Prof. Yunkai Li has conducted systematic research for 24 years in field crop drip irrigation technologies. He has developed water-saving and yield-enhancing technologies for drip irrigation in field crops, providing valuable guidance for farmers on the effective use of this technology and achieving large-scale water-saving effects. Furthermore, he has developed five marginal water drip irrigation technologies specifically for reclaimed water, high-sediment water, high-salinity groundwater, brackish water, and biogas slurry, which conserve water by substituting clean water with marginal water. Additionally, the applicant has invented a series of drip irrigation equipment to improve the performance and reliability of drip irrigation systems. 
He has established several key drip irrigation technologies, including high density cultivation of field crops, the integration of water, fertilizer, and pesticide applications, mechanized crop production, efficient agronomy, and intelligent irrigation. These advancements have led to the development of 21 comprehensive solutions for water saving and yield-enhancing drip irrigation for various field crops, such as corn, wheat, soybeans, potatoes, sugarcane, and cotton.
He has established a multi-scale quantitative assessment system and methodology for tracking Sustainable Development Goals (SDGs). Additionally, he has developed a life-cycle assessment method for evaluating the water-saving and carbon Environmental impact and sustainable development control of irrigated agriculture in seriously overdrawn groundwater area Global desert oasis regions to develop efficient drip irrigation drive SDGs realization path 3 reduction benefits of drip irrigation using footprint theories. Based on these methods, he assessed the impacts of drip irrigation technology on the water-energy-food-environment nexus and the SDGs network at the regional level, proposing collaborative improvement pathways for SDGs and policy recommendations for regional water-saving.
He has conducted detailed research on emitter clogging behaviors in drip irrigation systems, specifically focusing on five marginal water sources. Through extensive experimentation with various emitters and fertilizers, they have identified the induction, growth, and regulation mechanisms of clogging, advancing the analysis of drip irrigation equipment from qualitative to quantitative levels internationally. Additionally, they've proposed anti-clogging control thresholds for water quality parameters and developed a method to select fertilizers compatible with the equipment and water quality. Furthermore, they've devised efficient anti-clogging control technologies tailored for five marginal water sources, resulting in a significant increase in the safe operation time of drip irrigation systems by over 130%, thus encouraging the reuse and recycling of marginal water for irrigation purposes.
He has introduced ground breaking theories and methodologies for drip irrigation equipment design, resulting in the creation of a range of high-performance products. They've developed a novel approach for designing anti-clogging emitters utilizing vortex zone water flow to clean emitter channels' boundaries, alongside enhancing equipment material formulas. Notably, they've invented five innovative emitter products, including fractal channel emitters and flow-type drip irrigation tapes. Moreover, they've engineered four series of high-performance filtration equipment, encompassing combined, self-cleaning, and low-pressure permeable filters. Additionally, they've introduced seven multifunctional products for regulating water, fertilizer, and gas, such as micro-nano bubble generators, water-fertilizer-air integration machines, and variable-frequency magnetizers. These advancements collectively enhance drip irrigation systems' efficiency, reliability, and adaptability to various agricultural contexts.
He has harnessed cutting-edge information technologies like the Internet of Things (IoT), artificial intelligence (AI), and big data to develop a suite of software and hardware products. They've optimized the structure and placement of soil moisture sensors, reducing information perception costs significantly. Additionally, they've engineered low-power, cost-effective wireless nodes, along with dual-channel solenoid valves and intelligent fertilizer injectors for execution equipment. Their pinnacle achievement is a smart drip irrigation cloud service platform, integrating irrigation decision-making models based on extensive historical data from meteorological stations and fertilization models at the county scale. Leveraging these intelligent products, they've established a simplified smart drip irrigation technology model, tailored for crops like cotton, soybeans, and corn. Compared to traditional drip irrigation, this model achieves water savings of 13%-17%, fertilizer savings of 9.5%-12%, labor savings of over 20%, and efficiency improvements of over 18.2%.
He has pioneered twenty-one techniques aimed at both water-saving and enhancing the yield of field crops. These methods have undergone rigorous testing across various experimental stations and technology demonstration areas, as well as in over sixty drip irrigation projects. Comparatively, these techniques have shown remarkable water savings of 45.7%-61.3% in field experiments compared to traditional surface irrigation methods. Through the establishment of eight demonstration areas and collaborations with enterprises, the technology has been implemented across 212,247 hectares, resulting in an annual water savings of approximately 330.4 million cubic meters.
Moreover, his innovations have facilitated a shift from furrow and sprinkler irrigation to drip irrigation, especially in areas with high sediment-loaded water sources. This transition has led to substantial water savings, with drip irrigation projects in such areas saving 190 million cubic meters annually compared to furrow irrigation.
Additionally, their innovative solutions have enabled the utilization of reclaimed water, brackish water, and high-salinity underground water for drip irrigation, reducing the reliance on clean water sources. For instance, the promotion of reclaimed water drip irrigation in Beijing and brackish water drip irrigation in Xinjiang has significantly reduced clean water consumption in these regions.
Furthermore, his high-performance equipment and technology have been successfully transferred to several companies, leading to industrialization and international sales. Collaborations with enterprises have resulted in the production of drip irrigation machinery and products sold to seventeen countries, with notable market shares in China. These advancements are expected to have a significant impact on agricultural practices, particularly in terms of water conservation and irrigation efficiency.
He has established a comprehensive product promotion model integrating various channels and pathways, including technology promotion departments, enterprises, and experimental demonstration bases, to facilitate the dissemination of green and efficient full-chain drip irrigation technology.
Under the "Experiment + Demonstration Base + Promotion" model, they've established experimental stations and demonstration bases across several provinces, collaborating with local technical departments and farmers to address production challenges. Additionally, they've implemented the "Innovations Commercialization + Product Sales + Technical Engineering Application" model, wherein drip irrigation products have been industrialized and widely utilized across China and exported to 17 countries. Notably, technologies such as Anti-Clogging Control Technology for Poor-quality Water and Drip Irrigation Technology for high-sediment water have been promoted in multiple provinces, covering over 200,000 hectares.
Furthermore, their drip irrigation technologies have been selected for national promotion catalogues and received certifications from relevant authorities. They've conducted numerous technical training sessions in collaboration with national agricultural and water resources organizations, effectively promoting the application of key technologies and products nationwide.
China places significant emphasis on agricultural water conservation and food security, as evidenced by policy initiatives such as the "New Round of One Billion Tons Grain Capacity Enhancement Action Plan (2024-2030)" proposed by the State Council. Additionally, the objective outlined in "China’s No. 1 central document for 2024" aims to upgrade all 120 million hectares of permanent basic farmland to high standards. The "14th Five-Year Plan for Advancing Agricultural and Rural Modernization" targets the creation of 4 million hectares of efficient water-saving irrigation areas. In line with these policy objectives, the technological solutions developed by this project, including water-saving technology for field crops, marginal water drip irrigation, and serialized drip irrigation equipment, hold considerable promise.
Moreover, as global population and societal growth accelerate, the adoption of marginal water reuse technologies for irrigation, such as reclaimed water and brackish water, is increasing. The annual global volume of treated wastewater, including reclaimed water, stands at 188.1 billion cubic meters, while brackish water reserves are estimated to rival global freshwater sources. The technological solutions for marginal water source drip irrigation developed by the applicant not only address technical challenges in China but also offer support for promoting drip irrigation technology utilizing marginal water sources in regions like the Middle East, Africa, and along the Belt and Road initiative.
Prof. Yunkai Li has served as the organizer of the "Efficient Drip Irrigation Technology and Equipment Team," which is a core part of the Chinese National Key Laboratory of Efficient Use of Agricultural Water Resources and the Chinese Engineering Research Center for Agricultural Water-Saving and Water Resources. The team consists of 4 professors and 5 associate professors. As the leader of the team, the applicant is fully responsible for the formulation of research plans, the development of technologies, the transformation of achievements, and the promotion of applications

