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Capturing the variability in soil-landscape properties is a challenge for grain producers attempting to integrate spatial information into the decision process of precision agriculture (PA). Digital soil maps (DSMs) use traditional soil survey information and can be the basis for PA subfi eld delineation (e.g., management zones). However, public soil survey maps provide only general descriptions of soil-landscape features. Th erefore, improved DSMs are needed that use high-resolution data that more precisely model soil-landscape characteristics. Additionally, reliable methods are needed to validate DSM products for PA. Th e objective of this study was to validate with corn (Zea mays L.) yield data the performance of a new DSM product, termed Environmental Response Unit (ERU), compared with the USDA Soil Survey Geographic (SSURGO) soil map. Th e ERU was developed by integrating SSURGO information with highresolution elevation data. For validation, corn yield maps were collected and corrected for common data collection errors from 409 fi elds across Indiana, Iowa, Minnesota, and Nebraska in 2010 to 2012. Reductions in the area-weighted variance (R v ) of corn yield for ERU and SSURGO were calculated relative to the whole-fi eld variance. Th e average R v across all site-years for SSURGO and ERU was 16 and 25%, respectively, which equated to a 57% higher median yield variance reduction with ERU over SSURGO. Th is variance reduction technique showed the potential of ERU as an improved model better representing soillandscape properties that impact corn yield. Th is research also has application potential for determining the success of a DSM for identifying management zones in PA.

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Tolerance to herbivory is an important trait influencing invasive potential of exotic plant species. However, though many invasive plant species have been introduced as ornamentals, tolerance to herbivory has not been evaluated among cultivars of ornamental crops to assess relative invasive potential. A greenhouse study was performed to compare tolerance to simulated herbivory in five Cleome cultivars (Sparkler White, Sparkler Rose, Queen White, Queen Rose and Solo). The herbivory treatments simulated deer, rabbit and invertebrate herbivore damage by clipping the main stem, removing leaves, or punching out leaf pieces, respectively. Data were collected for flowering time, vegetative and reproductive biomass, ratio of reproductive: vegetative biomass (reproductive effort), number of flowering and vegetative shoots, ratio of number of flowering: total shoots (reproductive allocation), and number of ovules/flower. Cultivars showed different norms of tolerance ranging from under compensation to overcompensation with differences among cultivars within series. The response differed among patterns of simulated herbivory with stem clipping having the most dramatic and negative effect on plant growth and reproduction relative to whole leaf and partial leaf defoliation. The response also varied depending on cultivar and trait. For example, compensation in vegetative, but not reproductive, biomass, was observed across most cultivars after clipping. Significant interactions of herbivory treatment x cultivar were detected for total shoot number and the ratio of flowering: total shoots in the stem clipping experiment, indicating shifts in relative cultivar ranks. The implication of variation in tolerance to herbivory is discussed in relation to ornamental crop development and invasive species risk assessment.

Establishment potential is one of the primary components of invasive species risk assessment. Models that predict establishment of potentially invasive ornamental crops often ignore differences among cultivars and the variability in plant response to site-specific factors. The objective of this study was to determine the extent to which differences among cultivars and habitat characteristics affect establishment of 5 cultivars of ornamental cleome. Experiments were conducted to compare germination, survival, and growth of cultivars in cultivated (gardens) and noncultivated (roadsides and prairies) environments and, in prairies, the effects of competition (low, intermediate, and high). In the first experiment, germination, survival, and growth were recorded in gardens, prairies, and roadsides in four locations in Minnesota. In the second experiment, the effects of competition with resident species were studied in five seed lots from three cultivars in three prairie sites. Additionally, a quantitative description of germination and transplantable seedling quality, when grown under greenhouse production standards, was obtained and compared with results from the cultivated and noncultivated outdoor environments. Germination in greenhouse conditions was significantly greater (78%) than in garden, prairies, or roadsides (< 46%). Mortality was greater in noncultivated than in cultivated environments (3% wk−1 and 1.4% wk−1, respectively). Survival was affected by competition, which reduced population establishment. Cultivar differences were most pronounced at seedling emergence, whereas habitat characteristics were more influential at later stages of the life cycle. Germination and plant height were similar among noncultivated environments. Variability in seedling emergence, survival, and growth in response to cultivar, habitat, and competition are important determinants of establishment potential. Among the cultivars studied, the native cleome, roughseed clammyweed, has a greater establishment potential than the nonnative cleome, spiderflower.