Effect of utilization of treated wastewater and seawater with Clinoptilolite-Zeolite on yield and yield components of sorghum

Under conditions of water shortage, utilizing unconventional waters, such as treated urban wastewater and/or seawater, in combination with soil amendments such as zeolite, can reduce the harmful effects of drought stress on crop yield. To investigate the agronomic and physiological effects of a mix of water qualities and soil treatments on sorghum, a randomized split-plot research was conducted at Gharakheil agricultural research station, Ghaemshahr, Northeast Iran. Six combinations of water qualities and three different use of soil amendments were tested over two seasons in 2016 and 2017. The water quality treatments with increasing salinity included well water as the control (W1); 75 % well water and 25 % seawater (W2); 25 % well water and 75 % seawater (W3); 100 % treated urban wastewater alternating with 100 % seawater (W4); 50 % seawater and 50 % treated urban wastewater (W5) and 100 % treated urban wastewater (W6). The soil amendments were no-zeolite as the control (Z1) and calsic (Z2) and potasic (Z3) zeolite. With increasing salinity, the forage yield decreased significantly. Maximum and minimum forage yield were respectively 129.6 ton.ha−1 inW6-Z2 in 2016 and 46.9 ton.ha−1 in W3-Z1 in 2017. Irrigation Water Use Efficiency (IWUE) was the highest with the treated urban wastewater in combination with zeolite. All six combinations (W4-Z2, W4-Z3, W5-Z2, W5-Z3, W6-Z2 and W6-Z3) had significantly higher IWUEs (range 2.0–2.4) compared to the control (IWUE = 1.7) and the other soil and water treatments. The combinations of 75 % seawater and no zeolite had by far the lowest IWUE (range 1.1–1.7). The same trends were observed for the Leaf Area Index (LAI) and leaf and stem protein. The use of saline sea water increased the soil salinity levels significantly, but the levels were still well below the FAO threshold values for yield reduction. Overall, we can recommend use of treated wastewater in combination with calsic zeolite soil amendment as the combination that had the best effect on crop yield, IWUE, LAI and leaf and stem protein for sorghum production under the conditions of north of Iran.