Abstract:

In order to optimize the relevant technical elements of the bubbled-root irrigation， a dual-point source intersection infiltration test was carried out at Yuanzhishan experimental station of Northwest A&F University to study the influence of different irrigator spacing on the characteristics of the wet body and the law of water and nitrogen transport. Three levels of irrigator spacing （40， 50， and 60 cm） were set in this experiment， the mass concentration of fertilizer solution was 10 g·L^-1， and the flow rate of bubbled-root irrigation irrigator was 5 L·h^-1， the effects of different distance of irrigators on the infiltration characteristics of fertilizer solution， the migration law of wetting front， soil moisture， and distribution characteristics of ammonium nitrogen （NH{}_{\mathrm{4}}^{+}-N） and nitrate nitrogen （NO{}_{\mathrm{3}}^{-}-N）. The research showed that the cumulative infiltration amount and the increased infiltration amount of free infiltration and intersection infiltration under different conditions of the bubbled-root irrigation or the distance of the wetting front in different directions of the bubbled-root irrigation， which all had a positive proportional power function relationship with the distance between irrigators （R²>0.9， P<0.01）. The larger the distance between the irrigators， the smaller the migration distance of the wetting front moving upward and downward on the intersection surface （P<0.05）， and the reduction of soil moisture content on the infiltration side of the intersection was smaller than that on the free infiltration side， the larger the distance between the irrigators， the lower the wetness degree of the intersection surface （P<0.05）. Under the condition of free infiltration， the greater the distance from the water outlet of the irrigator， the decrease of NH{}_{\mathrm{4}}^{+}-N content was more significant （P<0.05）， while the decrease of NH{}_{\mathrm{4}}^{+}-N content on the convergent infiltration side was smaller than that on the free infiltration side. The NO{}_{\mathrm{3}}^{-}-N content varies greatly at different times and positions. After irrigation， the NO{}_{\mathrm{3}}^{-}-N content of the surface soil in the humid area decreased slightly. The longer the water distribution time， the higher the NO{}_{\mathrm{3}}^{-}-N content at different soil depths （P<0.05）. A mathematical model of the cumulative infiltration volume of the bubbled-root irrigation intersection infiltration， the migration distance of the wetting front with time and the distance of the emitters was established. The model parameters K and α， which varied with the distance of the irrigators in a power function relationship， and the value of K decreased with the increase of the distance， while the value of α increased with the increase of the distance. The relationship model about soil moisture content， NH{}_{\mathrm{4}}^{+}-N， NO{}_{\mathrm{3}}^{-}-N contents and the distance of the irrigators was established， and the soil moisture content， soil NH{}_{\mathrm{4}}^{+}-N and NO{}_{\mathrm{3}}^{-}-N contents at any point from the infiltration soil to the distance r from the irrigator center were quantitatively estimated， and the deviation of the estimation results was within ±10%. The results laid a scientific foundation for the further improvement of the water-saving irrigation technology of the bubbled-root irrigation.

Key words: bubbled-root irrigation, irrigation distance, wetting body, double point source convergence infiltration, water and nitrogen transport

摘要：

为研究不同灌水器间距对湿润体特性及水氮运移规律的影响，优化涌泉根灌灌水器相关技术要素，在西北农林科技大学远志山试验站进行了双点源交汇入渗试验。试验设置3个灌水器间距水平（40、50、60 cm），肥液质量浓度为10 g·L^-1，涌泉根灌灌水器流量为5 L·h^-1，探究不同灌水器间距对涌泉根灌肥液交汇入渗特性及湿润锋运移规律、土壤水分、铵态氮（NH{}_{\mathrm{4}}^{+}-N）和硝态氮（NO{}_{\mathrm{3}}^{-}-N）分布特性的影响。结果表明，涌泉根灌不同条件下，自由入渗和交汇入渗累积入渗量、增渗量以及不同方向湿润锋运移距离均与灌水器间距呈正比例幂函数关系（R²>0.9，P<0.01）；灌水器间距越大，交汇面向上、向下湿润锋运移距离越小（P<0.05）；交汇入渗侧土壤含水率降低幅度小于自由入渗侧，灌水器间距越大，交汇面湿润程度越低（P<0.05）；自由入渗条件下，距灌水器出水口距离越大，NH{}_{\mathrm{4}}^{+}-N含量降低越显著（P<0.05），而交汇入渗侧NH{}_{\mathrm{4}}^{+}-N含量降低幅度小于自由入渗侧；NO{}_{\mathrm{3}}^{-}-N含量在不同时刻、不同位置有较大差异，灌水结束后，湿润区表层土壤NO{}_{\mathrm{3}}^{-}-N含量略有降低，水分分布时间越长，不同土层深度处的NO{}_{\mathrm{3}}^{-}-N含量越高（P<0.05）。建立了涌泉根灌交汇入渗累积入渗量、湿润锋运移距离随时间和灌水器间距变化的数学模型，其中模型参数K、a与灌水器间距呈幂函数关系变化，K值随间距的增加而减小，a值随间距的增加而增大；建立了土壤含水率、土壤NH{}_{\mathrm{4}}^{+}-N及NO{}_{\mathrm{3}}^{-}-N含量与灌水器距离之间的关系模型，并对入渗土体任一点至灌水器中心距离r处土壤含水率、NH{}_{\mathrm{4}}^{+}-N及NO{}_{\mathrm{3}}^{-}-N含量进行了定量估算，估算结果偏差在±10%以内。研究结果为涌泉根灌节水灌溉技术的进一步完善奠定了科学基础。

关键词: 涌泉根灌, 灌水器间距, 湿润体, 双点源交汇入渗, 水氮运移