Nitrogen applied at 30 lb/a at the early vegetative stage reduced brown stem rot severity and increased soybean yield in studies conducted at Arlington, WI. The severity of brown stem rot is greater if soils are low in phosphorus and potassium (see Waller, 1992).

The severity of BSR is greatest when soil pH is near 6.0 and less severe when soil pH is 7.0 or greater. This conclusion is based on several years of small-plot and large-scale on-farm trials. Furthermore, the effect of soil pH modifies the effect of crop rotation, tillage and host resistance on brown stem rot potential (Figure 1)

Figure 1. Yield difference between BSR-resistant and BSR-susceptible cultivars is greatest at low soil pH. Data are from four years of field studies in Wisconsin.

Figure 2. Population density of Phialophora gregata in soybean root and stem tissue. The population density of P. gregata decreased as soil pH increased: In 1997 143,000 cfu (colony forming units of P. gregata), in 1998 21,000 cfu (root) and 11,000 cfu (stem).

References
Relationship between Soil pH and Brown Stem Rot of Soybean. N.C. Kurtzweil and C.R. Grau, Department of Plant Pathology, University of Wisconsin-Madison. Poster presented at the North Central Division meeting of the American Phytopathological Society, 2000

Waller, R. S., Nickell, C. D., and Gray, L. E. 1992. Environmental effects on the development of brown stem rot in soybean. Plant Disease 76:454-457.