- Rasiah, Velu, Armour, John, Florentine, Singarayer
- Authors: Rasiah, Velu , Armour, John , Florentine, Singarayer
- Date: 2012
- Type: Text , Journal article
- Relation: Journal of Environmental Hydrology Vol. 20, no. 13 (2012), p.
- Full Text: false
- Reviewed:
- Description: Reliable on-ground information on groundwater (GW) hydraulic heterogeneity is required to determine flow direction and quantities, but its experimental characterization is difficult because of the complexities associated with the interaction involving the temporal changes in space modified by regolith stratigraphy. The impact of the aforementioned variables, particularly stratigraphy in a 51 m thick highly weathered basaltic regolith in the northeast humid tropics of Queensland, Australia, on flow gradients and directions was investigated in this study. Regolith cores at 1 m increments indicated that there were 3 different major strata. The temporal changes in water table, hydraulic- and pressure- heads, and solute concentrations in space indicated the top 51 m aquifer was contiguous, dynamic and hydraulically differentiated into three segments which approximately corresponded with the regolith strata. The lateralflow and solute transport from each aquifer segment was controlled by depth to water table, the number of regolith layers the segment covered, and the solute concentration.
- Description: 2003010399
Nitrate import-export dynamics in groundwater interacting with surface-water in a wet-tropical environment
- Rasiah, Velu, Armour, John, Cogle, A.L., Florentine, Singarayer
- Authors: Rasiah, Velu , Armour, John , Cogle, A.L. , Florentine, Singarayer
- Date: 2010
- Type: Text , Journal article
- Relation: Australian Journal of Soil Research Vol. 48, no. 4 (2010), p. 361-370
- Full Text:
- Reviewed:
- Description: Solute import-export dynamics in groundwater (GW) systems interacting with surface-water are complex, particularly under farming systems receiving high fertiliser/pesticide inputs in high rainfall regions. We investigated whether any linkage existed between nitrate-N in: (i) leachate (LC) collected at similar to 1m depth under banana (Musa) and that in GW, and (ii) GW and drain-water (DW). We also assessed the hazard/risk of the concentrations against the trigger values proposed for the sustainable health of different aquatic ecosystems. The LC, GW, and DW samples were collected at short intervals during 3 consecutive rainy seasons (January-July) from a similar to 300-ha banana farm in the wet tropical Tully River Catchment in north-east Queensland, Australia. Water samples were analysed for nitrate-N, dissolved organic carbon, and electrical conductivity. The coefficients of variation, ranging from 13 to 132%, obtained for solute concentrations in LC, GW, and DW indicated large within-and between-season temporal variations. The mean nitrate-N concentrations in LC, GW, and DW were 5320, 4135, and 1976 mu g/L, respectively, and were orders of magnitude higher than the trigger values proposed for the sustainable health of most of the neighbouring aquatic ecosystems. Significant positive associations, with correlation coefficients ranging from 0.56 to 0.96, existed between rainfall received and LC volume collected, and between LC volume and solute concentration, including nitrate-N, in the LC. Similar associations existed between the solutes in (i) LC and GW and (ii) GW and DW. From these associations we conclude the unused/under-utilised nitrate that leached below the root-zone was imported into the GW by the percolating rainwater and was exported into the drain via GW base-flow discharge.
- Description: 2003008225
- Authors: Rasiah, Velu , Armour, John , Cogle, A.L. , Florentine, Singarayer
- Date: 2010
- Type: Text , Journal article
- Relation: Australian Journal of Soil Research Vol. 48, no. 4 (2010), p. 361-370
- Full Text:
- Reviewed:
- Description: Solute import-export dynamics in groundwater (GW) systems interacting with surface-water are complex, particularly under farming systems receiving high fertiliser/pesticide inputs in high rainfall regions. We investigated whether any linkage existed between nitrate-N in: (i) leachate (LC) collected at similar to 1m depth under banana (Musa) and that in GW, and (ii) GW and drain-water (DW). We also assessed the hazard/risk of the concentrations against the trigger values proposed for the sustainable health of different aquatic ecosystems. The LC, GW, and DW samples were collected at short intervals during 3 consecutive rainy seasons (January-July) from a similar to 300-ha banana farm in the wet tropical Tully River Catchment in north-east Queensland, Australia. Water samples were analysed for nitrate-N, dissolved organic carbon, and electrical conductivity. The coefficients of variation, ranging from 13 to 132%, obtained for solute concentrations in LC, GW, and DW indicated large within-and between-season temporal variations. The mean nitrate-N concentrations in LC, GW, and DW were 5320, 4135, and 1976 mu g/L, respectively, and were orders of magnitude higher than the trigger values proposed for the sustainable health of most of the neighbouring aquatic ecosystems. Significant positive associations, with correlation coefficients ranging from 0.56 to 0.96, existed between rainfall received and LC volume collected, and between LC volume and solute concentration, including nitrate-N, in the LC. Similar associations existed between the solutes in (i) LC and GW and (ii) GW and DW. From these associations we conclude the unused/under-utilised nitrate that leached below the root-zone was imported into the GW by the percolating rainwater and was exported into the drain via GW base-flow discharge.
