咸淡水组合灌溉下鲁北盐碱土壤水盐分布及脱盐特征OA

[Objective]This study aims to reveal the regulatory effects of diluted brackish water irrigation on water and salt dynamics in saline-alkali soil in Northern Shandong and to provide a safe irrigation scheme to alleviate agricultural freshwater shortage and soil salinization-alkalization.[Methods]Severely saline-alkali soils collected from the Kenli District were used in this study.Laboratory-based soil column simulation experiments and a one-dimensional algebraic model were used to investigate soil water-salt distribution and desalination characteristics under different combination ratios and irrigation sequences of brackish and fresh water.The five combination ratios were:all fresh water,all brackish water,and brackish-to-fresh water ratios of 1∶2,1∶1,and 2∶1.Two sequences were:brackish water irrigated before fresh water and fresh water irrigated before brackish water.[Results]As the combination ratio of brackish-to-fresh water increased,the soil water content in the same soil layer initially increased and then decreased.The highest soil water content was observed in the 5-15 cm layers under the brackish-to-fresh water ratio of 1∶2 and 15-55 cm layers under the ratio of 2∶1.Compared with the fresh water-first sequence,applying brackish water before fresh water resulted in higher soil water content.The one-dimensional algebraic model performed excellently in simulating vertical soil water distribution,with a normalized root mean square error<10%and an index of agreement>0.9.Soil salt content under the 1∶2,1∶1,and 2∶1 brackish-to-fresh water ratios,was lower than that under brackish water irrigation alone,and was consistent with that under fresh water irrigation alone in soil layers of 5-35 cm,5-25 cm,and 5-15 cm,respectively.Therefore,combined irrigation of brackish and fresh water produced the same desalination effect as using only fresh water in certain soil layers,especially under the 1∶2 brackish-to-fresh water ratio,where the effective desalination depth showed no significant difference from that produced by fresh water irrigation alone.Applying brackish water before fresh water was more effective for soil desalination in shallow soil layers(5-10 cm),whereas the fresh water-first sequence was more effective in deep soil layers(40-45 cm).[Conclusion]Considering both combination ratios and irrigation sequences,a brackish-to-fresh water ratio of 1∶2 combined with the irrigation sequence of brackish water first and then fresh water is recommended.