Air-to-Water Condensation Farming and Fogponics for "Zero-Watering" Horticulture in India: A Review of Technologies, Crop Suitability and Readiness for El Niño-Driven Water Scarcity
Abstract
India produced an estimated 369.05 million tonnes of horticultural produce from 29.48 million ha in 2024–25. Its per-capita water availability, however, has fallen to about 1,486 m³ (2021) and is projected to reach 1,367 m³ by 2031, below the 1,700 m³ water-stress threshold. Greenhouse warming is expected to strengthen the inverse El Niño–monsoon relationship. Future El Niño years may therefore cause crop-yield losses about 30% larger than those observed historically, and nearly 200 Indian districts have been identified as highly vulnerable in 2026. This review examines two complementary pathways that decouple high-value horticulture from rainfall and groundwater: (i) air-to-water condensation farming, in which atmospheric water generators (AWGs), sorbent-based harvesters, dew condensers or fog collectors, preferably solar-powered, supply condensate to the root zone of sheltered crops; and (ii) fogponics, an aeroponic variant that delivers nutrient solution as a 5–30 µm fog to suspended roots. Published evidence shows that solar-driven atmospheric water can irrigate leafy vegetables with growth comparable to tap water, that fog collectors can yield 2.9–3.3 L m⁻² day⁻¹ (annual mean) at favourable coastal sites, and that aeroponic seed-potato systems are commercially established in India. Specific energy demand nevertheless ranges from about 0.02 kWh L⁻¹ in humid air to 3.64 kWh L⁻¹ in very dry air, and levelized water costs of US$ 0.09–0.40 L⁻¹ have been reported. These figures confine the approach, at present, to high-value, small-footprint protected cultivation, nurseries and propagation. A crop-suitability matrix for Indian fruits, vegetables and flowers, an agro-climatic zoning framework, a sizing procedure and a research roadmap are proposed. "Zero watering" is best understood as zero dependence on irrigation from surface or groundwater, not zero water input. The technology can serve as climate-insurance infrastructure for nurseries and protected horticulture during El Niño years.
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Introduction
Horticulture is the fastest-growing segment of Indian agriculture. The Third Advance Estimates for 2024–25 place total horticultural production at 369.05 million tonnes from 29.48 million ha, about 4% higher than the previous year [1]. This output is grown on a shrinking water base. The Ministry of Jal Shakti reports that average annual per-capita water availability fell to 1,486 m³ in 2021 and will decline to 1,367 m³ by 2031; availability below 1,700 m³ is classed as water-stressed [2]. Groundwater, the backbone of horticultural irrigation in peninsular and north-western India, is already heavily used. Most fruit, vegetable and flower crops in rainfed or semi-irrigated tracts are highly sensitive to the timing and quantity of monsoon rainfall.
The El Niño–Southern Oscillation (ENSO) adds a recurrent shock to this structural scarcity. In June 2026 the USDA Foreign Agricultural Service reported that India was moving from ENSO-neutral conditions towards El Niño. The India Meteorological Department expected El Niño to influence the July–September monsoon, and the Government of India had identified nearly 200 districts as highly vulnerable to El Niño-related agricultural impacts [3]. Zhao et al. [4] showed that greenhouse warming strengthens rather than weakens the inverse ENSO–Indian summer monsoon rainfall relationship. Their constrained projections indicate that monsoon sensitivity to ENSO could be nearly 40% greater than historical levels, and that crop-yield losses in El Niño years could be about 30% larger than in the past. Horticulture therefore needs water sources that do not depend on the monsoon.
Conclusion
Air-to-water condensation farming and fogponics together offer a technically proven way to grow selected horticultural crops without drawing on rainfall, rivers or groundwater. Crop-level evidence confirms that atmospheric water can sustain leafy vegetables, that fog collection can feed greenhouse hydroponics, and that aeroponic seed-potato production is commercially established in India. The decisive constraint is energy per litre, which depends strongly on humidity. Current deployment is therefore rational mainly for nurseries, propagation, seed potato, leafy greens, strawberry and flowers in humid or foggy zones, and as climate-insurance infrastructure during El Niño years. With closed-loop recapture, solar integration, India-specific trials and supportive policy, "zero-watering" protected horticulture can become a practical part of India's adaptation to declining water availability and a strengthening El Niño threat.
References
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