Evaluation of yield and some physiological changes in corn and sorghum under irrigation regimes and application of barley residue,zeolite and superabsorbent polymer

In order to investigate the changes in chlorophyll fluorescence, chlorophyll, relative water content (RWC) and forage yield of corn and sorghum under various irrigation regimes and combination treatments of barley residue, zeolite and superabsorbent polymer, an experiment was conducted over 2 years in Kerman, Iran. A randomized complete block design arranged in a factorial split was used with three replications. Two irrigation regimes of normal and drought stress based on 70 and 140 mm cumulative pan evaporation, respectively, and two plant species (corn and sorghum) as factorial combinations were compared in the main plots. Five treatments, (1) 10 t ha^?1 zeolite + 4.5 t ha^?1 residue, (2) 60 kg ha^?1 superabsorbent + 4.5 t ha^?1 residue, (3) 5 t ha^?1 zeolite + 30 kg ha^?1 superabsorbent + 4.5 t ha^?1 residue, (4) 4.5 t ha^?1 residue and (5) – control, were compared in subplots. In both plants, forage yield, potential quantum yield (Fv/Fm), chlorophyll a, total chlorophyll and carotenoid contents decreased significantly under drought stress. Chlorophyll a content, SPAD index and Fv/Fm were higher in corn than in sorghum, but RWC was higher in sorghum. Corn produced higher forage yield (62.8 t ha^?1) than sorghum (49.3 t ha^?1). The application of 10 t ha^?1 zeolite with 4.5 t ha^?1 residue increased most traits more than any of the other treatments, but the superabsorbent had no significant effect on the studied traits.