Dean of the College of Water Resources and Civil Engineering, China Agricultural University

Reclaimed water (RW) applied in drip irrigation systems could be a solution to cope with the challenges of limited freshwater resources. Biofilm growth in irrigation systems is an unavoidable issue when using RW. To date, strong chemical bactericides mostly dominate the commercial market in controlling biofilms. However, recently scientists have been concerned about their real efficacy and environmental risks. This study assesses a low-concentration microbial antagonist (i.e., Bacillus amyloliquefaciens inoculums, BAI) intermittently injected into the systems to mitigate biofilm formation in three types of drip emitters using two kinds of treated RW. The results indicated that the application of BAI significantly (p < .05) mitigated the microbial biomass within biofilms when compared with the control groups (no-BAI). In addition, BAI reduced the contents of extracellular polysaccharides and proteins of biofilms, which decreased the total biomass in BAI treatments by 44.9%–73.8%. Consequently, BAI effectively improved the emitter performances and increased the discharge variation rate by 31.9%–44.3%. These findings might provide a new perspective to control biofouling when applying RW in irrigation systems, with potential implications for sustainable water management in agricultural production.

Presented at: 73rd IEC Meeting, Adelaide, Australia, 2022

The Hetao irrigation scheme is located in the northwest inland of China and the upper and middle reaches of the Yellow River. It is dry and rainless, with an average annual precipitation of 144mm and an average annual water surface evaporation of 2,377mm, and is one of the driest areas in the world. More than 90% of the water used in the irrigation scheme is from the Yellow River. The current irrigation area from the Yellow River is 11 million mu, involving 215,000 farmers and about 800,000 people.

The shortage of water resources is a common occurrence in the Hetao irrigation scheme, which has caused a bottleneck in economic and social development. Therefore, under the rigid constraints of the water resources management scheme, ensuring the irrigation scheme's sustainable economic and social development through the rational allocation and efficient development and utilization of water resources has become the most urgent and inevitable choice.

Shenwu irrigation canal is located in the west of the Hetao irrigation scheme, which takes water from the upstream of Sanshenggong water control project and uses water independently. The total irrigation area is 871,660 mu. From 2014 to 2018, Hetao Irrigation Scheme Water Resource Development Center organized the water rights trading project in Shenwu irrigation canal. By using the early-stage water resource fees transferred to industrial enterprises, the comprehensive water conservation transformation and construction of the water transmission and distribution channel project and the Shenwu irrigation canal field irrigation project are carried out. As a result, water is saved through the water conservation project. To ensure the water safety in the irrigation area, water rights are traded to industrial enterprises across regions and industries through the water rights trading platform.

From 2016 to 2021, the Hetao irrigation scheme began the 'household management of water rights' with "clear ownership, defined rights and responsibilities, and effective supervision" as the goal of water rights management. According to the irrigated land area of each water user, each water user is given the corresponding water rights. Such water rights may be traded, stimulating the farmers' awareness and potential for water conservation.

Within the Chinese Loess Plateau, water resources are scarce, and irrigation ef?ciency is a challenging issue. Traditional surface drip irrigation (SDI) methods have failed to improve irrigation ef?ciency and reduce surface evaporation in the region. An easy-to-install and practicable root-zone injection irrigation (RII) method, with a low risk of emitter clogging and which uses subsurface in?ltration-promoting apparatuses (SIPA) to deliver water directly to the root zone, was designed and tested in an apple orchard over 3 years in northern Shaanxi, China. In the 0–0.6 m soil layer (where the apple roots are concentrated), the RII method produced consistently higher soil water content than the SDI method over all three growing seasons. The soil water content was consistently higher than 60% of ?eld capacity, thus meeting the water requirements of fruit-bearing apple trees. In addition, the RII method alleviated soil desiccation, signi?cantly increased apple yields and improved fruit quality compared with the SDI method using the same volume of irrigation water. Both irrigation ef?ciency and water-use ef?ciency were improved with the RII method. These results provide a theoretical basis for the utilisation of the RII irrigation method in apple orchards in semi-arid regions, which may improve water conservation and the sustainability of apple production.

Keywords: Root-zone injection irrigation, subsurface, emitter clogging, surface drip irrigation

Presented at: 72nd IEC Meeting 2021, Marrakesh, Morocco

Secondary salinization induced by improper irrigation is recognized as a threat to agriculture all over the world, especially in arid and semi-arid areas. Secondary salinization is typically caused by flood irrigation because of the rise in the water table and the subsequent intense phreatic evaporation leading to an upward movement of salt contained in the groundwater which ultimately accumulates in the surface soil. Utilizing micro-irrigation techniques also leads to an increase in salinization, but in this case, secondary salinization is caused by insufficient leaching due to inadequate watering as demonstrated by Figure 3.7. An increase in salinization resulting from drip irrigation techniques has occurred in many dry areas including Israel, Egypt, the United States, Lebanon, China, among others.

Mulched drip irrigation (MDI) incorporates surface drip irrigation methods combined with film-mulching techniques both of which save water and labour while increasing the crop yield. In this study, a numerical model of soil water and salt movement under MDI conditions was developed. Guided by both experimental data and numerical simulations, soil water and salt distribution patterns at multiple spatio-temporal scales were ascertained, and an optimal irrigation schedule for the cotton-growing season coupled with comprehensive soil water and salt regulatory scheme for MDI was developed in an experimental research station in China. The model demonstrated high computational efficiency and robust numerical stability, making it suitable for long-term continuous simulations of soil water and salt migration under drip irrigation.

Irrigation quotas and intervals are two important parameters of the mulched drip irrigation system. From field experiments and theoretical analyses, it was found that, within a set range of water volumes, crop yields increase with irrigation quotas, however, water use efficiency tends to decrease. For a fixed irrigation quota, there exists an optimal irrigation interval that maximizes water use efficiency. This allows the determination of an optimal irrigation schedule, based on the integrated index of water and salt stresses. A holistic scheme of water and salt regulation for MDI cotton fields was developed by integrating an optimal irrigation schedule during the growth period, a flush scheme during non-growth periods, and a salinity reduction scheme of applying chemical ameliorants. This innovative technology has been extensively applied to a 20,000-ha region of cotton fields, resulting in the saving of 500 MCM of water.

During the growth period, by using optimizing irrigation systems, water-saving was achieved by improving the utilization efficiency of irrigation water. During the non-growth period, through flush irrigation scheme, yearly flush irrigation was replaced by a multi-year flush irrigation scheme, and the flush irrigation quota was reduced compared to traditional methods. The amount of water used for salt-leaching was also reduced. Additional water-savings were also realized by reducing the amount of salt leaching water through the application of chemical ameliorants. Compared to traditional irrigation methods, about 25% less water was required with the water and salt regulation scheme. Also, the cotton yield increased by 17% with stable soil salinity.

