土壤初始含水率对涌泉根灌土壤水分及氮素运移特性的影响

为了探究涌泉根灌水肥一体化灌溉在不同土壤初始含水率下水氮运移特性,通过室内肥液入渗试验,研究了不同土壤初始含水率(4.13%,7.21%,8.77%,11.06%,14.01%)条件下入渗特性、湿润锋运移、土壤水分以及铵态氮和硝态氮的运移特性,建立了涌泉根灌累积入渗量、各向湿润锋运移距离与不同土壤初始含水率之间的关系,提出了不同初始含水率下涌泉根灌累积入渗量、各向湿润锋运移距离的经验模型。结果表明:累积入渗量、各向湿润锋运移距离以及湿润体内水分和氮素的分布、转化等均不同程度地受到土壤初始含水率的影响。同一时刻条件下,累积入渗量随着土壤初始含水率的增大而减小,而湿润锋运移距离却呈现出增大的趋势;土壤初始含水率越大,湿润体体积越大,湿润体内水分、铵态氮和硝态氮的分布范围越广泛;距离灌水器出水孔越近,土壤中的铵态氮和硝态氮含量越高。入渗系数K随着土壤初始含水率的增大而减小,入渗指数α随着土壤初始含水率的增大而增大;水平湿润锋拟合参数a、b均随土壤初始含水率的增大而增大,竖直向下湿润锋运移指数c随着土壤初始含水率的增大而增大,入渗指数d随着土壤初始含水率的增大而减小。随着土壤水分再分布的持续进行,湿润体内水分分布越加均匀,采用克里斯琴森均匀系数Cu评价灌水结束、再分布1,3天条件下湿润体内水分分布均匀度依次为61.99%,74.27%和83.60%;湿润体内铵态氮含量逐渐减小,但铵态氮的分布区域基本无变化;湿润体内硝态氮分布区域变大,平均值呈增大,最值区域有下移趋势。研究成果为进一步研究涌泉根灌水氮高效利用技术奠定了基础。

Transport Characteristics of Water and Nitrogen Under Bubbled-root Irrigation with Soil Initial Water Content

To explore the water and nitrogen transport characteristics under water and fertilizer integration of bubbled-root irrigation,through the indoor fertilizer infiltration test,the migration characteristics of wetting front migration,soil moisture,ammonium nitrogen and nitrate nitrogen were studied under different soil initial water content (4.13％,7.21％,11.06％,14.01％).The relationships between the cumulative infiltration amount,the wetting front migration distance and the soil initial water content of bubbled-root irrigation were established.An empirical model was proposed to calculate the cumulative infiltration volume and the wetting front migration distance under different initial water content.Results showed that:The cumulative infiltration,the wetting front migration distance,the moisture in the body,the distribution and transformation of nitrogen were all affected by the initial water content of soil.At the same time,the cumulative infiltration reduced with the increase of initial soil water content,while the wetting front migration distance increased with the increase of initial soil water content.The higher the initial water content of soil was,the larger volume of wetting body was,and the wilder water,ammonium nitrogen and nitrate nitrogen distributed.The closer to the emitter outlet,the contents of ammonium nitrogen and nitrate nitrogen in the soil were higher.The infiltration coefficient K decreased with the increase of initial soil water content,while the infiltration index α showed an opposite trend.The fitting parameters a and b of horizontal wetting front both increased with the increase of initial soil water content.The vertical downward wetting front migration index c increased with the increase of initial soil water content,while the infiltration index d decreased with the increase of initial soil water content.With the continuous redistribution of soil moisture distribution,the moisture distribution in the moist body was more uniform,and the uniformity of water distribution evaluated by Christiansen uniformity coefficient Cu,in moist body was 61.99％,74.27％ and 83.6％,respectively,at the end of irrigation,redistribution of 1 day and 3 days.With the redistribution,the content of ammonium in the wetted body gradually decreased,but the distribution region of ammonium nitrogen was almost unchanged.With the redistribution,the distribution of nitrate nitrogen in the wetted area became larger,the average value of it increased,and the maximum value of it had a downward trend.The above research results can lay the foundation for further researches on water and nitrogen use efficient of bubbled root irrigation technology.