Reviews and prospects on science and technology of green manure in China

The paper summarized the history of production and scientific research on green manure (GM) in China since 1949, reviewed the main activities and achievements of the past 60 years, proposed the future tasks of GM. Since the middle and late 1950s, the production and scientific research of GM have experienced 3 periods of prosperity, depression, and recovery. The prosperous period lasted for nearly 30 years from the middle and late 1950s to the early 1980s, marking as the prosperous GM production and accumulations of scientific experiences of GM. Scientists summarized massive historical experiences, and concluded some important practices, techniques and theories, such as " Increasing nitrogen by improving phosphorous”, " Phosphorous works only for symptoms while GM plays the interior roles”, " Priming phenomena of GM”. The National Experiment Network of Green Manure (NENGM) was established at the same time. Driven by the huge demand, the production of GM achieved its summit in the 1970s, the planting area was about 1.3×10⁷ hm² in the most popular year. The second period was from the early 1980s to the beginning of this century, the average annual planting area of GM declined to the bottom of about 2.0×10⁶ hm², However, the scientific research during this period had got stable financial support, the NENGM carried out nationwide collaborative research and improved the GM subject systematically in the 1980s. In 1990s, the NENGM focused on improving economic benefits of GM, and made great efforts in expanding GM planting area. During this period, regional planning of GM in China was studied and established, GM genetic plasms were sorted out and evaluated, high yielding cultivars were selected or bred, plantation and utilization patterns with potential comprehensive benefits were evaluated and formulated, effects of GM on soil organic matter as well as conditions were clarified, and a number of historic literatures on GM were published. The third period was from the year of 2007 till now, both the production and research of GM were recovered rapidly. National and some provincial policies of subsidies were implemented for GM plantation, special scientific projects of GM were funded successively from 2008 to 2015, moreover, the China Green Manure Research System for GM got approval in 2016. By the efforts of the special scientific projects, the basis of GM germplasms was improved, lightened and simplified production was enhanced greatly, some new patterns and techniques were developed and applied, systems of GM-based high and stable yield as well as clean production were extended widely. Meanwhile, by the collaborative innovation research, GM was proved to be able to promote the ability of high and stable yield when combined with chemical fertilizers, enhance nutrient supply for crops, improve soil physical, chemical, biological properties, and mitigate greenhouse gas emissions. Practices of 60 years showed that GM was the important material basis for crop production and was an effective technical support for green agriculture. The develop concept of " Beautiful scenery is gold and silver mine” would guide the agricultural production in future. From now on, the GM scientific research should center around the GM industry chains, i.e., utilization and innovation of germplasms, simplified and effective GM production, construction of green production patterns based on GM, nutrient supplying and soil fertilizing technology by GM and the relative regulation mechanisms, ways for improving values and benefits of GM, macro strategies and industrial economics for GM production, etc., and then develop fundamental technologies, solve production problems, solid theory basis, and finally formulate technical and theoretical systems suitable for new agriculture situation.