Amount Of Irrigation Water Research Articles

GROUNDWATER USE EFFICIENCY FOR SUSTAINABLE AGRICULTURE: PROSPECTS IN BANGLADESH

Bangladesh is a developing country where contribution of agriculture in national GDP (Gross Domestic Product) is 12.68%. In agricultural sector, about 79% irrigation has been provided by groundwater. The extensive installation of deep tubewells (34,332) and shallow tubewells (1,483,332), in last two decades, helps in maximum utilization of groundwater which is leading Bangladesh to reach near to the self-sufficiency in rice production (35.3 metric tons in 2019). But the continuous production of boro rice in the dry season is a threat for groundwater use efficiency. Again, without sufficient irrigation water, assuring sustainable agriculture is not feasible. This review paper had been prepared on the developing scenario of groundwater and its utilization efficiency, problems in groundwater use and relevant remedies to attain sustainable agriculture in Bangladesh. Due to the over extraction of groundwater, the depth of groundwater table has been declined (15%) miserably. Using redundant amount of irrigation water, conveyance loss (8-40%), arsenic contamination, insufficient recharge of groundwater etc. are the major problems behind inadequate groundwater use efficiency. Using Alternate Wetting and Drying (AWD) method, reducing conveyance loss, diversifying cropping pattern, reforming national policies etc. are some effective measures to increase groundwater use efficiency required for sustainable agriculture. About 10,000 tk/ha can be saved just by minimizing the cost required to extract excess groundwater for irrigation. In Bangladesh, maximum national policies are focusing exclusively to the resource development rather than the resource management. The awareness can be built through different teaching programs among all the stakeholders. Rather than just imposing restriction on installation of tubewells, more constructive policies have to be announced by the policy makers. Seven different agencies are now working for the management of groundwater in Bangladesh. Besides other technical solutions, there should be a connection between different organizations related to the groundwater management for the effective implementation of their target policies.

Weather-driven synergistic water-economy-environment regulation of farmland ecosystems

Farmland ecosystems (FEs) constitute the most important source of food production, and water is one of the most important factors influencing FEs. The amount of water can affect the yield and thus the economic efficiency. Water migration can generate environmental effects through the migration of fertilizers. Interlinkages and constraints exist between the water, economy and environment, which require synergistic regulation. Meteorological elements influence the reference crop uptake amount and thus the water cycle processes and are key drivers of regulation at the water-economy-environment nexus. However, the weather-driven, synergistic water-economy-environment regulation of FEs has not been sufficiently researched. As such, this paper employed a dynamic Bayesian prediction of the reference evapotranspiration (ETo) and a quantitative characterization of the total nitrogen (TN) and total phosphorus (TP) contents in agricultural crops and soils via field monitoring and indoor experimental analysis. Consequently, multiobjective optimization modeling was conducted to weigh the mutual trade-offs and constraints between water, the economy and the environment. The proposed method was verified via an example involving the modern agricultural high-tech demonstration park in Harbin, Heilongjiang Province, China. The results indicated that (1) the effect of meteorological factors gradually decreased over time, but the prediction results were very accurate, and the higher the delay order of the dynamic Bayesian network (DBN) was, the more accurate the predictions; (2) ETo was significantly driven by meteorological elements, and the most important meteorological factor influencing ETo throughout the year was average temperature. When the average temperature was reduced by 10.0 %, ETo was reduced by 1.4 %, the required amount of irrigation water was reduced by 4.9 %, and the economic benefits of a single cube of water increased by 6.3 %; (3) resource-economy-environment multidimensional synergy enabled a 12.8 % reduction in agricultural ecosystem pollutant emissions, while the economic benefits per unit of water increased by 8.2 % and the system synergy increased by 23.2 %.

A comparative technical study for estimating seeped water from irrigation canals in the Middle Egypt (Case study: El-Sont branch canal network)