Proven to be one of the major agricultural technologies for saving water and increasing crop yields, drip irrigation technology has been applied on a large scale in the north-western and north-eastern regions of China as well as in other Central Asian countries. This technology has wide application prospects, especially in China and Central Asia, where more than 70 Mha of cotton is grown. It is estimated that promoting the application of this technology can generate more than 7 billion USD each year and save up to 17.5 BCM of water resources. It also has played an important role in regional economies, social development, and poverty reduction. The technology demonstrated that non-conventional and systematically calculated irrigation water requirements not only save water but also help in increasing the crop yield and it applies to a variety of crops.

To build water-saving irrigation systems for efficient and sustainable utilization of water resources, revolutionary policies for planning and implementing water-saving irrigation projects, promoting modernized transformation of irrigation schemes, enhancing awareness, and extending water-saving irrigation technology were implemented in China. As a part of the policy implementation, the construction of auxiliary facilities, up-gradation of existing equipment, and water-saving irrigation technologies demonstrations were organised in different districts.

Working out policies on promoting the development of water-saving irrigation: The policy draft document was accepted by the Government and included in the Outline of the National Agricultural Water Conservation Program (2012 - 2020). It was implemented as one of the key national policy areas for efficient and sustainable water management. Enterprises, village-level organizations, and individuals were encouraged to invest in water-saving facilities with financial subsidies from the government to purchase the requisite equipment. Additionally, Regulations for Irrigation and Drainage were composed to improve the comprehensive agricultural production capacity and to ensure national food security. The regulations were put into force as of July 1, 2016, in China.

Working out plans for water-saving irrigation development: National plans were formulated for developing modern irrigation, building auxiliary facilities, transformation projects in large and medium-sized irrigation schemes, water-saving irrigation in pastureland, upgrading large-scale pump stations, and the implementation strategies for saving water and increasing grain output in four provinces and autonomous regions in northeast China. They also restricted the over-extraction of groundwater to develop highly efficient water-saving irrigation in North and South China. These plans laid the foundation for the strategy, management, and investment of the national water-saving irrigation development.

Promoting investment in water-saving irrigation projects by Central Government: Discussions were held to increase Central Government’s investment in water-saving irrigation projects. The Central Government allocated 30 to 50 billion RMB (1 USD= 6.9 RMB) annually for developing water-saving irrigation projects, with the focus on the transformation of large and medium-sized irrigation schemes, large-scale development of efficient water-saving irrigation on the farm, and upgrading large-scale pump stations for irrigation or drainage. Along with adopting advanced agro-techniques and agricultural mechanization, such as laser control levelling equipment, comprehensive grain production capacity and efficient water resource utilization were also promoted, creating the base for modern agriculture.

With the implementation of these plans and policies, the water-saving irrigation area in China increased by 10.2 Mha, irrigation water application quota per hectare reduced from 5,910 m³ to 5,610 m³, irrigation water use efficiency increased from 47.6% to 53.6%, and water use efficiency increased by 12.6 %. Each year about 3,060 MCM of water is saved due to the development of water-saving irrigation in China. At present, there are more than 2,000 specialized manufacturers in China, whose water-saving equipment can annually irrigate more than 2 Mha.

To promote large-scale and integrated development with distinctive regional characteristics, efforts were made to construct the national demonstration counties for efficient water-saving irrigation across the country. To assess the effectiveness of the national demonstration counties, six national demonstration counties were selected for assessment.

Technical training programs were also organised for different regions, and levels. The main topics of the training were technology and application management of sprinkling irrigation, micro-irrigation, and pressurized water supply technology, IT application in irrigation schemes, calculation, and analysis of the water use efficiency in irrigation, and management of water-saving irrigation projects. Efforts were also made to limit the irrigation quota management and monitor the total water used for irrigation. Water use cooperation associations were promoted among the farmers to upgrade water management at the farm level. Comprehensive reform on agricultural water prices was launched, and a specialized user service system in water-saving irrigation was established. To tackle the water shortage problem the government targeted to expand water-saving irrigation area by 1.33 Mha every year and to reach 55% of water use efficiency in China by 2030. These targets were to be achieved by the implementation of the National Water Conservation Program, incorporating water-saving indicators, and modernising the irrigation schemes.

Irrigated farmland contributes approximately 75% of grain and more than 90% of vegetables produced in China. Unfortunately, the increasing water scarcity coupled with population increase and climate change has aggravated food security issues. Newly designed sprinklers and micro-irrigation systems have been implemented in China to improve the situation.

Following are the specific cases and findings reported after the implementation of these sprinklers:

1. Consumption mechanism of sprinkler water intercepted by the crop canopy: Lack of knowledge on canopy interception led to farmer’s hesitance in adopting the technology. Studies were conducted between 2001-2010 to quantify the amounts of canopy interception for sprinkled crops and to investigate their consumption mechanism. Results indicated that the interception varied with growing stages from 0.7 to 3 mm for winter wheat and 0.8 to 2.6 mm for maize. Moreover, the evaporation of water intercepted by canopy compensated for partial loss of sprinkler water as the plant transpiration and soil surface evaporation could be suppressed by increased humidity and reduced temperature within the sprinkled field resulting from the evaporation of the water intercepted. Through energy balance measurements (Bowen ratio and eddy covariance methods) and modelling, the net losses were separated from the gross losses and quantified to be 4.3-6.5% of the water applied during the irrigation season of maize and approaching zero for winter wheat. The net losses accounted for a relatively small portion of water applied, confirming the water-saving merits of sprinkler irrigation. Thus, a software package to determine net loss under varying environments and operation conditions of sprinkler irrigation systems was developed.
2. Droplet size distributions from sprinklers: Droplet size distribution from the sprinkler is an important parameter that controls evaporation loss from spray and soil erosion caused by droplet impact. Extensive measurements and modelling of droplet size distributions from different shaped sprinkler nozzles were conducted. These works significantly contributed to the development and revisions of Chinese national technical standards of sprinkler irrigation.
3. Design standards of sprinkler uniformity: Based on field observation, a sprinkler uniformity lower than the value suggested by the current standards (C_u = 80%) was recommended to reduce the installation and operation costs of sprinkler irrigation systems. Lateral and vertical redistribution of water and solutes in soil were caused by a non-uniform distribution. These findings were adopted in the development and revisions of the Chinese national standards related to sprinkler irrigation.
4. Variable rate irrigation for centre pivots: Variable rate irrigation (VRI) is an emerging efficient irrigation technology to determine the optimal cycle time of solenoid valves at specific travel speeds of the pivot. The traits of VRI system in enhancing water use efficiency and reducing deep percolation were evaluated for winter wheat and summer maize in the alluvial flood plain of China. VRI reduced irrigation water use by 17.6% during the irrigation season of maize and reduced the variability of deep percolation within the entire field. Fieldwork suggested that AWC (available water holding capacity) can be an alternative parameter for zone identification in VRI management.
5. Design of landscape sprinklers: The study assured that the arc-controlling unit of sprinkler rotation stays in place and undamaged when the sprinkler was accessed or driven by casual or misoperation, thus increasing sprinklers' service life and stability.
6. Transport of water and nitrogen in soil under drip fertigation: The study addressed the concerns about potential toxic rhizospheric environments caused by fertigation. The research included design and operation strategies for injectors, laboratory and fieldwork on nitrogen in homogeneous and heterogeneous soils, and the response of plant growth and crop yield and quality to water management practices and fertilizers under surface and subsurface drip irrigation.
7. Design standards of drip irrigation system uniformity: Extensive investigations were conducted on the influence of drip irrigation uniformity and spatial soil variability on the dynamics of water, nitrogen, and salts as well as crop yield and quality under a wide range of environments from arid to sub-humid, for cotton, maize, and vegetable crops. It was found that the effect of drip irrigation uniformity on crop yield and water and nitrogen deep percolation is less than expected. It was concluded that micro-irrigation system uniformities as low as 60%, although lower than the current standards, may be acceptable in terms of yield and nitrate leaching; and a lower uniformity coefficient can be used in the humid and semi-humid regions than in the arid regions.
8. Efficient and safe utilization of reclaimed sewage effluent through micro-irrigation: With the increasing use of reclaimed sewage effluent in irrigated agriculture, experiments were conducted to study pathogens behaviour in the soil-plant system. It was found that the potential pollution risk of E. coli to soil can be reduced. Using the 15N tracing technique, the effectiveness of nitrogen-containing in sewage to crop production was also quantified and No E.coli uptake was detected when drip irrigation was used.

