Characteristics, application and prospects of bubbled-root irrigation

Bubbled-root irrigation is an efficient water saving technique for irrigation of fruit trees that has been used in China. It is a subsurface micro-irrigation technology that can directly deliver water and fertilizer to the crop root zone for local irrigation. This study reviewed the characteristics, application status of the bubbled-root irrigation technique and proposed its development directions. The structural characteristics, working principles, irrigation methods, layout, hydraulic performance, costs and operation management of bubbled-root irrigation technology were summarized. The advantages of bubbled-root irrigation compared with traditional micro-irrigation were discussed. In addition, the application effect of this technology in fields was reviewed. The problems and developmental direction were proposed. The bubbled-root irrigation was better than drip irrigation, micro-sprinkling irrigation, and underground seepage irrigation because it overcame the shortcoming of those irrigation technologies such as the emitter clogging, aging of pipelines and low water use efficiency for fruit trees. The bubbled-root irrigation in fruit trees could not only save water and labors but also improve water and fertilizer use efficiency. Compared to the drip irrigation, the bubbled-root irrigation could lower the cost by 2 030 Yuan/hm2 and increase the benefit by 2 480 Yuan/hm2. Because the pipelines were buried into the soils, the influence of operations on soil surface such as tillage was small and thus it facilitated the field management. Meanwhile, the soil moisture condition could be improved by inhibiting evaporation and preventing soils from hardening and cracking. The technique had high water use efficiency and could enhance the yield. However, it would face challenges such as less practices, irrigation system to be optimized, the performance of emitter to be optimized an so on. Attentions should paid to the following areas: 1) improving and optimizing the performance of the irrigation equipment; 2) improving the level of informatization and automation management of bubbled root irrigation on the basis of the existing technology; 3) improving the performance of irrigation devices; and 4) optimizing irrigation systems of typical fruit trees. The bubbled-root irrigation has been promoted and applied in the Loess Plateau in northern Shaanxi, China and has achieved remarkable results. The use of bubbled-root irrigation technology for jujube irrigation greatly saved water and fertilizer consumption, alleviated the pressure caused by the serious shortage of water resources in northern Shaanxi and effectively improved the water and fertilizer utilization rate. However, the promotion and application of this technology also had certain limitations. Future studies should test if the technique is suitable to the other areas since the soil types, topographic conditions and the types of fruit trees in the other regions may change. The review would provide valuable information for the cultivation of fruit trees with less water and high yield.