Let's discuss the significance of water-saving irrigation for agricultural development

Water is an irreplaceable basic element in all life processes and an important foundational resource for maintaining national economic and social development. Water conservation is both a long-term strategic measure related to the sustainable development of population, resources, and environment, and an urgent task for current economic and social development.

China's flood irrigation not only wastes water resources but also easily hardens the land, reducing its permeability and causing losses to agriculture. There is an urgent need for an alternative method to change this situation and implement water-saving irrigation in agriculture.

The Significance of Water-Saving Agriculture

(1) Developing water-saving agriculture is a necessary choice

China's total water resources are 2.8 trillion cubic meters, lower than Brazil, Russia, and Canada, comparable to the United States and Indonesia. However, the per capita and per mu water resources are only about 1/4 and 1/2 of the world average, and the regional distribution is very unbalanced. In the areas north of the Yangtze River Basin, farmland accounts for 65% of the country's total farmland, while water resources only account for 19% of the country's total water resources. At present, the national water shortage in normal years is nearly 40 billion cubic meters, of which agricultural water shortage is about 30 billion cubic meters. Not only is there a shortage of water, but the water pollution situation is also becoming increasingly serious. Initial monitoring in early 2005 showed that 53.3% of the seven major rivers were polluted, with inferior V-class water accounting for 28.4%. In particular, the three major basins of the Yellow River, Huaihe River, and Haihe River in the north are both the most severely water-stressed and most seriously polluted areas in China. Since agriculture is a major water consumer, its water consumption accounts for about 70% of the country's total water consumption, and up to 90% in the northwest region, with 90% used for crop irrigation. Therefore, in order to cope with the increasingly serious water shortage situation and establish a water-saving society, especially developing water-saving agriculture, is a necessary choice.

Developing water-saving agriculture is the primary way to solve the water supply crisis in northern China. It is also a necessity for the construction of modern agriculture itself. The efficient use of water and soil resources, and the close combination of economic, ecological, and social benefits are goals pursued by sustainable agriculture. Water-saving irrigation, implemented according to the water resource conditions and agricultural water demand laws, is an important link in achieving this goal. To this end, we must break away from the traditional agricultural water use concepts and establish an agricultural water supply system that meets the needs of modern society and the development of modern agriculture. In this sense, water-saving agriculture is modern agriculture, and water-saving irrigation belongs to scientific irrigation.

(2) Large-scale savings in irrigation water is the main goal of implementing water-saving agriculture

Water-saving agriculture is suitable for implementation in all agricultural areas, but mainly refers to agriculture in arid, semi-arid, and semi-humid regions that makes efficient use of irrigation water based on the full utilization of natural precipitation. The central issue that water-saving agriculture needs to address is how to fully utilize local precipitation and significantly reduce irrigation water while maintaining the normal growth rate of agricultural production, thereby maintaining the sustainable utilization and regional balance of overall water resources.

(3) Water-saving agriculture is a systematic project

Agricultural water conservation is a systematic project, including: temporal and spatial regulation of water resources, full utilization of natural precipitation, efficient utilization of irrigation water, and improvement of plant's own water use efficiency. Its scientific and technological goals can be summarized as: improving the utilization rate, utilization efficiency, and production efficiency of water resources.

To this end, it is necessary to adopt comprehensive water-saving measures, including engineering, agricultural technology, biological, and management measures. The combination of various water-saving technologies, as well as the intercommunication between dryland agriculture and irrigation agriculture, is necessary for the successful implementation of agricultural water conservation and the achievement of the goal of substantially saving irrigation water.

　　      II. The Current Situation and Development Strategy of Water-Saving Agriculture in China

(1) Achievements and Existing Problems

At present, China has 838 million mu of farmland with irrigation conditions, and 750 million mu of farmland with actual guaranteed irrigation, accounting for about 40% of the total cultivated land. According to statistics in 1998, the area of various water-saving irrigation projects, including channel seepage lining, pipeline water conveyance, spray irrigation, and micro-irrigation, had reached 230 million mu, and increased to 300 million mu by 2003. In addition, agricultural measures have also played an important role in farmland water conservation; according to incomplete statistics, this has reached 195 million mu. Nearly half of irrigation agriculture has implemented certain water-saving measures. In 2003, the proportion of agricultural water consumption in China's total water consumption had dropped from 92% at the beginning of the founding of the People's Republic of China, and 88% in 1980, to 66%. The water consumption per unit area decreased from 494 m3/mu to 459 m3/mu. The average irrigation water utilization coefficient increased from less than 0.3 to 0.45, and the increase in grain yield per cubic meter of irrigation water also increased significantly, reaching 1.1 kg. Science and technology have played an important role in achieving water conservation and increased production.

