广西赤红壤甘蔗田间滴灌带合理布设参数确定

赤红壤是广西蔗区主要土壤类型之一,为探讨赤红壤蔗区滴灌条件下土壤水分运动规律,该文在试验基础上,利用HYDRUS-3D建立了双点源土壤水分运动数学模型,通过对照试验和模拟情况表明,HYDRUS-3D能较好地模拟试验土样的湿润锋运移规律和土壤含水率变化规律。在此基础上,利用HYDRUS-3D建模分析滴头间距、滴头流量对滴灌灌水均匀性的影响,结果表明:滴头间距对滴灌灌水均匀性影响较大,当滴头流量为1.38 L/h时,30、40、50 cm 3种滴头间距的滴灌带中,仅滴头间距30 cm的滴灌带满足试验土样灌水均匀性的要求;滴头流量对滴灌灌水均匀性也有一定影响,采用较大滴头能提高滴灌的灌水均匀性,但会增加单位灌溉面积设计供水能力,进而增加工程造价。综合考虑灌水均匀度、工程造价、工程运行管理模式以及糖料蔗不同生育期的用水需求,确定广西赤红壤蔗区滴灌带合理的滴头流量为1.38 L/h、滴头间距为30 cm、糖料蔗生育初期的适宜灌水时间为3.5 h,糖料蔗生育旺盛期适宜灌水时间为6.5 h。该结果可为广西赤红壤蔗区滴灌系统田间滴灌带合理设计提供参考。

Determination of drip tapes layout parameters for irrigation of sugarcane in latosolic red soil in Guangxi Autonomous Region

Abstract: Surface drip irrigation is commonly used for efficient water-saving irrigation in latosolic red soil of sugarcane fields in Guangxi Autonomous Region, China. Selection of appropriate layout parameters of drip tapes for irrigation in latosolic red soil of sugarcane fields has rarely been studied and it is important to improve irrigation quality and water use efficiency. The objectives of this study were: 1) to analyze the effects of the main technical parameters of drip tapes on the soil water movement and change in soil water content under drip irrigation; 2) to summarize the basic requirements of appropriately determining the main technical parameters of drip tapes; 3) to determine the appropriate design parameters of drip tapes for irrigation in latosolic red soil of sugarcane fields based on project cost, project management and operation patterns, and water demand of sugarcane crop in different growth stages. To address the above objectives, representative latosolic red soil sample was collected from sugarcane field in Guangxi. First, a laboratory experiment of water movement with surface drip irrigation was performed in soil columns under irrigation conditions with different emitter discharge rates and emitter spacing (30 cm vs. 1.38 L/h, 40 cm vs. 2.20 L/h, and 50 cm vs. 2.80 L/h, respectively). Changes in the surface ponding radius, wetted surface radius and vertical wetted depth were monitored during the experiment. Then, the main parameters for model building were from the physical properties of the soil and the results of the experiment. A model of soil water movement under double-point source of drip irrigation was built using HYDRUS-3D. Next, the effects of emitter spacing and emitter discharge rate on irrigation uniformity were analyzed using the HYDRUS-3D model. Appropriate parameters ranges for drip irrigation were determined based on the results of model analysis. Further, irrigation uniformity, project cost, project management and operation, and water demand of sugarcane crop at different growth stages were taken into consideration to determine appropriate design parameters of drip tapes for irrigation in latosolic red soil of sugarcane fields in Guangxi. The results showed that: 1) The simulation results of the Hydrus-3D model of soil water movement were reliable as compared with the experimental data, indicating the reliability of the model used for the following study; 2) Emitter spacing was the primary factor affecting irrigation uniformity; at the emitter discharge rate of 1.38 L/h, drip tapes with the emitter spacing of 30 cm yielded higher irrigation uniformity, compared with the larger emitter spacing (40 or 50 cm); 3) At the same emitter spacing, irrigation uniformity was improved with the higher emitter discharge rate; At the emitter spacing of 40 cm, drip tapes the higher rate (2.20 or 2.80 L/h) resulted in the higher irrigation uniformity. Given the slow water infiltration in latosolic red soil, we recommended to use drip tapes with lower emitter discharge rate on the premise of meeting the requirement of irrigation uniformity. Taking into account of project cost, project management and operation patterns and water demand of sugarcane, we suggested optimal layout parameters of drip tapes in latosolic red soil of sugarcane fields in Guangxi: emitter discharge rate 1.38 L/h, emitter spacing 30 cm, irrigation duration in the early and vigorous growth stage of sugarcane 3.5 and 6.5 h. This study provides guidance for drip irrigation project design in sugarcane fields.