irrigation without soil, water and root monitoring, respectively. Seasonal yield (Kc), the yield response coefficient (Ky), and pan coefficient (Kp) for corn were 0.80, 0.76 and 0.97, respectively.

Improved feed forward with bald eagle search for conjunctive water management in deficit region

Due to increasing requirements on water resources and a lower recharge rate, the farming seasons are a vital season for the management of groundwater and surface water resource management. This condition necessitates the use of combined water distribution to meet the full water requirements. Analysis of existing surface water resources and related restrictions, this research suggested an algorithm for aquifer stabilization and fulfilling optimum water requirements. To manage the optimum withdrawals and the subsequent drop, this technique first employed the MODFLOW model for simulating the water levels. Next, an improved feed-forward neural network (IFFNN) was combined with an optimization method to create a machine learning (ML) framework. During the last phase, the findings of the optimized connectives approach as well as the relevant fields technologies to determine using improved bald eagle search with least square SVM(IBES-LSSVM) method that predicted the level of water deficit for every period, especially during farming seasons. This approach is based on an improved bald eagle search (IBES) optimization technique for finding the best settings for a least-squares support vector machine (LSSVM). The findings revealed that between 2005 and 2020, the year with the biggest water deficit was 2018 when only roughly 64 percent of water need was satisfied by groundwater (69 percent) and surface water (64 percent) (33 percent). The water depth may have risen by around 0.7 m during the study period if the optimum model had been used. The outcome of this research will help the management forecast future water shortages and make smarter water strategic choices.

Evapotranspiration Based Irrigation Trials Examine Water Requirement, Nitrogen Use, and Yield of Romaine Lettuce in the Salinas Valley

Cool season vegetables require adequate soil moisture to assure that maximum yield and quality are achieved. On California’s central coast, where the majority of cool season vegetables are produced in the US, long-term overpumping of irrigation water has reduced groundwater levels and led to environmental degradation. Two evapotranspiration (ET) based irrigation field trials were performed near Salinas CA (USA) to determine if ET-based irrigation scheduling could conserve water while producing romaine lettuce (cv. Sun Valley) of commercially viable yield. Sprinklers were used for seed germination and crop establishment. Four drip irrigation treatments were then imposed using a randomized complete block design with six replications. The CropManage decision-support model was used to estimate the full (100%) crop water requirement based mainly on ET replacement. Other treatments included 50% 75% and 150% of the full water requirement. The 100% treatment received 185 mm of water in 2015 and 247 mm in 2016, both of which were well below prior guidance and grower reports. Yields from the 100% and 150% treatments were not significantly different and were similar to industry average, while yields were significantly lower for the 50% and 75% treatments. The 100% treatment had the highest water use efficiency, and the 100% and 150% treatments together had the highest nitrogen recovery efficiency. Irrigation of romaine near the 100% ET replacement level can potentially reduce environmental impacts associated with nitrate leaching and surface runoff.

Effects of regulated deficit irrigation on crop water productivity, yield components, and yield response factor of common bean (Phaseolus vulgaris L)

Due to declining water resources allocated to agriculture and rapid population growth, it is important to use water efficiently and increase crop water productivity (CWP). Deficit irrigation is considered an important strategy to achieve this goal. For this purpose, field experiments were conducted at the research farm of the Agriculture Faculty on Kabul University campus for two continuous years (2018-2019). The experiment consisted of four treatments, including full irrigation (ET100), 80% (ET80), 60% (ET60), and 40% (ET40) arranged in a randomized complete block design with three replications. Compared to ET100 and ET80, the ET60 and ET40 treatments significantly (P<0.05) reduced the duration of flowering and pod formation. The bean crop also showed best performance in plant height, number of leaves per plant, leaf area, leaf area index, number of pods per plant, number of seeds per pod, length of pod, 100-seed weight, and total grain yield in the ET100 and ET80 treatments. Moreover, significantly greater values of crop water productivity (CWP) and lower value of Ky were observed in ET80 compared to ET100, ET60 and ET40. Overall, the experiment results showed that regulated deficit irrigation can effectively increase water productivity. Supplying only 80% instead of full water requirement can result in a higher common bean CWP. This is of particular importance in water-scarce areas, where the water saved based on this practice can be used to irrigate additional acreage.

