不同氮肥液浓度下微孔陶瓷根灌土壤水氮运移与流失特性的数值模拟研究

Simulation of Soil Water and Nitrogen Transport and Loss Under Varying Nitrogen Concentrations Utilizing Subsurface Irrigation with Ceramic Emitters Solution

微孔陶瓷根灌(SICE)是一种新型地下节水灌溉技术,其可利用陶瓷灌水器内部微米级孔隙实现水肥液地持续微量供给,并以地下连续灌溉的方式为作物根区营造安全、稳定且适宜的土壤水分环境。区别于以间歇灌溉为主的水氮供施方式,目前利用SICE进行氮肥液持续微量供给时的土壤水氮运移及其流失特性尚不明晰,这限制了SICE在实际中的推广应用。因此,采用HYDRUS-2D建立了SICE持续微量供给下的土壤水氮联合运移模型,并于中国青海开展了微孔陶瓷根灌枸杞田间试验,用以模型校准和准确性验证,最后以地下滴灌(CK)为对照,利用模型研究了3种氮肥液浓度(211.54mg/L、169.23mg/L、126.92mg/L)下SICE土壤水氮运移与流失特性。研究结果表明,构建的土壤水氮联合运移模型在预测土壤水氮方面表现良好;与CK相比,SICE减缓了氮肥液进入土壤的速率,延长了水分与养分的有效供应时间(从6.67 h延长至480.00 h),降低了根层土壤中水分、铵态氮(NH4+-N)和硝态氮(NO3--N)的时间波动性,保证土壤水氮相对充足的同时还维持了土壤水氮环境的相对稳定,为枸杞水氮高效利用提供了有效保障;其次,在氮肥液持续微量供给期内,SICE将土壤水分、NH4+-N和NO3--N维持在枸杞根系密度最大处,充分保证了根、水、肥的高度匹配;此外,SICE在降低水分深层渗漏和氮素淋失方面表现明显优于CK,可将更多的水分和氮素保存在枸杞根系层中,增加氮素可用性的同时降低了硝酸盐污染地下水的风险。

Subsurface irrigation with ceramic emitter(SICE)is a new type of subsurface water-saving irrigation technology.It can use the micron pores inside the ceramic emitter to achieve a continuous micro-supply of water and fertilizer and create a safe,stable,and suitable soil moisture environment for the crop root zone by continuous subsurface irrigation.Different from the water and nitrogen co-application method based on intermittent irrigation,the soil water and nitrogen transport and loss characteristics of SICE are still unclear.which limits the application of SICE in practice.Therefore,in this study,HYDRUS-2D was used to establish a soil water and nitrogen combined transport model under SICE continuous micro-supply,and a field experiment of irrigating wolfberry with SICE was carried out in Qinghai,China,to calibrate and verify the accuracy of the model.Finally,subsurface drip irrigation(CK)was used as a control to study the soil water and nitrogen transport and loss characteristics of SICE under three nitrogen fertilizer concentrations(211.54 mg/L,169.23 mg/L,126.92 mg/L).The results showed that the combined transport model of soil water and nitrogen performed well in predicting soil water and nitrogen.Compared with CK,SICE slowed down the rate of nitrogen fertilizer entering the soil,prolonged the effective supply time of water and nutrients(from 6.67 h to 480.00 h),reduced the time fluctuation of water,ammonium nitrogen(NH4+-N)and nitrate nitrogen(NO3--N)in the root layer soil,ensured the relative abundance of soil water and nitrogen,and maintained the relative stability of soil water and nitrogen environment,which provided an effective guarantee for the efficient utilization of water and nitrogen in wolfberry.Secondly,during the continuous micro-supply period of nitrogen fertilizer solution,SICE maintained soil moisture,NH4+-N and NO3--N at the soil depth where the root density of wolfberry was the highest,which fully ensured the high matching of root,water,and fertilizer.In addition,SICE was significantly better than CK in reducing deep leakage and nitrogen leaching loss,which could save more water and nitrogen in the wolfberry's root layer,increase nitrogen availability and reduce the risk of nitrate contamination of groundwater.