A management practice of irrigation at 100% ET_C (evapotranspiration), along with a nitrogen application rate of 160 kg/ha was recommended and widely used in the region. On average, the requirement of seasonal irrigation and fertilizers reduced by 20-30% and 15-20%, respectively compared to traditional surface irrigation. Studies revealed that increasing frequency from traditional monthly fertilization to weekly fertigation for greenhouse vegetable crops can increase yield by 18% and reduce nitrogen usage by 15-30%. The three years of field experiments in the sub-humid region of Northeast China revealed the advantage of plastic mulch in saving water by 10-15% via reducing evaporation from the soil surface and enhancing crop growth through increasing soil temperature at the beginning stages of maize. Using two or three in-season fertigation splits could meet crop nutrients requirements on time, thus increasing crop yield by 5-10% and reducing the need for nitrogen. The estimated water saving was about 180 MCM in the three years of the experiment.

These technologies, mainly sprinkler and micro-irrigation, were extended to around 60,000 ha in several provinces covering winter wheat, maize, and several vegetable crops. Approximately estimated acreage of direct use was about 1,200 ha with total water savings of about 3.7 MCM and fertilizer reduced by 270 tons. Currently, drip irrigation has become an acceptable irrigating method for greenhouse vegetable crops in China. The developed management practices were used in 330 ha of maize cultivation (10 centre pivot installations) from 2012 to 2015. The estimated total accumulative water-saving was 1.6 MCM in the three years. It was further extended in two counties of Heilongjiang Province from 2012 to 2015, with a total acreage of about 3,400 ha maize irrigated by centre pivots. The amount of water savings was about 70 m³/ha with a total estimation of 14 MCM. Currently, the number of centre pivots and linear move systems in China has reached 7,000 installations with a total area of 40,000 ha. These management practices are planned to be implemented in a larger area and more water and fertilizer saving can be expected. These sprinklers contributed to the domestic industrialization of landscape sprinklers as well as water and soil conservation for landscape irrigation in China. They were also exported to the USA, Brazil, Mexico, Iran, and other countries. The findings provide a complete guide for the design, management, and evaluation of micro irrigation systems to maximize their benefits.

After three decades of research, the controlled irrigation methodology was introduced in paddy growing fields of Guangxi province, China, to overcome concurrent challenges. The technique includes an optimal combination of irrigation timing, frequency, irrigation control of water level in the field, and the amount of fertilizer.

China has a large output of paddy rice with an area of 461 million mu and an output of 185 MT, ranking the second and the first in the world respectively. Guangxi, the largest growing base of sugarcane in China, has a mango growing area of 900,000 mu and is also one of the most suitable places for the production of black tea, green tea, and Oolong tea. It has 1,500,000 mu tea gardens and 2,400,000 mu citrus growing area. Despite the rich rainfall and water resources in South China, the extremely uneven distribution of yearly rainfall led to an ever-increasing water shortage, weak infrastructures, insufficient innovating capacity, and low awareness of water-saving irrigation technologies. Most farmers lack the basic knowledge of selecting the time, amount, number, and mode of crops for irrigation. In South China, paddy fields are traditionally watered through flood and plot-to-plot irrigation with the help of gravity, and the fields are inundated for long periods which leads to plant diseases and pests, unproductive tiller, weak stem, and lodging, resulting in yield decline. Secondly, with annual water consumption reaching 12,000-15,000 m³/ha, the conventional irrigation method leads to water wastage and consequent farmers’ disputes over water sharing in dry seasons. To boost outputs, farmers have been applying fertilizers, pesticides, and herbicides in large quantities, leading to contamination of surface water and shallow groundwater.

To address these problems, after more than three decades of experimentation and studies at the Guilin Irrigation Experimental Station, a controlled irrigation methodology was devised. The controlled irrigation technique for paddy rice develops an optimal combination of irrigation timing, frequency, water, the water level in the field, and the amount of fertilizer. The technique has been promoted on a total area of 15.3 Mha in the region resulting in 28.7 BCM of water savings during the period 1990 to 2013. The innovation focuses on water content production function, irrigation principles, temporal and spatial changes, recycling rural sewages through fast infiltration, wetland general system, and farmland irrigation. It revolves around the connection of physiological water demand of paddy Rice, field water consumption, water, and fertilizer coupling, channel irrigation management, and ecological repair. This technology addresses four indices of the paddy rice irrigation system from the perspectives of water resource, environment, and management, i.e., irrigation time, irrigation number, irrigation quantity, and irrigation quotas which correspond to the total quantity control and quantity management technology adopted in the process of soil testing formula, fertilization time, fertilization number, fertilization load, and channel management.

As a result of these techniques, in an area of 667,000 ha with 1872 m³/ha under paddy, up to 1.25 BCM of irrigation water was saved cumulatively; crop yield increased by 300 kg/ha and 200,000 tons cumulatively, and farmers’ income was increased by 900 yuan/ha (USD 137) and 600 million yuan (94 million USD) in total. From 1990 to 2013, the cumulative water-saving in Guangxi Autonomous Region amounted to 28.704 BCM; total crop yield growth added up to 4.6 MT; and the income growth totalled 276 billion Yuan (44 billion USD), while the consumptions of fertilizer fell by 2.3 MT, and nitrogen and phosphorus elements washed away dropped by 30%, and the emission of non-point source pollution was reduced by 26 BCM.

Field surveys were carried out in the countryside in the irrigation zone and selected 240,000 mu farmlands in Pingle and Lipu counties as the pilot zone for water-saving irrigation of paddy rice. Significant achievements were made in the same year. The water consumption of late rice in Lipu was 290.5 m³/mu with scientific irrigation while the water consumption was 377.5 m³ in the conventional deep-water submerged irrigation, hence saving water by about 89 m³/mu. The output increased to 462.8 kg from 399.4 kg with scientific irrigation per mu hence increasing the output by 63.4 kg/mu. According to domestic experts, the incremental output per mu is 25.4 kg with scientific Irrigation based on a ratio of 0.4. In Pingle County, the incremental output per mu was 24.2 kg.