Integrating with the national project of irrigation canal lining in the Egyptian countryside, the present study is introduced. The study presents a technical comparison of differential equations that are usually used for estimating the seeped water from the earthen irrigation canals. The quantities of irrigation water that are lost due to seepage are great enough to decrease the wide gap between the needed and available water quantities that Egypt seriously suffers from. So, the accurate estimation of the seeped water quantities is very important. The study aims to select the suitable seepage equations for the Egyptian soil, climate, and the currently used distributed irrigation system. It is also to assess the understudy network by estimating the lost water quantities due to seepage by using the designed water sections’ dimensions and comparing the results with those obtained using the existing field dimensions. In addition, to determining the agricultural area that can be added to the current served area after preserving such great quantities. From the Assiut countryside, the El-Sont canal and its network were chosen to be a case study. After a careful technical reading of the seepage equations that researchers introduced previously, the closest relationships to the case study were used. Results indicated that using the suggested relationship by Nazir Ahmed and the Indian equation, gave the maximum seepage quantities for the entire El-Sont canal network with about 21.5% of the total canal head discharge. Most of this lost water can be saved due to the implementation of the national project for irrigation canal lining. This large amount of preserved water can be used to irrigate 15% of the currently served area.

Effect of Irrigation Water Management on Growth of Date Palm offshoots (Phoenix dactylifera) under the River Nile State Conditions*

the objective of this study was to investigate the effect ofdifferent irrigation water managements on the vegetative growth of datepalm offshoots. The experimental work was conducted at the JordanianBashair project in the River Nile State, for two consecutive seasons (2007and 2008). Two irrigation methods were used with three amounts ofirrigation water. The irrigation methods were the conventional basinsystem and two bubbler types, a locally made and an imported bubbler(Rain bird). The amounts of irrigation water were 50%, 75% and 100% ofthe crop irrigation requirement, as determined by CROPWAT computermodel version 2003, using the average of 30 years data. Data werecollected on plant height, stem size and number of leaves per offshoot, atage 12 months. The treatment affected significantly (P< 0.01) the growthparameters. The imported bubbler gave the highest mean values ofgrowth parameters, while the basin irrigation gave the lowest values. Thesame result was obtained with 100% Etc, compared with 75 % and 50 %Etc. The interaction of the irrigation system and amount of wateringsignificantly affected the growth parameters. The imported bubbler with100% Etc gave the highest average values of growth parameters, andbasin irrigation with 50% Etc showed the lowest values.

Effect of Irrigation Regime on Wheat (Triticum aestivum L.) Yield under Shambat Conditions, Sudan

This study was conducted with the objective of determining theeffect of application of different irrigation water amounts on the yield ofwheat grown on different seedbeds. Three irrigation water regimesnamely: 100%, 80% and 60% of crop evapotranspiration (Etc) were usedunder two types of seedbeds (sowing on the flat and sowing on ridges)over two successive seasons (2003/04–2004/05) at the DemonstrationFarm of the Faculty of Agriculture, University of Khartoum, Shambatusing a strip-split-plot design with three replications. The control was flatsown and with no-tillage. Data were collected to determine variablespertaining to plant population, plant height, number of tillers, leaf areaindex (LAI), number of spikelets/plant and grains/spike, 1000-grainsweight, harvest index (HI), total grain yield and water use efficiency(WUE). Results obtained revealed that, the watering regime of 60% ETcwas statistically inferior in almost all the mentioned parameters, and thatthe 100% and 80% ETc had similar results in both seasons.

Performance of Basin and Bubbler Irrigation Systems under River Nile State Conditions

This study was conducted in the Jordanian Bashair project,River Nile State, during two seasons (2007 and 2008) to evaluate theperformance of irrigation systems applying different amounts of irrigationwater. The treatments were surface irrigation method (basin irrigationsystem) and localized irrigation system with two types of distributors:locally made bubblers and imported bubblers. The irrigation wateramounts were given as percentages (50%, 75% and 100%) of date palmwatering requirement (ETc). ETc was obtained from the means of theprevious thirty years, using CROPWAT4 WINDOWS. The performanceof the irrigation system was evaluated with reference to the applicationand storage efficiencies and distribution uniformity. The experiment wasorganized in a split plot design with three replicates. The irrigationsystems showed negative effect on distribution uniformity and positiveeffect on application and storage efficiencies. The locally made andimported bubblers revealed highly significant (P ≤0.01) differences withapplication and storage efficiencies, while there was no significantdifference between them. The 50% ETc recorded high significant valuesof application efficiency, but less values of storage efficiency anddistribution uniformity. Interaction of the irrigation systems and amountsof water showed positive effect, whereas locally made bubblers showedhigher values of application and storage efficiencies with 50% and 100%ETc, respectively. On the other hand, the basin irrigation system gavehighest values of distribution uniformity with 75% and 100% ETc .Hence,it was concluded that using bubbler irrigation system would give highirrigation efficiency, thus saving water for other agricultural activities.

