Land application of spent gypsum from ditch filters: phosphorus source or sink?

Abstract

Agricultural drainage ditches can provide a direct connection between fields and surface waters, and some have been shown to deliver high loads of phosphorus (P) to sensitive water bodies. A potential way to reduce nutrient loads in drainage ditches is to install filter structures containing P sorbing materials (PSMs) such as gypsum to remove P from ditch flow. The objective of this study was to determine the effect of land-application of gypsum removed from such filters on soil P forms and concentrations. Gypsum was saturated at two levels on a mass basis of P and applied to two soils of contrasting texture, a silt loam and a sandy loam and applied at both a high and low rate. The treated soils were incubated in the laboratory at 25˚C, and samples were collected at 1, 7 and 119 days after initiation. Soil type, time after application, gypsum rate, and P saturation level all had a significant impact on soil P forms and concentrations. However, it appears that land application of spent filter gypsum at realistic rates would have little effect on soluble P concentrations in amended soils.

Gypsum amendment of soils reduces phosphorus losses in an agricultural catchment

“…The effect of gypsum on nutrient transport has been studied mostly under laboratory conditions (Zhu and Uusitalo et al 2012, Grubb et al 2011, Kumar and Saha 2011 with only a few examples from catchment scale studies (Cox et al 2005). For instance, gypsum was shown to reduce P losses from the slightly acidic Finnish soils in incubation-leaching studies (Pietola 2008) and in experiments with soil cores under artificial rainfall (Uusitalo et al 2012).…”

Using Flue Gas Desulfurization Gypsum to Remove Dissolved Phosphorus from Agricultural Drainage Waters

“…To prevent the subsequent dissolution and loss of As to receiving waters, the filter bed will have to be removed before complete dissolution of the gypsum. Incubation studies designed to evaluate the effects of land applying “spent” gypsum from a decommissioned filter bed concluded that there will be little effect on dissolved P concentrations in amended soils (Grubb et al, 2011a, 2011b). In these studies, spent gypsum did not appear to provide additional P fertilizer value.…”

Applied Manure and Nutrient Chemistry for Sustainable Agriculture and Environment

“…Important manure properties include P forms and amounts, pH, pH buffering capacity, and relevant cations. However, there are several studies that examined the use of P saturated PSMs as potential fertilizers (Dobbie et al 2005;Bird and Drizo 2009;Grubb et al 2011Grubb et al , 2012. The maximum benefit of reducing soluble P concentrations in runoff is realized in surface applications of the PSM-manure mixture with no incorporation.…”