Dairy slurry application to grasslands and groundwater quality in a volcanic soil

Abstract

Research in volcanic-ash soils has shown that they largely capture the dairy slurry following application to land; however, their hydrological properties would favor nutrient leaching. Our objective was to evaluate the contribution of biogeochemical and hydrological controls on the pollution of groundwater by cattle slurry applied to a permanent grassland growing on a volcanic soil. We sampled groundwater chemistry since 10 months before the fertilization (three samplings), and 16 months after, with samplings 1-2 months after the fertigation. Following fertilization, ammonium, exchangeable potassium, and magnesium soil concentrations increased in the fertilized plots compared to the control plots. In contrast, no effect of slurry on groundwater quality was detected, with the exception of dissolved organic nitrogen, a main component of dairy slurry that increased in the groundwater below the fertilized plots. Despite the fact that biogeochemical controls predominate, hydrological aspects would be important when rainfall is high, evapotranspiration is low, groundwater table level is high, and water movement in the saturated zone increases. We concluded that the application of slurry to pastures under rates comparable to a high fertilization in the short term, does not generally impact the groundwater quality in volcanic ash-derived soils.

Screening of Native and Exotic Tree Species in Chile for Element Absorption from Dairy Slurry

“…Soil retention was calculated as the difference in the soil pool between control and fertilized plots. Other sources were Staelens et al (2003) and Huertas et al (2016)…”

“…They attributed their findings to the high salt content of the raw effluents, as well as the flooding conditions that the trees were exposed to. Conversely, nationally, the evidence that native vegetation can fulfill a filter effect is only recently emerging (Cuevas et al 2014;Little et al 2015;Huertas et al 2016). These studies suggest an important role of soils and native vegetation in the control of diffuse pollution.…”

“…The stream protection derived from this riparian and swamp vegetation can be a benefit for the environmental sustainability of agricultural and livestock activities, in that organic residues derived from animal production are applied to the crops adjacent to such vegetation strips. This production grows with the human demand and the need to recycle the residues increases in parallel, causing an important environmental pressure to soils and water (Saunders et al 2012;Huertas et al 2016). A fundamental role in stream protection is provided by the arboreal vegetation, because it can take up and filter the elements in excess that have not been absorbed or retained by crops and grasslands (Lowrance 1998).…”

An unusual kind of diurnal streamflow variation

“…However, the floodplain groundwater showed no diurnal signal, probably because water is not a limiting resource in this environment, as tree roots are extensively submerged. Furthermore, during the course of slug tests Huertas et al (2016) observed a very fast recovery of the floodplainʼs water table, in the order of minutes, compared to slope wells (30 min) and upland wells (more than 1 h). The slope's groundwater could be difficult to relate to the local Et because its diurnal fluctuations were also very out-oftime with respect to common Et-cycles.…”

“…This pattern also discards recent causes used to explain the present DSS, such as water viscosity fluctuations (Schwab et al, 2016). The DSS has also been found to begin when monthly Et 0 surpasses monthly rain in November and ends when this pattern reverses (April; Huertas et al, 2016). Meteorological variables such as air temperature, solar radiation, and Et 0 are well known to progressively increase from winter to summer (Cruz and Calderón, 2008;Sánchez, 2016).…”