As the most important resource for life, water has been a central issue on the international agenda for several decades. Yet, the world’s supply of clean freshwater is steadily decreasing due to extensive agricultural demand for irrigated lands. Therefore, water resources should be used with greater efficiency, and the use of non-traditional water resources, such as Treated Wastewater (TW), should be increased. Reusing TW could be an alternative option to increase water resources. Thus, many countries have decided to turn wastewater into an irrigation resource to help meet urban demand and address water shortages. However, because of the nature of that water, there are potential problems associated with its use in irrigation. Some of the major concerns are health hazards, salinity build-up, and toxicity hazards. The objectives of this comprehensive literature review are to illuminate the importance of using TW in irrigation as an alternative freshwater source and to assess the effects of its use on soil fertility and other soil properties, plants, and public health. The literature review reveals that TW reuse has become part of the extension program for boosting water resource utilization. However, the uncontrolled application of such waters has many unfavorable effects on both soils and plants, especially in the long-term. To reduce these unfavorable effects when using TW in irrigation, proper guidelines for wastewater reuse and management should be followed to limit negative effects significantly.

Cadmium (Cd) and drought, as abiotic stresses, have long been significant challenges for crop growth and agricultural production. However, there have been relatively few studies conducted on the effects of drought stress on Cd uptake, especially regarding the differences in Cd uptake characterization in varieties with varying Cd accumulation under different drought stress. To investigate the effects of drought conditions on Cd uptake by wheat in different genotypes under specific background levels of Cd pollution, we validated the differences in root absorption characteristics of low- (YM) and high-grain Cd accumulating wheat genotypes (XM) using non-invasive micro-test technology, and we conducted a hydroponic experiment on the Cd addition and different drought levels in a climate-controlled chamber. The biomass, root morphology, Cd uptake, and accumulation were determined under Cd (100 µmol L⁻¹) and different drought levels of 0% (0 MPa), 5% (−0.100 Mpa), 10% (−0.200 Mpa), and 15% (−0.388 Mpa) simulated by polyethylene glycol (PEG-6000). We found that the simultaneous exposure to Cd and drought had a suppressive effect on the total root lengths, root surface areas, and root volumes of XM and YM, albeit with distinct patterns of variation. As the concentration of PEG-6000 increased, the Cd concentrations and the amount of Cd accumulated in the roots and shoots of XM and YM decreased. Specifically, the Cd concentration in the roots exhibited a reduction ranging from 12.51% to 66.90%, while the Cd concentration in the shoots experienced an even greater decrease of 50.46% to 80.57%. The PEG-6000 concentration was significantly negatively correlated (p < 0.001) with Cd concentration of roots and shoots and Cd accumulation in roots, shoots, and the whole plants and significantly negatively correlated (p < 0.05) with the total length, surface area, and volume of roots. This study confirms that drought stress (5% PEG-6000) can decrease the uptake and accumulation of Cd in wheat seedlings without significant inhibition of biomass, and the change of root morphology (root length) and the decrease of Cd concentration in roots may be the main direct pathways for achieving these effects under drought stress. This research provides a new perspective and idea for water management in Cd-contaminated farmland.

Rising freshwater scarcities pose a serious threat to agricultural production. Reclaimed water (RW) is increasingly utilized as one of the alternative resources for irrigation in agriculture. Microbial communities play crucial roles in the soil microenvironment and can be used as effective indicators to assess the ecological influence of RW irrigation in soil. However, there is a lack of research on the effects of RW with different irrigation techniques on soil attributes and microbial communities. The present experiment was conducted in China to investigate the effect of two kinds of water qualities (RW and clean water (CW)), two kinds of irrigation methods (full irrigation (FI) and alternate partial root-zone irrigation (APRI)), and two kinds of irrigation techniques (furrow irrigation (FUI) and subsurface drip irrigation (SDI)) on soil chemical properties, heavy metal concentrations, and bacterial community structure. The APRI treatments received 70% of the irrigation water volume of FI. The results revealed that electrical conductivity (EC), nitrate nitrogen (NO₃⁻-N), and heavy metal (Cu, Cd, Pb, Zn) concentrations in soil irrigated with RW were significantly higher in comparison to the soil irrigated with CW. SDI significantly decreased the contents of TN by 4.88%, the EC by 13.78%, and the heavy metal Cd concentration by 13.14% in soils than that irrigated with FUI treatment. APRI significantly decreased the heavy metal Cu concentration in soils by 6.26% compared to FI treatment. Proteobacteria, Chloroflexi, Acidobacteria, and Gemmatimonadetes in soil irrigated with RW were more abundant than that irrigated with CW. The irrigation water quality, soil moisture content, heavy metal content, TN, and EC under various irrigation techniques and methods significantly affected the structure of soil bacterial communities. In conclusion, we highlight that the SDI-APRI treatment can be an efficient irrigation practice for reducing the EC, heavy metal pollution, and the security risks of soil irrigated by RW.

