Biochar‐Amended Soils: A Water‐Saving Strategy for Quinoa Cultivation in the Andes

ABSTRACT Introduction Previous studies showed that biochar amended soils significantly enhanced the growth and yield of quinoa under water limitations. So it becomes an emerging agronomic strategy to consider for sustainable quinoa production. Biochar can specifically be considered for the area particularly receiving low annual rainfall and more vulnerable to current climate change conditions. Materials and Methods A field experiment was conducted using the quinoa variety INIA 415 Pasankalla, employing a factorial design to assess the effects of different application rates of biochar made of municipal pruning waste and agricultural waste (0, 1, 2, and 3 t·ha⁻¹), and three irrigation intervals (irrigation every 5 days, irrigation every 10 days, and irrigation every 15 days). The volumetric soil moisture content, the soil hydraulic properties, and quinoa's biometric characteristics and yield components were evaluated. Results The results indicated that the longest irrigation intervals (10 and 15 days) resulted in soil moisture levels between 19% and 40% below the wilting point (soil matric potential: −1.5 MPa), creating water stress conditions. However, biochar application increased the field capacity from 0.31 to 0.38 g H₂O g⁻¹ soil, raised soil air content from 22% to 29% at irrigation, and promoted the quinoa's soil water absorption below the wilting point. Furthermore, the application of 3 t·ha⁻¹ of biochar significantly enhanced quinoa yield, increasing it from 3.18 to 4.22 t·ha⁻¹, along with improvements in leaf area, total biomass, root length, and panicle length by 70.74%, 76.54%, 14.34%, and 16.55%, respectively. Conclusions It was concluded that a 3 t·ha⁻¹ biochar application mitigated the negative effects of water stress caused by prolonged irrigation intervals. This biochar treatment improved the soil's physical properties and enabled the quinoa variety INIA 415 Pasankalla to achieve yields close to its theoretical productive potential.