Performance of the CSM-CROPGRO-soybean in simulating soybean growth and development and the soil water balance for a tropical environment

Continuous monitoring of soil water content is a crucial element for sustainable agricultural water management. The goal of this study was to use the Cropping System Model (CSM)-CROPGRO-Soybean model in conjunction with field data to determine the impact of different irrigation regimes, soil texture, and tillage practices on soybean [Glycine max (L.) Merr.] growth, development, and yield for tropical conditions. Field experiments were conducted at two sites: (i) Piracicaba with conventional tillage (PI-1, season 2016–2017), and no-tillage practices (PI-2, season 2017–2018), where the experiments were irrigated with full water requirements; and (ii) Teresina under conventional tillage (season 2019) with two irrigation treatments of full (TE-1) and 50% (TE-2) water requirements. Soil water content was measured for all experiments using an electromagnetic probe installed at several depths. The results showed that the model was able to simulate soybean growth and development for the different sites, with a very good agreement (D-statistic > 0.8) between the simulated and observed data. In addition, the soil water content was simulated with satisfactory accuracy (D-statistic > 0.5). Following model evaluation, long-term hypothetical scenarios for different soil tillage practices and water management regimes were simulated for Piracicaba and Teresina sites. The results showed that the use of no-tillage could reduce the average amount of irrigation in Piracicaba by 30% and in Teresina by 17%, achieving the same yield level as conventional tillage. Thus, the CSM-CROPGRO-Soybean can be used as a tool for determining optimum water management practices for tropical environments.

Estimation of evapotranspiration and crop coefficient of drip-irrigated orange trees under a semi-arid climate

A sustainable agricultural system requires increasing water use efficiency and enhancing knowledge of crop water use. This prerequisite is more pronounced in the regions with inadequate water resources and limited observational data such as southern Iran. Therefore, this study aimed at finding the water requirement of mature orange trees (Citrus sinensis (L.) Osbeck, cv. Tarocco Ippolito) by identifying standard evapotranspiration rate and crop coefficients (single and dual). Seventy-two orange trees in a drip-irrigated orchard with loam soil were classified into six treatments and irrigated at 100%, 90%, 80%, 70%, 60%, and 50% of reference evapotranspiration rate during 2017 and 2018. Soil moisture variability and crop physiological responses, including stem water potential (Ψstem), net photosynthesis (An), and stomatal conductance (gs) were measured. Our results showed that irrigating at 90% ETo provided the full water requirements of the trees. The mean crop evapotranspiration rate was calculated as 5.2 mm day−1, with the crop coefficient ranging from 0.65 to 0.95. The average irrigation rate performed traditionally in the region was 19% higher than the actual requirement. Analysis of physiological response highlighted the controlling role of stomata in regulating transpiration and maintaining leaf turgor. During the peak water-stress, gs ranged from 0.11 to 0.12 molm−2 s−1 in fully irrigated trees, to 0.04–0.08 molm−2 s−1 in highly stressed trees. Our findings will provide a useful guideline for the local growers and agencies to achieve better irrigation scheduling and higher water productivity for the region.

Physiological responses of orange trees subject to regulated deficit irrigation and partial root drying

Variations in climate, crop, and field conditions have caused different results in applying regulated deficit irrigation (DI) and partial root drying irrigation (PRD) for citrus. In this study field grown, Washington Navel orange trees were exposed to RDI and PRD practices at two reduced irrigation levels: 80% and 50% of full water requirement under a semi-arid climate. Applying DI-80 and PRD-80 resulted in a moderate water stress condition for the experimented trees and saved ~ 15% of the seasonal irrigation without significant yield reduction (~ 3 to 5%). Applying DI-50 and PRD-50 saved up to 40% of the seasonal irrigation, but the trees experienced a severe water stress condition with ~ 28% yield reduction in DI-50 and 19% in PRD-50 trees. The fruit weight was not significantly affected by the irrigation techniques, and the yield reduction in DI treatments was attributed to the fruitlet abscission and the lower number of fruits per tree. A higher leaf water potential, more controlled vegetative growth and greater yield resulted from the trees irrigated at 80% irrigation level. Internal fruit composition was equally enhanced in DI and PRD fruits and was more notable at the 50% irrigation level. A more effective drought management mechanism was found in the PRD-treated trees and was more notable and beneficial in the severe water stress level. In high water stress conditions, the soil water content (SWC) had a more remarkable impact on controlling the stomatal response compared to vapor pressure deficit (VPD), while in low water stress conditions, the effect of VPD was more evident.

