Phosphorus transport in subsurface flow from a stony soil under irrigated and non-irrigated lucerne

ABSTRACT

The extent of phosphorus (P) loss from soils under deep rooting crops such as lucerne is currently unknown. This study used large lysimeters (2.0 by 1.5 m) to quantify the amounts and forms of P in drainage under lucerne from two sites, a non-irrigated dairy system and an irrigated dairy system that also received farm dairy effluent (FDE). Results showed despite greater P inputs to the irrigated compared to the non-irrigated site, there was no difference in total P concentrations in drainage. There were also no differences in the forms of P lost between sites, which were dominated by particulate P (48%–52%). More P was lost from the irrigated (0.262 kg ha⁻¹) than the non-irrigated site (0.164 kg ha⁻¹). The larger P loss was a result of irrigation producing more drainage (42%) than observed at the non-irrigated site. The amount and forms of P lost from lucerne were similar or lower than losses reported for similar soils under grass/legume-based pasture swards amended with P fertiliser and FDE. Because P leaching was regulated by drainage volume rather than P input, management of irrigation water to reduce drainage from the root zone will likely help minimise P leaching.

KEYWORDS:

• Lucerne
• leaching
• phosphorus
• irrigation
• dairy effluent

Acknowledgements

Chikako van Koten provided statistical advice and analysis. We are grateful to Lincoln University and the Ashley Dene Research and Development Station for ongoing use of the study sites.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

Funding for this work was provided by the Ministry of Business Innovation and Employment AgResearch Strategic Science Investment Funds contract number A20560, the Our Land and Water National Science Challenge (contract C10X1507), and the Ministry for Business, Innovation and Employment Endeavour Fund contract number C09X1610 to Manaaki Whenua – Landcare Research.