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Potential phosphorus release from catch crop shoots and roots after freezing-thawing

Liu, Jian, Khalaf, Rafa, Ulén, Barbro, Bergkvist, Göran
Plant and soil 2013 v.371 no.1-2 pp. 543-557
Cichorium intybus, Dactylis glomerata, Lolium perenne, Phacelia tanacetifolia, Raphanus sativus, Sinapis alba subsp. alba, Trifolium pratense, catch crops, chicory, phosphorus, radishes, roots, shoots, surface area
Background and aims: Catch crops used for mitigating nutrient losses to water can release phosphorus (P) when exposed to repeated freezing-thawing cycles (FTCs). This study sought to evaluate potential P losses from shoots and roots of eight catch crops. Methods: Shoots and roots sampled from perennial ryegrass (Lolium perenne L.), cocksfoot (Dactylis glomerata L.), chicory (Cichorium intybus L.), phacelia (Phacelia tanacetifolia L.), red clover (Trifolium pratense L.), white mustard (Sinapis alba L.), oilseed radish (Raphanus sativus var. oleiformis L.) and white radish (R. sativus var. longipinnatus L.) were treated with no freezing, one single FTC, four continuous FTCs and four discontinuous FTCs. All samples were analysed for water-extractable P (WEP), and root samples also for characteristics such as specific root surface area (SSA). Results: Freezing-thawing significantly increased potential P losses from both shoots and roots compared with no freezing. The two radish species and white mustard contained significantly higher concentrations of WEP than the other species, among which chicory and phacelia had the lowest WEP. On average, shoots had 43 % higher WEP than roots. Cumulative P release from shoots and roots was strongly correlated with their total-P content (p = 0.006 and p = 0.002, respectively). Cumulative release of P from taproots was correlated with SSA (p = 0.03). Conclusions: Chicory, and possibly phacelia, appear to be promising catch crops for P. © 2013 The Author(s).