The response of sugar beet to different irrigation levels and foliar application of micronutrients under drip irrigation system

The present study was conducted to evaluate the response of sugar beet (Beta vulgaris L.) cv. esperanza to different water levels and foliar application of micronutrients in 2016. Three irrigation regimes were applied; well watered (D1.00), moderate stress (D0.66), and severe stress (D0.33). In each irrigation treatment, there were two different applications as being foliar application of mixed micronutrients and not. The degree of water deficit had significant effects on the growth, root and sugar yield. Decreasing amount of water from D1.00 treatment to D0.33 treatment restricted sugar beet development, and caused plants to be small. The amount of irrigation water and evapotranspiration in the full irrigation treatment were 867 mm and 894 mm, respectively. Therefore, compensating full water requirement and foliar application of micronutrients had a significant effect on the root (13 899 kg da-1) and sugar yield (2 246 kg da-1). It is concluded that full water requirement of sugar beet should be met throughout the entire growing season, but if water scarcity exists water may be saved just only in the ripening period to get an economical yield since during the establishment and vegetative periods of sugar beet was more sensitive to limited water supply.

The Integrated Levels Impacts of Farmyard Manure with Phosphorus Fertilizers and Irrigation on Soil Properties and Wheat Productivity under Saline Soils in North Delta, Egypt

To study the effect of Farmyard manure with or without phosphorus fertilization and irrigation deficit under salt affected soils on yield and yield components of wheat (Triticum aestivum L) and some soil properties as well as productivity of irrigation water (PIW) and economic return an experiment was conducted at North Nile Delta area for two winter seasons (2016/17 and 2017/18). A split-plot complete randomized plot design with three replicates was used. Two irrigation levels, Ifull (50 % moisture depletion) and Id (70 % moisture depletion) occupied the main plots. Farmyard manure (FYM) and two P sources (super phosphate, Ps, and ammonium phosphate, Pa) were applied to the sub-main plots. The results can be summarized as follows:FYM improved wheat productivity. So, FYM increased the grain yield and straw yield by 40.85 and 14.54, %, respectively over the control.The grain yield was increased by 13.25 and 15.90 %, while the increases in the straw yield were 5.19 and 1.71 % in plots received Ps or Pa, respectively. P fertilization combined with FYM was more effective on wheat productivity. Therefore, the application of Ps+ FYM increased the grain and straw yields, by 56.50 and 17.92%, respectively, also the corresponding increases with Pa+FYM were 56.37 and 14.17%, respectively over the control. Irrigation deficit (Id) adversely affected the wheat productivity. Id decreased the grain yield and straw yield, by 11.75 and 5.30 %, respectively compared to Ifull.FYM application with or without P fertilizers were more pronounced relative to P fertilizers individual or untreated soils in reducing the salinity and sodicity of the soil. Data showed 15.62 and 14.26% decreases in ECe for Ps+FYM and Pa+FYM, respectively than untreated soils. The corresponding values of SAR were 8.45 and 8.06%, respectively.Irrigation at 50% soil moisture depletion resulted in decreased ECe (9.70%) and SARe (7.39 %) than irrigation at 70% depletion. The application of FYM with or without P fertilizers resulted in enhancing the HC, AW, SP and buke density comparing to P fertilizers alone or untreated soils especially with the irrigated at 50% soil moisture depletion. FYM application with or without P fertilizers in heavy clay salt affected soils were more pronounced in enhancing PIW and increasing net return and economic efficiency relative to P fertilizers alone or untreated soils especially when irrigated at 50%soil moisture depletion.The maximum net return and economic efficiency for wheat yields were achieved from Ps +FAY under full water requirements.

