Lime and Gypsum as Source Measures to Decrease Phosphorus Loss from Soils to Water

Abstract

Phosphorus (P) loss from agricultural soils to water is a major contributor to eutrophication. In an incubation experiment with five contrasting soils, lime and gypsum showed potential as source measures to decrease P loss risk, as assessed by water extractions. Soils were incubated with lime to achieve a target pH of 6.5 and with gypsum at equivalent Ca rates for 108 days. P was added (17 kg P ha −1 ) as KH 2 PO 4 in solution. Gypsum appears to have greater potential as a source measure, decreasing molybdate-reactive P (RP) solubility by 14-56% and organic P (OP) by 10-53% across all soils. RP and Ca may have precipitated or cosorbed, and OP may have been stabilised in organic matter complexes due to the bridging effect of Ca and the flocculating effect of increased ionic strength. Greater effectiveness of gypsum may be due to its higher solubility and the fact that it increases Ca concentrations without increasing pH. Lime decreased RP solubility in two soils (by 4% and 20%) but increased solubility in two and had no effect in a third. The overall effect of lime may depend on several competing effects of raised pH and Ca concentration that may vary in importance depending on soil characteristics such as base cation and P status. For the highest P status soil, both lime and gypsum were effective, decreasing RP solubility by 4% and 15%, respectively. Targeted treatment of high P soils may be an effective and economical strategy to minimise P losses.

What is more important for enhancing nutrient bioavailability with biochar application into a sandy soil: Direct or indirect mechanism?

“…2. The increased P solubility with decreasing soil acidity has been explored in previous studies (Murphy and Stevens, 2010). The results indicated that the increasing of soil pH with biochar application may be important for the enhanced P availability.…”

Efficiency of Drainage Practices for Improving Water Quality in Lithuania

“…This results in a greater solubility of phosphorus due to the amount of ammonium ions, which is high in manure and slurry. According to Murphy and Stevens (2010), soil acidity neutralization with lime and gypsum to a pH of 6.5 results in decreasing molybdate-reactive P solubility by 14% to 56% and decreasing organic P by 10% to 53%.…”

A review of phosphorus and sediment release from Irish tillage soils, the methods used to quantify losses and the current state of mitigation practice

“…Until now, the majority of research in Ireland has focused on quantifying nutrient and, to a lesser extent, sediment losses from permanent grassland at laboratory- (Doody et al 2006;Murphy 2007;Murphy and Stevens 2010), plot/field- (Tunney et al 2007;Kurz et al 2000;Douglas et al 2007) and catchment-scales (Smith et al 1995;Scanlon et al 2004;Jordan et al 2005a;2005b;Smith et al 2005;Jordan et al 2007). Modelling of diffuse P loss from grassland catchments has also been undertaken by Jordan et al (2000), Daly et al (2002), Scanlon et al (2005) and Nasr et al (2007), with the aim of improving management strategies to minimise P loss.…”