Study on Grading Standard of Idesia polycarpa Maxim. Seedling Quality

The seedlings of Idesia polycarpa Maxim. with seedling age of 0.3-0.7 in the two naturaleedling raising types of marginal mountains around Sichuan Basin and Sichuan Basin were used as research object. The four indexes of seedling height, ground diameter, main root length and number of grade I lateral roots were measured. Using “normal distribution method” and “K-means clustering method” to study the classification, it is pointed out that the normal distribution method is more in line with the production practice. Combined with the relevant requirements of national and provincial standards, the classification results were fitted correction, and the quality of Idesia polycarpa Maxim. seedlings was finally divided into two grades by region. Marginal mountains around Sichuan Basin: Grade I seedling height > 59 cm, ground diameter > 0.75 cm, taproot length > 15 cm, number of grade I lateral roots > 6, grade II seedling height 36 cm~59 cm, ground diameter 0.45 cm~0.75 cm, taproot lengt≥12 cm, number of grade I lateral roots ≥ 4; Sichuan Basin: Grade I seedling height > 52 cm, ground diameter > 0.65 cm, taproot length > 15 cm, number of grade I lateral roots > 5, grade II seedling height 30 cm~52 cm, ground diameter 0.35 cm~0.65 cm, taproot length ≥11 cm, number of grade I lateral roots≥3.