Measures and effects on soil Cd remediation and safe rice production: a meta-analysis of 10-year Chinese patents.

Rice is the staple food for 1/3 of the world's population, but soil pollution with cadmium (Cd) is harmful to rice production and human health. Therefore, how to reduce the Cd content in rice grains is a hot topic worldwide. However, so far, little is known about Cd remediation technologies for paddy soils from the perspective of patents. Therefore, a meta-analysis was performed to assess the effects of measures based on 1402 observations from 336 patents from 2011 to 2021. The spatio-temporal analysis showed that the number of patents was positively related to the general economic development of the country, but hardly related to the regional economy or the level of provincal Cd pollution. The meta-analysis showed that the overall effect of Cd reduction was slightly higher for combined technologies (59%) than for single technologies (57%). Among all technology classifications, soil applications, which are mainly based on nutritional elements, were the most commonly used technology that could reduce the Cd content in rice grains by 57%. The plant biotechnology was the most effective and could reduce Cd content in rice grains by 76%. Further analysis showed that macronutrients (calcium, phosphorus, and sulfur) were preferred in soil amendments, while micronutrients (silicon, zinc, and selenium) were preferred in foliar amendments. NRAMP5 and HMA3 were the most important genes for manipulating Cd uptake in rice, while Bacillus and Pseudomonas were the most important bacterial taxa for bioremediation of Cd. Overall, this study compiled data on Cd remediation of paddy soil from 10 years of Chinese patents, providing a theoretical basis for better production of low Cd crops and protection of human health.