Evaluation of the efficiency of liquid organic fertilizers enriched with different iron sources on maize (Zea mays L.) growth and post-harvest soil enzymatic activity

Document Type : Research Paper

Authors

1 Department of Soil Science and Engineering, Faculty of Agriculture, University of Zanjan, Zanjan, Iran

2 Department of Soil Science, Faculty of Agriculture, University of Zanjan. Zanjan, Iran

3 Farhikhtegan Zarnam Industrial Research Group, Alborz Province, Hashtgerd City, Iran

4 . Department of Soil Science, Faculty of Agriculture, University of Zanjan. Zanjan, Iran

10.22059/ijswr.2026.406875.670059

Abstract

A greenhouse experiment was conducted using a completely randomized factorial design with three replications to evaluate the effects of different levels of amino acid–rich soluble organic fertilizers enriched with various iron sources on maize growth and soil enzymatic activity in calcareous soils. Fertilizer type was considered as the first factor at eight levels, and fertilizer application rate as the second factor at two levels. The treatments included: control (C); 3% iron-containing ferrous sulfate solution (S); organic fertilizer without iron enrichment (O); separate application of organic fertilizer without iron and 3% ferrous sulfate (OS); organic fertilizer enriched with 3% iron from ferrous sulfate (A); organic fertilizer enriched with 1.5% iron from Fe-EDTA and 1.5% from ferrous sulfate (AE); organic fertilizer enriched with 1.5% iron from Fe-DTPA and 1.5% from ferrous sulfate (AD); and organic fertilizer enriched with 1.5% iron from Fe-EDDHA and 1.5% from ferrous sulfate (AH). These fertilizers were applied via fertigation at two levels, 50 and 100 L ha⁻¹, corresponding to 0.08 and 0.16 g per 3 kg of soil, respectively. The results showed that all fertilizer treatments increased fresh and dry weights of shoots and roots, plant height, and soil enzymatic activity compared to the control. The AH treatment at 100 L ha⁻¹ (AH100) exhibited the highest yield, increasing dry shoot and root weights and plant height by 34%, 31%, and 36.9%, respectively, compared to the control, as well as enhancing alkaline phosphatase, catalase, and urease activities by 23.2%, 22.3%, and 21.5%, respectively. Application of the organic fertilizer containing Fe-EDDHA significantly improved maize growth and physiological status, which was attributed to enhanced iron nutrition, chlorophyll content, and soil biological activity.

Keywords

Main Subjects

Introduction

During the wet-milling process of maize in grain refineries, a by-product rich in organic matter, known as corn steep liquor is generated. Through enzymatic and fermentative hydrolysis, corn steep liquor can release bioactive compounds that act as signaling molecules and plant growth stimulators, making it a promising raw material for the production of soluble organic fertilizers. Moreover, considering the widespread iron (Fe) deficiency in neutral and alkaline soils, developing iron-enriched fertilizers that are both effective in correcting this deficiency and more environmentally compatible is regarded as an important strategy in iron nutrition management. Accordingly, this study was conducted with the aim of producing soluble organic fertilizers enriched with different iron chelates and evaluating their effects on maize growth and soil enzyme activity under calcareous soil conditions.

Material and Methods

A factorial greenhouse experiment with two factors—fertilizer type and application rate—was conducted in a completely randomized design using fertigation, with three replications under controlled conditions, in the greenhouse of the Farhikhtegan Zarnam Industrial–Research Group during the winter of 2024. The experimental treatments included: control without fertilizer (C); ferrous sulfate solution containing 3% iron (S); unenriched liquid organic fertilizer (O); separate application of unenriched liquid organic fertilizer and ferrous sulfate solution containing 3% iron (OS); liquid organic fertilizer enriched with 3% iron from ferrous sulfate (A); liquid organic fertilizer enriched with 1.5% iron from Fe-EDTA chelate and 1.5% iron from ferrous sulfate (AE); liquid organic fertilizer enriched with 1.5% iron from Fe-DTPA chelate and 1.5% iron from ferrous sulfate (AD); and liquid organic fertilizer enriched with 1.5% iron from Fe-EDDHA chelate and 1.5% iron from ferrous sulfate (AH). The fertilizer treatments were applied at two levels (50 and 100 L ha⁻¹) in two separate stages during the growth period of hybrid maize 703 planted in 3-kg pots.

