Calcite in combination with olive pulp biochar reduces Ni mobility in soil and its distribution in chili plant.

The presence of Ni above the permissible limit in agriculture soils poses negative effects on soil health, crop quality, and crop productivity. Surprisingly, the usage of various organic and inorganic amendments can reduce Ni mobility in the soil and its distribution in the crops. A pot experiment was conducted to elucidate the effects of olive pulp biochar (BR), calcite (CAL), and wheat straw (WS), as sole amendments and their mixtures of 50:50 ratio, added to Ni polluted soil on Ni mobility in the soil, Ni immobilization index (Ni - IMi), soil enzymatic activities, Ni distribution in parts of chili plant, Ni translocation factor and bioaccumulation factor in fruit, plant growth parameters and oxidative stress encountered by the plants. Outcomes of this pot experiment revealed that amendments raised soil pH, improved soil enzymatic activities, values of Ni - IMi, while significantly reduced bioavailable Ni fraction in the post-harvest soil. However, the highest activities of acid phosphatase, urease, catalase, and dehydrogenase by 50, 70, 239, and 111%, respectively, improvement in Ni - IMi up to 60% while 60% reduction in the bioavailable Ni fraction was observed in BR + CAL treatment, compared to control was noted. Among all amendments, the top most reduction in Ni concentrations in shoots, roots, fruit, Translocation Factor (TF), and Bioaccumulation Factor (BAF) values of fruit by 72%, 36%, 86%, 72%, and 86%, in BR + CAL treatment, compared to control. Moreover, the plants growing on BR + CAL amended Ni contaminated soil showed the topmost improvement in plant phonological parameters while encountered the least oxidative stress. Such findings refer to the prospective usage of BR + CAL at 50:50 ratio than BR, CAL, WS alone, and BR + WS as well as WS + CAL for reducing Ni mobility in the soil, improving Ni - IMi, soil enzymatic activities, plant phonological and oxidative stress while reducing Ni distribution in plant parts. Novelty statementIn this experiment, it was hypothesized that amending Ni polluted soil with olive pulp biochar (BR), CAL, and WS as alone soil amendments and their combinations at 50:50 ratios can reduce Ni bioavailability in soil, Ni distribution in chili plant and oxidative stress encountered by the plants. Moreover, these amendments may improve, soil enzymatic activities, Ni immobilization index, plant phenological traits. Therefore, it was aimed to undertake useful scientific planning and research, to restore and rehabilitate the dwellings, biological resources and to minimize the sufferings of the peoples in nutrient-poor Ni contaminated soils, by improving soil health and chili productivity.

Arbuscular mycorrhizal fungi and pistachio husk biochar combination reduces Ni distribution in mungbean plant and improves plant antioxidants and soil enzymes.

Soil pollution with nickel (Ni) casts detrimental effects on the quality of crops. Low-cost amendments can restrict Ni mobility in soil and its uptake by the plants. In this pot experiment, the effects of pistachio husk biochar (PHB) and arbuscular mycorrhizal fungi (AMF) on the distribution of Ni in mung bean and its bioavailability in Ni-spiked soil were evaluated. Plant parameters like Ni plant height, root dry weight, shoot dry weight, grain yield, chlorophyll contents, oxidative stress, Ni distribution in the roots, shoot, and grain, as well as the nutritional potential of grains, were measured on plants grown on Ni-contaminated soil amended or not (control) with AMF, zeolite (ZE), PHB, ZE + AMF, and PHB + AMF. Moreover, DTPA (diethylenetriamine pentaacetate)-extractable Ni in the soil, microbial biomass carbon (MBC), total glomalin (TG), extractable glomalin (EG), mycorrhizal root colonization (MRC), and the activities of soil enzymes (i.e. urease, acid phosphatase, and catalase) were also assessed after the plant harvest. With few exceptions, all treatments had significant effects on plant and soil parameters. The PHB + AMF treatment showed the topmost significant increment in plant physical parameters while reducing the Ni distribution in plant parts and oxidative injury. Based on these findings, it is proposed that PHB + AMF treatment can reduce Ni distribution and oxidative stress in mung bean plants and improve the biochemical compounds in grain.

Prospective usage of magnesium potassium phosphate cement combined with Bougainvillea alba derived biochar to reduce Pb bioavailability in soil and its uptake by Spinacia oleracea L.

