不同滴头流量和灌水量下农田土壤湿润体特征及其估算模型

Characteristics and estimation model of wetted soil volume under different drip discharge rates and irrigation amounts

为了准确估算滴灌条件下农田土壤湿润体,利用亮蓝染色剂示踪技术分别在陕西杨凌(粘壤土)、甘肃武威(沙壤土)和宁夏盐池(沙土)3个试验站点开展了农田滴灌试验。试验设不同灌水量和滴头流量,研究不同土壤质地条件下灌水量和滴头流量组合对农田土壤湿润体的影响,进而探求不同土壤质地的土壤湿润体估算模型。结果表明:在相同的土壤条件下灌水后农田土壤形成的湿润体随灌水量的增加而增大,在相同灌水量下增加滴头流量能够显著增加水平方向的湿润距离,相较于小滴头流量(1.38 L·h^-1)而言,大滴头流量(3.0 L·h^-1)形成宽浅形湿润体。在相同的灌水量和滴头流量下,农田土壤湿润体的垂向湿润距离随土壤饱和导水率(Ks)的增加而增加,随灌水前土壤有效持水能力(Δθ)的增加而减小,而水平方向的湿润距离随土壤饱和导水率(Ks)和有效持水能力(Δθ)的增加而减小。在试验的基础上,利用土壤饱和导水率(Ks)、灌水前土壤有效持水能力(Δθ)、灌水量(v)和滴头流量(q)建立了湿润体垂直和水平方向湿润距离的估算模型(幂函数连乘模型),并结合湿润体形状利用椭圆方程描述湿润体的轮廓形状(湿润体估算模型)。经试验数据验证,农田土壤湿润体估算模型能够很好估算湿润体轮廓,模拟值和试验实测值的决定系数(R^2)在0.93~0.99之间,均方根误差(RMSE)在1.3~4.1 cm之间。

In order to accurately estimate the wetted soil volume of farmland under drip irrigation conditions,we conducted an experiment at three experimental sites including Yangling(clay loam)in Shaanxi Province,Wuwei(sandy loam)in Gansu Province,and Yanchi(sand)in Ninxia Municipality)using bright blue stain tracer technology in 2017-2018.To study the effects of irrigation amount and drip discharge rate on wetted soil volume under different soil conditions,the experiment set different irrigation amount and drip discharge rate.The result showed that wetted soil volume of farmland after irrigation increased with increasing irrigation amount under the same soil condition.Increasing the drip discharge rate significantly increased the horizontal wetted distance,compared with small drip discharge rate,the wide and shallow wetted volume was formed in large drip discharge rate.The vertical wetted distance increased with increasing soil saturated hydraulic conductivity(Ks),and decreased with increasing soil water holding capacity(Δθ)before irrigation when irrigation amount and drip discharge rate were the same.The wetted distance in horizontal and vertical directions was estimated using soil saturated hydraulic conductivity(Ks),soil water holding capacity(Δθ),irrigation amount(v),and drip discharge(q)on the basis of the experiment.Simultaneously,we established wetted soil volume estimation model.The estimated value of the model agreed well with the measured value(R2 ranged between 0.93~0.99,RMSE ranged from 1.3 to 4.1 cm).