INFLUENCE OF DEFICIT IRRIGATION AND PARTIAL DRY OF ROOT ZONE ON SQUASH CROP YIELD AND WATER USE EFFICIENCY

The main objectives of this research were to study the effects of sustained deficit irrigation (SDI) and partial drying of root zone (PRD) on yield and water use efficiency of squash (Cucurbita Pepo, L. Oto) crop. To fulfill these purposes, a field study was conducted in the experimental farm of Faculty of Agriculture, at Moshthor, Benha University, Egypt, for the two successive seasons of late summer (2016 and 2017), under both drip surface (DSI) and subsurface irrigation (SSDI) systems. Five irrigation treatments were undertaken. The first (FI-100%) was corresponding to full crop water requirements (FWR), and soil water deficit was replenished to field capacity when 50% of the available water was exhausted, depending on root depth which was predicted by a root depth model. The second treatment was corresponding to 80% of the FWR (SDI-80%), the third one was corresponding to 70% of FWR (SDI-70%), the fourth one was corresponding to 70% of the FWR and partial drying of root zone (SDI-70%+PRD), and in the last treatment (SDI-50%), the crop was irrigated at 50% of full water requirement FWR. In the treatment (SDI-70%+PRD), the root zone was irrigated partially but from alternate laterals. The results show that surface drip irrigation (DSI) resulted in lower WUE and lower yield of squash than the sub-surface drip irrigation (SSDI), although with the subsurface drip irrigation system water consumption is less than with the surface drip irrigation by 5 %. The treatment (FI-100 %) resulted in both the highest WUE and squash yield either with surface or sub-surface. The treatment SDI-80% resulted in WUE and yield not significantly different from FI-100%. SDI-70%+PRD resulted in WUE and yield almost equal to those achieved with SDI-80%.

Water use and fruit yield of mango (Mangifera indica L.) grown in a subtropical Mediterranean climate

ABSTRACTMango (Mangifera indica L.) is one of the most important fruit crops in tropical and subtropical regions worldwide. On the coast of Granada and Malaga (SE Spain), irrigated subtropical fruit species have been introduced and cultivated on terraces with a considerable economic importance as the only European production region. The subtropical fruit production in this zone is possible with intensive irrigation on terraces, which are economically more profitable than traditional rainfed crops (almond and olive), which have been replaced or abandoned. A 2-year monitoring period was conducted using drainage lysimeters to determine the crop coefficients (Kc) and fruit yield in mango (Mangifera indica L. cv. Osteen) orchards. Also, some quality parameters such as titratable acidity, total soluble solids, and vitamin C were evaluated under these conditions. The averaged Kc values of mango trees varied within production cycle of 0.43, 0.67, and 0.63 at flowering, fruit set, and fruit growth, respectively. In this study, the fruit yield under full water requirements (100% ETC) averaged 24.1 kg tree−1, amounting to 21.2 kg ha−1 mm−1 in terms of water-use efficiency. The quality parameters of the mango fruits harvested in the study area were satisfactory. Thus, this study highlights the need to optimize the irrigation-water use according to actual mango requirements, thereby achieving more sustainable Mediterranean subtropical farming in orchard terraces.

Comparison of traditional and modern deficit irrigation techniques in corn cultivation using treated municipal wastewater

PurposeDeclining water resources, increasing drought period and increasing irrigated area cause a shift to deficit irrigated production which is not based on full water requirement. This study was conducted to investigate the impacts of two different deficit irrigation methods, including traditional deficit irrigation (TDI) and partial root-zone drying (PRD) on water use efficiency (WUE) in corn cultivations located at the lands close to the Shahrekord wastewater treatment plant.MethodsA factorial design was employed, consisted of fifteen treatments and three replications. The first factor was three water applications, including 60, 80 and 100 (control) percent of plant water requirement. The second factor was three water sources, including 100% fresh water (FW), 50% water and 50% wastewater (5050), 100% wastewater (WW). T-Tape irrigation type system was used for irrigation of corn (Zea mays L.). The third factor was water management in three levels: full irrigation (FI), PRD and TDI.ResultsThe result showed that dry and fresh weight, leaf area index (LAI), dry biomass percentage and WUE were affected by water requirement at 5% probability level expect of height plant that is affected at 1% probability level. Water quality was affected on all the study indicators of corn plant expect of WUE. WUE among PRD by deficit irrigation treatments were higher than TDI and it was the minimum in FI. The dry and wet weight and LAI were maximum at FI and then PDR80 than TDI80. The height of corn plants were high at FI and TDI80 than PRD80.ConclusionFinally, wastewater application in treatment named 5050-PRD80 and 5050-TDI80 compensated water deficit in WUE, LAI and dry biomass percentage. PRD method recognized more suitable than TDI for corn plants.

