Foxtail Millet (Setaria italica L.) in Rice-Based Cropping Systems: A Climate-Smart Approach to Sustainable Natural Farming

Abstract

Rice-based production landscapes in South and South-East Asia face a linked set of constraints: rainfall uncertainty, irrigation pressure, methane emissions from flooded rice, large post-rice fallow areas, declining returns from input-intensive cereal production, and nutritional dependence on a narrow set of staples. Foxtail millet (Setaria italica (L.) P. Beauv.) is increasingly discussed as a short-duration, C4 cereal that could diversify these systems, yet the evidence supporting its specific placement in rice-based natural-farming systems remains fragmented. This critical narrative review synthesises crop physiology, rice-fallow agronomy, diversification research, natural-farming evidence, and food and farm-economic studies to determine which claims are well supported and which still rely on extrapolation. Literature published from 1 January 2000 to 17 July 2026 was selected through scholarly database and citation searching, with emphasis on verified peer-reviewed studies and methodologically informative field evidence. The strongest evidence concerns foxtail millet's drought-responsive physiology, genetic variation in water-use traits, short crop duration, and adaptation to low-water environments. Rice-fallow research independently shows that residual soil moisture, timely establishment, drainage, and reduced soil disturbance can support profitable post-rice intensification, although most such experiments involve pulses or other dry-season crops rather than foxtail millet. Evidence for natural farming suggests potential reductions in purchased inputs and improvements in selected soil and biodiversity indicators, but foxtail-millet-specific, replicated, multi-year comparisons under natural-farming protocols remain scarce. Mitigation claims require particular caution: replacing a flooded rice phase with an aerobic millet can plausibly avoid methane-generating conditions, but net greenhouse-gas benefits have rarely been measured for complete rice-foxtail sequences. The review therefore identifies foxtail millet as a credible climate-adaptation and diversification candidate, not as a universally superior substitute. Future work should prioritise multi-location rice-to-foxtail trials, whole-system water and greenhouse-gas budgets, cultivar-by-management interactions, weed and nutrient strategies compatible with natural farming, and market-linked profitability. The central research need is to move from trait-based promise to systems-level evidence under realistic farmer conditions.