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2報) 葡萄硝子室土壤の含塩度及び硝酸態窒素の変化について

In a previous investigation it was observed that the nature of glasshouse vine soils resembled more or less to that of semiarid soils and sometimes, a large amount of soluble salts, especially sulfate and nitrate, was found to accumulate in old glasshouse soils. A further study was taken to obtain detailed information on the characteristics of glasshouse soils, with special reference to the seasonal change of salinity and nitrate content of these soils associated with vine affected by apparent excess soluble salts. The soils investigated in this study were taken in July 1957, January 1958 and December 1958 from vine glasshouse, distributed in Ichinomiya-cho, Okayama Prefecture. Electrical conductivity, pH, humus and nitrate nitrogen were determined and soluble salts and 10 % HCL soluble constituents were analysed with some typical soils. The following general conclusions were drawn: 1) The normally dominant ions in the 1: 5 extracts were Ca. SO4 and NO3, but sometimes K, Mg, Na and Cl ions were relatively high also. 2) Of 10 % HCL soluble constituents, CaO and SO3 were markedly high in surface soil and P2O5 and K2O were relatively high also as compared to normal arable soils in Japan. It was shown that the greater part of P2O5 was fixed to surface layer but a fairly amount of K2O was also contained in lower layers. 3 ) No significant differences in soil salinity and nitrate content were shown between the soil samples taken in summer time and those taken in winter time. On the contrary, the soil crust scraped from soil surface in winter time contained a large amount of soluble salts, especially nitrate. Of all the samples examined, as much as 60 % showed the conductivity more than 15 millimhos/cm and contained nitrate nitrogen more than 600 p.p.m. The dominant salt in saturated extracts of soil crusts was calcium nitrate and a part of calcium sulfate was also found in these extracts. 4) The salinity and nitrate content were significantly decreased by renewal of surface layer of old glasshouse with fresh hillside soil deposits, accompanied with the increase of yield and improvement of quality of grape. The findings are believed to warrent the conclusions that the renewal of surface layer of old glasshouse is the best remedy for vine suffered injury from high concentration of salts.