Biofilm biofertilizer mitigates water stress in rice: impact on growth, yield, and grain quality

Introduction Continuous flooding in paddy ( Oryza sativa L.) cultivation challenges sustainable agriculture and food security amid climate change. Biofilm biofertilizer (BFBF) can improve soil organic matter and nutrient content without compromising yield, but its effect on plant water use and grain quality under restricted irrigation remains untested. This study evaluated BFBF's effect on rice water consumption under progressively limited irrigation. Methods A 3-month pot experiment used wetland (At 314) and dryland (Bg 251) rice varieties under two fertilizer practices, chemical fertilizer (CF, 340 kg NPK ha −1 ) and BFBF (225 kg NPK ha −1 + 2.5 L BFBF ha −1 ), and three water treatments (flooded, 100% field capacity, 65% field capacity), in a three-factor factorial completely randomized design ( n = 3). Total water usage, water use efficiency (WUE), net assimilation rate (NAR), relative growth rate (RGR), yield components, macronutrients (carbohydrates, proteins, lipids), and heavy metal content were recorded; significance was assessed via three-factor ANOVA (variety × fertilizer × water) with Tukey’s HSD test ( p < 0.05). Results Total water use was significantly reduced under BFBF only in the wetland variety (ca. 12% under flooded, 10% at 100% field capacity, and no reduction at 65% field capacity). Grain Cd and Pb fell by 34 and 81%, respectively, under BFBF. Carbohydrate, protein, and lipid contents, Fe and Zn concentrations, and yield components were unaffected by fertilizer practice, varying only by variety and/or water treatment. BFBF increased NAR and RGR by ca. 33 and 7%, respectively, across all water treatments. Overall, BFBF matched full-rate CF for yield and nutritional composition while reducing water use and heavy-metal accumulation under dryland, water-limited conditions. Conclusion Collectively, these results position BFBF as a candidate drought-resilience strategy for rice cultivation, reducing water demand and heavy-metal accumulation without compromising grain yield or quality, particularly for dryland, water-limited conditions. Multi-season field trials are needed to confirm these responses at scale.