This study involved exploring the opportunities of using regulated deficit irrigation and partial root zone drying approaches as water-saving irrigation methods in a tomato crop (Solanum lycopersicum L.) based on irrigation scheduling. The Partial Root Zone Drying Irrigation practice simply involved interchanging the wet and dry sides in subsequent irrigations. The field experiment was conducted in the Kingdom of Saudi Arabia, during the fall season of 2014-2015 and 2015-2016. The following three irrigation treatments were tested during both years under a drip irrigation system: (1) full irrigation (FI), as a control treatment; (2) regulated deficit irrigation (RDI); and (3) partial root zone drying irrigation (PRD). Both RDI and PRD treatments received 70% of the irrigation water volume of full irrigation (FI). The obtained results indicated that the soil water content of PRD treatment was higher and conserved more soil moisture than that in the RDI treatment. Data for both years indicated that FI exhibited the highest stomatal conductance (gs) values while PRD exhibited the lowest gs values among all the treatments. Under PRD treatment, the dry fruit yield was the highest when compared with RDI and FI treatments for both years. Deficit irrigation treatments result in higher abscisic acid (ABA) concentration in the xylem when compared to that in FI. The vast majority of most extreme irrigation water use efficiency (IWUE) values were involved with PRD while most of the minimum IWUE values were coupled with FI. These results indicate the effects of deficit level irrigation on IWUE

The growing population in the face of water scarcity inevitably necessitates the quest for alternative sources of irrigation water, which integrates them with irrigation strategies for improved agricultural productivity to meet the Sustainable Development Goals. A three-year field experiment was conducted in 2017, 2018, and 2019 to investigate the effect of water quality (reclaimed water (RW) and clean water (CW)), irrigation techniques (subsurface drip irrigation (SDI) and furrow irrigation (FUI)), irrigation methods (full irrigation (FI) and alternate partial root-zone irrigation (APRI) (70% ETc)), and their interactions on the fresh fruit yield (FY), irrigation water use efficiency (IWUE), and nitrogen use efficiency (NUE) of tomatoes. Further, electrical conductivity (EC), pH, and organic matter (OM) of soil were evaluated. The experiments were undertaken over three growing spring seasons in a greenhouse at the Chinese Academy of Agricultural Sciences in Henan Province, China. Throughout the three years of this study, the yield, the IWUE, and the NUE values of all treatments under RW were higher than those corresponding values under CW. The trend was the same under SDI as it was under FUI. Statistical analyses revealed that there was no significant effect (P > 0.05) of water quality, irrigation technique, and irrigation methods on the soil EC, pH, and OM over the three years. In addition, the interaction between the different experimental factors over the three years of the study was not significant. In conclusion, the application of RW under SDI can result in saving CW and increasing productivity without any negative effect on the investigated soil properties. Furthermore, when RW-SDI is used in conjunction with APRI, it can result in increasing IWUE.

As the most important resource for life, water has been a central issue in the international agenda for several decades. Yet, the world’s clean freshwater supply is steadily decreasing due to climate change and extensive agricultural water demand for irrigated lands. Therefore, in addition to rational water use, we should use non-traditional water resources like Reclaimed Wastewater (RW). The present experiment was carried out in China over three years (2017, 2018, and 2019) to study the effects of two types of water qualities (reclaimed wastewater (RW) and clean water (CW)), two types of irrigation methods (Full irrigation (FI) and alternate partial root-zone irrigation (APRI)), and two types of irrigation techniques (Furrow irrigation (FUI) and subsurface drip irrigation (SDI)) on the main tomato fruit quality parameters. The APRI treatments obtained 70% of the FI irrigation water volume. The irrigation treatments of this study were: (1) SDI with APRI; (2) SDI with FI; (3) FUI with APRI; and (4) FUI with FI. These treatments were under RW and CW. Thus, the experiment consisted of eight treatments. The tomato fruit quality parameters studied were vitamin C (VC), total acidity (TA), protein content (PC), and total soluble sugar content (TSS). The results reveal that many measurements under reclaimed water (RW) had the highest values compared with clean water (CW), except in protein content (PC). The vast majority of values measured for PC under CW were slightly greater than the values under RW. Moreover, the results reveal that tomato quality in many measurements under APRI treatments increased compared with FUI. The statistical analysis generally shows that the fruit quality parameters were not significantly (p > 0.05) affected by the interaction between the irrigation treatments. In conclusion, the treatment SDI-APRI under RW can be an efficient irrigation method to reduce the consumption of clean water. Additionally, SDI-APRI offers a safe option because the physical contact between the wastewater, crops, and the farmers is minimized compare with the FUI treatment.