Can phosphorus fertilizers sparingly soluble in water decrease phosphorus leaching loss from an acid peat soil?

Abstract

© 2016 British Society of Soil Science The potential risk of phosphorus (P) loss in surface run-off can be decreased using sparingly soluble forms of P fertilizer (e.g. reactive phosphate rock (RPR)). However, it is unclear whether RPR can decrease P loss in leachate, especially when applied to soils with a small anion storage capacity (viz. P sorption capacity) and pH. Our hypothesis was that at low soil pH, the solubility of RPR would increase and result in P losses in leachate similar to those receiving single superphosphate (SSP), but at higher pH, less P would be lost from soils receiving RPR than SSP. Lysimeters containing a crushed, sieved acid mesic Organic (viz. peat) subsoil (30–60 cm) were limed to pH 4.5, 5.5 or 6.5 and treated with SSP or RPR at rates of 0, 50, 100 or 200 kg P/ha. Lysimeters were sown with ryegrass and watered over 12 months under controlled conditions and the leachate collected. Losses of filtered (< 0.45 μm) reactive inorganic P (FRP) and unreactive or organic P (FUP) in leachate were greatest for pH 4.5 treatments and least for the pH 6.5 treatments. The difference in FRP and FUP leachate losses in RPR- and SSP-treated soils was smaller at pH 4.5 and 5.5, and increased at pH 6.5 as losses from soils receiving RPR decreased compared to those receiving SSP. The results suggest that RPR can be used as a strategy to decrease P losses in leachate from an acid Organic soil with small P sorption capacity when limed to > pH 5.5.