Potassium Fertilizer Rate Recommendations: Does Accounting for Soil Stock of Potassium Matter?

Profitability, yield, and fertilizer use are compared across three different potassium (K) fertilizer rate recommendation ideologies. Existing agronomic, build and maintain rate recommendations (KE) are compared to profit-maximizing rates with and without taking long-run soil-test K (STK) implications into account. Regardless of starting STK, K use equilibrated over the course of 3 years irrespective of ideology. Since taking long-run STK into account did not alter ending STK and only led to a miniscule yield effect, we encourage producers to use annual profit-maximizing K rates that were 3-11% lower than KE rates and generated more profit with minimal yield loss.

Automated summary

This study compares three different potassium (K) fertilizer rate recommendation ideologies in terms of profitability, yield, and fertilizer use. The results show that K use equilibrates over a 3-year period regardless of the starting soil-test K (STK) level, and considering long-run STK implications has minimal effect on yield. Therefore, the study encourages producers to use annual profit-maximizing K rates, which are 3-11% lower than the existing recommendations (KE), as they generate more profit with minimal yield loss.