BIOMASS PRODUCTION AND N-USE OF FIBRE SORGHUM UNDER DIFFERENT COVER CROPPING MANAGEMENT, NITROGEN INFLUXES AND SOIL TYPES IN CENTRAL GREECE

Field experiments were carried out over a period of three years to evaluate the effect of cover cropping faba bean with fibre sorghum, compared to mono-crop cultivation, on yield (dry matter), nitrogen utilization efficiency (NUE) and N fertilizer recovery fraction of sorghum. Experimental sites were located in central Greece on a fertile, clayey to loamy textured soil, and on a sandy soil of moderate fertility. A factorial combination of four nitrogen application rates (0, 50, 100, 150 kg ha(-1)) and three legume treatments (incorporated into the topsoil or harvested before the sowing of sorghum and mono-cropping) were tested in a split plot design in three blocks. The results showed importance of legume cover crops for both soil types as sorghum total dry biomass yield for clayey soil fluctuated from 23 to 27 t ha(-1) for control plots, from 25.2 to 30.9 t ha(-1) when faba bean was harvested and from 26.3 to 32.5 t ha(-1) when incorporated, and for sandy soil the yield fluctuated from 18.1 to 22.1 t ha(-1) for control plots, from 22 to 27 t ha(-1) when faba bean was harvested and from 23.1 to 28.1 t ha(-1) when incorporated. The NUE was estimated at 62 kg kg(-1) and 60 kg kg(-1) for clayey and sandy soils respectively. The N recovery fraction was doubled after incorporating faba bean as green manure, reaching large amounts for both soil types.