Results and Discussion

The results showed that the different fertilizer treatments had a significant effect on maize growth characteristics, yield, and microbial activity. The greatest plant height (119.63 cm), as well as the highest fresh and dry biomass of shoots and roots, were observed in the AH100 and AH50 treatments, respectively. Root length and leaf number increased by 32% and 20% compared with the control. Total chlorophyll increased by 28.8%, and carotenoids increased by 17.6% relative to the control. In contrast, the control treatment recorded the lowest values in all measurements. Regarding iron content, the highest Fe concentration was recorded in treatment (E) (117.37 µg g⁻¹ dry matter). In addition, urease and alkaline phosphatase activities in the soil increased by 23.2% and 21.5%, respectively, in the AH100 treatment compared with the control. The combination of liquid organic fertilizer with Fe-EDDHA chelate enhanced nutrient uptake—especially iron—due to its rich content of iron, organic nitrogen, amino acids, carbohydrates, and its microbial-stimulating properties. As a result, plant growth and yield were considerably improved.

Conclusions

The results of this study indicated that application of organic fertilizer containing Fe-EDDHA significantly improved the growth and physiological traits of maize. This fertilizer increased plant height, fresh and dry weights of shoots and roots, chlorophyll content, and soil enzyme activities, including urease, phosphatase, and catalase. The greatest positive effect was observed in the AH100 treatment (100 L ha⁻¹, equivalent to 0.16 g per 3 kg of soil), highlighting the effective role of chelated iron in plant nutrition, chlorophyll enhancement, and photosynthetic efficiency. In addition, due to its content of organic matter and amino acids, this fertilizer may improve the physical, chemical, and biological properties of soil, including stimulating beneficial microbial activity. These components may also enhance plant nitrogen nutrition and growth stability by supplying organic nitrogen and improving its uptake efficiency. Furthermore, under greenhouse conditions, application of 100 L ha⁻¹ (0.16 g per 3 kg of soil) of Fe-EDDHA–containing organic fertilizer improved iron nutrition in calcareous soils. However, due to the pot-based nature of the experiment, the results reflect plant responses under controlled conditions and cannot be directly extrapolated to field conditions. Therefore, definitive recommendations regarding this treatment require field experiments to evaluate the persistence and effectiveness of its effects under real production conditions.

Author Contributions

Conceptualization, A. A. and A. G.; methodology, A. A. and A. G; software, A. A.; validation, A. A. and A. G.; formal analysis, A. A. and A. G.; investigation, A. A. and A. G.; resources, A. A. and A. G.; data curation, A. A. and A.G.; writing—original draft preparation, A. A.; writing—review and editing, A. G.; visualization, A. A.; supervision, A. G.; project administration, A. G., M. J. A. A. S.; funding acquisition, A. A., A. G., and M. J. A.

All authors have read and agreed to the published version of the manuscript.

Data Availability Statement

The data supporting the findings of this study are available in the manuscript. If the study did not report

any data, you might add “Not applicable” here.

Acknowledgements

The authors would like to thank Zanjan Universities, Farhikhtegan Zarnam Research Industrial Group and Iranian Company for Maize Development for providing all the needed facilities.

Ethical considerations

The authors avoided data fabrication, falsification, plagiarism, and misconduct.

Conflict of interest

The author declares no conflict of interest.

