A rainfall simulation study on the relationships between soil test P versus dissolved and potentially bioavailable particulate phosphorus forms in runoff

Abstract

Runoff from clayey soils often contains abundant particulate phoshorus (PP), part of which may solubilize in surface waters. Monitoring losses of potentially bioavailable forms of PP is expensive, calling for other ways to predict them. Such predictions could be based on soil loss and available soil P indices, e.g., agronomic P status. To study correlations between P pools in runoff versus soil P saturation (by Mehlich 3 extraction; DPSM3) and acetate soil test P (PAc), 15 clayey soils of south Finland were subjected to laboratory rainfall simulation. Runoff from these simulations was analyzed for concentrations of suspended soil (TSS), dissolved molybdate-reactive P (DRP), total P (TP), and, as normalized to soil loss, potentially bioavailable forms of PP: desorbable (anion exchange resin-extractable, AER-PP/TSS) and redox-labile PP (bicarbonate- dithionite-extractable, BD-PP/TSS). Correlation coefficients (r2) between DPSM3 and DRP, AER-PP/ TSS, and BD-PP/TSS equaled 0.92, 0.77, and 0.45, respectively. Runoff P forms were also correlated to soil PAc with r2 values of 0.84, 0.56, and 0.58 for DRP, AER-PP/TSS, and BD-PP/TSS, respectively. Prediction of soil loss-normalized concentrations of potentially bioavailable PP by the agronomic PAc test was considered possible. However, such predictions have a high degree of uncertainty, evidenced by comparison to published field data. Acceptably accurate predictive equations would require a large material as a basis for their construction, and soils should probably also be grouped according to other soil properties that would account for variation in P sorption capacity.;

The effects of gypsum on the transfer of phosphorus and other nutrients through clay soil monoliths

“…The relationship between soil test P (P Ac ) and average DRP indicated that a unit of P Ac concentration in the soil corresponded to about 10 µg l -1 DRP in percolation water. This finding is consistent with results of earlier rainfall simulations by Uusitalo and Aura (2005), conducted on 13 clay soils with P Ac concentrations up to 25 mg l -1 . In that study a unit increase in P Ac was accompanied by a 9 µg l -1 increase in DRP.…”

“…Rainfall was simulated using a stationary drop-former type rain maker as described in Uusitalo and Aura (2005). This device pumps deionized water through a column maintained at a constant water level into 0.51 mm diameter capillary tubes.…”

Recycling nutrients from horse manure: effects of bedding type and its compostability

“…On top of the mesh, a manure sample was weighed according to the volume weight of the material to obtain a three-litre sample volume, which corresponded to 0.28 ± 0.05 kg manure dry mass (dm) and formed an approximately 5 cm-thick layer. The containers were positioned to have a 4% slope towards the drainage outlet while subjected to artificial rainfall of 8-10 mm h -1 under a stationary drip type rainfall simulator (Uusitalo and Aura 2005) for a period of 2 h 15 min. The percolated water was collected from the start of the rain until 10 min after its end.…”

Stratification of soil phosphorus, pH, and macro-cations under intensively cropped grass ley

“…For mineral soils, the following equation was used that was derived by Saarela (2008) from the data obtained by Uusitalo and Aura (2005) using simulated rain:…”