Combining biochar (BR) with other immobilizing amendments has additive effects on Pb immobilization and been recognized to be effective for the restoration of Pb polluted soils. However, the impacts of different proportions between BR and a highly efficient Pb immobilizing agent called "magnesium potassium phosphate cement (MC)" have never been earlier investigated. This work aimed to investigate the consequences of BR and MC alone and their mixtures of 25:75, 50:50, and 75:25 ratios on Pb bioavailability, Pb immobilization index (Pb-IMMi), and enzymatic activities in Pb polluted soil. Furthermore, amendments effects on Pb distribution in spinach, growth, antioxidant capacity, biochemical, and nutritional spectrum were also investigated. We found that MC alone performed well to immobilize Pb in soil and reducing its distribution in shoots, but was less efficient to improve soil enzymatic activities and plant attributes. Conversely, the application of BR alone stimulated soil enzymatic activities, plant growth, and quality but was less effective to immobilize Pb in soil and reducing shoot Pb concentrations. The combinations of BR and MC of various ratios showed variable results. Interestingly, the most promising outcomes were obtained with BR50%+MC50% treatment which resulted in enhanced Pb-IMMi (73%), activities of soil enzymes, plant growth and quality, and antioxidant capacity, compared to control. Likewise, significant reductions in Pb concentrations in shoots (85%), roots (78%), extractable Pb (73%) were also obtained with BR50%+MC50% treatment, compared to control. Such outcomes point towards a cost-effective approach for reducing Pb uptake by the plants via using MC and BR at a 50:50 ratio.

Efficacy of chitosan-coated textile waste biochar applied to Cd-polluted soil for reducing Cd mobility in soil and its distribution in moringa (Moringa oleifera L.).

Soil pollution with Cd has promoted serious concerns for medicinal plant quality. Amending Cd-polluted soils with textile waste biochar (TWB) coated with natural polymers can lower Cd bioavailability in them and reduce associated environmental and human health risks. In this study, we explored the impacts of solely applied TWB, chitosan (CH), their mix (TWB + CH) and TWB coated with CH (TBC) in Cd-polluted soil on Cd distribution in moringa (Moringa oleifera L.) shoots and roots as well as plant-available Cd in soil. Moreover, amendments effects on plant growth, dietary quality, and antioxidative defense responses were also assessed. Results revealed that the addition of TWB, CH, and TWB + CH in Cd-polluted soil reduced Cd distribution in shoots (56%, 66%, and 63%), roots (41%, 48%, and 45%), and plant-available Cd in soil (38%, 52%, and 49%), compared to control. Interestingly, the TBC showed significantly the topmost response for reducing Cd concentrations in shoots, roots, and soil by 73%, 54%, and 58%, respectively, relative to control. Moreover, amending Cd-polluted soil with TWB, CH, and TWB + CH depicted significantly better effects on plant growth, dietary quality, and activities of soil enzymes but the topmost response was observed with TBC treatment. Compared with control, TBC improved plant growth parameters: shoot length (81%), root length (90%), shoot fresh weight (60%), root fresh weight (76%), shoot dry weight (75%), root dry weight (68%) contents of chlorophyll-a (42%) and chlorophyll-b (74%), and soil enzyme activities: urease (130%), catalase (138%), protease (71%), cellobiohydrolase (45%), acid phosphatase (34%), peroxidase (60%), ß-glucosidase (152%), chitinase (62%), and phosphomonoesterase (139%). Furthermore, TBC treatment arrested Cd-induced oxidative stress via escalating the activities of antioxidant enzymes as well as improved moringa dietary parameters (protein, tannins, lipids, alkaloids, saponins, terpenoids, flavonoids, and tocopherols contents). Such findings suggest that the TBC has an immense perspective to remediate Cd-polluted soils and prevent human health risks associated with Cd exposure through the diet.

Confident performance of chitosan and pistachio shell biochar on reducing Ni bioavailability in soil and plant plus improved the soil enzymatic activities, antioxidant defense system and nutritional quality of lettuce.

