Project Details:

Recalibration of Phosphorus and Potassium Recommendations for High-Yielding Soybeans in North Carolina

Parent Project: This is the first year of this project.
Checkoff Organization:North Carolina Soybean Producers Association
Categories:Soil fertility
Organization Project Code:20-062
Project Year:2020
Lead Principal Investigator:Luke Gatiboni (North Carolina Soybean Producers Association)
Co-Principal Investigators:

Contributing Organizations

Funding Institutions

Information and Results

Click a section heading to display its contents.

Project Summary

The use of best management practices and technology might allow some fields in NC to yield 70 bu/A or more, defined as high-yielding soybeans. Although soil test phosphorus (P) and potassium (K) levels have been recently confirmed as sufficient, it is unclear if these levels are sufficient for high-yielding soybeans. Recalibration of soil test P and K for high-yielding soybeans is the objective of this research, which will occur at four farmer field sites that routinely harvest > 70 bu/ac soybeans. We will measure the plant tissue-P and -K, and yield during two cropping years. The results will be compared with those coming from three long-term P and K experiments conducted in different regions of North Carolina, in which the yield expectations are close to the average for the state. We ask that the NC Soybean Producers’ Association support the costs of a part-time undergraduate student, field supplies, travel costs, and, soil and plant analysis. Results from this project will be used to help determine the necessity of modifications in P and K recommendations for high-yielding soybeans in North Carolina.

Project Objectives

- Investigate the necessity of higher rates of phosphorus and potassium for high-yielding
soybeans (> 70 bu/A) in North Carolina;
- Investigate optimal levels of phosphorus and potassium in the plant tissue of high-yielding
soybeans in North Carolina and compare it with results from regular soybean yields;
- Determinate the exportation of phosphorus and potassium by grain in high-yielding
soybeans in North Carolina.

Project Deliverables

Progress of Work

Final Project Results

High-yielding soybeans fields producing more than 60 bu/acre require excellent management and are exporting more nutrients than average-yielding fields. There is uncertainty if the current recommendations of phosphorus (P) and potassium (K) fertilizers for North Carolina are adequate for high-yielding fields. We applied rates of P and K on two on-farm, high-yielding soybean fields and on three long-term trials at Research Stations of North Carolina. We did not observe an increase in crop yields when the P-index and K-index were higher than 50 at any of the trials. This means the current recommendations presented in the “Crop Fertilization Manual” are adequate even for high-yielding fields. The findings of this study show that our producers can keep using the current fertilizer recommendations, even in high-yielding fields, and they will not run short of nutrients. The results of this project will help our farmers to avoid unnecessary application of fertilizers, cut costs, and increase their profit.

Benefit to Soybean Farmers

Performance Metrics

Project Years