The impact of lime admixture into trench backfill on the variation of phosphorus in drainage outflow

Abstract

One of the tasks of environmental protection is to achieve good ecological status of water bodies and reduce agricultural non-point pollution. As the drainage outflow may be identified as the leading source of water quality, reduction of nutrient transport through drains is therefore of great importance. The field studies on the impact of lime admixture into trench backfill on the amount of phosphorus contained in drainage outflow were conducted in a site located in south-western Lithuania. Heavy-textured clay loam soils prevailed in the catchment. The site was drained by a composite subsurface drainage system with drain spacing of 16 and 24 m. To improve water permeability, drainage trenches were backfilled with soil mixed with 0.6% CaO. Results of seven-year studies (1999-2005) on water quality are reported in this paper. The significant differences between orthophosphate concentrations in control drainage outflow and the treatments with lime added into the trench backfill were estimated. In water of the control drainage these concentrations were found to be 2.8 times higher. A slightly decreasing trend of total phosphorus (r = 0.49) and orthophosphates (r=0.54) was determined in the stream where drainage water discharged. Annual median phosphorus concentrations have generally remained steady in the outflow of limed drainage treatments. Lime admixture reduces the annual load of total phosphorus and orthophosphate by two and three times respectively, compared with a conventional drainage system. Copyright (c) 2007 John Wiley & Sons, Ltd.

One of the tasks of environmental protection is to achieve good ecological status of water bodies and reduce agricultural non-point pollution. As the drainage outflow may be identified as the leading source of water quality, reduction of nutrient transport through drains is therefore of great importance. The field studies on the impact of lime admixture into trench backfill on the amount of phosphorus contained in drainage outflow were conducted in a site located in south-western Lithuania. Heavy-textured clay loam soils prevailed in the catchment. The site was drained by a composite subsurface drainage system with drain spacing of 16 and 24 m. To improve water permeability, drainage trenches were backfilled with soil mixed with 0.6% CaO. Results of seven-year studies (1999-2005) on water quality are reported in this paper. The significant differences between orthophosphate concentrations in control drainage outflow and the treatments with lime added into the trench backfill were estimated. In water of the control drainage these concentrations were found to be 2.8 times higher. A slightly decreasing trend of total phosphorus (r = 0.49) and orthophosphates (r=0.54) was determined in the stream where drainage water discharged. Annual median phosphorus concentrations have generally remained steady in the outflow of limed drainage treatments. Lime admixture reduces the annual load of total phosphorus and orthophosphate by two and three times respectively, compared with a conventional drainage system.