Nickel being a toxic heavy metal is considered as a hazardous pollutant in the soil environment. The cultivation of edible vegetables on Ni contaminated soil can deteriorate plant quality which causes critical health issues to humans and animals. Therefore, the remediation for such Ni polluted soils has currently become a great challenge for the researchers. Contrastingly, lowering bioavailability of Ni in those soils based on applying appropriate immobilizing amendments demonstrating a target to relieve virulence to plants can remarkably diminish the environmental hazard. In this experiment, biochar (BR) along diverse clays like bentonite (BE), cationic-zeolite (C-ZE), chitosan (CN) and attapulgite (AP) as individual doses at 2% each in a soil synthetically spiked with Ni (at 50 ppm) magnificently immobilize Ni and curtailed its bioavailability to lettuce (Lactuca sativa L.). In addition, the related influences of planned treatments on translocation of Ni to shoots and leaves, antioxidant preventive system over oxidative injury, biochemistry and nutritional ability of lettuce were monitored. Results suggested that the CN2% treatment performed excellently in terms of reducing Ni concentrations in leaves and roots of lettuce plants along bioavailable Ni in the soil after plant harvest. Surprisingly, the BR2% treatment efficiently promoted enzymatic activities in the soil and developed moisture content, photosynthesis, biomass, biochemistry, and nutrition (both micronutrients and macronutrients) and antioxidant preventive system while diminished Ni oxidative injury in lettuce plants over rest of the treatments. Finally, our results confirmed that individually applying CN at 2% in a Ni contaminated soil could significantly control Ni bioavailability, whereas, application of BR at 2% could remarkably develop aforementioned parameters in lettuce plants.

Effects of biochar and zeolite soil amendments with foliar proline spray on nickel immobilization, nutritional quality and nickel concentrations in wheat.

Since Ni-rich soils are a threat to the environment, growing edible crops on Ni-rich soils can pose a serious risk to human, animal, plant and ecosystem health and, hence, is considered as a challenging task for the researchers. Contrarily, limiting the bioavailability of Ni in such soils upon the addition of suitable amendments cum foliar spray of proteinogenic amino acids having an objective to alleviate stress to crop plants can considerably reduce the environmental risk. In this pot trail, we substantiate the effects of biochar (BR) and zeolite (ZL) addition in the soil along with proline (PN) spray on the resistance, and stress responses of wheat against Ni as well as on Ni translocation and accumulation in wheat plants grown on a Ni-rich soil contaminated by electroplating effluent. The treatments, applied with and without PN spray, involved: no amendment; BR; ZL; and a concoction of both amendments (BR50%+ZL50%). We found that BR50%+ZL50% treatment significantly immobilized Ni in the soil, reduced its accumulation in the shoot, root, and grain, blocked membrane lipid peroxidation and showed an improvement in photosynthetic parameters, the status of antioxidant activities, grain biochemistry and grain yield, compared to the control. Interestingly, exogenous PN spray caused a significant additive effect on the aforementioned parameters in the wheat plants grown on BR50%+ZL50% treated soil. Our results involved a reduced Ni bioavailability in wheat rhizosphere due to BR50%+ZL50% in soil and, furthermore, the additive effect of PN spray to scavenging ROS, obstructing peroxidation of lipid membrane and, thus providing resilience to wheat plant against Ni stress. The suggested technique can make Ni-rich soils suitable for cultivation and production of high-quality food by minimizing Ni bioavailability and toxicity to plants.

Promoting the productivity and quality of brinjal aligned with heavy metals immobilization in a wastewater irrigated heavy metal polluted soil with biochar and chitosan.

Depleting aquifers, lack of planning and low socioeconomic status of Pakistani farmers have led them to use wastewater (WW) for irrigating their crops causing food contamination with heavy metals and ultimately negative effects on human health. This study evaluates the effects of chitosan (CH) and biochar (BC) on growth and nutritional quality of brinjal plant together with in situ immobilization of heavy metals in a soil polluted with heavy metals due to irrigation with wastewater (SPHIW) and further irrigated with the same WW. Both CH and BC were applied at three different rates i.e. low rate [(LR), BC0.5%, CH0.5% and BC0.25%+CH0.25%], medium rate [(MR), BC1%, CH1% and BC0.5%+CH0.5%] and high rate [(HR), BC1.5%, CH1.5% and BC0.75%+CH0.75%]. Result revealed that brinjal growth, antioxidant enzymes, and fruit nutritional quality significantly improved from LR to HR for each amendment, relative to control. However, these results were more prominent with BC alone and BC+CH, compared with CH alone at each rate. Similarly, with few exceptions, significant reduction in Ni, Cd, Co, Cr and Pb concentrations in the root, shoot and fruit were found in sole CH treatment both at LR and MR but in both CH and BC+CH treatments at HR, relative to control. Interestingly, the concentrations of Fe in the roots, shoots and fruit were more pronounced at BC treatments relative to CH and BC+CH treatments at each rate, compared to control. Overall, the BC+CH treatment at HR was the most effective treatment for in situ immobilization of heavy metals in SPHIW and further irrigated with the same WW, compared to rest of the treatments. This study indicates that BC0.75%+CH0.75% treatment can be used to reduce mobility and bioavailability of heavy metals in SPHIW and facilitates plant growth by improving the antioxidant system. However, the feasibility of BC0.75%+CH0.75% treatment should also be tested at the field scale.

