作物主动汲水技术内涵与研究进展

持续创新农田灌溉技术,有利于应对农业水资源短缺、耕地资源不足,也是确保中国粮食安全的重要技术基础。该研究提出了"作物主动汲水"（Crop Initiative Draw Water,CIDW）概念,并分析其得以实现的基本条件是：土壤水非饱和性、外界水水势始终小于大气压、外界水和作物根系的距离有效性、高效的水势能差转化界面。综合文献划分出了压力势差（Pressure Potential Difference, P-CIDW)、渗透势差 (Osmotic Potential Difference, O-CIDW)和重力势差作物主动汲水（Gravitational Potential Difference,G-CIDW）等3种形式的CIDW,并分析了它们的势能特征和基本实现途径。进一步,从硬件设备技术、作物表现、水盐运移与分布、土壤生境等几个方面,重点综述了P-CIDW的研究进展。近十多年来的研究表明,相比漫灌、沟灌、滴灌等传统灌溉技术,适宜参数的P-CIDW能够显著地提高作物产量与水分利用效率、养分吸收和肥料利用率、根际土壤酶活性和微生物多样性、水肥耦合效应,明显地影响了作物生理生化指标、土壤养分有效性和养分空间分布;土壤质地及其剖面构型显著地影响了P-CIDW下的水盐运移与分布;利用初始土壤含水率和基质势、渗水器导水率、供水压力以及时间等参数,可以半机理半经验地估测P-CIDW的累积入渗量。最后展望了CIDW研究的未来,认为,土壤水分-作物关系的基础理论急需要突破、研发高效的势能转化界面材料仍然是发展CIDW技术的关键任务、尽快制定P-CIDW技术标准、P-CIDW控压方法还需要革命性的创新。

Connotation and research progress of crop initiate water drawing technology

Continuous technological innovation of farmland irrigation is a critical component of the strategy for dealing with the shortage of water resources and arable land resources around the world, and is a key to ensuring food security for a growing population especially in developing countries such as China. In this study, a concept of crop initiate drawing water (CIDW) was proposed, and four basic preconditions for its included: 1) soil is always water unsaturated, and planted crops must be upland crops; 2) external water potential outside the soil-root system is maintained less than atmospheric pressure; 3) the distance between external water and crop roots is kept as short as possible; and 4) a high efficiency water permeable interface capable of enduring the matric potential difference and another form opposite potential difference. For CIDW, there is invariably matric potential difference between the external water and soil-root system, and another mainly opposite potential difference which determinates the operation mechanism and its category. According to the literature, three type of CIDW were identified, namely pressure potential difference (P-CIDW), osmotic potential difference (O-CIDW) and gravitational potential difference (G-CIDW). The characteristics and operating conditions of the these three types of potential differences were analyzed and described. At present, the overwhelming majority of published studies of CIDW have focused on P-CIDW, only few studies have explored O-CIDW and G-CIDW. The significant advances in hardware included: 1) the form of negative pressure in the P-CIDW system has gradually changed from water pressure to air pressure; 2) the devices used to maintain negative pressure are now small, light, require no energy and are high precise(volume and weight are only one to ten percent of that of traditional devices); and 3) a new organic negative pressure water seepage material, namely polyvinyl formal (PVFM), has been invented and verified to be significantly superior to traditional materials like ceramics. At the same time, a large body of literature investigating the most efficient and suitable way to apply P-CIDW fully showed: 1) compared with traditional irrigation technologies such as flood irrigation, furrow irrigation and drip irrigation, P-CIDW with suitable parameters could significantly improve crop yield or water use efficiency, nutrient uptake, fertilizer utilization efficiency, enzyme activity, microbial diversity in the soil rhizosphere, and a coupling effect of water and fertilizer; 2) P-CIDW could significantly affect crop physiological and biochemical indexes and soil nutrient availability and spatial distribution, and whether those effects were beneficial or not depended on different research conditions; 3) soil texture and its profile configuration significantly affected soil water and salt transport and distribution under P-CIDW; and 4) by integrating initial soil moisture content and matrix potential, hydraulic conductivity of emitter, head of water supply and time, the cumulative infiltration under P-CIDW could be semi-theoretically and semi-empirically estimated. Finally, the future of CIDW was speculated on, and it concluded: 1) there was an urgent need to develop a basic theory explaining the soil moisture to crop relationship, 2) development of high efficient potential difference interface materials for CIDW was key; 3) the technical standards for P-CIDW should be formulated as soon as possible; and 4) the revolutionary innovation for methods of maintaining pressure in P-CIDW system was needed.