The potential of near infra-red spectroscopy (NIRS) for predicting the sprouting capacity of potato (Solanum tuberosum L.) tubers was investigated. The experiment was conducted for 2 years using 'Superior' and 'Atlantic' potatoes. A total of 380 potato tubers (200, Superior; 180, Atlantic) weighing 100-200 g were scanned by NIRS, and the sample sets were divided into four groups; three groups were classified based on the cultivars or years as follows: 'Superior', 2004; 'Superior', 2005; 'Atlantic', 2005; the fourth group contained the total number of samples. The reference value for the sprouting capacities was measured by determining the sprout weight after 30 days of incubation at 20°C. The first derivative transformation equation for raw optical data was standardized by applying standard normal variate (SNV) and detrending (DT) algorithms, and calibration equations between them were developed by modified partial least square (MPLS) regression. The coefficient of determination (r 2 ) ranged from 0.868 to 0.965 with a standard error of calibration (SEC) from 0.31 to 0.40 for the calibration sets; r 2 ranged from 0.724 to 0.904 with a standard error of prediction (SEP) from 0.532 to 0.602 for the four validation sets. These results indicate that the calibration model obtained from this experiment is applicable to all the different cultivars for different years, and the NIRS method is a powerful tool for the predictive assessment of the sprouting capacity of potato tubers.

Competitive ability, allelopathy, made the common ragweed (Ambrosia artemisiifolia var. elatior) one of the most dangerous weeds in Korea. The aim of this research was to evaluate the role of common ragweed as test species under laboratory bioassay and glasshouse conditions. Inhibition effect of the leaf extract was higher than that of stem and root parts extracts on germination and seedling growth of weeds. The 5% concentration of leaf extract of common ragweed inhibited the germination rate of Echinochloa crus-galli, Digitaria sanguinalis and Cyperus microiria by 68.3, 74.6 and 87.3%, respectively, as compared to the control. Generally, increasing incorporation concentration inhibited seedling growth of weeds. Incorporation of 5% common ragweed residue significantly reduced the plant length of E. crus-galli, D. sanguinalis and C. microiria by 48, 63 and 68%, respectively, as compared to the control. Also, the values of dry weight were 72, 78 and 71%, respectively. Contrarily, the emergence rate of soybean and corn was not affected by the incorporation of 5% concentration of common ragweed residue. However, the dry weight was inhibited by 37 and 28%, respectively. These results suggest that common ragweed had the ability to control some weed species using toxic compounds like natural herbicide.

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