- Description: 2003008225
Characterising and improving the deteriorating trends in soil physical quality under banana
- Rasiah, Velu, Armour, John, Moody, P., Pattison, A., Lindsay, S., Florentine, Singarayer
- Authors: Rasiah, Velu , Armour, John , Moody, P. , Pattison, A. , Lindsay, S. , Florentine, Singarayer
- Date: 2009
- Type: Text , Journal article
- Relation: Australian Journal of Soil Research Vol. 47, no. 6 (2009), p. 574-584
- Full Text:
- Reviewed:
- Description: Deterioration in soil physical quality under intensive tillage practices is a norm rather than an exception. The objectives of this study were to (i) evaluate total porosity (TP) as an indicator parameter to assess the impact of banana cropping on compaction and infiltration in soils, and (ii) assess the effectiveness of different interrow grass-covers in minimising the deteriorating trends. Depth-incremented TP under banana rows and interrows from 4 sites, corresponding forest sites, and from 3 interrow grass-cover treatments were computed from bulk density measurements. The TP results show the compacted depth ranged from 0.35 to 0.45m in banana rows and from 0.35 to 1.0m in the interrows. The TP in 0.10m depth increments decreased in the order: forest > rows > interrows, and was positively correlated with soil organic C (OC) and negatively with wheel traffic stress (WTS). The multiple regression analysis showed that 77% of the variability in TP was accounted for by clay + silt, OC, and WTS. We show that a threshold compaction index (DIt) of 0.81-0.83 can be estimated from TP regardless of the soil type. Depending on the soil type and the cultural practices followed, infiltration decreased from 0.75 mm/s in rainforest to 0.23 mm/s under banana in 1 soil type compared with 2.55 mm/s in forest and 0.85 mm/s under banana in another. After 18 months of interrow grass-covers we found the deterioration in TP was minimum under the indigenous grass-cover but not under the 2 improved species. We conclude the interrow grass-covers were effective in minimising WTS associated compaction and reduction in infiltration.
- Authors: Rasiah, Velu , Armour, John , Moody, P. , Pattison, A. , Lindsay, S. , Florentine, Singarayer
- Date: 2009
- Type: Text , Journal article
- Relation: Australian Journal of Soil Research Vol. 47, no. 6 (2009), p. 574-584
- Full Text:
- Reviewed:
- Description: Deterioration in soil physical quality under intensive tillage practices is a norm rather than an exception. The objectives of this study were to (i) evaluate total porosity (TP) as an indicator parameter to assess the impact of banana cropping on compaction and infiltration in soils, and (ii) assess the effectiveness of different interrow grass-covers in minimising the deteriorating trends. Depth-incremented TP under banana rows and interrows from 4 sites, corresponding forest sites, and from 3 interrow grass-cover treatments were computed from bulk density measurements. The TP results show the compacted depth ranged from 0.35 to 0.45m in banana rows and from 0.35 to 1.0m in the interrows. The TP in 0.10m depth increments decreased in the order: forest > rows > interrows, and was positively correlated with soil organic C (OC) and negatively with wheel traffic stress (WTS). The multiple regression analysis showed that 77% of the variability in TP was accounted for by clay + silt, OC, and WTS. We show that a threshold compaction index (DIt) of 0.81-0.83 can be estimated from TP regardless of the soil type. Depending on the soil type and the cultural practices followed, infiltration decreased from 0.75 mm/s in rainforest to 0.23 mm/s under banana in 1 soil type compared with 2.55 mm/s in forest and 0.85 mm/s under banana in another. After 18 months of interrow grass-covers we found the deterioration in TP was minimum under the indigenous grass-cover but not under the 2 improved species. We conclude the interrow grass-covers were effective in minimising WTS associated compaction and reduction in infiltration.
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