The effect of liming on some chemical properties and maize production on a highly weathered Fiji soil

The impact of liming on maize production (both with and without added fertilizer) and on the chemical properties of a Typic Palehumult from the wet zone of south-east Viti Levu, Fiji, was studied. A field trial involving lime, N, P and K fertilizers and poultry manure indicated that the addition of lime alone had a marked effect on maize production, with yields being more than doubled. The addition of fertilizers in the absence of lime also produced a significant yield increase and poultry manure was shown to be an effective alternative or additive to commercial fertilizers. A low initial soil Mg level led to problems with plants on unlimed plots and was also reflected in the low Mg levels in the tissue analyses. The effect of lime could be related to changes in soil chemical properties through the influence on pH, KCl-extractable AI, Al saturation percentage, exchangeable Mn and the change in the ion exchange and surface charge properties. Although pH0 values of the soils could not be determined (all < pH 3.5), the net negative surface charge increased with liming; the cation retention sites thus created were dominated by Ca. The critical Al saturation percentage for marked yield reductions in maize production would appear to be greater than 30%.