Biomass production and phosphorus retention by catch crops on clayey soils in southern and central Sweden.

Catch crops are a potential option to reduce phosphorus (P) losses, but little is known about their establishment success and capacity to retain P on clayey soils in regions with short autumns, e.g. Sweden. This study screened biomass production and P retention by eight catch crop species: the perennials chicory ( Cichorium intybus L.), cocksfoot ( Dactylis glomerata L.), perennial ryegrass ( Lolium perenne L.) and red clover ( Trifolium pratense L.) and the annuals phacelia ( Phacelia tanacetifolia L.), white mustard ( Sinapis alba L.), oilseed radish ( Raphanus sativus L. oleiformis ) and white radish ( R. longipinnatus ). The catch crops were grown at six field sites, where the perennial species were under-sown with barley and the annual species were after-sown following barley harvest. Biomass production, P content in above-ground and below-ground plant parts and content of available P in the soil were determined in autumn and survival rate of the catch crops in the following spring. Biomass production and P retention in autumn both differed significantly between species ( p < 0.0001), and were greatly affected by site-specific conditions and time of sowing, which differed between experiments. Growth of catch crops can also be suppressed by low precipitation. Content of P in roots varied substantially between species, a factor which must be considered in species comparisons. The under-sown species produced more or equivalent amounts of biomass, retained more or equivalent amounts of P in autumn and survived better over winter than the after-sown species. Thus under-sown catch crops generally seem more suitable as catch crops for P. [ABSTRACT FROM AUTHOR]