Soil Amendments and Foliar Melatonin Reduced Pb Uptake, and Oxidative Stress, and Improved Spinach Quality in Pb-Contaminated Soil.

Amending Pb-affected soil with biochar (BH) and magnesium potassium phosphate cement (MKC) reduces Pb uptake in plants. Moreover, foliar applications of melatonin and proline are also known to reduce plant oxidative stress and Pb uptake. However, little is known about combining both techniques, i.e., adding a combo immobilizing dose (CIA = mixture of BH and MKC at 50:50 ratio) in Pb-polluted soil and foliar application of proline and melatonin for reducing Pb uptake and oxidative stress in spinach. Control, proline, melatonin, CIA, CIA+proline, and CIA+melatonin were the treatments utilized in this pot study to see their effects on reducing plant oxidative stress, Pb uptake, and improving spinach quality in Pb-polluted soil. Moreover, Pb bioavailability, enzymatic activities, and numbers of bacteria, fungi, and actinomycetes in the soil were also evaluated. The effect of CIA on reducing Pb in the soil-plant system and improving soil enzymes and microbial numbers was more pronounced than melatonin alone. The most effective treatment was CIA+melatonin reducing Pb availability in soil (77%), shoots (95%), and roots (84%), alleviating oxidative stress, and improving plant biomass (98%) and nutrients. Soil enzymatic activities and the number of microorganisms in the rhizosphere were also highest with CIA+melatonin. Results highlight the significance of CIA+melatonin, as an inexpensive approach, in remediating Pb-polluted soil and improving spinach quality. However, further research is needed to understand the significance of CIA+melatonin on different crops and various soil Pb concentrations before employing this technique commercially in agriculture and environment sectors.

Aspergillus niger-mediated release of phosphates from fish bone char reduces Pb phytoavailability in Pb-acid batteries polluted soil, and accumulation in fenugreek.

Soil receiving discharges from Pb-acid batteries dismantling and restoring units (PBS) can have a high concentration of phytoavailable Pb. Reducing Pb phytoavailability in PBS can decline Pb uptake in food crops and minimize the risks to humans and the environment. This pot study aimed to reduce the concentration of phytoavailable Pb in PBS through Aspergillus niger (A. niger)-mediated release of PO43- from fish bone [Apatite II (APII)] products. The PBS (Pb = 639 mg kg-1 soil) was amended with APII powder (APII-P), APII char (APII-C), and A. niger inoculum as separate doses, and combining A. niger with APII-P (APII-P + A. niger) and APII-C (APII-C + A. niger). The effects of these treatments on reducing the phytoavailability of Pb in PBS and its uptake in fenugreek were examined. Additionally, enzymatic activities and microbial biomass carbon (MBC) in the PBS and the indices of plant physiology, nutrition, and antioxidant defense machinery were scoped. Results revealed that the APII-C + A. niger treatment was the most efficient one. Compared to the control, it significantly reduced the Pb phytoavailability (DTPA-extractable Pb fraction) in soil and its uptake in plant shoots, roots, and grain, up to 61%, 83%, 74%, and 92%. The grain produced under APII-C + A. niger were safe for human consumption as Pb concentration in grain was 4.01 mg kg-1 DW, remaining within the permissible limit set by WHO/FAO (2007). The APII-C + A. niger treatment also improved soil pH, EC, CEC, MBC, available P content and enzymatic activities, and the fenugreek quality parameters. A. niger played a significant role in solubilizing PO43- from APII-C, which reacted with Pb and formed insoluble Pb-phosphates, thereby reducing Pb phytoavailability in PBS and its uptake in plants. This study suggests APII-C + A. niger can remediate Pb-polluted soils via reducing Pb phytoavailability in them.

Impacts of oxalic acid-activated phosphate rock and root-induced changes on Pb bioavailability in the rhizosphere and its distribution in mung bean plant.

