Surface Broadcast and Incorporated Lime: Impact on Soil pH, Soil pH Distribution and Soybean Yield Response to Fertilizers

In recent years, the Ontario soybean crop has expanded to exceed the acreage of corn. Yet, compared to corn, far less research has been done on its P and K needs. Soybeans are more frequently planted with reduced or no tillage, and this raises further questions regarding optimum placement of P and K and their interaction with lime. The objective of this project is to determine the rate of reaction and depth of influence of lime in soil under reduced tillage systems and to assess lime’s effect on soybean yield response to applied nutrients. This study is being carried out with funding from the Ontario Agri-Business Association, the Canadian Fertilizer Institute, and three soil testing laboratories: Agri-Food Laboratories, Guelph; A&L Canada Laboratories East, London; and Stratford Agri-Analysis, Stratford.

Researchers have concluded that much of the pH change induced by lime occurs within the first few weeks after lime application, though effects in the following one to two years do continue slowly. Without tillage, the effect of lime on soil pH did not extend below the top two inches. Within-season, soil pH fluctuated by up to 0.5 units. In 1998, soybean yields responded to the P and K starter at one site, where soil test K was medium. At this same site, soybean manganese (Mn) uptake was enhanced by the P and K starter, but reduced by lime. Again at this site, in 1999 the corn crop yielded 37 percent more with starter, despite severe drought that limited corn yields to 65 bu/A. There were no interactions between lime and starter fertilizer at any of the three sites. ON-19