A secular variation of soil properties in paddy fields abandoned to cultivate in hilly and mountainous areas [Japan]
1998
Takuma, K. (Tottori Univ. (Japan). Faculty of Agriculture) | Yasuda, H. | Yamamoto, S.
This paper investigates what effects of changes in the land environmental conservation function accompanied by the abandonment of cultivation come out on the physical property and strength of paddy field soil and organic matter due to the secular variation of soil. The authors think that, in the abandoned paddy field of hilly and mountainous area, water is not artificially supplied and its soil structure is developed by the supply of organic matters such as litter and by the activity of animals in the soil, and a coarse pore space is increased. Consequently, its permeability increases. From the viewpoint of soil strength, cone index decreases in the lower layer soil which swells and becomes soft. And changes in ignition loss are recognized in the surface layer on which the humus of vegetation is accumulated. Its increase is 2.6-5.0 % for the surface layer abandoned for more than 25 years. The water retentivity is recognized as well and the soil becomes clearly sandy by the abandonment of cultivation. The authors think that the land environmental conservation function will be decreased by these facts making the land to be a waste and dry land increasing a coarse pore space without forming an aggregate structure
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