Nutrient Dynamics in Soft Rock and Sand Compound Soil under Different Water Management Strategies

Studying the ameliorative effects of psammitic soft rock and combined water measures in Mu Us Sandy Land (northern Shaanxi, China) is of great significance for improving soil quality and ensuring food security in sandy regions. The 0-30 cm soil layer was filled with a mixture of soft rock and sand, with four volume ratios: 0 : 1, 1 : 5, 1 : 2, and 1 : 1 (soft rock: sand). The irrigation method used drip irrigation, with two irrigation regimes during the maize growth period: full irrigation (4350 m(3)/ha) and incomplete irrigation (2925 m(3)/ha), divided into 10 irrigation sessions. The soil nutrient content was measured annually after the maize harvest. Field trials were conducted, with each experimental plot covering 60 m(2) and three field replicates for each treatment. The experimental data from four years (2020 to 2023, planting years 11 to 14) were selected for analysis. The results showed that the nutrient content of the soil increased significantly under incomplete irrigation. The average content of SOM (soil organic matter) and TN (total nitrogen) increased by 4.29 and 0.86 g kg(-1), respectively, after 14 years of planting compared with 11 years, particularly in the 1 : 2 compound soil. The average content of AP (available phosphorus) under incomplete irrigation increased by about 71% compared with that under full irrigation. The content of AK (available potassium) increased by about 12%, with the 1 : 5 compound soil showing the largest increase. After 14 years of planting, the NN (nitrate nitrogen) content in the 1 : 1 compound soil decreased by about 14 similar to 34% compared with 11 years of planting. The average content of AN (ammonium nitrogen) under incomplete irrigation increased by about 7% compared with that under full irrigation. In summary, this study revealed the dynamic changes of nutrients in compound soil under different management conditions, demonstrating that the comprehensive fertility of the 1 : 2 compound soil was superior. These findings provide a scientific basis for optimizing agricultural management strategies for sandy land.