Pilots were also conducted for the cultivation of sugarcane, mangos, tea, and citruses in Liuzhou, Laibin, Nanning, Chongzuo, and Baise of Guangxi Province, with a cumulative promotional area of 3 million mu; saving water and fertilizers by 36,000 m³ and 45 million kg cumulatively and respectively and increasing incomes by 4.5 billion Yuan (700 million USD).

The water-saving irrigation technology was mainly characterized by a combination of drip irrigation, micro-irrigation, and soil testing formula fertilization in the implementation of sugarcane, mango, tea, and citrus in an area of 3 million mu. The economic and social benefits from the irrigation experiment were obtained every year since the 1960s. In 1992 and 1993, 1.78 Mha of rice field was spread with the “shallow water, wet and dry irrigation method” in the Guangxi region. The total water saved was 2.53 BCM and the total increased rice yield of rice was 672000 tons in two years. The average value of saving water was 1.42 ton/ha and the average value of the increase in yield was 377.1 kg/ha. The total direct economic benefit was 543 million RMB (8,38,10,518.7 USD) with an average direct benefit of 304.5 RMB/ha (47 USD). 86 countries, 922 townships, 1132 irrigation districts, 6302 villages, and 25 million framer families were involved in the project implementation and benefitted from the technique.

Water scarcity is a big crisis in South China. Focus on water conservation using simplified and scalable technology is a necessity. The canal linking, thin and exposed irrigation for paddy, and economical sprinkler, and other micro-irrigation are some of the water-saving technologies which were implemented and studied in a research area. In the agricultural area of 5.11 Mha of farmland, 5.15 BCM of water was saved, 1.58 billion kg of grain increase was witnessed, and 0.30 billion KW of power was saved using these technologies. Besides ecological bene?t, the direct economic bene?t was RMB 11.98 Yuan (USD 1.93 billion).

To overcome deficiencies of the conventional long-standing irrigation water practice in paddy cultivation thin and exposed irrigation method was suggested, whereas “thin” refers to a thin irrigation layer (around 20 mm) and “exposed” refers to ?eld surface being exposed to the air to absorb oxygen and emit harmful gases. It was found that as long as there is water in the root system, the paddy can grow normally. Even though the straw was not inundated by water and the yield was very high. With no-water layer irrigation, the soil moisture in the ?eld was kept at 100% only in striking root period, then the soil moisture was kept between 70% and 95% to make full use of precipitation and two to six times of irrigation, while there was no water layer on the ?led surface. The average irrigation quantity for flood irrigation is 1000 m³/ha, however thin and exposed irrigation saved up to 53% of irrigation water. The yield increased from 685 kg/ha in case of flood irrigation to 1080 kg/ha. The water productivity with the new technology was 2.8 kg/m³.

Another contribution was the development of low costs sprinklers by reducing the material cost through “economical sprinkler and micro-irrigation”. Furthermore, the idea of “miniaturization of irrigation unit” emerged. The irrigation unit is the irrigation area covered by one pumping station. The cost for pipes accounts for 50% to 60% of the total expense, and the cost of the pipes is determined by the diameter, while the diameter for pipes is determined by the rotation area. After theoretical calculation and consultations, the rotation area was controlled around 0.67 ha, with 15 rotations, the controlled irrigation unit area was around 10 ha, and the farmers’ managed the system within a radius of 400 m. The idea brought forward the conception of “permeable lift loss hgp”. The common approach was to design the sprinkler and micro-irrigation, and ?nally calculate the total lift (H) of the system. Low costs sprinklers made using PE pipes reduced the overall costs making this technology more economical. The cost was cut down to the extent of 50% leading to its further extension.

Thin wall and multiple holes sprinkler hose replaced micro-sprinkler nozzle, saving around RMB 45,000-6,000 yuan/ha. Thick walls of drip irrigation tubes were replaced with thin walls, and then reduced the waste of pipe materials caused by blocking of drip holes. Finally, the expensive fertilizer applicator was replaced with the simple negative pressure absorption instrument of pumps.

The technology was widely implemented in Yuyao municipality. In 1990, three different canal lining types were developed based on different groundwater tables and soil type. Special water plugs with steel wire meshed concrete pipes were used in the thin walls. Since 1994, this technology has been extended in Zhejiang province over 4.20 Mha in total, where 3.91 BCM of water and 0.26 billion KW of power have been saved and 1.45 kg of grain has been increased, the economic bene?t was RMB 3.63 billion Yuan (USD 0.70 billion).

In 2008, the Chinese Ministry of Water Resources, the Department of Irrigation and Rural Water Supply as well as China Irrigation and Drainage Development Centre investigated the technology and approved its extension in China. In 2009, Zhejiang provincial government extended it over 67,000 ha of farmland in Zhejiang province. So far, this technology has been extended in over 6,30,000 ha of farmland and 1,55,000 ha of livestock farms in South China. It saved 0.94 BCM of water, and farmers’ net income was increased by RMB 7.25 billion (USD 1.17 billion).

By the end of 2012, this technology was extended in over 2,80,000 ha of farmland, saved 0.30 BCM of water, increased 0.13 billion kg of grain, and saved 34 million KW of power, the direct economic bene?t was RMB 1.1 billion yuan (USD 0.18 billion). It can be seen that water-saving could be achieved by assessing the soil moisture at the root level and determining the right water requirements thereby changing the conventional method of flood irrigation with limited supply to sprinkler technology making it more affordable and available for multiple users. Over and above these land farm applications developed the supply-side infrastructure and the conveyance losses were reduced to a large extent and the concept of piped irrigation was established.

The Jiamakou Irrigation Scheme (JIS) was constructed from July 1958 to July 960, and it is the first large high-lift irrigation scheme in the Yellow River Basin in China. After nearly 40 years of operation and obvious wear and tear, some problems emerged, such as outdated facilities, obsolete infrastructure, overstaffing, organizational overlapping, and old-school management.

In 1998, the scheme was revived, the pumping stations and irrigation canals were rehabilitated to provide better services. The rehabilitation and reform innovations in JIS were extended in 10 large irrigation schemes in Shanxi Province, 3 large irrigation schemes in Gansu Province, and 2 large irrigation schemes in Henan Province of China. The reforms covered an area of 6,45,000 ha and 630 MCM water was saved in three years.

The reform and innovations were implemented gradually in the irrigation scheme. First of all, the infrastructure and facilities of the scheme were upgraded for enhancing the system capacity for water supply, delivery, measurement, and control. Secondly, management system reforms were introduced to strengthen the operation and maintenance of the system. Benchmarking was also adopted to evaluate the progress. The monitoring and analytical results indicated that water use efficiency, water productivity, and sustainability of the JIS system have improved significantly.

The Geographic Information System, water measurement techniques, digital and image technologies were integrated into irrigation water management information system. Technical improvements were conducted to increase the operational duration of the pump. It led to an increased 2,630 hours of operation, reduced annual maintenance cost up to 10% of the original cost, and the service life of the impeller jumped from 1,000 hours to 4,000 hours. Cast-in-place U-type concrete section and arc-bottom trapezoidal section were used in the main canal, which is the largest cast-in-place concrete canal in China with a discharge of 30.5 m³/s. It has a strong frost resistance, a low coefficient of roughness, a high flow rate, and good sediment transport capacity. In 2001, a floating pumping station was designed which could accommodate the fluctuating water level of the Yellow River.