While summarizing achievements, we should also see some existing problems: 

(1) Achievements should not be overestimated. Water waste in China's agriculture is still quite serious, and there is still a large gap in water use efficiency compared with developed countries;

(2) Agricultural water conservation is undoubtedly a national strategic goal. However, how to convert national goals into farmers' goals and public goals, and thus establish an effective approach with joint investment from the state, society, and farmers, and a long-term mechanism for developing agricultural water conservation that suits China's national conditions, needs to be resolved as soon as possible;

(3) Relevant national departments and many provinces (regions) have formulated several plans or proposals for developing water-saving agriculture, which have played a certain guiding role. However, whether the main goals determined and the measures prepared to be adopted are feasible, and especially whether the goal of substantially saving irrigation water can be achieved, still needs further scientific demonstration;

(4) In terms of scientific research on water-saving agriculture, the state has continuously launched projects since the '8th Five-Year Plan', and has achieved many results. However, some projects have mainly pursued the water-saving indicators and demonstration areas at that time, and have not made sufficient efforts in tackling technological difficulties and key technologies, and have not conducted in-depth research on macro-strategic issues.

(2) Several Issues Concerning the Development Strategy of Water-Saving Agriculture

1. On Strategic Positioning. Developing water-saving agriculture is a major strategic measure to ensure the steady and rapid development of China's national economy and the sustainable utilization of water resources, and an important component of building a water-saving society. Some experts suggest that water security should be placed on the same level of importance as energy security and food security, which is very correct. In fact, some countries have already done so. Their basic approach is to strive to maintain a balance between water supply and demand, leaving no gap.

2. On Goals and Speed. While maintaining the normal growth rate of agricultural production, the main goal should be to substantially save irrigation water. What is meant by "substantial"? By drawing lessons from the successful practices of advanced water-saving counties and cities in northern China, summarizing existing scientific research results, listening to the opinions of relevant experts, and referring to foreign experiences, we believe that it is possible to develop the capacity to save 100 billion cubic meters of irrigation water on the existing basis within about 15 years, that is, around 2020. The development speed proposed in some current agricultural water conservation plans is too slow.

3. Regarding Development Models. Water-saving agriculture encompasses three types: water-saving irrigation agriculture, limited irrigation agriculture, and dryland agriculture. Multiple options exist between irrigation agriculture and dryland agriculture, providing favorable conditions for the effective implementation of agricultural water conservation. With scientific and technological advancements and further water scarcity, limited irrigation will become the main trend for the future development of water-saving agriculture in water-scarce areas. Sufficient attention should be given to its promotion and implementation.

4. Regarding Technological Selection. Water-saving irrigation technology and dryland technology should be given equal importance, striving for partial high-yield dryland farming to reduce reliance on irrigation. In terms of water-saving irrigation, the current priority should be modernizing irrigation district management and addressing water losses during the water conveyance process. Regarding irrigation methods, based on China's national conditions, in the near to medium term, spray and micro-irrigation should be actively promoted where conditions permit. However, nationwide, improving surface irrigation should still be the main focus. Furthermore, relying solely on the promotion of water-saving technologies is insufficient to fundamentally achieve regional water resource balance and coordinated development of resources and the economy. Therefore, further research is necessary at the macro level, such as establishing a water-saving agricultural structure.

(III) Development Trends of Water-Saving Agriculture in Different Regions of Northern China

1. Arid Regions: Arid regions in China account for 30.8% of the country's land area, concentrated in the Northwest, with Xinjiang having the largest area. Xinjiang is a typical inland arid area where agriculture is impossible without irrigation. The total agricultural water consumption is 77.8 billion m³, accounting for 90% of the total water consumption; the per-mu irrigation quota is approximately 800 m³, double that of North China. In addition, a large amount of water is also needed to ensure the construction of protective forests within the oases and the protective function of the natural oases in the oasis-desert transition zone. Therefore, the large water consumption for agriculture and ecology in Xinjiang has objective needs; at the same time, data show that the water resource development and utilization rate in Xinjiang accounts for about 55% of the surface water resources, and the development level is already high, but the net utilized water only accounts for 18% of the total surface water resources, indicating that there is still potential to be tapped. By summarizing the achievements made in various parts of Xinjiang in promoting water-saving irrigation, experts believe that it is possible to reduce the average irrigation quota from 800 m³/mu to 600 m³/mu in the near future. For the future, it is suggested to further discuss the following issues:

(1) Ecological water is of special significance to the sustainable development of Xinjiang's agriculture and the entire economy. Therefore, scientifically determining the appropriate ratio of ecological water to socio-economic water is an important issue. Some experts suggest that ecological water consumption should not be less than 50% of the total water consumption. This requires special demonstration and specific implementation.

