Contrasting patterns and drivers of soil micronutrient availability in paddy and maize fields of eastern China

Micronutrient deficiencies, known as ‘hidden hunger’, harm the growth and development of plants and people alike. However, less attention has been paid to soil micronutrients, the main source of micronutrients for plants and humans, than macronutrients (e.g. N and P availability). Understanding the geographic distribution of soil micronutrients across different agricultural fields is critical to support crop production and quality. Here we investigated the micronutrient composition (total and available copper, iron, manganese and zinc) of parallel 114 maize and rice fields in major crop production regions of eastern China. We found that available iron, copper and manganese were significantly higher in paddy soils than in maize soils, and total zinc was significantly higher in maize soils than in paddy soils. There was geospatial variation in the composition of micronutrients across latitudinal gradients and crop types. Soil organic matter and pH drove geographic variation of available micronutrient concentrations and ratio of total to available micronutrient, which were specific to micronutrient and crop type. Available Fe was decoupled with environment and total metal in paddy fields. Our study sheds light on the distribution patterns and environmental drivers of soil micronutrients in eastern China, and provides theoretical guidance for agricultural practice and fertilization management.