Feedback regulation of irrigation via soil moisture monitoring and its effects on plant growth and physiology

Currently, 80% of the world's available fresh water resource is used for irrigated agriculture. Growers usually try to ensure profitable crop production rather than considering possible environmental impacts, which can lead to misjudgement of the plant's actual needs and result in under- or over-irrigation. To understand how manual watering influences soil water status, soil moisture sensors were deployed in a representative commercial nursery. By automatically scheduling irrigation according to soil moisture thresholds, this work tries to understand the effects of deficit irrigation (under-irrigation - applying less than full water requirements) on possible growth regulation through changes in leaf water status, gas exchange and plant hormone balance. Tomatoes (Solanum lycopersicum Mill. 'Ailsa Craig') were grown in a peat-based substrate in a controlled environment, and exposed to different irrigation treatments by varying the number of drippers in the pot (1 water deficit, 2 control). Hand-watering in a commercial nursery resulted in significant variation in soil water content that may compromise crop uniformity and quality. In contrast, feedback regulation of irrigation via soil moisture monitoring provides a useful tool to water plants according to their actual water needs, with significantly less variation in soil moisture. Under-irrigating containerised tomato plants significantly reduced evapotranspiration, crop fresh weight, height and leaf area and decreased leaf water potential and stomatal conductance. Although foliar concentrations of the phytohormone abscisic acid (ABA) varied throughout the treatment period, ethylene emission from shoot increased. However, the role of these plant hormones during water deficit requires further experimentation using mutants deficient in these hormones. Although deficit irrigation as applied here limited tomato vegetative growth, further long-term experiments (that measure fruit yield) are needed to evaluate whether automatic irrigation scheduling can be used as a water-saving technique.

Yield and water use efficiency of furrow irrigated potato under regulated deficit irrigation, Atsibi-Wemberta, North Ethiopia

The pressure on availability of water in Tigray regional state is likely to increase as the requirement for food production in couple with rapidly growing of the population is at increasing rate. Hence, improving water productivity using regulated deficit irrigation is important to reduce the water consumption while minimizing adverse effects on the crop yield. This study was conducted in the eastern zone of Tigray regional state, Atsibi Womberta district. The aim of this study was to determine the yield and water use efficiency of potato under deficit irrigation practice in the 2012 growing period. The effect of water deficit or water stress on crop yield and water use efficiencies were evaluated. Guasa variety potato was grown under eight (T1–T8) irrigation treatments. The treatments were replicated three times under completely randomized blocks experimental design. Water was applied to every furrow using watering can with fixed interval and variable depth irrigation scheduling technique was selected. Yield of potato was significantly (p<0.05) affected by water stress (deficit irrigation). The highest yield was found in T1 (18770kg/ha) which was not subjected to water stress (full water requirement) whereas minimum yield of potato was obtained under the fully stressed treatment T8 (7037kg/ha). There was no significant different between the yield of T1 (18770kg/ha) and T6 (14440kg/ha) which was 25% deficit throughout the growing season. According to the result obtained, stressed at the middle stage was affected more the yield of potato as compared to other treatments. This showed that stressing the crop at flowering/middle stage is sensitive to deficit irrigation. Giving 65% of crop water requirement throughout the growing season is better than stressing the crop only at the middle stage. The second sensitive period for water stress is the late crop stage. Crop water use efficiency was not statistically significant. Though it was not significantly different, T6 (2.86kg/m3) and T4 (1.60kg/m3) had the highest and the lowest water use efficiency respectively. This elaborated that applying 75% of crop water requirement has better water use efficiency than optimal or “no stress” irrigation. It can be conclude that using deficit irrigation is a good water management technique to save irrigation water without reducing the yield of potato. For dry land areas like The Tigray regional state of Ethiopia and other similar agro-ecology elsewhere in the world with scarce water and agricultural water management is very poor. The authors of this study would like to recommend farmers, water managers, water use associations and decision makers to use water efficiently using deficit irrigation and increase their agricultural production by expanding irrigable land with the same amount of water in a given irrigation scheme

OPTIMIZING TOMATO PRODUCTIVITY AND WATER USE EFFICIENCY USING WATER REGIMES, PLANT DENSITY AND ROW SPACING UNDER ARID LAND CONDITIONS

