Residual effect of calcium silicate on ph, phosphorus, and aluminum in a tropical soil profile

Abstract

The distribution of soil pH, extractable soil P, and AI was studied during 5 years of cropping in the soil profiles of a gibbsihumox soil at one P level (280 kg P/ha), three Si levels (0,830, and 1.660 kg Si/ha), and three pH levels (5.5, 6.0, and 6.5). The effect of residual Si on increased P availability was evident only in the surface layer. There was no indication of P movement below 15-cm depth as very little P was detected in the 15- to 30-cm soil layers. The differential in the observed soil pH due to initially adjusted pH values was persistent during the length of experiment as the soil pH values were higher at pH 6.5 treatment than that at pH 5.5 or 6.0 to a depth of 90 cm. The soil pH values were lower in the 15- to 30-cm soil depth than that in the 0- to 15-cm depth. This phenomenon was observed at all pH treatments at the 27-, 40-. and 56-month sampling and demonstrated that more of the liming material reacted with the surface soil and less moved to subsurface layer. The high AI concentrations were consistent with the specially low pH at 15- to 30-cm depth. The AI concentrations ranged from 35 to 126 ppm in the 15- to 30-cm layer compared to a range of 1 to 92 ppm in the 0- to 15-cm layer. These results indicate that liming material should be mixed with the top 30-cm layer instead of only 15 cm to ensure greater reduction in Al solubility and possibly reduced root injury. © 1980 Taylor & Francis Group, LLC.