Effects of Irrigation Regimes and the Use of Barley Residue, Zeolite and Superabsorbent Polymer on Forage Yield and Water Use Efficiency of Maize and Sorghum in Double Cropping System under Minimum Tillage

To study the effects of different irrigation regimes and the use of barley residue، zeolite and superabsorbent polymer on yield and water use efficiency of maize (SC 704) and sorghum (cv. Pegah) under minimum tillage، an experiment was conducted over two consecutive years (2012-2013) in Kerman، Iran. A randomized complete block design arranged in a factorial split was used with three replications. Irrigation regimes in two levels، normal (irrigation based on 70 mm evaporation from pan class A) and water deficit stress (irrigation based on 140 mm evaporation from pan class A) and plant species included two levels، maize and sorghum، as factorial combinations were compared in main plots. Combination treatments of zeolite، superabsorbent polymer and barley residue with 5 levels، were assigned to subplots that were as follows: I. 10 tha-1 zeolite plus 4. 5 t ha-1 barley residue (ZR)، II. 60 kgha-1 superabsorbent polymer plus 4. 5 tha-1 barley residue (SR)، III. 5 tha-1 zeolite plus 30 kgha-1 superabsorbent polymer plus 4. 5 tha-1 barley residue (ZSR)، IV. 4. 5 tha-1 barley residue (R)، V. Control (C). Based on the results، maize produced 62. 17 and 14. 03 tha-1 fresh and dry forage yield respectively، while the fresh and dry forage of sorghum were 47. 6 and 9. 29 tha-1 in the first cutting and 66. 62 and 13. 22 tha-1 in the sum of the two cuttings. In both plants water use efficiency and forage yield under water stress increased and decreased، respectively. Water use efficiency for fresh and dry forage yield of maize was 6. 31 and 1. 42 kgm-3 while this trait for fresh and dry forage yield of sorghum was 5. 06 and 1. 01 kgm-3 respectively. Application of 10 tha-1 zeolite plus 4. 5 tha-1 barley residue (ZR) with production of 66. 9 tha-1 fresh forage yield and 6. 8 kgm-3 water use efficiency in maize and production of 72. 07 tha-1 fresh forage yield and 5. 44 kgm-3 water use efficiency in sorghum had the highest values than any of the other treatments. Water stress increased the forage crude protein content but zeolite decreased it. For a double cropping system in the temperate zones of Jopar in Kerman، barley residue can be recommended after maize planting under minimum tillage together with application of 10 t ha-1 zeolite and 4. 5 t ha-1 barley residue.