Effects of various soil structure and irrigation regimes on rio-red grapefruit yield and morpo-physiology

The research was carried out in 2011 using Rio-Red grapefruit trees in Research Station of Cukurova University, Agricultural Faculty, Citrus experiment Station, Adana Latitude, 5°2 ’ N Longitude, 6°50’ E, altitude 27 m).In the study, it was aimed to determine the effects of the amount of irrigation water applied at different levels to the trees growing in soils of different soil texture on fruit development and yield, tree trunk development, tree canopy volume development, leaf area index(LAI) and photosynthesis rate. The research area soils contain three different groups in terms of resistivity values and the trees are grown in soils electrical conductivity (ECa) with T1: 86-109, T2: 23-37 and T3: 62-72 ECavalues.In the experiment, three different irrigation levels I100, I70 and I50 water was applied. The average amount of irrigation water applied to grapefruit trees ranged from 332,48 mm (I100) to 178,92 mm (I50). Actual plant water consumption was between 810.5 mm (I100) and 694.4 mm (I50) according to the water budget method. Yields related to irrigation on trees in the plot varied between 883 (I70) and 828 (I50) kg per tree on average. It has been determined as 1050 kg on average from the fully irrigated I100. Photosynthesis values were measured as 2.64 umol/m2/s for I50, 3.48 umol/m2/s for I70 and 4.77 umol/m2/s for I100. Consequently, the effects of irrigation treatmentson fruit yield are not statistically significant, water reduction can be recommended for the region in order to save water for the farmers in this study.

BLUEPRINT FOR RECORDING DATA ON RED ONION FARMING ACTIVITIES USING THE BPR METHOD

To advance agriculture in Indonesia, farmers must be able to calculate the need for fertilizer, optimal use of pesticides, the amount of irrigation water required, the type of seed and the suitable land area in order to get maximum and sustainable agricultural yields. Besides that, farmers must also know the efforts in preventing and handling diseases. Therefore, researchers developed a prototype for recording data on agricultural activities both carried out by farmers and recording the condition of agricultural land by IOT. The Business Process Reengineering method is used to obtain an AS-IS system analysis so that a blueprint model is obtained that is suitable for recording agricultural activities. So that red onion farmers can manage customer relationships while performing their agricultural activities using this web-based information system application prototype. The results of the recording carried out by farmers and IOT using the Laravel web-based application development and using PostgreSQL version 14 can be used to provide input and notifications to farmers regarding actions that need to be taken.

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.

Evaluation of AquaCrop for potato yield and biomass simulation under different water amounts in drip and furrow irrigation methods

AbstractPotato is one of the most important crops for meeting food needs worldwide. The water requirement of this crop is high, and its yield is sensitive to the amount of irrigation water. Studying different amounts of irrigation water in irrigation methods is not only expensive but also time‐consuming, so it is necessary to use water‐driven crop models such as AquaCrop. This research aims to evaluate the accuracy of AquaCrop for simulating potato yield and biomass in Iran at three irrigation levels (full irrigation [FI] stands for 100%, I80 for 80% and I65 for 65% of the crop water requirement) via two irrigation methods (furrow irrigation and drip irrigation). For furrow irrigation, the normalized root mean square error values in the FI, I80 and I65 treatments varied between 17% and 28% for yield and 12% and 17% for biomass. These results for drip irrigation were 17%–22% (yield) and 9%–18% (biomass). For furrow irrigation, the average root mean square error values for potato biomass and yield were 0.89 and 0.68 t ha−1, respectively. The corresponding results for drip irrigation were 0.79 and 0.64 t ha−1, respectively. Based on all the results, the accuracy of AquaCrop was good for both irrigation methods, even though its accuracy under severe water stress conditions (I65) for the drip irrigation method was better than that for furrow irrigation.

