THE EFFECT OF BRUSHING ON THE GROWTH AND QUALITY OF FIELD-GROWN ROOT CROPS

Shoots of field-grown plants of European radish (Raphanus sativus L. 'Comet'), Japanese radish (daikon) (R. sativus L. 'Mino-wase'), and Asian turnip (Brassica rapa L. 'Hinona') were brushed twice daily, 40 cycles (back-and-forth strokes equal one cycle), for 8 (short-term) or 13, 21, or 14 days (long-term), respectively. European turnip (B. rapa L. 'Hikari-kabu') plants were grown in a raised bed in an uncovered plastic house and were brushed for 9 or 21 days. Short-term brushing reduced root dry weight and the root: shoot dry weight ratio (R:S) of European radish, whereas the treatment increased these measurements for Asian turnip and European turnip. Short-term brushing had no effect on growth of Japanese radish plants, but increased root dry weight gain by both turnip cultivars, thereby increasing their R:S ratios. Long-term brushing reduced root dry weight gain and the R:S ratio of European radish and root dry weight of Asian turnip but had no effect on these measurements for the other crops. Long-term brushing reduced cracking of European radish roots, thereby resulting in a higher proportion of oblong (medium quality) roots. Consequently, the percentage of marketable-quality roots of European radish was increased by brushing. Long-term brushing increased the percentage of medium-sized roots of Asian turnip at the expense of large-sized roots. Brushing had no effect on root quality of European turnip.