Drawdown of soil phosphorus by crop removal: A meta-analysis of 56 fields with interrupted fertilization

Phosphorus (P) is an essential nutrient applied as fertilizer in agricultural fields. However, excessive fertilization leads to P build up in soils, increasing its potential to cause environmental pollution. The objective of this study was to evaluate the average P drawdown rate of 56 sites with drawdown management presented in 14 publications. Soil test P (STP) results were converted to Mehlich-3 equivalent and resampling analysis was used to compare the annual drawdown rate in fields grouped by four initial STP classes. The STP was reduced by 4.3%–8.2% per year, depending on the initial STP class. It took from 8.4 to 15.9 years to reduce the STP by half. The resulting equations from this meta-analysis can be used by landowners to estimate the time needed for STP drawdown by cropping without additional P to achieve the desired STP concentration.

Core Ideas

• Cropping without phosphorus (P) fertilization is one of the few options to reduce soil test P (STP).
• A meta-analysis of the annual P drawdown rate was performed using 56 sites presented in 14 publications.
• Fields were grouped into four initial STP classes based on Mehlich-3 STP equivalent.
• The STP was reduced from 4.3% to 8.2% per year in fields with high and low initial STP.
• The time needed to reduce the STP by half varied from 8.4 to 15.9 years depending on the initial STP.