(2) The irrigated area of agriculture in Xinjiang is about 60 million mu. Whether it can continue to expand in the near future, some experts believe that, according to the surface water resource situation, except for a few rivers that still have some potential for water diversion, other areas should not expand the irrigated area. Agriculture should develop under the premise of water conservation, following the principle of "increasing production with less land increase, and increasing land with less water increase." However, there are also different opinions on this.

(3) How to develop water-saving agriculture based on Xinjiang's socio-economic and climatic and geographical conditions? In our view, efforts should be made from the outset to develop towards modernization, such as the extensive use of pipeline water conveyance, laser land leveling, the development of micro-irrigation and spray irrigation, the application of self-control technology for precision irrigation, the adjustment of agricultural structure to expand the scale of operation, and the establishment of a unified water-saving management, scheduling, and monitoring system. However, this requires significant economic investment and strong technological support to be successfully implemented.

2. Semi-arid Regions: The semi-arid regions of China, centered on the Loess Plateau in the Northwest, account for about 1/5 of the country's land area. Due to severe soil and water loss and frequent droughts, coupled with the fact that the average precipitation in this region is still within the range that allows for normal farmland production, the low productivity easily leads to the reality of excessive reclamation and deforestation, making the semi-arid region the most ecologically fragile region in China. The per capita and per-mu water resources in this region are both low. In most places, the irrigated area is less than 20% of the cultivated land area, with dryland farming as the main type. Water use in irrigation agriculture is relatively reasonable, but there is still considerable potential for agricultural water conservation. Calculations show that the total annual precipitation in the Loess Plateau region is 300 billion m³, about 5 times the amount of surface water resources. Therefore, strengthening soil and water conservation work and vigorously tapping into the potential of precipitation production will play a crucial role in the future development of this region. The vegetation construction of the Loess Plateau should mainly rely on natural precipitation. While continuing to improve basic farmland construction, agricultural production should pay close attention to the improvement of dryland farming techniques and the development of small-scale irrigation. Long-term experiments and demonstrations at multiple points have proved that it is possible to achieve an average grain yield of about 200 kg per mu in this region in the near to medium term by making good use of existing technologies. Therefore, the current priority should be to strengthen research and widely promote two practical technologies: one is covering technology, and the other is rainwater collection and supplementary irrigation technology.

3. Semi-humid Regions: The Huang-Huai-Hai semi-humid region is an important grain production base in China, but it is also a region with severe water scarcity, with a water utilization rate of 73%. Taking Shandong Province as an example, the average precipitation in this province is 676.5 mm, but the per capita water resource availability is only 344 m³, and the per-mu availability is 307 m³, indicating that moderate precipitation and water scarcity are its important characteristics. Since the founding of the People's Republic of China, the irrigated area in Shandong has increased by about 7 times, and the current effective irrigated area has reached 72.7% of the cultivated land area, and the irrigation water utilization coefficient is higher than the national average, indicating that its irrigation development has been rapid, which is another characteristic. Generally speaking, in normal years, high-yield dryland grain production can be achieved in semi-humid regions (for example, after many years of research and practice, Laiyang Agricultural College believes that dryland wheat yield reaching 500 kg per mu is mature technology). In view of these characteristics, we believe that there is considerable water-saving potential in the Huang-Huai-Hai semi-humid region. It is suggested that in the future, following the principle of "giving equal importance to both water and dryland farming, and making up for deficiencies with surpluses," we should promote the rapid development of water-saving agriculture. "Giving equal importance to both water and dryland farming" mainly emphasizes that both waterlogged and dryland should be based on the full utilization of precipitation, effectively strengthening the construction of high-yield dryland farms, and making technical reserves for converting some waterlogged land into dryland or semi-dryland; "making up for deficiencies with surpluses" refers to actively adopting a strategy of making up for poor harvest years with good harvest years and regional adjustments to adapt to drastic interannual climatic changes, appropriately extending the grain production planning cycle, and fully tapping the climatic production potential of semi-humid regions.

