圧密条件下における土壌物理性の変化と草類根系の発達

Soil Compaction Effects on Root Developments of Grasses and Some Soil Physical Properties

河野 憲治

尾形 昭逸

多幾山 進

日本土壌肥料學雜誌

永年放牧草地では長期にわたる家畜の踏圧のため,圧密により土壌の物理性が劣悪化し,牧草の生育が不良となる.そこで(1)永年牧草地の土壌物理・化学性の特徴の把握,(2)牧草の生育,とくに根系の発達と土壌物理性に及ぼす圧密の影響と土性との関連や(3)土壌物理性の変化を示す簡易な指標について検討した.その結果,1) 放牧草地では採草地に比較して酸素拡散速度では一定した傾向が認められなかったが,とくに表層 10 cm 以内で土壌硬度や固相率が高く,気相率や通気係数が低いなどの特徴が認められた.2) 土壌圧密によって,シコクビエの地上部と根部乾物重,根長および通気係数や気相率は著しく低下し,土壌硬度と固相率は上昇し,これらの低下あるいは上昇の程度は,粗砂,細砂含量の低い土壌ほど顕著であった.3) 通気係数,硬度,気相率のうち,とくに通気係数と圧密条件下におけるシコクビエの生育,とくに根系の発達とは高い相関が認められた.また通気係数は現地でも簡易に測定でき,測定値のばらつきも小さかったことから,圧密条件下の根系発達の指標として最適と考えられた.

Soil physical properties of grazing land and meadow may vary due to differences in management and animal activity such as animal trampling. This may also affect the growth of the cultivated forage crops. To evaluate how soil physical properties and growth of African millet (Eleusine coracana, G_<AERTN>) is affected by soil compaction, three levels of compaction and four different soil textural classes were used for a frame experiment. Soil physical properties such as air permeability, three phases and hardness of soils and oxygen diffusion rate were measured. Total root length, tops and root weight and their mineral contents were determined. Similar parameters were also measured for grazing land and meadows. In the frame experiment, soil compaction increased the solid phase and hardness of soils, while air phase and permeability of soils in the upper 10 cm were decreased. Similarly, tops and root weight and total root length of African millet were decreased by soil compaction. Effects of soil compaction on the soil physical properties measured varied depending on the sand content. Regardless of level of compaction, the growth of African millet increased with increasing sand content. Significant differences were observed in the air permeability, soil phase and hardness of the upper 10 cm of grazing land and meadow, while no significant differences in their soil chemical properties were observed. Coefficient of air permeability of grazing land was observed to be lower than that of meadow. However, values for soil hardness and solid phase of grazing land were significantly lower than that of meadow. Forage fresh yields in grazing land were significantly lower than that of meadow. Coefficient of air permeability used as a index of soil air permeability was highly correlated with growth and total root length. Among the several soil physical properties considered, coefficient of air permeability was the best index to measure soil physical properties in relation to growth of African millet under soil compaction.

根系発達

土壌物理性

土壌圧密

通気係数

air permeability

root development

soil compaction

soil physical properties

農業 [ 610 ]

日本語

社団法人日本土壌肥料学会

Copyright (c) 1992 社団法人日本土壌肥料学会

本文データは学協会の許諾に基づきCiNiiから複製したものである

[ISSN] 0029-0610

[NCID] AN00195767

[NAID] 110001747799 ～の異版である