A field experiment was conducted to study the effect of water regime (W), row spacing (RS) and plant density (D) on growth and productivity of tomato cv. 'Pito Pride' at the Agriculture Experimental Station of King Abdulaziz University. Two water regimes, W1 (70% of water requirement) and W2 (full water requirement) were studied. Under each water regime three row spacings (RS1, RS2, RS3) and two plant densities D1 (single plant per dripper) and D2 (two plants per dripper) were investigated. Results revealed that W1 reduced number of days to flowering and fruit setting, plant height, plant fresh weight and total yield, while it increased water productivity (WP). Decreasing RS increased water supply and total yield but decreased growth characteristics. D2 increased total yield by 122–168% and WP by 131–180% compared to D1. Interaction between the three variables investigated was significant for all assessed characteristics except fruit yield per plant, total fruit yield and WP. These characteristics were affected by the interaction between RS and D. The highest total yield and WP were obtained from the RS2-D2 treatment. This treatment increased total yield per ha by 11–331% and WP by 12–300% compared with the maximum and minimum yield of other investigated treatments of both seasons. Copyright © 2014 John Wiley & Sons, Ltd.

English

The experiment was conducted by combining two factors namely; irrigation scheduling with three levels and nutrient management with five levels. The two factors were crossed factorially; irrigation treatments were arranged in vertical strips and integrated nutrient management arranged in horizontal&ndash;strip with strip plot design replicated three times. Field soil was sampled for physical and chemical property determinations. Equal amount of irrigation water were applied before the initiation of irrigation treatments. Once the drip system was installed, irrigation was done on the basis of daily evapotranspiration (ETo) value of the previous day. Growth and canopy characteristics such as plant height, stem diameter, lateral branch length, canopy width and canopy depth were measured and canopy cover was estimated. Additionally yield and yield components at harvest were measured from sample fruits. Physiological data such as chlorophyll content, quantum yield, and Ft were assessed. Data were subjected to analysis of variance as per the design using the SAS Software. Among irrigation levels tested, highest total yield 82.14 t ha-1, was recorded from full irrigation treatment followed by 57.30 t ha-1 from 80% ETc irrigation levels and lowest total yield 49.30 t ha-1 from 60% of full irrigation depth. This finding indicated that tomato should be irrigated at full water requirement to get maximum fruit yield. From this investigation, the total fruit yield was recorded from N 185 kg ha-1 P 60 kg ha-1 combination and N 75 kg ha-1 P 50 kg ha-1 treatment combination with 67.483 and 67.31 t ha-1 respectively. Application of N 185 kg ha-1 P 60 kg ha-1 combination (grower&#39;s check) did not contribute to much yield difference but would encourage luxury consumption and environmental pollution. Thus combinations of full irrigation treatment with N 75 kg ha-1 P 50 kg ha -1 nutrient application would be recommended for verification for tomato production around Melkassa. &nbsp; Key words: Drip irrigation, N and P nutrient, evapotranspiration (ETo), ETc, tomato.

Regulated deficit irrigation in persimmon trees (Diospyros kaki) cv. ‘Rojo Brillante’

The response of persimmon trees to deficit irrigation applied in three different phenological stages was evaluated during three consecutive seasons in a commercial orchard planted with the cv. ‘Rojo Brillante’, the most important cultivar in the Mediterranean basin. The experiment was performed in a drip-irrigated orchard located in Valencia, Spain, planted with eight-year-old trees at a spacing of 5.5m×4m and grafted on the rootstock Diospyrus lotus. Three regulated deficit irrigation (RDI) regimes were tested and compared to a Control treatment irrigated at full water requirements. In the RDI treatments, moderate water restrictions (50% of Control irrigation), were applied during one of three periods (i) RDIspring, where water restrictions were applied from late May to mid July; (ii) RDIsummer, deficit irrigated from mid July to late August and; (iii) RDIfall, in which water restrictions were applied from late August early September to mid November. Results showed that persimmon fruit growth was sensitive to water stress. RDI reduced final fruit weight being this reduction more marked in the most stressed treatment (RDIsummer). This decrease in fruit weight was also because spring and specially summer RDI treatments increased the number of fruit harvested. Thus, RDI techniques allowed water savings of up to 20% without any reduction in yield increasing significantly the water use efficiency. In spite of the similar yields obtained in RDI and control trees, the economic return was negatively affected by deficit irrigation, because the lower fruit weight resulted in a decrease in the fruit commercial value. In conclusion, fruit growth of persimmon cv. ‘Rojo Brillante’ was shown as highly sensitive to deficit irrigation. Based on the results obtained, RDI would need further research in order to define an RDI strategy that could increase water use efficiency without affecting the economic return.