Application of artificial neural networks and partial least squares regression to predict irrigated land soil salinity in the Rift Valley Region, Ethiopia

Study regionRift Valley-Awash River Basin, Ethiopia Study focusIrrigation schemes in Awash Basin, Ethiopia, are severely affected by the buildup of soil salinity. The main source of the salinity is shallow groundwater heightened by improper irrigation practices and management. However, salinity predictions have not been developed based on direct measured data for the basin. Therefore, this study aims predicting topsoil salinity in irrigated land from basic hydrological parameters using two approaches: Artificial neural networks (ANNs) and Partial least squares regression (PLSR). Irrigation water amount, water table depth, precipitation and estimated canal seepage were considered for variable inputs. New hydrological insightsOur results showed that ANNs were superior over PLSR in predicting soil salinity, explaining 77% vs. 45% of the variance in soil salinity with root mean square error (RMSE) of 0.12 vs. 0.94 dS/m. In both models, groundwater depth is the most influential variable for soil salinity prediction, with relative contributions of 63% and 65% for PLSR and ANNs, respectively. Though, irrigation water is non-saline river water, it contributes to the rising groundwater table which contains high salinity. Our study demonstrates that proper irrigation management, use of drainage system, and reducing high seepage from the irrigation canal system will sustain the depth of the water table, and simultaneously reduces top-soil salinity accumulation and productivity loss in the Rift Valley Region of Awash Basin.

Effect of Irrigation Water Amount and Planting Pattern on Water Use and Yield of Cotton in Northern Xinjiang, China

This study aimed to clarify the effect of irrigation water amount and planting pattern on water use and yield of cotton in Northern Xinjiang. A field experiment was conducted during 2020–2021 comprising four irrigation water amounts (360, 450, 540, and 630 mm) and two planting patterns (same row spacing, R1; and wide-narrow row planting, R2). The results showed that the evapotranspiration (ET), soil evaporation (Es), and plant transpiration (T) of cotton under both planting patterns increased with the increasing irrigation amount. During the entire growth period, the annual average daily ET and T under R2 were higher than those under R1, but the annual average daily Es under R2 were lower than those under R1. The daily Es was highest between one and four days after irrigation. The Es/ET under R1 was approximately 27.45%–31.82%, and that under R2 was approximately 24.52%–28.56% under the four irrigation treatments. The relationship between the Es/ET and leaf area index was fitted based on an exponential equation (R2>0.85). The yield increased with an increase in the irrigation amount, although there was no significant difference between the yields obtained with 540 mm and 630 mm irrigation amounts. The water use efficiency (WUE) increased first and then decreased with an increase in irrigation water amount, with the highest WUE observed under the 540 mm condition and the lowest under the 630 mm condition.

MINIMIZATION OF WATER NEEDS IN IRAQI AGRICULTURE IN LIGHT OF THE PREVAILING CROPPING COMBINATION DURING

The research aims to study the optimal allocation of irrigation water that is used to irrigate various agricultural crops at the level of Iraq. In order to achieve the goal of the research, two economic models were formulated according to the linear programming technique. The first model aimed to minimize the water needs of the prevailing crop combination during the average period (2017-2020), while the second model aimed to maximize the total profit margin of the water unit for the crop combination that minimizes the water needs during the same period. The first model was estimated with two proposed plans. The first proposed plan included non-imposing legislative restrictions related to the allocation of certain areas for basic agricultural crops that bias the food security requirements of the population, as well as crops that were recently banned from import by the Iraqi government, while the proposed second plan included the imposition and addition of restrictions of legislative areas that did not appear in the table of the optimal solution for the first plan. Results indicated that there is a surplus of water resource for the proposed economic plans according to the two estimated models, its quantity amounted to about 363.361, 9.178 million m3 for each plan, respectively, compared to the total amount of irrigation water needed for the current cropping combination, which was estimated at about 4.736726 billion m3 during the average mentioned period. Results of the analysis of the two estimated models also showed a preference for the results of plans with legislative restrictions as a result of the expansion in the cultivation of most basic and important crops and vegetables for local consumption.

Research on the characteristics of drought stress state based on plant stem water content

There is a close relationship between plant stem moisture and plant drought stress. In this study, we tried to explore the variation law of stem water content of plants of different body types under drought stress. In this paper, small Cinnamomum kotoense Kanehira et Sasaki and large Malus micromalus Makino were used as materials to create a drought stress state by artificially controlling the amount of irrigation water, and the change law of plant stem water during this period was analyzed. The results showed that the ability of large mature trees to cope with drought stress was stronger, and the stem water content could be maintained for a longer time under drought stress. Large trees are more resilient after watering. Small plants are more prone to air embolism due to drought stress due to their thin stems, blocking water transport and causing plant death. Recovery is weaker after watering. In this experiment, when the degree of drought stress exceeds 70%, there is a threshold of plant death. When the degree of stress exceeds this threshold, there is a high probability of eventual death. At this point the stem water will be irreversibly lost, and even watering will not be able to restore it. In this study, it was also found that the change of plant stem water under drought stress would have a lag, and the higher the stress level, the greater the lag degree. In this study, the plant state under drought stress was analyzed by the stem water of the plant, which can judge the current life state of the plant more quickly and easily. This could turn into a more efficient way of analyzing plants in the future.

