微咸水膜下滴灌对盐碱化农田土壤斥水特征的影响

Effect of Mulched Drip Irrigation with Brackish Saline Water on Soil Water Repellency Characteristics of Saline-Alkali Field

在内蒙古河套灌区布置了2年大田试验,研究了不同覆膜方式下微咸水滴灌对盐碱化农田土壤水、盐分布及其土壤斥水性的影响。采用滴水穿透时间(Water drop penetration time,WDPT)法测定土壤斥水性,得到了不同土壤斥水性随含水率变化的规律。结果表明,膜下滴灌盐碱化农田土壤的斥水性在表层土壤与电导率呈正相关,与土壤pH值无显著相关性。弱碱性微咸水滴灌条件下,单次滴灌降低了滴头附近土壤的WDPT,但增加了远离滴头土体的WDPT;高频滴灌(灌溉频率为3 d)可显著降低土壤剖面整体的WDPT。膜下滴灌盐碱化农田土壤的斥水特征曲线均可用Gaussian和Lorentzian模型进行描述。滴灌对土壤斥水性最大时对应的土壤含水率(θm)影响不大(P>0.05),而对斥水性消失时对应的土壤含水率(θc)影响显著(P<0.05)。Lorentzian模型对盐碱化农田土壤的斥水特征曲线的拟合效果更优,通过该曲线可准确得到特定土壤的θm和θc。本研究可为微咸水滴灌及斥水性土壤的合理利用提供理论依据。

A two-year field experiment was conducted to investigate soil electric conductivity(EC 1∶5),soil pH value,and soil water repellency(SWR)in response to mulching method(M1:fully mulched,M2:partially mulched)and dripped irrigation frequency with brackish saline water in the Hetao Irrigation District under arid growing conditions.SWR was assessed by using the water drop penetration time(WDPT)method,and soil-water repellency characteristic curves(SWRCC)were built.Results demonstrated that SWR and EC 1∶5 showed a significant positive correlation in mulched drip irrigated saline-alkali field;while it was not so obvious between SWR and soil pH value.Under the experiment condition with weak alkaline and brackish irrigation water,WDPTs of the soil near drip emitters were decreased on the 7th day after each drip irrigation at low irrigation frequency;whereas,WDPTs of the soil away from drip emitters were increased on the 7th day after a single irrigation.WDPTs were overall decreased after high frequency irrigation(once every three days).SWRCC in mulched drip irrigated saline-alkali soil can be well fitted by Gaussian and Lorentzian equations.The SWRCC curves showed that drip irrigation showed no effect(P<0.05)onθm(the volumetric soil moisture when WDPT was maximum),whereas significantly changedθc(the volumetric soil moisture when WDPT was less than 5 s).Lorentzian equations showed better performance for SWRCC regression than Gaussian equations,andθm andθc can be obtained from Lorentzian curve.The research result can provide assistance for utilization of drip irrigation with brackish saline water and water repellent soil.