Carbon-nitrogen sequestration potentials and structural stability of a tropical Alfisol as influenced by pig-composted manure
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Department of Soil Science and Land Management, University of Agriculture, PMB 2240, Abeokuta 110001, Ogun-State, Nigeria
Int. Agrophys. 2010, 24(4): 333–338
The organic carbon (OC) and total nitrogen (N) stocks (kg m-2) within the aggregates were estimated from the elemental concentrations and bulk density values. Soil aggregation by water-stable aggregates (WSA) showed significant (p0.05) increase in the proportion of macroaggregates > 0.50 mm than aggregates < 0.50 mm with addition of the compost. Mean-weight diameter (MWD) was significantly higher in uncultivated forestland than cultivated land, whereas addition of compost to the cultivated land improved the stability of this soil over the control. The OC stocks (kg m-2) within the aggregates of cultivated land amended with pig-composted manure followed the pattern observed for the forestland ie OC was preferentially sequestered within the macroaggregates (> 0.25 mm) than microaggregate fraction (< 0.25 mm); while the distribution of N was relatively uniform within the aggregates. Application of the compost to the cultivated plots significantly improved total N stocks (kg m-2) over that observed for the forestland. The results also revealed that application of pig-composted manure improved the structural stability better at 10 Mg ha-1 than 5 and 15 Mg ha-1 rates. The C-N sequestration in cultivated land was also higher than the baseline forestland with addition of 10 Mg ha-1 manure over other rates. Overall, this study showed that application of compost at 10 Mg ha-1 is adequate to improve the stability and enhanced C-N storage within this fragile tropical soil.