Claypan soils cover a significant portion of Missouri and Illinois crop land, approximately 4 million ha. Claypan soils, characterized with a pronounced argilic horizon at or below the soil surface, can restrict nutrient availability and uptake, plant water storage, and water infiltration. These soil characteristics affect plant growth, with increasing depth of the topsoil above the claypan horizon having a strong positive correlation to grain crop production. In the case of low productivity soil, the use of perennial bioenergy crops has been proposed. Bioenergy crops, such as switchgrass (Panicum virgatum), have better water and N use efficiency (WUE and NUE, respectively), can decrease erosion, and decrease herbicide use once established, compared to traditional crops. Research is limited comparing the effects of claypan topsoil depth on water and nutrient use efficiency on grain and perennial warm season grasses. The objective of this study was to compare the effects of depth to claypan on nitrogen use efficiency and water use efficiency for switchgrass and corn crops. This experiment was conducted at the University of Missouri South Farm Research Center on the Soil Productivity Assessment for Renewable Energy and Conservation (SPARC) plots, near Columbia, MO, from 2009-2013. The SPARC plots are a completely randomized design with varying topsoil depths for corn and switchgrass. Switchgrass was planted in 2009 and harvesting initiated in 2010. Corn is in a rotation with soybean. Above ground corn and switchgrass biomass were analyzed for N content, with the corn grain and stover analyzed separately. Water use efficiency was calculated using two methods: a two-layer soil plant available water capacity (PAWC) method and a partial water budget method.  Initial analyses show switchgrass production to be much less sensitive to topsoil depth than corn.  Years when precipitation was average or greater than average, switchgrass yield was nearly stable over all topsoil depths.  Corn production over all years of this study decreased with decreasing topsoil depth, but for two different reasons.  Years with above average precipitation, corn growth is limited by N, supporting the concept of a higher propensity for N loss from dentrification with shallower topsoil depths.  Years with average or less than average precipitation corn grain production is limited by water availability. A more quantitative analysis of these observations taking into account water balance information is being conducted to show the N and water use efficiency differences of these two contrasting crops over topsoil depths.