Research strategy of reclamation and management for low-yield rice paddy soils

The land reserves which can be potentially opened for farming purpose are extremely limited in China, the amelioration of farmlands with low productivity plays all important roles in the grain production increment. Low-yield rice paddy soils constitute high proportion in the total low fertility soils, many studies have been carried out to investigate their fertility characteristics and effective technologies for their improvements. However, these researches are scattered, lack of systematic integration, have not formed strategic management rules. Therefore, the types of low yield rice paddy soils, the novel technologies and approaches are reviewed, and the possible technological breakthrough is proposed. According to the data from the Ministry of Agriculture of the Peoples’ Republic of China, there are about 7.67×107 ha low-yield rice paddy soil nationwide, which can be divided into four major groups: cold-gleyed paddy soil, bonded paddy soil, harden paddy soil and contaminated paddy soil, according to their intrinsic constraints or detrimental condition. The soil quality assessment was crucial for chosing suitable improving method of low-yield rice paddy soil. Four approaches were commonly used to evaluate soil quality: dynamics method, integrated scoring method, multiple-variable indicator kring (MVIK) method, and relative quality method. Basically, the soil quality assessments are based on the employment of GIS and the soil biological properties. Through the use of new technologies including isotope probing, fourier transform infrared spectoroscopy (FTIR) and CPMS13C-NMR spectra, the analyses of soil organic C distribution in micro-aggregate, humus transformation and their binding mechanism with soil minerals have been deep into micro-level. Meanwhile, the application of new analytic methods such as high-throughput sequencing, soil macro genomics and macro transcriptome also made the relative researches to molecular level.Rrecommended fertilization based on yield response and agronomy efficiency will continually to be the core of nutrient management of paddy fields for exploring the yield increase potentials. For the assessment of soil quality, specific researches are still needed for individual limiting factors in different low-yield paddy soils. The criteria of soil biological properties are also need to be strengthened in the assessment of soil quality. For the amelioration of the low-yield paddy soils, studies related to the forming mechanism of soil barrier and the corresponding amendment ways still need to be carried out. The reformation of other types of low-yield paddy soils including new-reclaimed, salinized, calcified and contaminated paddy fields are also need concerning. The effects of long-term amendments on soil humus structure, enzymes, microbial diversity and functional gene in aggregate level are always need to be traced. Technologies including crop residue incorporation, recommended fertilization, selectivity of resistant cultivars and mass control deserve focused in agricultural management of low-yield rice paddy soil.