References

Abdo, A. I., El-Sobky, E. S. E., & Zhang, J. (2022). Optimizing maize yields using growth stimulants under the strategy of replacing chemicals with biological fertilizers. Frontiers in Plant Science, 13, 1069624.
Abujabhah, I. S., Bound, S. A., Doyle, R., & Bowman, J. P. (2016). Effects of biochar and compost amendments on soil physico-chemical properties and the total community within a temperate agricultural soil. Applied soil ecology, 98, 243-253.
Adzikro, M. H., Laila, A., Farmawaty, A. A., & Sulistyorini, E. (2025). Effects of NPK, Amino Acid Liquid Organic Fertilizer on Maize (Zea mays L.) Growth and Yield. Jurnal Agroekoteknologi Terapan (Applied Agroecotechnology Journal), 6(1), 65-73.
Alalaf, A. H., Alalam, A. T. S., & Al-Zebari, S. M. K. (2022). The effect of spraying amino acid fertilizer on the growth characteristics and mineral content of pomelo (Citrus grandis. L) seedlings. Iranian Journal of Ichthyology, 9, 123-126.
Algethami, J. S., Irshad, M. K., Javed, W., Alhamami, M. A., & Ibrahim, M. (2023). Iron-modified biochar improves plant physiology, soil nutritional status and mitigates Pb and Cd-hazard in wheat (Triticum aestivum L.). Frontiers in Plant Science, 14, 1221434.
Ali Asgharzad, N. (2006). Laboratory methods in soil biology. p 540. Tabriz: Tabriz University Press.
Álvarez-Fernández, A., Garcıa-Marco, S., & Lucena, J. J. (2005). Evaluation of synthetic iron (III)-chelates (EDDHA/Fe3+, EDDHMA/Fe3+ and the novel EDDHSA/Fe3+) to correct iron chlorosis. European Journal of Agronomy, 22(2), 119-130.
Al-Zubaidi, M. S. K., Bader, B. R., Abood, M. A., Hamdi, G. J., & Al-Afraji, H. R. J. (2021). The effect of adding solid and chelated liquid iron on the growth and yield of broad bean. Journal of Agricultural Science, 188-194.
Areche, F., Aguilar, S. V., More Lopez, J. M., Castañeda Chirre, E. T., Sumarriva-Bustinza, L. A., Pacovilca-Alejo, O. V., Camposano Cordova, Y.F., Montesinos, C. C., Quincho Astete, J. A., Quispe-Vidalon, D., & Salas-Contreras, W. H. (2023). Recent and historical developments in chelated fertilizers as plant nutritional sources, their usage efficiency, and application methods. Brazilian Journal of Biology, 83, e271055.
Atik, A. (2013). Effects of planting density and treatment with vermicompost on the morphological characteristics of oriental beech (Fagus orientalis Lipsky.). Compost Science & Utilization, 21(2), 87-98.
Blazquez, M. A., Nelson, D. C., & Weijers, D. (2020). Evolution of plant hormone response pathways. Annual Review of Plant Biology, 71(1), 327-353.
Bremner, J. (1996). Nitrogen total. Methods of Soil Analysis. In: D. L. Sparks et al. (Eds). Method of Soil Analysis. Part 3. pp. 1085-1121. Chemical Methods. American Society of Agronomy and Soil Science Society of America. Madison. WI. USA.
Cho, M. H., Park, H. L., & Hahn, T. R. (2015). Engineering leaf carbon metabolism to improve plant productivity. Plant Biotechnology Reports, 9(1), 1-10.
Ebrahimi, M., Khajehpour, M. R., Naderi, A., & Nassiri, B. M. (2014). Physiological responses of sunflower to water stress under different levels of zinc fertilizer. International Journal of Plant Production, 8(4).
Garcia-Sanchez, F., Camara-Zapata, J. M., & Navarro-Morillo, I. (2024). Use of Corn Steep Liquor as a Biostimulant in Agriculture. Horticulturae, 10(4), 315.
Gee, G. W., & Boder, D. (2002(. Particle-size analysis. In: Dane, J. H. and G. C. Topp. (Eds.). Methods of Soil Analysis. Part 4- Physical Methods. Agronomy Monograph. No 9. American Society of Agronomy and Soil Science Society of America. Madison. WI, PP. 255-293.
