Phosphorus in agricultural soils around the Baltic Sea – comparison of laboratory methods as indices for phosphorus leaching to waters

Abstract

In this study we investigated the phosphorus (P) content of Baltic soils. In the first set of analyses, 99 soil samples from the Baltic states and Sweden (soil set 1, representing seven different catchments or experimental plots) were analysed for soil P using four extraction methods: ammonium lactate (PAL), double lactate (PDL), Mehlich 3 (PM3) and carbonate (POlsen) (r = 0.85–0.97). In absolute values, results from PM3, PDL and POlsen gave means of 71, 61 and 20%, respectively, of the value from the PAL extraction method. Significantly different relationships were found between P soil concentrations and pH of the extract. In addition, soil pH and organic matter content were found to be of importance. Secondly, we tested 110 soil samples (soil set 2) from five different Swedish monitoring fields with clay soils where PAL clearly correlated with soil P extracted in calcium chloride (PCaCl2) (r = 0.95). Values of a single‐point phosphorus sorption index (PSI) correlated with the aluminium concentration (AlAL) in the lactate extract (r = 0.91) and with (AlOX) in the oxalate extract (r = 0.96). None of the soil P tests with different extraction agents – calcium chloride (PCaCl2), water (Pw), POlsen or PAL– correlated with the mean annual flow‐weighted concentration (1999–2010) of dissolved reactive P (DRP) in drainage water. Neither was there any clear relationship between DRP concentration in drainage water and these tests combined with PSI or with other sorption indices including extracted Al and iron (Fe). However, DRP was related to the clay content of the topsoil (r = 0.91, P < 0.05).

Phosphorus Leaching from an Organic and a Mineral Arable Soil in a Rainfall Simulation Study

“…The P‐AL values exceeded the Olsen P values for both soils, suggesting dissolution of more P bound to Fe and Al oxides and also to Ca, due to the lower pH P‐AL extraction compared with the higher pH Olsen P extraction (Eriksson et al, 2013). Bulk density was significantly lower in the organic soil (Table 1), which was attributed to the high total C content.…”

Effect of organic and mineral fertilizers on soil P and C levels, crop yield and P leaching in a long term trial on a silt loam soil

“…P-CaCl 2 results from an extraction with a weak CaCl 2 solution to imitate the salt condition of soil water (Eriksson et al, 2013) and estimates the soil solution P concentration (Hesketh and Brookes, 2000) or the easily soluble P fraction (Djojic and Mattsson, 2013). The hot water extraction method, which is used to estimate the easily available organic C (HWC) (Ghani et al, 2003) and N pool (Keeney and Bremner, 1966), can also be used to determine the easily available organic P pool (HWP), since the high temperatures lead to decomposition of organic compounds (Füleky and Czinkota, 1993).…”

“…More P was extracted with HWP, and HWP turned out to have a lower variability than P-CaCl 2 . The ammonium lactate acid in the P-AL measurement leads to a dissolution of Al and Fe from their oxides followed by a P release, and inhibits any secondary P resorption in the extracts (Eriksson et al, 2013). P-AL can be considered as an agronomic soil P test, to estimate the desorbable P of the soil in the longer term.…”

Effects of aluminium water treatment residuals, used as a soil amendment to control phosphorus mobility in agricultural soils

“…In addition, the soils were analysed for pH, using 5 mL soil (dried at 30 °C) and 25 mL distilled water shaken for 5 min (Eriksson et al 2oio), and P-AL (Egnér et al i960). Soils for rain simulation/leaching experiments were also analysed for complementary P-related factors (four replicate analyses per soil): WSP (Eriksson et al 2012), lactate-extracted iron (Fe-AL) and aluminium (Al-AL) (Ulén 2006), and PSI (PSIi with a moderate P addition) (Börling et al 2001). Based on P-AL, Fe-AL and Al-AL values, molar-based DPS-AL was calculated.…”

“…In Sweden, plant-available P (P-AL) concentration in soil is commonly determined by acid extraction with ammonium lactate (AL), according to Egnér et al (i960). The P-AL method produces higher numerical values (mean 140%) than the Mehlich-3 method for soils in the Baltic region (Eriksson et al 2012). Together with water-soluble P (WSP), P-AL is considered a good indicator of P leaching for the commonly acid Swedish soils (Ulén et al 2on).…”