Managing Phosphorus in Cropland for Sustainable Development

The use of phosphorus (P) fertilizer in crop production is critical for global food security, but it also has significant environmental impacts. To address those challenges, improving the efficiency of phosphorus use (PUE) in crop production is essential. Improvement of PUE not only relies on advancement in technologies and management practices, but also socioeconomic factors and ecological conditions, which are poorly understood from regional to global scales.

Focusing on P budgets of crop production on a national scale, including inputs, such as fertilizer and manure application and outputs such as yield, we synthesized data by country and crop type for the past five decades and examined the historical trends of P budgets and PUE. We found that major developing countries are currently experiencing increasing P yield but decreasing PUE, while developed countries like U.S. have large legacy P stored in the soil and therefore are improving PUE by applying less fertilizer.

In addition, we studied the impact of ecological and socioeconomic factors on PUE. Fiber crops and soybean have relatively high PUE, while fruits and vegetables are currently less efficient in P use. Fertilizer to crop price ratio and nitrogen use efficiency (NUE) have a positive relationship with PUE on a global scale. The Environmental Kuznets Curve (EKC) hypothesis about the relationship between GDP per capita and PUE is supported in more than 30 countries and regions, where PUE first decreases with GDP per capita at the early development stage, then starts to level off or even increases at a later stage.

The reported P content of crops are inconsistent. To estimate the uncertainty in P budgets and PUE caused by that inconsistency, we conducted uncertainty tests with Monte Carlo simulation. The results indicate that variation in the reported range of crop P content will not significantly affect either P budget or PUE estimates from their long-term mean trend.

In the next phase of our study, we will estimate P demand by geographic region and crop type using the identified relationships between PUE and key drivers to support national policy making for various scenarios of sustainable development.