The aim of the study was to determine the changes in aggregate size distribution and water retention of hemic (moderately decomposed) and sapric (strongly decomposed) peat materials from agricultural liming and fertiliser application. Sapric (0–30 cm) and hemic (40–60 cm) peats were collected from a secondary peat swamp forest with a peat depth of > 2.5 m and were used as a potting medium for maize plants. The maize was cultivated in a net-house for 17 weeks with four treatments applied to both peat materials. The treatments were: control (C), compound fertiliser NPK(MgS) (12:12:17:2) (T1), dolomite adjusted to pH 5.5 (T2), and NPK fertiliser combined with dolomite (T3). The aggregate size distribution and water-holding capacity (pressure plate method) were determined before and after the plant growth period. It was found that hemic and sapric peat materials showed different responses to the application of lime and fertiliser. For hemic peats, both T2 and T3 resulted in significant reductions of aggregate size and water-holding capacity, whereas no changes occurred in T1. For sapric peats, T3 caused a reduction in large soil aggregates and water-holding capacity, but no changes were observed in T1 and T2. This indicates that applications of lime and fertiliser may promote the peat decomposition process, causing large-sized organic matter particles to break down and resulting in a loss of soil water-holding capacity.
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