Since 1981 average corn yields have increased by 80%, soybeans by 35%, and winter wheat by 65%. The current OMAFRA fertility recommendations were established a number of years ago when yields were lower. There is concern that the current OMAFRA recommendations do not adequately provide for modern crop yields. The OMAFRA recommendations are also based on the sufficiency approach. The sufficiency approach aims to supply the needs of the current crop by taking into consideration the soil test and the immediate economic return to applied P and K. This approach does not aim to build the soil test to any given value. It is also called the “feed the crop” approach. Another strategy to fertilizer recommendations is to “feed the soil”. This method is called the “build and maintain” approach. Building phosphorous and potassium levels in soil represents a significant expense to growers, and can pose economic (ie. land rental) and environmental (phosphorous runoff) risks if soil test values are built excessively high. The sufficiency approach also poses risks because it may not supply adequate nutrients in a year with high yield potential. It also does not allow for a grower to mitigate environmental risks by managing application timing throughout the cropping rotation. Due to the limited amount of data available, this research is being conducted to investigate how starter fertilizer selection (product, rate) and soil fertility management strategy (sufficiency or build and maintain) influence the economics and productivity of corn, soybeans and wheat over the long term in Ontario.

Read the entire report here: Re-evaluating Phosphorus and Potassium Management for Soybeans