Abstract
Five crops with different seed size, corn (Zea mays), soybean (Glycine max), Japanese radish (Raphanus sativus), carrot (Daucus carota) and komatsuna (Brassica rapa), were used in the present examination. With the aim of clarifying the effectiveness of soil clod-size on emergence and early growth of these crops, emergence ratio, plant length and dry weight of top and root were measured using wagner pot (1/2000a) contained with 5 levels of soil clod-size, <4mm, 4-10mm, 10-20mm, 20-40mm and 40-50mm in diameter. Emergence ratio in any crops decreased as soil clad-size was large, especially in carrot. Emergence ratio was inhibited in the 20 mm-soil clod in corn and soybean that produce large seed, however, it was inhibited in 10mm soil clod in carrot that has small and flat seed. There is not a significant difference in plant length and top dry weight in all crops among the soil clad-size less than 40mm. On the other hand, root dry weight became small as soil clod-size was large, and soil clod-size affected the root growth more than top growth comparatively. From these result, it is necessary to prepare the soil clod less than 10mm in seeding ditch to obtain high emergence ratio and vigorous early growth for all crops in reduced tillage.
