Boron deficiency of soybean [Glycine max (Merr.) L.] has become a common problem in northeast Arkansas. Research has demonstrated that 0.28 to 1.1 kg B/ha can significantly increase soybean seed yields on alkaline silt loams. The research objectives were to evaluate i) the immediate and residual influence of a single B application on soybean tissue B concentration and yield; ii) how B rate applied the previous year influences rice growth, tissue B concentration, and yield; and iii) the influence of B rate on Mehlich-3 extractable B in the surface and subsoil during a two or three-year period. Boron was applied at rates of 0, 1.1, 2.2, 4.5, 6.7, and 9.0 kg B/ha on two silt loam soils in eastern Arkansas during May 2002. Plots were seeded to soybean in 2002, rice in 2003 and soybean in 2004. Mehlich-3 soil B, plant tissue B concentration, and crop grain yield were measured each year. Mehlich-3 extractable B in the top 10 to 15 cm of soil increased linearly as B rate increased each year. Soybean and rice grain yields were not influenced by B application rate. Boron concentrations of soybean trifoliate leaves in 2002 and 2004 and rice flag leaves in 2003 increased as B rate increased. Rice (2003) and soybean (2004) tissue B concentration data suggest that a single application of B increases B uptake for at least 2 years following the year of application. Compared with the unfertilized control, application of 1.1 kg B/acre, the maximum rate recommended for soybean, significantly increased soybean trifoliate B concentration in 2004 only at one site. A single application of B at the recommended rate has some residual benefit, but B may need to be applied directly to soybean for several years to provide sufficient B nutrition on B-deficient soils.