Rhizosphere acidification in leguminous plants can release P from the dissolution of phosphate compounds which can reduce Pb bioavailability to them via the formation of insoluble Pb compounds in their rhizosphere. A soil polluted from Pb-acid batteries effluent (SPBE), having total Pb = 639 mg kg-1, was amended with six different rates (0, 0.5, 1, 2, 4 and 6%) of oxalic acid-activated phosphate rock (OAPR) and their effects on pH, available P and bioavailable Pb concentrations in the rhizosphere and bulk soils of mung bean plant were evaluated. Furthermore, the effects of these variant OAPR rates on Pb concentrations in plant parts, bioaccumulation factor (BAF) and translocation factor (TF) for Pb in grain and traits like productivity, the activities of antioxidant enzymes, and grain biochemistry were investigated. Results revealed that increasing rates of OAPR significantly increased pH values and available P while decreased bioavailable Pb concentrations in the rhizosphere over control. The highest dissolution of P in the rhizosphere was with 4 and 6% OAPR rates. As a result, the formation of insoluble Pb compounds affected on reduced Pb concentrations in shoots, roots, and grain in addition to lower grain BAF and TF values for Pb over control. Likewise, the highest plant productivity, improved grain biochemistry, high Ca and Mg concentrations, least oxidative stress, and enhanced soil alkaline phosphatase activity were found with 4 and 6% OAPR rates. The OAPR 4% rate is suggested for reducing grain Pb concentration, cell oxidative injury, and improving grain biochemistry in mung bean.

Potential of pistachio shell biochar and dicalcium phosphate combination to reduce Pb speciation in spinach, improved soil enzymatic activities, plant nutritional quality, and antioxidant defense system.

Lead-contaminated soils are becoming an ecological risk to the environment because of producing low-quality food which is directly causing critical health issues in humans and animals. We hypothesized that incorporation of dicalcium phosphate (DCP), eggshell powder (ESP) and biochar (BH) at diverse rates into a Pb-affected soil can proficiently immobilize Pb and decline its bioavailability to spinach (Spinacia oleracea L.). A soil was artificially spiked with Pb concentration (at 600 mg kg-1) and further amended with DCP, ESP, and BH (as sole treatments at 2% and in concoctions at 1% each) for immobilization of Pb in the soil. The interlinked effects of applied treatments on Pb concentrations in shoots and roots, biomass, antioxidants, biochemistry, and nutrition of spinach were also investigated. Results depicted that the highest reduction in DTPA-extractable Pb and the concentrations of Pb in shoots and roots was achieved in DCP1%+BH1% treatment that was up to 58%, 66%, and 53%, respectively over control. Likewise, the DCP1%+BH1% treatment also showed the maximum shoot and root dry weight (DW), chlorophyll-a (Chl-a) and chlorophyll-b (Chl-b) contents and relative water content (RWC) in spinach up to 92%, 121%, 60%, 65%, and 30%, respectively, compared to control. Likewise, DCP1%+BH1% treatment noticeably improved antioxidant enzymes, biochemistry, and nutrition in the leaves. Moreover, the DCP1%+BH1% treatment depicted mostly enhanced activities of dehydrogenase, catalase, acid phosphatase, alkaline phosphatase, phosphomonoesterase, urease, protease and B-glucosidase in the post-harvested soil up to 118%, 345%, 55%, 92%, 288%, 107%, 53% and 252%, respectively over control.

Associative effects of lignin-derived biochar and arbuscular mycorrhizal fungi applied to soil polluted from Pb-acid batteries effluents on barley grain safety.

