Impact of farm‐dairy effluent application on the amounts and forms of phosphorus loss by leaching from irrigated grassland

Abstract

Sufficient evidence exists to support the hypothesis that the eutrophication of surface waters is accelerated by increased transfer of nutrients (e.g., phosphorus, P) from landscape to water. The objective of this paper is to combine the results of a lysimeter experiment that used intact soil monolith lysimeters (50 cm diameter, 70 cm deep) and a field experiment that used field plots (10 × 2 m 2 ) of a Lismore stony silt loam soil (Udic Ustochrept). The soils received mineral P fertiliser alone at 45 kg P ha -1 yr -1 or in combination with farm-dairy effluent (FDE) at 200 or 400 kg N ha -1 yr -1. Annual mean total P concentrations and losses were two-to threefold higher from the soil amended with both FDE and P fertiliser than P fertiliser alone. The higher losses as particulate unreactive P during irrigation seasons are attributed to the regular inputs of high intensity flood irrigation, which increased the transfer of soil particles from the soil profile. Greater than 60% of P loss occurred immediately following FDE application over a 2-year period, highlighting the importance of preferential flow in this soil. Phosphorus-31 nuclear magnetic resonance analysis showed that FDE was rich in inorganic orthophosphate (86%) while leachate contained only 12% of inorganic orthophosphate. This indicated that inorganic P applied in FDE was sorbed because of the high P fixation capacity of Lismore subsoil, which is due to higher amounts of Fe and Al. On the other hand, orthophosphate monoesters and diesters were only 13% of P in FDE, compared with 88% in leachate suggesting that organic P forms are mobile in the soil profile, and are selectively transported through soil. The Olsen P and isotopic exchange parameters (concentration of inorganic P in the soil solution (C P ) and the quantity of P that is immediately available to plants (E 1min )) of Lismore soil increased with increase in P application from mineral P fertiliser and FDE. This suggests that P fixation sites in soil may be getting saturated with applied P inputs.

Different efficiencies in organic P exploitation of two Italian alfalfa (Medicago sativa) landraces involving a possible adaptation pattern of the phytase encoding MsPHY1 gene

“…Organic P represented about one‐fifth of total P in leachates and confirmed that this P form was mobile in the soil profile (Toor, Condron, Di, Cameron, & Sims, 2004a, 2004b) with a potential impact on the surface and groundwater systems. Inorganic P accounted for about 80% of the total P in the leachates, and the maximal losses were found in the IP treatment (Figure 3a); the soluble liquid form (KH 2 PO 4 ) in which inorganic P has been supplied could have influenced the dynamics of losses.…”

“…Interestingly, phytate was reported to reach 29% and 34% of total P in poultry and pig manure, respectively, due to the higher grain component in animal diets and the absence of rumen microflora secreting phytases in monogastric animals (Li et al., 2014). However, when considering leachate from soils receiving dairy farm effluents, organic P forms, either particulate or dissolved, can equal or even exceed inorganic P forms, suggesting that they are less strongly absorbed onto soil colloids and more mobile in the soil profile (Chardon, 1997; Toor, Condron, Di, Cameron, & Sims, 2004a, 2004b). The increasing agricultural practice of applying manure/slurry on arable or permanent crops can result in the accumulation of surplus P in soils characterized by high agronomic P status and/or in P losses with a potential impact on the surface and groundwater systems (Schoumans et al., 2014).…”

A National Assessment of the Potential Linkage between Soil, and Surface and Groundwater Concentrations of Phosphorus

“…For example, Toor et al . () measured losses of 0.3‐2.3 kg P/ha over two years deeper than 0.7 m below the ground surface. There is much overseas data to show that P is mobile in aquifers comprised of sand and alluvial gravels due to high transmissivity, potential for bypass flow, and low P sorption capacity (Stollenwerk, ; Corbet et al ., ).…”

Treating farm dairy effluent with poly‐ferric sulphate dramatically reduces phosphorus and E. coli leaching through subsurface drains—A physical drainage model study

“…It is common practice to irrigate FDE onto pastoral land to recycle the nutrients, making FDE an economically valuable resource for dairy farms (Di et al, 1998, 1999; Laubach et al, 2015; Minogue et al, 2010). However, research has shown that when FDE is applied onto shallow free‐draining soils or soils with artificial agricultural drainage systems, there is a high risk of phosphate (P) being transferred into surface waters and groundwater (Cameron & Di, 2019; Houlbrooke & Monaghan, 2009; McDowell et al, 2019; Monaghan & Smith, 2004; Toor, Condron, Cade‐Menun, et al, 2004; Toor, Condron, Di, et al, 2004). Figure 1 illustrates how FDE is applied to land over a subsurface tile drain system.…”