Chia is generally grown under rainfed conditions and is often under water deficit conditions during the critical period of flowering and grain filling when yield is determined. The objective of this study was to determine how intercepted photosynthetically active radiation (iPAR), radiation use efficiency (RUE), water use efficiency (WUE), and grain yield were affected by different soil water availabilities during the critical period for yield in chia. Four levels of total available water (TAW) during the critical period were obtained using supplemental drip irrigation including: T90 (90% TAW), T65 (65% TAW), T45 (45% TAW), and T30 (30% TAW). No reductions in iPAR and RUE (dry matter or yield per unit of intercepted radiation) were found between T65 and T90, which led to similar dry matter and grain yield. Water availabilities equal to or lower than 45% of TAW decreased iPAR, RUE, dry matter, and grain yield. The decrease in RUE under low TAW was associated with reductions in WUE (dry matter per mm of evapotranspiration) and in crop conductance (gc; evapotranspiration per unit of iPAR). These reductions in WUE and gc occurred, respectively, due to the greater contribution of soil evaporation to crop evapotranspiration and less transpiration per unit of intercepted radiation when TAW was 45% or lower. The use of supplemental irrigation to ensure 65% of TAW in the soil during the critical period for yield would reduce the importance of soil evaporation and increase crop transpiration by increasing crop ground cover and would lead to improved grain yields in chia.

奇亚籽一般在雨养条件下生长，在开花和灌浆的关键时期（决定产量）常常处于缺水条件下。本研究的目的是确定奇亚籽产量关键时期不同土壤水分利用率对截获光合有效辐射（iPAR）、辐射利用效率（RUE）、水分利用效率（WUE）和谷物产量的影响。通过补充滴灌获得了关键时期的四个水平的总可用水（TAW），包括：T90（90％TAW）、T65（65％TAW）、T45（45％TAW）和T30（30％TAW）。T65 和 T90 之间没有发现 iPAR 和 RUE（每单位截获辐射的干物质或产量）减少，这导致干物质和谷物产量相似。可用水量等于或低于 TAW 的 45% 会降低 iPAR、RUE、干物质和谷物产量。低 TAW 条件下 RUE 的降低与 WUE（每毫米蒸散量干物质）和作物电导度（gc；每单位 iPAR 蒸散量）的降低有关。WUE 和 gc 的减少分别是由于当 TAW 为 45% 或更低时，土壤蒸发对作物蒸散的贡献较大，而每单位截获辐射的蒸腾量较少。在产量关键时期，使用补充灌溉确保土壤中 TAW 含量达到 65%，将降低土壤蒸发的重要性，并通过增加作物地面覆盖来增加作物蒸腾，从而提高奇亚籽的谷物产量。低 TAW 条件下 RUE 的降低与 WUE（每毫米蒸散量干物质）和作物电导度（gc；每单位 iPAR 蒸散量）的降低有关。WUE 和 gc 的减少分别是由于当 TAW 为 45% 或更低时，土壤蒸发对作物蒸散的贡献较大，而每单位截获辐射的蒸腾量较少。在产量关键时期，使用补充灌溉确保土壤中 TAW 含量达到 65%，将降低土壤蒸发的重要性，并通过增加作物地面覆盖来增加作物蒸腾，从而提高奇亚籽的谷物产量。低 TAW 条件下 RUE 的降低与 WUE（每毫米蒸散量干物质）和作物电导度（gc；每单位 iPAR 蒸散量）的降低有关。WUE 和 gc 的减少分别是由于当 TAW 为 45% 或更低时，土壤蒸发对作物蒸散的贡献较大，而每单位截获辐射的蒸腾量较少。在产量关键时期，使用补充灌溉确保土壤中 TAW 含量达到 65%，将降低土壤蒸发的重要性，并通过增加作物地面覆盖来增加作物蒸腾，从而提高奇亚籽的谷物产量。分别是由于当 TAW 为 45% 或更低时，土壤蒸发对作物蒸散量的贡献较大，而单位截获辐射的蒸腾量较少。在产量关键时期，使用补充灌溉确保土壤中 TAW 含量达到 65%，将降低土壤蒸发的重要性，并通过增加作物地面覆盖来增加作物蒸腾，从而提高奇亚籽的谷物产量。分别是由于当 TAW 为 45% 或更低时，土壤蒸发对作物蒸散量的贡献较大，而单位截获辐射的蒸腾量较少。在产量关键时期，使用补充灌溉确保土壤中 TAW 含量达到 65%，将降低土壤蒸发的重要性，并通过增加作物地面覆盖来增加作物蒸腾，从而提高奇亚籽的谷物产量。