Hershkowitz, J. A., Dey, M. G., Heins, R., & Bugbee, B. (2025). Fertigation with Fe-EDTA, Fe-DTPA, and Fe-EDDHA Chelates to Prevent Iron Chlorosis of Sensitive Species in High-pH Soilless Media. HortScience, 60(3), 404-410.
Hsu, H. J. (1996). U.S. Patent No. 5,504,055. Washington, DC: U.S. Patent and Trademark Office.
Jalali, M. (2020). Effect of iron-amino acid chelates on antioxidant capacity and nutritional value of soybean. Journal of Plant Productions, 43(4), 477-486.‎
Ji, R., Dong, G., Shi, W., & Min, J. (2017). Effects of Liquid Organic Fertilizers on Plant Growth and Rhizosphere Soil Characteristics of Chrysanthemum. Sustainability, 9(5), 841.
Johnson, J. L., & Temple, K. L. (1964). Some variables affecting the measurement of “catalase activity” in soil. Soil Science Society of America Journal, 28(2), 207-209.
Lightenthaler, H.K. (1987). Chlorophylls and carotenoids: pigments of photosynthetic biomembranes. Methods in enzymology, 148, 350-382.
Lindsay, W. L., & Norvell, W. (1978). Development of a DTPA soil test for zinc, iron, manganese, and copper. Soil science society of America journal, 42(3), 421-428.
Loeppert, R. H., & Suarez, D. L. (1996). Carbonate and gypsum. Methods of soil analysis: Part 3 chemical methods, 5, 437-474.
Lucena, J. J., Barak, P., & Hernández-Apaolaza, L. (1996). Isocratic ion-pair high-performance liquid chromatographic method for the determination of various iron (III) chelates. Journal of Chromatography A, 727(2), 253-264.
Mohammed, S., & Kanimarani, S. A. (2020). Humic acid and iron chelate foliar application influence on growth and quality of two lettuce cultivars (Lactuca sativa L.).
Molnar, Z., Solomon, W., Mutum, L., & Janda, T. (2023). Understanding the mechanisms of Fe deficiency in the rhizosphere to promote plant resilience. Plants, 12(10), 1945.
Navarro-Morillo, I., Navarro-Perez, V., Perez-Millan, R., Navarro-León, E., Blasco, B., Cámara-Zapata, J. M., & Garcia-Sanchez, F. (2023). Effects of root and foliar application of corn steep liquor on pepper plants: a physiological, nutritional, and morphological study. Horticulturae, 9(2), 221.
Nelson, D. W. & Sommers, L. E. (1996). Total carbon, organic carbon and organic matter. In: D. L. Sparks et al., (Eds.). Methods of Soil Analysis. Part III. 3rd Ed. Soil Science Society of America Inc. American Society of Agronomy Madison. WI. PP. 61-1010.
Niharika, P., Mahendran, P. P., Prabhaharan, J., Gurusamy, A., Prasanthrajan, M., Chandrakumar, K., & Yuvaraj, M. Amino acid-chelated micronutrients: A new frontier in crop nutrition and abiotic stress mitigation.
Ning, X., Lin, M., Huang, G., Mao, J., Gao, Z., & Wang, X. (2023). Research progress on iron absorption, transport, and molecular regulation strategy in plants. Frontiers in plant science, 14, 1190768.
Noroozlo, Y. A., Souri, M. K., & Delshad, M. (2019). Stimulation effects of foliar applied glycine and glutamine amino acids on lettuce growth. Open Agriculture, 4(1).
Obayori, O. S., Salam, L. B., Anifowoshe, W. T., Odunewu, Z. M., Amosu, O. E., & Ofulue, B. E. (2015). Enhanced degradation of petroleum hydrocarbons in corn-steep-liquor-treated soil microcosm. Soil and Sediment Contamination: An International Journal, 24(7), 731-743.
Olsen, S. R. (1954). Estimation of available phosphorus in soils by extraction with sodium bicarbonate (No. 939). US Department of Agriculture.
