Long Term Wheat Fertility Trials at Oklahoma State University.

Soil fertility can be a primary limitation in crop production. At locations in Altus, Lahoma, and Stillwater, OK, replicated trials were used to compare the yield variations due to different macronutrient treatments. These studies have been conducted to determine long-term responses of continuous winter wheat to nitrogen (N), phosphorus (P), potassium (K), lime, and manure, all while collecting long-term data that provides a stable infrastructure for future experiments around the world. Applications of N have been the only fertilizer source to significantly increase yield. Responses to P and K have been small. This long-term data, when combined with records of yearly weather conditions, has allowed for the identification of weather patterns that favor maximum yields. Following 100 years with no fertilization, the check plot in the Magruder Plots, located in Stillwater, OK, has consistently averaged 16 bushels per acre. As our world sees a strong shift to the subject of sustainability, long-term data like this will be a key asset to feeding our growing world. Winter wheat’s response to P and K has been difficult to predict, while the effects of applied N are generally more apparent. Plant response to nutrient application is largely dependent on the initial, naturally occurring, fertility of the soil.