Effects of compost organic amendments on chemical composition and in vitro digestibility alfalfa (Medicago sativa L.)

The following fertiliser treatments were compared during the years 2002 and 2003 on alfalfa forage (Medicago sativa L.): compost obtained from the organic fraction of the Municipal Solid Waste (MSW); olive pomace compost (OPC); mineral fertiliser (Min). All the treatments allowed a distribution of 75kg ha-1 of P2O5. Three cuttings occurred: at 168, 206 and 351 days after compost application (DAA) in 2002; 119, 152 and 320 DAA in 2003. Cumulative biomass and dry matter yields were measured during each experimental year. Furthermore, chemical composition and in vitro digestibility of dry matter (DMd), organic matter (OMd), crude protein (CPd) and NDF (NDFd) were determined. MSW treatment showed a significantly (P<0.01) higher content of ADL than OPC and Min (77.0, 66.0 and 65.0g kg-1 DM, respectively). Fertiliser treatments also affected (P<0.01) digestibility parameters. In fact, DMd and OMd values showed the same trend with lower percentages in MSW treatment than in the OPC and Min ones. The NDFd differed in all treatments having the highest value in OPC (40.1%). The results indicated that the soil distribution of organic materials offer the possibility to reduce the application of mineral fertilisers and production costs without decreasing alfalfa yield, forage chemical composition and in vitro digestibility.