引黄灌区播前土壤水盐含量和向日葵出苗率对不同春灌模式的响应机制

Response Mechanisms of Pre-sowing Soil Water and Salt Content and Sunflower Germination Rate in Yellow River Irrigation District to Different Spring Irrigation Patterns

摘要:

在北方盐渍化灌区，春灌能明显提高土壤水分并降低土壤盐分，然而传统春灌定额较大，春灌时间难以确定，故优化春灌模式（定额和时间）对于提高农业用水效率和生产力具有重要意义。本研究于2022—2023年在内蒙古自治区鄂尔多斯市黄河南岸灌区设置135mm和180mm（W1、W2）2个春灌定额水平，以及播前18d、播前12d和播前6d（T1、T2、T3）3个灌水时间，共6个处理的田间试验以及2个春灌定额室内入渗试验，研究春灌定额和时间对土壤入渗以及向日葵出苗率的影响，并基于HYDRUS模型探索不同处理下播前土壤水盐动态变化，向日葵播前水盐与不同春灌模式的关系。结果表明，春灌定额越高，湿润锋运移距离与累计入渗量越大，通过构建向日葵出苗率与播前土壤水盐含量定量关系，得出最优含水率（SWC）和电导率（EC）分别为0.254cm3/cm3和0.683dS/m，利用HYDRUS模型对不同春灌模式水盐运移进行模拟，结果显示HYDRUS模型能较好模拟春灌有压入渗和重分布阶段的水盐动态，在验证期，SWC均方根误差（RMSE）、决定系数（R2）、平均相对误差（MRE）平均值分别为0.02cm3/cm3、0.96、7.7%，EC分别为0.32dS/m、0.90和9.9%。相同春灌定额下，越早春灌，播前EC越高、SWC越低，与播前18d春灌处理相比，推后春灌6d和12d处理，播前耕层（0~30cm）2年平均EC降低10.1%和16.8%，平均SWC提高3.4%和6.2%。在相同春灌时间下，与低春灌定额（W1）相比，高春灌定额（W2）在播前耕层2年平均EC降低13.4%，平均SWC提高4.5%。基于HYDRUS模型情景分析灌溉定额90~315mm、播前3~18d不同春灌模式下的播前土壤水盐含量，并利用最优SWC和EC进行寻优，得出该地区适宜春灌模式：春灌定额为180mm、春灌时间为播前18d和春灌定额为135mm、春灌时间为播前15d，该研究结果可为黄河流域盐渍化灌区农业节水以及农业生产提供理论支撑。

Abstract:

In northern saline-affected irrigation districts, spring irrigation significantly increases soil moisture and reduces soil salinity. However, traditional spring irrigation quotas are relatively high, and the optimal timing for spring irrigation is difficult to determine. Therefore, optimizing spring irrigation patterns (quotas and timing) is crucial for enhancing agricultural water use efficiency and productivity. The research was conducted in the irrigation district south of the Yellow River in Ordos City, Inner Mongolia, during 2022—2023. Two spring irrigation quota levels (135mm and 180mm, denoted as W1 and W2) were established, along with three irrigation timing points: 18 days before sowing (T1), 12 days before sowing (T2), and 6 days before sowing (T3), totaling six treatments. Additionally, two indoor infiltration experiments were conducted to examine the effects of spring irrigation quotas and timing on soil infiltration and sunflower emergence rates. Using the HYDRUS model, the pre-sowing soil water-salt dynamics under different treatments and the relationship between pre-sowing water-salt conditions and various spring irrigation patterns were explored. It was found that higher spring irrigation quotas resulted in greater wetting front migration distances and cumulative infiltration volumes. By establishing a quantitative relationship between sunflower emergence rate and pre-sowing soil water-salt content, the optimal soil water content (SWC) and electrical conductivity (EC) were determined to be 0.254cm3/cm3 and 0.683dS/m, respectively. The HYDRUS model was employed to simulate water-salt transport under different spring irrigation patterns. Results indicated that the HYDRUS model effectively simulated water and salt dynamics during the pressurized infiltration and redistribution phases of spring irrigation. During the validation period, the root mean square error (RMSE), coefficient of determination (R2), and mean relative error (MRE) for SWC averaged 0.02cm3/cm3, 0.96, and 7.7%, respectively, while corresponding values for EC were 0.32dS/m, 0.90, and 9.9%. Under identical spring irrigation quotas, earlier irrigation resulted in higher pre-sowing EC and lower SWC. Compared with the 18days pre-sowing irrigation treatment, delaying irrigation by 6days and 12 days reduced the 2-year average EC in the tillage layer (0~30cm) by 10.1% and 16.8%, respectively, while increasing the average SWC by 3.4% and 6.2%. Under identical spring irrigation timing, compared with the low spring irrigation quota (W1), the high spring irrigation quota (W2) reduced the 2-year average pre-sowing EC in the plow layer by 13.4% and increased the average SWC by 4.5%. Based on HYDRUS model scenario analysis of pre-sowing soil water and salt content under spring irrigation regimes with irrigation quotas ranging from 90mm to 315mm and timing from 3 days to 18 days before sowing, optimization was conducted using optimal SWC and EC values. The optimal spring irrigation regime for this region was determined as follows: spring irrigation quota of 180mm with timing 18 days before sowing, or spring irrigation quota of 135mm with timing 15 days before sowing. These findings can provide theoretical support for agricultural water conservation and production in saline-affected irrigation areas of the Yellow River Basin.