An integrated and scientific irrigation management system, which included human resources management, water supply management, water-entity management, assets management, financial management, information management, and technological advancements was implemented and it proved successful. With these reforms, the efficiency of JIS improved remarkably. The establishment of WUAs strengthened the tertiary canal management, facilitated farmers' participation in the system’s maintenance, and decision-making.

Water-saving: The water use efficiency at the main and branch canals increased from 0.68 in 1996 to 0.83 in 2012. More than 18 MCM water was saved every year, and about 120 MCM of water was saved from 2000 to 2012.

Increased revenue: The annual added value of irrigation water increased from 570 million RMB Yuan (93.4 million USD) to 1,730 million RMB Yuan (283.6 million USD) and added value of per cubic meter of irrigation water in the JIS increased from 10.62 RMB Yuan (1.74 USD) to 22.34 RMB Yuan (3.66 USD). During the same period, the annual net income per farmer increased from 5,040 RMB Yuan (826 USD) to 14,100 RMB Yuan (2,311 USD).

Increased irrigated area: The irrigated area increased from 12,333 ha in 1998 to 33,530 ha in 2007. With the north extension project in 2008, the irrigated area increased to 60,600 ha in 2012.

Increased income of staff: The annual average income of each staff member increased from 3,300 RMB Yuan (540 USD) in 1998 to 35,263 RMB Yuan (5,780 USD) in 2012.

Social benefits: FAO’s 2006 five-day assessment of the irrigated area stated "The overall irrigation benefits, water use efficiency and irrigation water productivity are all higher, compared with other irrigated areas with the same conditions and lead the way in China and the Asia-Pacific region"  The innovations and experiences in JIS have been summarized and replicated in other irrigation schemes. In the JIS operation, three primary elements of the water supply were reformed, known as the “three flows”: the commodity (water) flow, the capital (water fee) flow, and the information (water information) flow. The same model and concept can be followed in similar large projects.

Food security is facing the challenge of severe water scarcity in China. Agricultural non-point source pollution caused by unreasonable irrigation and drainage management is increasing in intensity. In China rice is a major staple food crop and is grown on 30 Mha. With rapidly growing sectoral demands, the Government has been investing and promoting various water-saving technologies like the Controlled Irrigation Technology. The technology saves irrigation water, increases grain yield, enhances rice quality, reduces agricultural non-point pollution and greenhouse gas emission from paddy fields.

Controlled irrigation (CI) is a new and widely adopted water-saving irrigation technology for rice cultivation in China. The concept of rice-controlled irrigation defines the lower limits of root layer soil moisture in different growth periods and forms a practical model of CI technology. The irrigation thresholds of the technology were determined based on the sensitivity of rice to soil moisture conditions and water requirements at different growth stages. A set of field characterization indicators for different rice growth stages were established. For example, when the tread does not trap the foot, and cracks of about 10 mm wide appear in the paddy fields during the late tillering stage, irrigation should be applied until the soil moisture reaches saturation level in the observed root zone. After the crop’s regreening stage, there is no need for ponding water. In case of rainfall, flooded water up to 5 cm depth can be maintained for less than 5 days to take full advantage of the rainfall. In large irrigation districts, CI technology can be implemented based on the management of the irrigation frequency and irrigation duration.

Under CI technology, the transpiration and evaporation of rice were reduced by 20.7-43.8% and 7.9-21.9%, respectively compared to traditional irrigation. Similarly, seepage and water use in paddy fields were decreased by 38.4-61.4% and 29.4- 36.9%, respectively compared with traditional irrigation. The yield and water use efficiency of rice increased by 3.2-12.4% and 47.4-74.1% respectively, compared with conventional irrigation.

Application of the CI technology not only leads to a reduction in irrigation water, increase in yield, enhancement of rice quality, but also results in the reduction of nitrogen, phosphorus losses, and methane emission from paddy fields by 80%, 65%, and over 80%, respectively. The efficient irrigation and drainage mode has been widely applied in rice irrigation districts of Jiangsu Province, and Heilongjiang Province, and Ningxia Hui Autonomous Region in China. A cumulative 4.46 BCM of irrigation water was saved because of the efficient irrigation and drainage technology. The accumulated total benefits were increased by 2.08 billion yuan (0.33 billion USD).

From 1991 to 1995, the CI technology in rice was widely applied in the Xiaobudong irrigation district and the Nansihu irrigation district in Shandong Province. While the application area reached 33,300 ha, the irrigation water was reduced by 120 MCM, and the accumulated total benefits were increased by 2.82 million yuan (4,35,260 USD). The technology was widely applied in the irrigation districts of Beijing suburbs, Shanghai state farms, Hunan Province, Jiangxi Province, Anhui Province, Hainan Province in China.

Subsequently, the technology was promoted in the Ruhai irrigation district, Jiangdu irrigation district in Jiangsu Province, the Qingtongxia irrigation district in Ningxia Hui Autonomous Region, and the Ganfu Plain irrigation district in Jiangxi Province of China. The cumulative saved irrigation water was by 4.46 BCM, and the accumulated total benefits were increased by 2.08 billion yuan (321 million USD). In Ningxia Hui Autonomous Region, the accumulated application area reached 95,600 ha. The irrigation water was reduced by 580 MCM, and the accumulated total benefits increased by 98.04 million yuan (15.32 million USD). The total yield was increased by 48.94 million kg.

Overall, the CI technology has been adopted over 3 Mha of rice grown area, saved about 9 BCM of water, and increased the rice grain production by about 1.6 MT, annually. This integrative water-saving mode of rice irrigation district can be applied to more than 5.33 Mha in the northern rice grain-producing areas in Heilongjiang, Jilin, and Liaoning provinces, and can be widely applied in mid-eastern provinces in China (Jiangsu, Zhejiang, Anhui, Jiangxi, etc.) to achieve a comprehensive extension. The expected applied area of technological achievements can reach about 16.7 Mha, more than 50% of China's rice fields.

Prof. Kang Shaozhong’s research is mainly on the principle and practice of water-saving agriculture and water management during the past 25 years. He has developed theories and practices to improve crop water use efficiency and regulated deficit irrigation by studying the water transport in soil-plant-atmosphere continuum (SPAC) and its regulation mechanisms for improving water use efficiency, presented the controlled indicators in Northwest China for high efficient irrigation by studying calculation method of crop water requirement and evapotranspiration model, and established the optimal regional water management model by studying the impacts of water-saving irrigation and regional irrigation development on hydrological processes and eco-environment. The high efficient irrigation model and new water-saving method developed by him have been extended broadly in Northwest China. His main contributions and achievements for water-saving agriculture and irrigation management have the following aspects:

(1) He developed the calculation method of crop evapotranspiration in arid and semiarid areas, and presented the high efficient irrigation models in Northwest China.

He presented a rice evapotranspiration calculation method and irrigation regime in Hanzhong basin of Shaanxi Province in 1980’s. Application of the results in water management in 80,000 hectares led to irrigation reduction by 10% and yield increase by 15% in rice production.

He presented a crop evapotranspiration model suitable to arid and semiarid areas of Northwest China, and found that crop evapotranspiration is apparently influenced by soil water content only when the relative soil available water content is lower than 0.5 in the Loess Plateau. The result supplied a basis for deficit irrigation in Loess region. And the method of calculating the ratio of soil evaporation and crop transpiration developed by him, which was applied by some scientists in China, is apparently better than the model raised by Richie and Burnet, and by Childs.

