The long-term impact of irrigation on selected soil properties and grain production

A sustainable agricultural system depends on good soil quality and crop performance. However, information is limited about the influence of long-term irrigation schedules on soil properties and crop performance on fields without crop residue incorporation or machine tillage. In this study, we investigated the changes of soil bulk density (BD), saturated hydraulic conductivity (K-sat), water-stable aggregate, soil organic matter (SOM), and total nitrogen (TN) at the depths of 0 to 5, 5 to 10, 10 to 20, and 20 to 40 cm relative to different irrigation amounts based on a 17-year-long experiment in a double-cropping system with crop residue removed and manual tillage in the North China Plain. Results showed that BD increased as the irrigation amount increased. Saturated hydraulic conductivity reached a maximum level at a moderate irrigation level. Irrigation timing also affected soil BD and K-sat. Water-stable aggregates did not show consistent trends. Soil organic matter and TN showed similar decreasing trends with increased irrigation amount. No significant relationships were found between soil physical properties and grain yield. However, SOM did affect crop production significantly. Overall, results indicated that continuous irrigation without crop residue return negatively affected soil properties and crop performance. Soil quality and crop production may benefit from a reasonable irrigation strategy and the return of crop residue to the field.