Effects of irrigation and cultivation on the chemical indices of saline-sodic soils in a calcareous environment

摘要

Studies on saline-sodic soils have a growing concern during time in many arid and semiarid nations due to human population pressures and need to produce more food and fiber. Nevertheless, little data are available about the quality attributes of the soils when affected by irrigation and cultivation. This study highlights the response of selected chemical indicators of four soil types (Aquic Natrargids, Sodic Aquicambids, Typic Aquisalids, and Typic Halaquepts) associated with calcareous salt-affected soils when changing to cropland. The results revealed a considerable drop in the amounts of soil pH (0.2-0.8 unit), electrical conductivity (69-82%), sodium absorption ratio (62-73%), exchangeable Na (65-90%), and exchangeable sodium percentage (52-69%) following the conversion of saline-sodic soils to cropland, indicating that the processes of desalinization and desodification were promoted by cultivation practices. For the majority of the study soils, an increasing pattern was recorded in the values of organic carbon (15-130%), total N (37-157%), available P (1-7%), exchangeable Ca (20-96%) and Mg (83-94%), and DTPA-extractable Mn (8-85%), Zn (48-85%), Cu (7-75%) with cultivation, whereas the amounts of cation exchange capacity, exchangeable K, available K, and DTPA-extractable Fe were decreased by 1-29, 8-54, 10-60, and 2-54%, respectively. Based on the land productivity index (LPI), 75% of the soils had an increasing trend (a rise of 10-31%) in the LPI [with the improvement of the productive class from average (LPI=20-34) to good class (LPI=35-64)] and 25% had a decreasing pattern (a drop of 10%) after cultivation.