Moreover, he presented a new method to calculate the soil water-modified coefficient in crop evapotranspiration model under deficit irrigation, analyzed the effects of soil surface wetting patterns (partial rootzone wetting), cultivate patterns (plastic film mulching), groundwater table, and irrigation methods (drip irrigation under plastic film mulching) on crop coefficient, presented a relationship of crop coefficient and groundwater table, and crop coefficients in drip irrigation under plastic film mulching and in different wetting patterns. The results modified and supplemented the data recommended by Irrigation and Drainage Book 56 of FAO in 1998, supplied a scientific basis for water-saving irrigation in China.

He studied and presented water requirement indicators of wheat, maize, cotton, rice, oil bearing crops, millet, potato, sorghum, peanut, Chinese cabbage, tomato and tobacco based on the lysimeter experiment data, and made the isoline maps of water requirement for 6 main crops and irrigation water requirement in different hydrological years, studied and presented the high efficient irrigation models for wheat, maize, cotton, rice, oil bearing crops, millet, potato, sorghum, peanut, Chinese cabbage, tomato and tobacco and different regions in Shaanxi Province. The results have been extended and applied in accumulated 15,233,333 hectares in Shaanxi Province in recent 10 years, 7.125×108 m 3 of water was saved in irrigation, and the cost of ?71,250,000 was saved in crop production.

(2) He developed and extended the technique of controlled alternate partial root-zone irrigation in China.

He and Prof. Zhang Jianhua (Hong Kong Baptist University) developed a new irrigation method systematically, so called controlled alternate partial root-zone irrigation (CAPRI), in 1996 to improve crop water use efficiency by exploiting the plant physiological responses to partial soil drying in their rootzone. It is a new irrigation technique that can improve crop water use efficiency without significant yield reduction and exposes approximately half of the root system to soil drying while the remaining root system is irrigated as in full irrigation. The wetted and dried sides of the root system are alternated on a time cycle according to crop water requirements and soil drying rate. The method was developed on the basis of four theoretical backgrounds. Firstly, fully irrigated plants usually have widely opened stomata. A small narrowing of the stomatal opening may reduce water loss substantially with little effect on the photosynthesis. Secondly, part of the root system in drying soil can respond to the drying by sending a root-sourced signal to the shoots where stomata may be inhibited so that water loss is reduced. Thirdly, controlled partial root-zone wetting and drying alternately can stimulate the root uptake ability for soil water and nutrients. Fourthly, partial root-zone watering can enhance soil water movement from the wetted part to the dried part, and reduce the depth of water infiltration. Therefore the ineffective percolation can be reduced.

He and Prof. Zhang Jianhua (Hong Kong Baptist University) developed a new irrigation method systematically, so called controlled alternate partial root-zone irrigation (CAPRI), in 1996 to improve crop water use efficiency by exploiting the plant physiological responses to partial soil drying in their rootzone. It is a new irrigation technique that can improve crop water use efficiency without significant yield reduction and exposes approximately half of the root system to soil drying while the remaining root system is irrigated as in full irrigation. The wetted and dried sides of the root system are alternated on a time cycle according to crop water requirements and soil drying rate. The method was developed on the basis of four theoretical backgrounds. Firstly, fully irrigated plants usually have widely opened stomata. A small narrowing of the stomatal opening may reduce water loss substantially with little effect on the photosynthesis. Secondly, part of the root system in drying soil can respond to the drying by sending a root-sourced signal to the shoots where stomata may be inhibited so that water loss is reduced. Thirdly, controlled partial root-zone wetting and drying alternately can stimulate the root uptake ability for soil water and nutrients. Fourthly, partial root-zone watering can enhance soil water movement from the wetted part to the dried part, and reduce the depth of water infiltration. Therefore the ineffective percolation can be reduced.

(3) He studied and demonstrated systematically regulated deficit irrigation technology for field crops in Northwest China.

He with his colleagues studied systematically and extended regulated deficit irrigation technique for maize, wheat, cotton and other crops in Shanxi, Gansu, Shaanxi and Xinjiang of Northwest China from 1995-2002. In the experiments, controlled soil water deficit, either mild (50%-60% of field capacity) or severe (40%-50% of field capacity), was applied at both the seedling and the stem-elongation stages. A soil drying at the seedling stage plus a further mild soil drying at the stem-elongation stage is the optimum regulated deficit irrigation method for the maize production in this semi-arid area. The results on maize in Shanxi and Shaanxi, cotton in Xinjiang and Gansu, wheat in Shaanxi and Gansu also suggested that RDI should be applied at the early growth stage.

The degree of water deficit can reach 45%-50% of field capacity, which has no bad effect on crop yield and can increase crop water use efficiency obviously. From the research, it concluded that the feasible regulation deficit indicator of winter wheat as follows: the soil moisture content should not be below 60% of field capacity in 0-50 cm soil layer before living through winter, not be below 55% of field capacity in 0-50 cm soil layer from returning green to rising stages, be higher than 65% of field capacity in 0-50 cm soil layer in jointing stage, not be below 65% of field capacity in 0-80 cm soil layer in pregnant spike stage, be higher than 60% of field capacity in 0-100 cm soil layer in tassel to milking prophase, can be below 50%-55% of field capacity in 0-100 cm soil layer in milking evening without obvious reduction of yield. For maize, moderate or light water deficit is feasible, with the soil moisture above 50% of field capacity in seedling season, light water deficit is compatible, with the soil moisture above 60% of field capacity in jointing season, and sufficient irrigation for other periods. For cotton, bad effect of soil moisture as low as 48% of field capacity on cotton alimentation growth can be recovered by irrigation in budding season, and under condition of high soil moisture in the prophase, the soil moisture as low as 45% of field capacity has no bad effect on yield in flower and belling evening seasons.

Based on the experiments, he presented the optimal technique system of regulated deficit irrigation, the results were applied 6,667 hectares in Hongdong of Shanxi Province, irrigation water use was reduced 34.1% and crop yield was increased 19.3% on average than that of the conventional irrigation method?and the benefit of ?10,566,800 was got by extending the technique in this county. The technique was also extended in Minqin and Wuwei of Gansu Province for 1,787 hectares?2,140,000 m3 of irrigation water was saved?and the electric energy of 385,200 Kw·h for pumping groundwater was also saved?the benefit of ?667,100 was got in the region.

Furthermore, He and Prof. Chen Yaxin wrote a book of ?Principle and Practice of Deficit Irrigation?which was published by China Water Resources and Hydro-power Press in 1995 and cited more than 200 times by scientists, engineers, irrigation managers and postgraduates, it has been playing an important role for expanding deficit irrigation technology in China. And the research result in this area was published in ?Agricultural Water Management??Vol.55, No.3, p.203-216, 2002?in title of “Effects of limited irrigation on yield and water use efficiency of winter wheat in the Loess Plateau of China”was one of the most downloaded 25 papers of the journal in 2002.

(4) He developed the optimal irrigation technique parameters to improve water and fertilizer use efficiency for drip irrigation, sub-surface drip irrigation, and surface irrigation methods, studied the suitable flow measurement facilities and standardization for U-shape canals, and presented the flow measurement equipment for irrigation water with high sediment content in Northwest China.

