Effects of soil compaction on the germination of red morningglory (Ipomoea coccinea L.)

Abstract

In order to evaluate the effect of soil compaction on the germination of red morningglory (Ipomoea coccinea L.) field experiments and pot experimets were conducted. In the the soybean (Glycine max (L.) Merrill) field of different compaction level of clayey gray lowland soil, germination numbers and depth of red morningglory was observed. Pot experiments were conducted to evaluate the effect of soil compaction on the depth and the ratio of red morningglory germination. Bulk density (BD) was used as the indicator of soil compaction. Two types of soils, clayey gray lowland soil and sandy yellow soil of weathered granite origin were utilized. Three compaction levels were set, the lower one simulated ‘just after tillage’, the higher one simulated ‘no tillage’ and the midst.

Maximum germination depth in the field of gray lowland soil was ca. 8 cm in low BD but turned shallower to ca. 4.5 cm in high BD. The similar tendency was observed in the pot of gray lowland soil. From the depth of 1 cm, germination ratio was more than 95% in all BD of both soils, but from 5 cm, the ratio decreased as BD got higher and from 10 cm no germination observed.

From the above observations, soil compaction affects on the depth and the ratio of red morningglory germination. Thus, the field observations of fewer sprouts in the compaction-partial seeding plot was derived from prevention of germination from deeper soil due to higher compaction.