Balancing crop productivity, soil health and heavy metal dynamics in industrial effluent irrigation of okra (Abelmoschus esculentus (L.) Moench)

Vollständiger Abstract

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In water-scarce peri-urban agriculture systems of South and Southeast Asia, the use of industrial effluents for irrigation is gaining momentum. Okra (Abelmoschus esculentus (L.) Moench), being a popular vegetable crop, is grown under effluent-irrigated conditions due to its adaptability and economic importance. The review presented here compiles research articles published from 2000 to 2025 studying the effects of irrigation with distillery, textile, tannery, paper and pulp and sugar mill effluents on okra, focusing on plant growth, physiological response, soil health and heavy metal accumulation. Accumulated evidence demonstrates a concentration-dependent response of okra and soil systems to industrial effluent irrigation. Effluent suitability for agriculture is strongly industry-dependent: distillery and sugar mill effluents, at low dilution, supply useful nitrogen (N), potassium (K) and organic matter with comparatively lower heavy-metal risk, whereas tannery and textile dyeing effluents carry substantially higher chromium, cadmium and lead loads and require treatment before safe reuse. Nitrogen, phosphorus (P), K and organic matter are often supplemented for improved seed germination, vegetative development, chlorophyll production, yield and nutrient availability, particularly at low effluent dilutions (5–25 %). Osmotic stress, oxidative damage, growth inhibition and a reduction in photosynthetic activity occur at concentrations exceeding 50 %. Regardless of effluent type, continued irrigation increases soil salt content, alters microbial and enzyme activity and drives accumulation of heavy metals cadmium, chromium, lead and nickel, which translocate to edible pods and can exceed recommended food safety limits, posing a measurable health concern. Knowledge gaps remain regarding varietal differences in metal uptake, stress tolerance mechanisms, molecular responses and their long-term field-scale implications under tropical conditions. Mitigation strategies showing the most promise include biochar amendment, phytoremediation crop rotation, constructed wetland pre-treatment and precision dilution.