Impact of deficit irrigation and addition of biochar and polymer on soil salinity and tomato productivity

The aim of this study is to investigate impact of soil amendments (4% biochar, 0.4% polymer, and a combination of them) on soil moisture and salinity distribution, tomato yield, and water-use efficiency (WUE). Open-field experiments were conducted during two successive growing seasons in 2017 and 2018. The experiment consisted of three levels of irrigation treatments: 100%, 80%, and 60% of crop evapotranspiration (ET c ); and two different water qualities: fresh 0.9 dS m −1 and saline electrical conductivity 3.6 dS m −1 . Results revealed that at 100% of ET c , soil water distribution increased by 12.94%, 37.87%, and 42.21% at depths 0–15, 15–30, and 30–45 cm, with the addition of biochar, respectively, compared with control at same depths under freshwater, but the addition of polymer was increased by 6.35%, 16.56%, and 16.37%, respectively. While combination treatments increased by 15.70%, 24.80%, and 41.26%, at the depths aforementioned. Salt concentration was increased by 59.10% with biochar, whereas decreasing by 7.19% and 57.63% with polymer and mixture treatments, respectively. The results also showed that biochar and mixture treatments improved yield compared with the polymer and control, whereas saline water decreased the yield compared with freshwater. With deficit irrigation, WUE was increased by 28.54%, 40.98%, and 68.93% at 100%, 80%, and 60% of ET c , respectively, indicating it could be used as an irrigation management strategy under arid and semiarid field conditions.