Eco-Physiological and Productive Response of Deficit Irrigated Potatoes

A comprehensive study on both the eco-physiological and productive response of potatoes to dynamic deficit irrigation is lacking. Therefore, the aim was to study, over two growing seasons and on two potato cultivars—Arinda and Timate, the effects of five irrigation regimes (I0–dry control, I1—irrigated control, I2—supply 100% of the maximum evapotranspiration—ETm from tuber initiation up to 50% of tuber growth and 0% ETm from 50% to the end of tuber growth, I3—supply 100% of ETm from tuber initiation up to 50% of tuber growth and 50% ETm from 50% to the end of tuber growth, I4—supply 100% of ETm from tuber initiation up to 50% of tuber growth and 75% ETm from 50% to the end of tuber growth) simultaneously on the crop physiology (via chlorophyll fluorescence and leaf gas exchange traits), above-ground biomass yield, tuber yield and its components, irrigation water use efficiency (IWUE), source/sink ratio and tubers’ dry matter content. Regardless of cultivars and seasons, in I3 and I4 for eco-physiological and productive traits, values comparable with I1 were found. Compared to I1, I2 reduced tuber yield by about 18% but increased the IWUE by about 110%, saving a high amount of irrigation water (about 1500 m3 ha−1 per season). Arinda appeared more susceptible than Timate to water deficit in the second part of tuber growth, namely I2, from an eco-physiological point of view, but no differences between cultivars were found from a productive point of view. It was possible to effectively apply dynamic deficit irrigation to save irrigation water without compromising yields strongly.

Model-Based Approach for Treated Wastewater Reuse Strategies Focusing on Water and Its Nitrogen Content “A Case Study for Olive Growing Farms in Peri-Urban Areas of Sousse, Tunisia”

One of Tunisia’s main challenges is to conserve and protect water resources for current and future generations. Using non-conventional water in agriculture, such as treated wastewater, can be a sustainable water-saving solution. Therefore, the objectives of this study are (i) to analyze the value chain of treated wastewater for olive growing farms production and (ii) to apply mathematical modeling to maximize the olive production in optimizing irrigation distribution and nitrogen amendment in olive growing farms. The work is carried out in a peri-urban irrigated perimeter of Msaken, Sousse, which is mainly occupied by olive trees and irrigated by treated wastewater. A SWOT analysis is also applied to identify the strengths and weaknesses of reuse in this study area. Moreover, mathematical models are used to determine the optimal schedule for fertigation with treated wastewater. In this process, data on rainfall, soil, water quality and olive production were collected from local farmers, local decision makers, field and laboratory experiments. SWOT results determine farmers’ perceptions of reusing treated wastewater for irrigation. The viability analysis, in terms of soil humidity and nitrogen, shows that the nitrogen stress is not a limiting factor for olive biomass production, but water stress is. This analysis provides numerical values for the maximum irrigation rate and total amount of irrigation water to ensure maximum olive production. It was found that the maximum irrigation could be 5.77 m3/day/ha and the total annual water requirement is 1240 m3/ha. Modeling appears to be an important tool to help local decision makers and to support and encourage local farmers to reuse treated wastewater under safe conditions and without environmental risks.

A Review on Regulation of Irrigation Management on Wheat Physiology, Grain Yield, and Quality.

Irrigation has been pivotal in sustaining wheat as a major food crop in the world and is increasingly important as an adaptation response to climate change. In the context of agricultural production responding to climate change, improved irrigation management plays a significant role in increasing water productivity (WP) and maintaining the sustainable development of water resources. Considering that wheat is a major crop cultivated in arid and semi-arid regions, which consumes high amounts of irrigation water, developing wheat irrigation management with high efficiency is urgently required. Both irrigation scheduling and irrigation methods intricately influence wheat physiology, affect plant growth and development, and regulate grain yield and quality. In this frame, this review aims to provide a critical analysis of the regulation mechanism of irrigation management on wheat physiology, plant growth and yield formation, and grain quality. Considering the key traits involved in wheat water uptake and utilization efficiency, we suggest a series of future perspectives that could enhance the irrigation efficiency of wheat.