While disobeying environmental regulations of Pakistan, several Pb-acid batteries recycling and repairing units discharge their effluents into water canals that irrigate arable fields. Resultantly, serious ecological risks, as well as human health hazards through consumption of edible crops grown on such Pb-polluted soils have been reported. In this experiment, we observed associative effects of amending a soil polluted from Pb-acid batteries effluents (SPB) with arbuscular mycorrhizal fungi (AMF) and lignin-derived biochar (LBC) on barley grain safety to human health. The SPB was treated with AMF inoculum (a consortium of four AMF species), lignin (LN), and LBC, as sole treatments and AMF inoculum with LN and LBC. Barley parameters involving Pb distribution in grain and other parts, grain biochemistry, and nutrition were assessed. Likewise, Pb bioavailability in SPB, AMF root colonization, soil enzymes, microbial biomass carbon (MBC), and AMF produced total glomalin related soil protein (TGSP) were also scoped. Additionally, human renal cells (HEK 293) cytotoxicity test was performed by opting barley grain-related Pb concentrations. Results show that LBC + AMF significantly reduced grain Pb concentrations below the critical limit [4.67 mg kg-1 (WHO/FAO standard)], AMF colonization, MBC, soil enzymology, and TGSP, compared to control. Likewise, rest barley parameters were also improved in this treatment. Contrary to other treatments, grain produced on LBC + AMF did not result in (a) cell apoptosis, (b) cell distortion and (c) cohesion loss. Immobilization of Pb in SPB was due to the dilution effect of Pb adsorption on LBC, AMF mycelium and TGSP which resulted in a significant drop of grain Pb concentrations below the critical limit and ultimately no harm to HEK 293 cells. Our findings endorse that grain produced at LBC + AMF treatment are safer for human consumption and will not pose health risks. The LBC + AMF application can remediate SPB for safer cereal production.

Co-inoculation effect of Rhizobium and Achillea millefolium L. oil extracts on growth of common bean (Phaseolus vulgaris L.) and soil microbial-chemical properties.

Essential oils (EO) of several plant species have the potential to combat plant and fungal diseases. However, the effects of Achillea millefolium EO on the development of common bean (Phaseolus vulgaris L.), is still unknown. Moreover, its effect on N2-fixing bacteria, and in general on soil properties has not been studied yet. A greenhouse trial was set up to evaluate both the influence that Achillea millefolium EO and the inoculation with three different Rhizobium strains have on the bean plant and on the chemical and microbiological properties of an agriculturally used Cambisol. Non-inoculated pots were used as control. Our findings showed a decrease in bacterial colony forming units due to EO application and an increase following the Rhizobium inoculation compared to the control. The EO application decreased soil basal respiration and activities of dehydrogenase, urease, ß-glucosidase and acid phosphatase. Such effects were stronger with higher oil concentrations. Moreover, the treatments combining Rhizobium inoculation with EO showed a positive effect on nodulation and plant height. Overall, the combined application of Achillea millefolium EO and rhizobia works as an efficient biocide that could be applied in organic agriculture without hampering the activity of nodule-forming N-fixing bacteria and the development of common bean.

Radiation efficiency and nitrogen fertilizer impacts on sunflower crop in contrasting environments of Punjab, Pakistan.

Sunflower (Helianthus annuus L.) is the leading non-conventional oilseed crop in Pakistan. Nitrogen fertilizer can affect plant growth and productivity by changing canopy size which has an effect on the radiation use efficiency (RUE) of the crop. The response of sunflower hybrids in terms of phenology, fraction of intercepted radiation (F i), and RUE to nitrogenous rates (0, 60, 120, 180, and 240 kg ha-1) was studied in three field experiments conducted in three various environments: Multan (arid), Faisalabad (semi-arid), and Gujranwala (sub-humid) during spring seasons 2008 and 2009. The treatments were laid out according to a randomized complete block design with split plot arrangements, keeping the sunflower hybrids in main plots and nitrogen rates in sub-plots, and replicated three times. The results showed Hysun-38 took a maximum number of days to anthesis (101) as compared to Pioneer-64A93 (100) and Hysun-33 (99). The mean values of F i were 0.850, 0.903, and 0.978, and the estimated values of RUE for total aboveground dry matter were 2.14, 2.47, and 2.65 g MJ-1 at experimental locations of Multan, Faisalabad, and Gujranwala, respectively. The values of RUE for grain yield (RUEGY) were 0.78, 0.98, and 1.26 g MJ-1 at experimental locations of Multan, Faisalabad, and Gujranwala, respectively. The average RUEGY values over three locations were 2.61, 2.60, 2.43, and 2.36 g MJ-2 in N4 (180 kg ha-1), N5 (240 kg ha-1), N3 (120 kg ha-1), and N2 (60 kg ha-1) treatments, respectively. Increasing rates of N increased RUEGY over the standard treatment N3 (120 kg N ha-1); however, the averaged values over three locations were 1.22, 1.08, 0.99, and 0.92 g MJ-2 in N4, N5, N3, and N2 treatments, respectively. Therefore, optimum water and N doses are important for attaining higher RUE, which may enhance sunflower growth and yield.