Spatio-Temporal Variations of Nitrogen to Phosphorus Ratios (N: P) in Farmland Topsoils of Fujian Province, China

The ecological stoichiometry of nitrogen to phosphorus ratios (N: P) plays a pivotal role in understanding elemental balance within ecological systems. Deeper understanding the dynamic changes of soil N: P ratios is vital for gaining insight into nitrogen and phosphorus cycling in ecosystems, soil management practices, and ensuring food security. This study aimed to provide a theoretical foundation for understanding of the dynamic N and P cycles within terrestrial ecosystems. Methods: The spatio-temporal variations of N: P ratios and impact factors in cropland topsoils during 1983 to 2018 in Fujian Province, China were studied and discussed by the models of geostatistics, gravity center shift and grey correlation. Results: The N: P ratios in farmland topsoils were 2.01, 2.21, and 1.80 in 1983, 2008, and 2018, respectively, exhibiting a moderate degree of variability. The gravity center of topsoil N: P ratios shifted to northwest during both 1983-2008 and 1983-2018, while it shifted to southwest during 2008-2018. Conclusions: Short-term changes in the topsoil N: P ratio was found to be influenced by N and P fertilizer applications and mean annual temperature, while the long-term changes were closely associated with soil organic matter content, mean annual precipitation, and the proportion of the primary industry. These findings offer valuable insights for formulating soil management strategies and promoting sustainable agricultural development in the study region.