Effects of soil compression on the soil drying in seedbed and imbibitions of soybean [Glycine max] seeds in heavy clayey upland field converted from rice [Oryza sativa] paddy
2008
Takahashi, T.(National Agricultural Research Center, Joetsu, Niigata (Japan) Hokuriku Research Center) | Hosokawa, H. | Matsuzaki, M.
The heavy clayey upland soils converted from rice paddies, which is a dominant soil type in Hokuriku region in Japan, has a difficulty in germination and/or emergence due to soil drought. The drought is caused by both the soil physical property that soil available water content for plants is low, and the practical property that seeding is conducted from late May to early June, when soil dried strongly. To facilitate seed imbibitions, we studied the effects of soil compression on soil drying and imbibitions of soybean seeds. Tillage starts drying soil. The water content of soil within 50 mm depth kept higher amount by soil compressed by seeder (6 kPa) than that of uncompressed soil and the rate of imbibitions of soybean seeds increased significantly. Furthermore uncompressed soil made extremely dried layer around 10-40 mm depth, which involved the location of soybean sown (20-30 mm). Such a dried layer did not observed at compressed soils clearly. This result indicated that seedbed without uncompression inhibited movement of soil water from lower to upper layers due to small contact area of soil clods. There was no significant effect of compression on imbibitions experiment under the system without water evaporation in laboratory study. The result supported our hypothesis well. We concluded that the major mechanism of compression on facilitation of imbibitions was supplying of water from lower layer but not increasing the contact area between soil clods and seeds, and that soil compression on the morrow of tillage is the one of an effective techniques to facilitate seeds imbibitions in the case that sown depth was around 20-30 mm. Our results also imply that the machinery which conduct tillage, seeding and compress within one process is the one of the best device to improve imbibitions of soybean seeds.
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