title: Freeze-thaw effects on phosphorus loss in runoff from manured and catch-cropped soils.
abstract: Concern over nonpoint source P losses from agricultural lands to surface waters in frigid climates has focused attention on the role of freezing and thawing on P loss from catch crops (cover crops). This study evaluated the effect of freezing and thawing on the fate of P in bare soils, soils mixed with dairy manure, and soils with an established catch crop of annual ryegrass (Lolium multiflorum L.). Experiments were conducted to evaluate changes in P runoff from packed soil boxes (100 by 20 by 5 cm) and P leaching from intact soil columns (30 cm deep). Before freezing and thawing, total P (TP) in runoff from catch-cropped soils was lower than from manured and bare soils due to lower erosion. Repeated freezing and thawing significantly increased water-extractable P (WEP) from catch crop biomass and resulted in significantly elevated concentrations of dissolved P in runoff (9.7 mg L(-1)) compared with manured (0.18 mg L(-1)) and bare soils (0.14 mg L(-1)). Catch crop WEP was strongly correlated with the number of freeze-thaw cycles. Freezing and thawing did not change the WEP of soils mixed with manures, nor were differences observed in subsurface losses of P between catch-cropped and bare soils before or after manure application. This study illustrates the trade-offs of establishing catch crops in frigid climates, which can enhance P uptake by biomass and reduce erosion potential but increase dissolved P runoff.
authors.affiliation: Norwegian Centre for Soil and Environmental Research, Jordforsk, Aas. marianne.bechmann@jordforsk.no
authors.forename: Marianne E
authors.initials: ME
authors.lastname: Bechmann
authors.forename: Peter J A
authors.initials: PJ
authors.lastname: Kleinman
authors.forename: Andrew N
authors.initials: AN
authors.lastname: Sharpley
authors.forename: Lou S
authors.initials: LS
authors.lastname: Saporito
mesh_terms: D000383:Agriculture / Q000379:methods*; D002980:Climate; D005615:Freezing; D008129:Lolium; D008372:Manure; D010414:Pennsylvania; D010758:Phosphorus / Q000378:metabolism*; D012987:Soil
chemical_list: D008372:Manure; D012987:Soil; D010758:Phosphorus