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Lookup NU author(s): Dr Elizabeth Stockdale
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Phosphorus (P) availability to crops in organic systems can be a major issue, with the use of readily available forms often restricted. One product that can be used in organically managed systems, that is also relatively easily accessible to growers, is phosphate rock, although its solubility and therefore crop availability is often poor. One possible approach to improve this situation is co-composting phosphate rock with selected organic waste materials. Various ratios of phosphate rock and cabbage (Brassica oleracea L.) residues were co-composted and the products tested at different rates of application. The effects were assessed over 12 weeks using oilseed rape (Brassica napus L.) and perennial ryegrass (Lolium perenne L.) as bioassay crops in a pot experiment. At harvest, estimates of P derived from cabbage and phosphate rock for the lowest of two rates of compost were approximate to 2 and 10 mg P pot1 for oilseed rape, compared to 5 and 2 mg P pot1 for perennial ryegrass, respectively. Roots tended to have higher P concentrations than shoots. The crops showed differences in their abilities to access various P sources, with oilseed rape effectively taking P from phosphate rock, whereas perennial ryegrass was more effective at accessing cabbage-derived P (the main substrate in the compost). Oilseed rape was able to take up 20% of the total P applied as phosphate rock, whereas perennial ryegrass took up less than 5% of the total P applied from this material. Both pre- and post-application solubilisation/transformation mechanisms were involved in supplying plant-available P. Quantifying the relative contribution from individual P sources remains problematic even within this relatively simple system.
Author(s): Walker RL, Edwards AC, Maskell P, Watson CA, Rees RM, Knox OGG, Stockdale EA
Publication type: Article
Publication status: Published
Journal: Journal of Plant Nutrition and Soil Science
Print publication date: 28/06/2012
ISSN (print): 1436-8730
ISSN (electronic): 1522-2624
Publisher: Wiley - V C H Verlag GmbH & Co. KGaA
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