Abstract
Mulberry field soil was acidified gradually by continuous cultivation for about 10 years on volcanic ash soils underlying Jyoso-clay bed at Tsukuba upland. The methods of soil management, the important analytical data of soils and the process of acidification over the experimental period were as follows : 1) Two fields were used according to the depth from surface of clay bed. Field No. 205 was characterized at the depth of 150cm and field No. 125 at the depth 300cm. The different properties of the two fields seemed due to the clay bed depth. Field No. 205 has larger content of humus, higher soil moisture potential and shallower ground water table than field No. 125. But the major clay mineral of both fields was allophane. 2) After 8 years, the soil in the control plot (non plantation) showed 5.1-5.2 [pH(H_2O)] and 4.4-4.5 [(pH(KCl)], while the depth of 20cm in the inorganic fertilizer plot showed 4.0-4.2 [pH(H_2O)] and 3.9-4.0 [pH(KCl)] at the depth of 20cm. 3) The exchange acidity Y_1 also exceeded 20 in upper layer in inorganic fertilizer plot ; however, the value of acidity was higher in field No. 205 than in field No. 125. 4) To prevent the acidification, application of lime with organic matter was the most effective. 5) The mulberry roots developed into the deeper layer, avoiding acidified layer. The phenomenon would be able to explain why the leaf yield did not become so much lower in the acidified plot.
