葡萄硝子室土壤の化学的組成,とくに可溶性塩類の異常集積に関する研究 (第1報) 葡萄硝子室土壤の化学的組成の特徴について

There are several problems with respect to soil managements of glasshouse vineyard. It has been recognized that the vine cultivated in glasshouse grows weak very faster than that cultivated in field. It may be supposed that the nature of glasshouse soil should affect directly or indirectly on the growth of vine in glasshouse. The purpose of this investigation is to study the effects of soil managements on the chemical composition of glasshouse vine soils and to compare the chemical properties of these with normal arable soils in connection with the growth of vine. Surface soils (0-10 cm) and subsoils (30-40 cm) used were taken from 67 glasshouse distributed in Tsudaka-cho, Okayama Prefecture. Electrical conductivity of saturated soil extracts, pH, humus and nitrate nitrogen were determined and soluble salts of 1 : 5 soil extracts were analysed with some typical soils. The results obtained may be summarized as follows: 1) It was found that the salinity of glasshouse soils, expressed as electrical conductivity was generally high as compared to normal arable soils, ranging from 1.15 to 22.81 millimhos/cm with the surface soils and from 0.70 to 7.96 millimhos/cm with the subsoils. Of all the soil samples examined, 63% of surface soils and 22% of subsoils showed the conductivity more than 4 millimhos/cm. 2) The normally dominant salts in the extracts was calcium sulfate but nitrate, chloride and bicarbonate were relatively high also. 3) The nitrate nitrogen content was also generally high, ranging from 11 to 815 p.p.m. in surface soils and from 3 to 236 p.p.m. in subsoils. Of all the soil samples examined, 48% of surface soils and 15% of subsoils contained nitrate nitrogen more than 100 p.p.m. 4) The reaction of most soils was found neutral to slightly alkaline, in pH range of 5.8 to 7.6 with surface soils and 5.1 to 7.6 with subsoils. 5) The content of humus was generally low, ranging from 0.62 to 4.36% in surface soils and from 0.32 to 2.52% in subsoils. As it had been expected, the nature of glasshouse soil was found to have more or less the characteristics of the soils formed under the semiarid climatic conditions. On the basis of these findings, it can be concluded that the injury of vine in old glasshouse is due partly to the accumulation of soluble salts, especially sulfate and nitrate in the soils. We found that the conductivity method provided reliable estimate of salinity of soils in relation to the adverse effects of soluble salts on the plant and a modification of the Spurway technique, which had been developed by authors could be used as the rapid method for routine nitrate determination.