Effect of brackish water irrigation on soil salt balance and yield of both winter wheat and summer maize

There is rich brackish water and a shortage of fresh water in the coastal low plains of Hebei Province. The reasonable exploitation and utilization of brackish water has become an important way of meeting the conflict between water supply and demand in the region. An experiment was conducted in Nanpi Eco-Agricultural Station of Chinese Academy of Sciences in 2011–2015. The objective of the experiment was to study the effect of brackish water irrigation during winter wheat growth period on the yield of winter wheat and the following crop, summer maize. The study also investigated soil salinity balance in winter wheat/summer maize double cropping system. The irrigation treatments in 20132014 included CK (rainfed farming), F1 (one fresh water irrigation at jointing stage), B21 (one brackish water irrigation of 2 g.L^-1 at jointing stage), B31 (one brackish water irrigation of 3 g.L^-1 at jointing stage), B41 (one brackish water irrigation of 4 g.L^-1 at jointing stage), B51 (one brackish water irrigation of 5 g.L^-1 at jointing stage), B32 (two brackish water irrigations of 3 g.L^-1 at jointing and grain-filling stages), F2 (two fresh water irrigations at jointing and grain-filling stages), F3 (three fresh water irrigations at jointing, heading and grain-filling stages), F1B31 (one fresh water irrigation at jointing stage and one brackish water irrigation of 3 g.L^-1 at grain-filling stage), and B31F1 (one brackish water irrigation of 3 g.L^-1 at jointing stage and one fresh water irrigation at grain-filling stage). The irrigation treatments in 20142015 were CK, F1, B31, B41, B51 and B42 (two brackish water irrigations of 4 g.L^-1 at jointing and grain-filling stages). The results showed that higher winter wheat yield was obtainable under irrigation at jointing stage and grain-filling stage, with an average yield of 6 593.4 kg.hm^-1. Irrigation of brackish water with less than 5 g?L1 salinity at joining stage did not reduced winter wheat yield compared with fresh water irrigation. Winter wheat yield increased by 10%30% under brackish water irrigation at joining stage compared with that under CK. It was possible to replace fresh water irrigation with brackish water irrigation during winter wheat growth. However, soil salt content in the 020 cm topsoil was more than 1 g.L^-1 in brackish water irrigation treatments, which affected summer maize germination and growth during early growth stage. If irrigated with 600750 m³.hm^-1 of fresh water after summer maize planting, the yield of summer maize did not reduce obviously. There was a heavy leaching of soil salt driven by precipitation in June through September. Over 300 mm rainfall during summer season could keep the soil salt balance for winter wheat and summer maize double cropping system. As over 73% of summer precipitation in Cangzhou region exceeded 300 mm, it ensured the safety of the brackish water irrigation instead of fresh water irrigation one time during winter wheat growth period.