Foliar antitranspirant and soil superabsorbent hydrogel affect photosynthetic gas exchange and water use efficiency of maize grown under low rainfall conditions

BACKGROUND Two lysimeter experiments with maize plants were conducted to investigate the effect of combined superabsorbent polymer (SAP) and fulvic acid (FA) application on photosynthetic gas exchange and water use efficiency (WUE) under deficit irrigation conditions. Soil SAP (45 kg hm−2) was applied while sowing, and FA solution (2 g L−1) was sprayed onto the crop canopy three times at later plant growth periods. RESULTS Combining SAP and FA application significantly improved plant photosynthesis, chlorophyll contents and instantaneous WUE while maintaining optimal leaf stomatal transpiration. The effect of using the combined chemicals on photosynthesis and leaf instantaneous WUE was superior to the effects of their individual applications. Compared with plots not treated with chemicals, soil SAP significantly improved the yield by 12% and grain WUE by 10% when averaged across the two experiments, whereas foliar FA application did not affect yield and grain WUE. In contrast, the combined use of the two chemicals significantly increased the yield by 20% and grain WUE by 26%, largely attributed to the increase in grain number. CONCLUSION Soil SAP and foliar FA use under low rainfall conditions had little influence on crop water consumption but improved plant WUE by enhancing photosynthesis and increasing kernel number. © 2018 Society of Chemical Industry