Soil phosphorus dynamics as affected by a green manure crop grown with phosphate rocks

Melissa Arcand¹ and Derek Lynch²

Phosphorus (P) dynamics were examined in organically and conventionally managed field soils that had been amended in the previous year with buckwheat straw (Fagopyrum esculentum). The buckwheat had been fertilized with various sources and rates of phosphate rock (PR). Immediately following harvest, the buckwheat straw (2.73 to 3.04 t DM ha-1) was returned to half of each plot from which it originated, resulting in a split plot design with PR as the main plot and straw mulch as the subplot.

The P applied as mulch, which ranged from 12.16 to 36.01 kg P ha-1, was 4, 49, 83, and 184 % greater than the control, for main plots which had received Volcanaphos, Calphos, and TSP at 800 (V800), 400 and 800 (C400, C800), and 800 kg P ha-1 (T800), respectively. The cumulative soil P flux (µg P 10 cm-2) determined in situ using PRSTM-probes (anion exchange membranes), for C800 and T800 was significantly greater (8.52 and 95.2, respectively) than the control (5.21 µg 10 cm-2) over 8 weeks. Soil (0 15cm) samples analyzed for NaHCO3 extractable P (STP) showed that C400 and C800 significantly increased STP compared to control (7.22, 7.73, and 6.23 mg P kg soil 1, respectively). Despite significant mulch and PR effects, the low STP and P flux suggests limited potential for short-term recycling P through green manure biomass.


Source
Organic Agriculture Research Symposium held at the 25th Guelph Organic Conference, University of Guelph, January 2006


Author Locations & Affiliations
(1) Department of Land Resource Science, University of Guelph, Guelph, Ontario, Canada N1G 2W1.
(2) Department of Plant and Animal Sciences, Nova Scotia Agricultural College (NSAC), P.O. Box 550, Truro, Nova Scotia, Canada B2N 5E3.
Corresponding author: Melissa Arcand marcand@uoguelph.ca


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