Soil-moisture-monitored supplemental irrigation technology for wheat achieves high yield and water savings
China Science and Technology Network News (Reporter Wei Dong, Correspondent Yang Yu) Although the wheat harvest has ended, the villagers of Meihua Town, Gaocheng District, Shijiazhuang City, Hebei Province, still fondly recall the soil-moisture-monitored supplemental irrigation technology they used for wheat. "With this technology, when the average irrigation water per mu was only 67.6 cubic meters, 37.7 cubic meters less than traditional irrigation methods, the yield per mu still reached 601.2 kilograms. Next year we will continue to use this technology to strive for high yields." According to reports, this water-saving and high-yield technology was created by a team led by Professor Yu Zhenwen of Shandong Agricultural University, an academician of the Chinese Academy of Engineering, and has been listed by the Ministry of Agriculture as a 2016 main agricultural extension technology.
In Academician Yu Zhenwen's view, in the past, production practices habitually used flood irrigation without considering soil moisture conditions. This not only caused a waste of water resources, but was also detrimental to wheat growth. To research water-saving and high-yield technology, the first thing is to clarify which key periods of wheat growth require watering and what the optimal irrigation amount is.
The Huang-Huai-Hai region is China's main wheat-producing area, and the contradiction between water resource supply and demand is prominent. For example, the average annual precipitation in Hebei Province is about 500 millimeters, and 60% to 70% of it is concentrated in June, July, and August after the wheat harvest. Precipitation during the wheat growing period can only meet 25%-40% of its needs. The irrigated area in the Huang-Huai-Hai wheat region accounts for 42% of the national total, while agricultural irrigation water accounts for 70% of total water used for production and domestic life. Low water use efficiency and serious waste are prominent problems in China's agricultural production.
The innovation team led by Yu Zhenwen began research on the theory and technology of soil-moisture-monitored supplemental irrigation in 2000. For more than ten years, the team conducted a large number of research experiments from aspects such as crop physiology, crop nutrition, and ecology, focusing on the effects of different irrigation conditions on wheat yield, quality, and nutrient requirements. They analyzed the water requirements of wheat at each key growth period and clarified the optimal water requirement. Research found that among the 9 growth periods of wheat - sowing, overwintering, green-up, standing-up, jointing, heading, flowering, grain filling, and maturity - the sowing, jointing, and flowering periods are the key irrigation periods, and a fixed irrigation of 40 cubic meters per mu can ensure high yield.
However, because soil moisture conditions differ across regions and periods, the water requirements for crop growth also differ. "For example, if it rained a few days before the jointing period, then still applying a fixed 40 cubic meters per mu would also cause waste," said Yu Zhenwen. For this reason, the innovation team focused on in-depth research on soil-moisture-monitored supplemental irrigation, determining that the optimal relative soil water content during the key growth periods of wheat should be 70% to 75%. Based on this, they considered the amount of supplemental irrigation water, and clarified that the most suitable soil layer depth for measuring soil water content is 0 to 40 cm. "Research shows that at this depth the root system is dense, and using data measured at this depth for soil-moisture-monitored supplemental irrigation gives the best results," introduced Academician Yu Zhenwen. Because the irrigation amount of soil-moisture-monitored supplemental irrigation is significantly less than that of traditional irrigation, the amount of nitrogen leached into deeper soil layers when water infiltrates is also greatly reduced, reducing nitrogen pollution of groundwater, which is of great significance for protecting the ecological environment.
The water-saving effect of soil-moisture-monitored supplemental irrigation technology has been verified in practice. Test results in many places in Shandong and Hebei show that compared with traditional irrigation, this technology can reduce irrigation water by 35 to 70 cubic meters in different precipitation year types, increase water use efficiency by more than 10%, and grain yield is higher than or equal to that of traditional irrigation, with yield per mu reaching 550 to 600 kilograms. According to reports, during the research process, the innovation team published 77 research papers, providing a large amount of theoretical basis for further exploration of water-saving and high-yield technology. They also selected a portable domestically produced soil moisture measuring instrument and formulated a calculation formula for soil-moisture-monitored supplemental irrigation, so that technicians can calculate the amount of supplemental water needed in a wheat field in just a few minutes, which is simple and quick.
In order to ensure high wheat yield with the least water, the research group carried out demonstration and extension while conducting research. At present, this technology has been demonstrated and extended in more than a dozen counties and cities in Shandong and Hebei. "Calculated on the basis of saving 37.7 cubic meters of water per mu of wheat field in Gaocheng, Hebei this year, if fully extended throughout Hebei, the province's 30 million mu of wheat could save more than 1.13 billion cubic meters of water in a single season. This is not only an economic account, but also an ecological account." According to Academician Yu Zhenwen, the research group is currently studying the combination of soil-moisture-monitored supplemental irrigation and integrated water-fertilizer technology. In the future, the irrigation water use efficiency and yield of wheat will be further improved, and it will play an important role in the sustainable development of agricultural production.