Effect of Temporal Soil Water Fluctuation on Water Use Efficiency of Broomcorn Millet (Panicum miliaceum L.) at Jointing Stage

Abstract

【Objective】 Soil water in the field experiences spatiotemporal variation due to irrigation and rainfall evens, but its impact on crop growth is unclear. Using millet as a model plant, this paper investigates the effect of temporal soil moisture fluction on its water use efficiency. 【Method】 Experiments were conducted in pots with two soil water treatments: keeping the soil water content stable (SW), or temporally fluctuating it (FW). The former was achieved by keeping the pressure of irrigation water negative (NPI), and the latter by manual irrigation. In both treatments, the average soil water content was kept at 24.94%~25.61% (W1) or 21.12%~22.60%. The changes in growth, photosynthesis, stomatal characteristics, biomass allocation and physiological traits of the millet were measured in each treatment. 【Result】 ① Keeping soil water content stable significantly promoted crop growth. 60 days after start of the experiment, keeping soil water content stable in the range of 24.94%~25.61% (SW1) increased plant height, stem diameter and leaf area by 33.0%, 13.04% and 127.36%, respectively, compared to FW1, while SW2 increased plant height, stem diameter and leaf area by 51.94%, 144.70% and 13.91%, respectively, compared to FW2. ② Compared to FW, SW increased photosynthesis, dry matter accumulation and water use efficiency. During the experimental period, the photosynthetic traits of the millet in SW were significantly higher than those in FW. ③ In addition, SW1 increased fresh biomass and water use efficiency by 222.45% and 200.00%, respectively, compared to FW1, while SW2 increased the fresh biomass and water use efficiency by 352.54% and 260.00%, respectively, compared to FW2. On average, SW increased length and width of leaf stomata while reducing leaf stomatal density. SW and FW treatments did not show significant influence on root malondialdehyde (MDA), root antioxidant enzymes (SOD, POD, CAT), leaf malondialdehyde (MDA), leaf proline (Pro), leaf superoxide dismutase (SOD) and leaf catalase (CAT) contents, but impacted root pro, leaf POD and leaf abscisic acid contents significantly. 【Conclusion】 The broomcorn millet responded differently to stable and fluctuating soil water content, with stable soil water content being more favorable to growth, photosynthesis and water use efficiency of the crop.

Keywords

• soil moisture temporal variance
• broomcorn millet
• water use efficiency