He studied systematically the water and fertilizer movement in soil profile and soil-root system, water and fertilizer use efficiency in root-zone under different irrigation scheduling, irrigation technique parameters, different fertilizer use patterns, different depths of irrigation pipe for drip irrigation, sub-surface drip irrigation, and surface irrigation methods. He presented the optimal irrigation technique parameters for the lower cost sub-surface drip irrigation system suitable to apple orchards in north part of Shaanxi in order to improve water and fertilizer use efficiency, the results supplied the rational technique parameters for designing and managing irrigation systems, and were applied in large area in apple orchard irrigation of Shaanxi Province.

Evaluation has been made of the existing flow measurement techniques by him and his colleagues, selective and adoptive models which apply to the flow measurement techniques of different U-shaped channels have been given in Northwest China, he with his colleagues presented the design and standardization of flat parabolic non-floated segment of U-shaped channel flow measurement flume, and 28 standard flumes were proposed by using the form coefficient of the parabolic (P) as the index. The examinations and observations both in the lab and on the spot had shown that the measured values were identical with the theory value, which indicated that the flume can meet the demand of flow measurement. More than 2650 standard flow measurement flumes were expanded in Guanzhong canal irrigation districts of Shaanxi province and in Huangyang and Yingda irrigation districts, which controlled irrigation areas of about 6666.7 hectares.

(5) He studied systematically the groundwater management model in Fen-Wei Plain with a shallow groundwater table for water-saving and controlling soil salinity.

He presented the coefficients of groundwater use in winter wheat and maize growing seasons under different water tables were obtained based on the measured data by lysimeters in Yangling of Shaanxi province, and Qixian of Shanxi province. He found that yield and water use efficiency of winter wheat was decreased with groundwater table lifted when the depth of water table was shallower than 1.5 m, and the water table should be controlled deeper than 1.5 to 2.0 m in order to improve yield and water use efficiency in winter wheat growing season, deeper than 1.0 to 1.5 m for maize in Fen-Wei Plain of Shanxi and Shaanxi province. He established soil water and salt adjustment and control model, and simulation model of groundwater table for infiltration and evaporation processes, presented irrigation models under different groundwater tables. The irrigation model responded to the impact of groundwater table could reduce one time irrigation in generally compared to the conventional irrigation model in the region. The research results have been extended 3,333 hectares in Fenhe irrigation district during 1998-2001, and 840 m3 irrigation water could be saved for per hectare and each year, totally 11,200,000 m3 of irrigation water was saved in the region during 1998-2001.

(6) He studied systematically the reasonable allocation of water resources and water-saving in agriculture and ecology in Shiyanghe river basin of Gansu province in Northwest China, presented and extended six strategic measures for sustainable use of water resources and six kinds of water-saving models in agriculture and ecology which have been played an important role in this region.

The Shiyanghe river basin is a typical interior river basin with an area about 4.16×104 km2 . The area faces water shortage and environmental deterioration in the arid northwest of China. Due to its arid climate, limited water resources and some inappropriate water-related human activities, the area has developed serious loss of vegetation, and gradual soil salinization and desertification, which have greatly impeded the sustainable development of agriculture and economy in this region. The proportion of water use in the upper and middle reaches compared to the lower reach was increased from 1:0.57 in the 1960s, to 1:0.27 in the 1970s and 1:0.09 in the 1990s. A reduction of about 74% in the river inflow to the lower reaches and a 15-m drop in the groundwater table has occurred during the last four decades. The integration studies for reasonable allocation of water resources and water-saving in agriculture and ecology in Shiyanghe river basin have been carried out by him and his colleagues from 1995 up to now, which has been playing an important role to promote science research and subject progress, and sustainable utilization of water resources in the inland river basin of Northwest China. The research included applied basic theory, applied technology development and demonstration zone establishment. The applied basic theory study includes water resources transformation and ecology change mechanism, regional crop and plant evapotranspiration distribution and variation with time, water transport in soil-plant-atmosphere continuum and crop water-saving mechanism, water-saving potential evaluation model and reasonable allocation model of water resources in Shiyanghe river basin. The applied technology development includes no-full irrigation and regulated deficit irrigation technology for wheat, maize, cotton, grape, water melon and others, controlled alternate partial root-zone irrigation technology for grape, maize and cotton, drip irrigation technology for mulching cultivated cotton with plastic film and artificial planting ecological vegetation, irrigation and water resources management decision support system. And demonstration zone establishment includes water-saving in agriculture and in artificial ecological vegetation.

Based on the research works, strategies for improving the water–soil environment of the basin, such as the protection of the water resources of the Qilian Mountains which is the source of water in this basin, sustainable use of water resources, maintenance of the balance between land and water resources, development of water-saving agriculture, diverting of water from other rivers and control of soil desertification, were proposed. And the guidelines were also presented for reconstruction of the sustainable water management and development of agriculture in this region. He expanded a rainfall high efficient use model which includes rainfall harvesting technology, limited irrigation technology, and agronomic methods to improve crop water use efficiency in the upper reach of Shiyanghe river basin, irrigation water high efficient use model which includes canal flow monitoring and controlling technology, improving surface irrigation method by using small border irrigation, leveling land, using water-saving irrigation scheduling and so on in the middle reach, water-saving model by well water pumping in the lower reach. The technologies and models of water-saving were used about 333333.3 hectares, and about 5.60×108 m 3 of water use was saved in agriculture in Shiyanghe river basin from 1996-2003.

(7) He established academic organization and research laboratory of water-saving in agriculture, organized international and national conferences on water-saving in agriculture, and popularized and extended water-saving technologies in agriculture

He sponsored and established Agricultural Soil and Water Branch of Chinese Agricultural Engineering Society, and was selected as the Chairman of the branch, and organized academic conferences in Shaanxi, Inner Mongolia, Beijing and Shenyang for water-saving agriculture and sustainable use of water resources, also organized an international conference of water-saving in agriculture and sustainable use of water resources in Yangling in 2003. More than 300 participants attended the conference and came from USA, UK, Australia, Germany, France, Italy, Portugal, The Netherlands, Switzerland, Denmark, Yugoslavia, Japan, India, Thailand, Indonesia, Iran, Syrian, and China.

He established the Key Lab of Water-saving in Agriculture by Ministry of Agriculture, and the Key Lab of Agricultural Soil and Water Engineering in Arid and Semiarid Areas by Ministry of Education, and established the Research Center of Water-saving in Agriculture and Water Resources in Northwest Sci-Tech University of Agriculture and Forestry, and also established the Center for Agricultural Water Research in China, China Agricultural University.

He supervised 36 Ph.D students and 46 M.Sc. students for water-saving and irrigation management studies. He presented some suggestions to Chinese government about establishing national nets of water-saving irrigation experiment and monitoring, and importing the advanced water-saving technologies from developed counties according to Chinese conditions. He took part in the management of state key science and technology project of “Research on Water-saving Techniques in Agriculture and Development of New Products and Equipments for Water-saving in Agriculture”. He organized and took part in the research on “State Development Strategy of Science and Technology in Water-saving Agriculture of China in the Future 20 Years”, and the research on “State Development Strategy of Water-saving Agriculture in China during ‘the Eleventh Five Year Plan’ ”.

He wrote or organized several popular books about water-saving technology and irrigation water management in arid and semiarid areas for farmers and irrigation managers. He organized or lectured more than 20 classes of training irrigation managers and farmers in Shaanxi, Shanxi, Hubei, Henan, Beijing and Gansu Provinces. His works extended and popularized water-saving technology in agriculture. He made great contributions and achievements in water-saving theory development and technology application.