The Influence of Plant Type, Substrate and Irrigation Regime on Living Wall Performance in a Semi-Arid Climate

Living walls are fast becoming a ubiquitous feature of modern living and are widely implemented in commercial buildings in both internal and external environments. However, there are several challenges associated with maintaining healthy plant growth on these water sensitive urban design systems. This experimental study of an instrumented prototype-scale living wall has found that there is a close relationship between the plants, substrates and adopted irrigation regimes. In this study, plant selection was found to be more critical than either substrate or irrigation regime selection. This research also found that both the location of the plants on the wall and irrigation volume significantly affected the plants’ ultimate total dry weight. In particular, plants were found to grow taller on the upper section of the living wall compared to the middle and lower sections. It is recommended that particular attention should be given to plant location and the amount of irrigation water supplied at different positions on the living wall.

Modelling Yield Response and Water Use to Salinity and Water Relations of Six Pepper Varieties

Better understanding of crop yield response under salinity and water deficit conditions is essential to meet food need under the circumstance of population growth and climate extremities. It has been well known that plant species response differently under stress conditions. Recent studies show that these different responses occur not only among species but also in different varieties within the same species. The aims of the study are to examine and to compare yield, yield response factors (ky), salinity thresholds, biomasses, and water productivity responses of six varieties of pepper plant (Sürmeli-Hot, Yalova, BT016-Hot, BT 016, BT Ünsal, BT Demok) under salinity conditions. In another experiment under the same conditions (location, time, growth media etc.), water deficit was applied to two of these six varieties (BT Ünsal and BT Demok) separately, and their responses to salinity and water deficit conditions were compared. The experiment was carried out in containers. The amount of irrigation water was determined manually by weighing each container. Water deficit treatments were consisted of meeting 120, 100, 70 and 50% of soil water depleted from field capacity. Water salinity levels were 0.25 (control), 2, 4 and 6 dS m-1. There was no difference in yield under non-stress and excessive stress conditions, but the yield difference was as high as 38.9% under moderate stress conditions. Varietal differences were also observed for water productivity. Salinity threshold values vary between 0.89 and 1.83 dS m-1. Yield response factor (ky) were high for all varieties under salinity. Comparing the ky values obtained under water deficit and salinity experiments, sensitivity to salinity induced water stress was found higher than that of applied water deficit itself. Using salinity (Model 1) and water deficit (Model 2) data set of two varieties, two models were created plotting relative yield and water potentials (osmotic potential + matric potential) and compered their predications statistically. Statistically better predictions were obtained from Model 2.

Effect of rural domestic sewage regeneration irrigation on paddy soil properties and water and nitrogen utilization in southern China

AbstractRural domestic reclaimed water (RDRW) for agricultural irrigation is an effective way to alleviate the contradiction between the supply and demand of water. In this research, four kinds of irrigation water sources (primary and secondary treated water [R1 and R2], purified water [R3] and river water [CK]) and three kinds of water level regulations (low, medium and high water level control [W1, W2 and W3]) were set to study the impact of RDRW irrigation and its reuse on the properties of paddy soil, water and nitrogen utilization and yield of rice through a combination of field experiments and laboratory and numerical analysis methods. The results showed that compared with river water (CK) irrigation, pH (0–40 cm), electrical conductivity (EC) and organic matter (OM) content (60–80 cm) increased, and ammonium‐nitrogen (NH4+‐N) (0–20 cm) and nitrate‐nitrogen (NO3−‐N) (40–60 cm) content accumulated under RDRW irrigation. Under high water level regulation (W3), NH4+‐N and NO3−‐N content increased, showing the opposite changing trend compared with W1 and W2 regulations. With RDRW irrigation, water and nitrogen use efficiency and rice yield were significantly increased. Under RDRW irrigation, irrigation water use efficiency (IWUE), nitrogen use efficiency (NUE) and rice yield were increased by 48%–70%, 10%–22% and 5%–13%, respectively, compared with CK irrigation. In addition, path analysis established by structural equation modelling (SEM) showed that the irrigation water amount (IWA) had a significant positive impact on NUE and NH4+‐N but had a significant negative impact on IWUE and EC. NUE, IWUE, NO3−‐N and EC had a significant positive impact on yield. The path of IWA= > IWUE= > yield showed a complete mediation effect, the path of IWA= > EC= > yield and NUE= > EC= > yield both showed a partial mediation effect, and the effect size was 27.9% and 25.0%, respectively.