Application of a superabsorbent hydrogel for improving water productivity and quality of saffron (Crocus sativus L.) under water deficit conditions

Abstract

Water deficit regimes and techniques using moisture-absorbent materials are the main approaches to achieving the goals of sustainable agriculture and water resources conservation in arid and semi-arid areas. A field experiment as a split-plot based on randomized complete blocks design with three replications at the research farm of the Saffron Institute of the University of Torbat Heydarieh during three consecutive crop years (2015–16, 2016–17, and 2017–18). The main plots consisted of three irrigation regimes 20 (W1), 35 (W2), and 50-day irrigation interval (W3), and the sob-plots included without application (H0) and application of superabsorbent hydrogel (H1). The research findings showed that the highest values of the plant leaf number (19.3, 21.3, and 33.5, respectively) and the dry leaf yield (2291.9, 3837, 4979.5 kg ha����� 1, respectively) during the experiment years were achieved from the application of hydrogel under full irrigation condition (W1H1). The improvement in these crop parameters was significantly higher when the hydrogel was used under water deficit compared to well-watered conditions. Based on the three-year means, the highest increase in the leaf number (18.1 %) as a result of the hydrogel application was observed in the W3 treatment, while the highest increase in the dry leaf yield (24.8 %) was observed in the W2 treatment. The fresh flower yield also peaked in the W1H1 treatment (776.5, 1421.1, and 2074.8 kg ha����� 1, respectively). Similarly, dry stigma yield reached its highest values (6.3, 11.2, and 17.0 kg ha����� 1, respectively) in the W1H1 treatment. While the highest increase in the two mentioned traits due to hydrogel application in the experiment years (25.3 and 32.9 %, respectively) was obtained when the saffron plants were subjected to a 35-day irrigation interval. While the W1H1 treatment displayed the highest corm number (122.8, 252.8, and 341.4) and corm yield (19.8, 31.7, and 45.1 t ha����� 1), the effect of hydrogel in improving these parameters was greater under prolonged irrigation intervals, so that the highest increase in the corm number (19.6 %) was obtained under 35-day irrigation interval and in the corm yield (21.9 %) was observed under 50-day irrigation interval. The flower-to-stigma conversion factor and water productivity achieved their peak values in the W2H1 treatment (0.98, 1.1, and 1.0 %, and 0.0018, 0.0020, and 0.0043 kg m����� 3, respectively). Furthermore, the W2H1 treatment exhibited the highest concentrations of crocin (11.9 and 12.2 %), picrocrocin (6.7 and 5.8 %), and safranal (2.6 and 2.4 %) in the last two years of the experiment. This underscores the potential of hydrogel application in enhancing not only yield-related parameters but also the quality attributes of saffron. In summary, the findings highlight the positive influence of superabsorbent hydrogel in mitigating the impact of water deficit on saffron cultivation, offering a promising avenue for sustainable and efficient water management in arid agricultural regions.