Implication of green manure crop cultivation with rock phosphate in organic rotations

摘要

Low levels of total and available phosphorous (P) are common in organic production systems. As part of a wider experimental programme the direct application of phosphate rock (PR) to rotation experiments took place at three farms with low P status soils. Green manures (including forage rye, forage rape, field beans) were sown directly after autumn application of PR and their influence on P availability was measured through the following two crops at the sites. Effectiveness varied between the type ofgreen manure employed and location. Forage rye plus PR in particular showed significantly increased yields (-10% compared to forage rye only) by the following grain crop and economic analysis indicated that the costs of application were recoverable, with the exception of field beans. For producers facing limited available soil P conditions the experimentation provides useful guidance on rotational crop choice and PR applications.