Relationship between compost pH buffer capacity and P content on P availability in a virgin Ultisol
Journal
Soil Science
Journal Volume
172
Journal Volume
172
Journal Issue
1
Journal Issue
1
Pages
68-85
Start Page
68
End Page
85
ISSN
0038075X
Date Issued
2007-01
Author(s)
Abstract
Compost as input in managing P fertility offers the opportunity to expand and sustain agricultural production on Ultisols, thereby enhancing food security in the tropics, where Ultisols occupy about 18% of the landmass. This, therefore, necessitates the determination of compost biochemically based selection criterion to ensure maximum effect. Studies were conducted on an uncultivated clayey Ultisol soil to evaluate the effects of six compost sources in various combinations with lime or chemical fertilizer P on P sorption by laboratory incubation and on plant availability of P by bioassay in plastic house, using kale as the assay crop. The degree of P sorption in this soil was controlled by the antagonistic relationship between compost proton consumption capacity and the amount of P added by the compost, as indicated by the regression equation PSI = 202 pH - 0.61 P added - 330 (R = 0.84). Low pH buffer capacity was superior to high pH buffer capacity in mitigating the effect of soil P sorption. This is more apparent at high application rates, at which composts with low pH-buffering capacity marginally increased soil pH to effect precipitation of exchangeable Al, but not extensively as to generate new sorption surfaces through Al hydrolysis and Al hydroxyl polymerization or to precipitate calcium phosphates. This is consistent with observed increases in measured available P parameters, such as Bray 1P, Bray 1P = - 7.96 pH + 0.20 P added + 99 (R = 0.91), and CaCl2-P, and plant growth and P nutrition parameters in the soil samples treated with low buffer capacity composts compared with the high pH buffer capacity composts. This compensation effect of total P content of compost for pH buffer-induced P sorption can be a guiding criterion in ensuring effectiveness in managing the P fertility of Ultisols.
Subjects
Al polymerization
Exchangeable Al
P sorption
pH buffer
Total P
Ultisol
SDGs
Type
journal article