Abstract
Under conditions of compacted and non-compacted covering-soils, the strength of plumule-elongation of two-rowed barley, Seijo No.17, was measured using with unbonded gauge type transducer and balancing null recorder at 20°C in darkness. In almost all the experiment, soil moisture content was about 13%, depth of seeding was about 3.5 cm, hardness of seeding bed was about O.2kg/cm3, hardness of covering-soil was O and O.1kg/cm3, a seed weight was about 40∼45mg and pulumule length at the start of measurement was about 3 cm long. The following results were obtained. 1. Under both conditions of covering-soil, compacted and non-compacted, strength of plumule-elongation increased with time and reached a, maximum about 24 hours after the start of measurement, respectively. However, the maximum strength of plumule-elongation under compacted covering-soil was stronger than that under non-compacted (Fig.2). 2. The more seed size was large, the more strength of plumule-elongation was vigorous under both conditions of compacted and non-compacted. The effect of hardness of covering-soil on the strength of plumule-elongation seemed to be strongcr in small seeds than in large seeds (Table 1 ). 3. In each stage of plumule elongation (1, 3, 5 cm), the strength of plumule-elongation was larger under compacted covering-soil than under non-compacted, respectively. The strength of plumule-elongation under compacted covering-soil decreased with increasing plumule elongation, but the strength under non-compacted showed almost all the same value in three stages of plumule (Table 2). 4. The strength of plumule-elongation became stronger as the degrees of hardness of covering-soil increased from 0kg/cm3 to 0.2kg/cm3 (Fig.3). 5. Under compacted covering-soil, the strength of plumule-elongation was strongest at 13% soil moisture, though the strength was strongest at 16% soil moisture under non-compacted (Fig.4). 6. The area of cross section of plumule and their sheath thickness was larger in the plumule grown under compacted covering-soil than in the plumule grown under non-compacted. In this case, the increase of area of cross section by compaction seemed to be larger in the smaller seeds (Table 3). Furthermore, bending strength of plumule grown under compacted covering-soil was stronger than that grown under non-compacted (Table 4). 7. From the above results the reason why the strength of plumule-elongation is stronger under compacted covering-soil than under non-compacted may be due to increase of thickness of plumule and to increase of pressure of covering-soil around the plumule preventing its bending (Table 6). In view of strength of plumule-elongation, it may be said that moderate compaction of covering-soil was favorable for emergence of two-rowed barley