Puglisi, I., Brida, S., Stoleru, V., Torino, V., Sellitto, V. M., & Baglieri, A. (2021). Application of novel microorganism-based formulations as alternative to the use of iron chelates in strawberry cultivation. Agriculture, 11(3), 217.
Rengel, Z., Cakmak, I., & White, P. J. (Eds.). (2022). Marschner's mineral nutrition of plants. Academic press.
Rhoades, J. D. (1996). Salinity: Electrical conductivity and total dissolved solids. Methods of soil analysis: Part 3 Chemical methods, 5, 417-435.
Riaz, N., & Guerinot, M. L. (2021). All together now: regulation of the iron deficiency response. Journal of Experimental Botany, 72(6), 2045-2055.
Schenkeveld, W. D. C., Dijcker, R., Reichwein, A. M., Temminghoff, E. J. M., & Van Riemsdijk, W. H. (2008). The effectiveness of soil-applied FeEDDHA treatments in preventing iron chlorosis in soybean as a function of the o, o-FeEDDHA content. Plant and Soil, 303(1), 161-176.
Sida-Arreola J. P., Sanchez-Chavez E., Avila-Quezada G. D., Zamudio-Flores P. B., & Acosta M. C. (2015). Iron biofortification and its impact on antioxidant system, yield and biomass in common bean. Plant, Soil and Environment 61(12):573-576.
Sure, S., Arooie, H., Sharifzade, K., & Dalirimoghadam, R. (2012). Responses of productivity and quality of cucumber to application of the two bio-fertilizers (humic acid and nitroxin) in fall planting.
Syam, N., Hidrawati, Sabahannur, S., & Nurdin, A. (2021). Effects of Trichoderma and foliar fertilizer on the vegetative growth of black pepper (Piper nigrum L.) seedlings. International Journal of Agronomy, (1), 9953239.
Tabatabai, M. A. (1982). Soil enzymes. Methods of soil analysis: Part 2 chemical and microbiological properties, 9, 903-947.
Tadros, M. J., Omari, H. J., & Turk, M. A. (2019). The morphological, physiological and biochemical responses of sweet corn to foliar application of amino acids biostimulants sprayed at three growth stages. Australian Journal of Crop Science, 13(3), 412-417.
Thomas, G. W. (1996). Soil pH and Soil Acidity. In: D. L. Sparks et al. (Eds). Methods of Soil Analysis. Part3. 3rd Ed. Am. Soc. Agron. Madison. WI. PP. 475-490.
Tsai, H. H., & Schmidt, W. (2020). pH-dependent transcriptional profile changes in iron-deficient Arabidopsis roots. BMC genomics, 21(1), 694.
Wang, Z., Wang, K., Jiang, Q., Liu, C., Shan, J., & Teng, H. (2023). Mutual feeding mechanism of carbon, nitrogen and enzyme activity in Northeast China black soil under snow cover change. Applied Soil Ecology, 190, 104991.
Yadav, V., Sharma, Y. K. and Singh, H. (2018). Iron impact assessment in maize: Growth, biomass, pigments and related enzymes. Research in environment and life sciences, 11(02) 63-68.
Zahedifar, M., Moosavi A. A., Gavili, E., & Ershadi, A. (2025). Tomato fruit quality and nutrient dynamics under water deficit conditions: The influence of an organic fertilizer. PLoS ONE, 20(1), e0310916.
Zhang, J., Bei, S., Li, B., Zhang, J., Christie, P., & Li, X. (2019). Organic fertilizer, but not heavy liming, enhances banana biomass, increases soil organic carbon and modifies soil microbiota. Applied soil ecology, 136, 67-79.
Zuluaga, M. Y. A., Cardarelli, M., Rouphael, Y., Cesco, S., Pii, Y., & Colla, G. (2023). Iron nutrition in agriculture: From synthetic chelates to biochelates. Scientia Horticulturae, 312, 111833.
Iranian Journal of Soil and Water Research
Volume 56, Issue 12
March 2026
Pages 3489-3508

Files

Share

How to cite

Statistics