　　       III. Several Scientific and Technological Issues That Need to Be Addressed to Accelerate the Development of Water-Saving Agriculture

(I) Scientific Formulation of a Comprehensive Development Plan for Agricultural Water Conservation

To adapt to the reality of increasingly scarce water resources, the formulation of agricultural water conservation plans must first update the concept, that is, the principle of agricultural water use must change from "meeting demand with supply" to "meeting demand with supply." Based on this, research should be conducted to determine the carrying capacity of water resources in different regions, and propose corresponding scales and speeds of agricultural development to achieve a basic balance between the supply and demand of agricultural water resources. Second, a broad concept of water resources should be established, which means that not only should controllable surface water and groundwater be valued, but also the entire natural precipitation. When formulating agricultural water conservation plans, both water-saving irrigation and dryland agriculture should be considered comprehensively; when evaluating the water resource status of a region, all types of water resources should be comprehensively considered. Establishing an agricultural structure adapted to water resources, namely a water-saving agricultural structure, is a neglected difficulty. In order to achieve the goal of saving a large amount of agricultural water, this must also be given sufficient attention.

(2) Implementing Alternative Strategies for Conventional Irrigation Water

To alleviate the tense situation of agricultural water use, some experts have put forward the concept and vision of replacing conventional irrigation water. It should be said that the largest alternative and further exploitable water source is precipitation; the second is wastewater and micro-reduced water. Utilizing treated industrial wastewater and domestic sewage (recycled water) in agricultural irrigation is one of the main technologies in the next stage of irrigation water saving after pipeline water conveyance and the adoption of advanced local irrigation methods. In some developed countries, the area of irrigation using recycled water has accounted for 30% of the total irrigated area. It is suggested that, combined with the establishment of a pollution prevention system, the use of recycled water for agricultural irrigation should be treated as a major measure to solve China's future water shortage, and research and demonstration should be strengthened to gradually expand its implementation.

(3) Establishing a Limited Irrigation System

Promoting limited irrigation and adopting a planting system that combines dry farming techniques with supplementary irrigation is a necessary choice for water-scarce areas in the future. The theoretical basis of limited irrigation is basically clear, that is, water deficit does not always reduce yield, and moderate drought at certain growth stages of many crops and fruit trees is beneficial to both water saving and increased yield. This understanding has been confirmed in numerous experiments. The current key is to solve the feasibility problem under field production conditions.

Establishing a limited irrigation system under field conditions will ultimately lead to precise irrigation on demand. Precise irrigation is based on the actual water requirements of crops and uses information technology to provide "non-sufficient" water to farmland. It is not so much the establishment of a new irrigation system as the determination of a farmland response system to water shortage. To effectively implement precise irrigation, the following conditions must be met:

①. Mastering reliable and detailed data on crop water requirements;

②. Using information technology;

③. Providing technical parameters that connect the two, especially indicators of the degree of crop water deficit;

④. Applying advanced irrigation methods. The above conditions can only be achieved through multidisciplinary cooperation.

(4) Attaching Importance to Biological Water-Saving Technologies and Cultivating Water-Saving and Drought-Resistant New Varieties

At present, biological water-saving technologies in the strict sense are still in a secondary position. However, it can be foreseen that when water loss, leakage, and evaporation are effectively controlled, and the spatiotemporal regulation of water is fully utilized, biological water saving—improving plant water use efficiency (WUE) and drought resistance—will become more important and can be regarded as the key link and ultimate potential for achieving further large-scale savings in agricultural water use. To tap the efficient water use of plants themselves, breeding drought-resistant and water-saving new varieties and new types is considered a core goal. It has been proven that WUE is a heritable trait, and the differences in WUE between species and varieties are significant. However, breeding work aimed at drought resistance and high WUE has progressed slowly. The difficulty may be that under conventional breeding conditions, drought-resistant and water-saving traits are often difficult to combine with high-yield traits. In recent years, research on gene recombination using gene engineering techniques to create drought-resistant and water-saving new types has been very active and has become a hot topic of concern for biologists and agricultural workers. However, its complexity should be fully recognized. Although there is good prospect for obtaining transgenic plants that are water-saving and drought-resistant and can be widely used in production, it should not be claimed that this will be achieved soon. Current work should focus on the following points:

(1) Exploring drought-resistant and water-saving germplasm resources;

(2) Attaching importance to the interrelationship of water-saving and drought-resistant breeding at different levels, and closely combining conventional breeding with genetic engineering breeding;

(3) It is more feasible to focus the current research on obtaining drought-resistant and water-saving transgenic plants on forestry and grass plants;

(4) Strengthening basic research on biological water saving, clarifying the extent to which different water-saving and drought-resistant mechanisms play a role, and seeking key water-saving and drought-resistant major genes. Given the huge potential impact of biological water-saving research on future agricultural water saving, it is recommended that it be included in the national science and technology plan and given long-term and stable support.