Contrasting the influence of crop rotation on phosphorus balances and losses in agricultural fields across a tile-drained landscape in Ohio, USA

Abstract

Excess phosphorus (P) applied to agricultural fields accumulates in the soil profile and is susceptible to leaching, subsequently impacting adjacent and downstream aquatic ecosystems. Planting a series of crops in a field over a given period of time is considered conservation crop rotation, which may reduce nutrient losses by reducing P inputs (i.e., including crops with lower P requirements) and increasing P demand (i.e., by increasing biodiversity, vegetative land cover, and length of the growing season). Here, we calculated P balances (Inputs–Outputs) in agricultural fields with corn-soybean rotations (CS) and corn-soybean-wheat rotations (CSW) to determine P accumulation or depletion. We then compared P losses, as dissolved reactive P (DRP) and total P (TP), between the CS and CSW rotations. Results indicated annual P deficits in CS (median = −9 kg P/ha) and CSW (median = −5 kg P/ha) fields. However, DRP and TP losses persisted and were significantly greater from CSW (median = 0.5 kg DRP/ha and 2 kg TP/ha) compared to CS fields (median = 0.1 kg DRP/ha and 1 kg TP/ha), likely due to elevated soil test phosphorus (STP) concentrations in CSW fields. The fraction of applied P exported from fields as both DRP and TP was also greater in CSW (DRP = 2%; TP = 9%) compared to CS (DRP = 1%; TP = 3%), further confirming more available P susceptible to loss. Findings here highlight the need for further research between conventional and conservation crop rotation on fields with similar STP concentrations and emphasize the importance of P application in accordance with fertility recommendations.