Organic fertilizers derived from plant materials Part I: Turnover in soil at low and moderate temperatures

Abstract

AbstractThe aim was to investigate different organic fertilizers derived from plant materials with respect to their nitrogen and carbon turnover in soil in comparison with organic fertilizers derived from animal‐waste products. In a 64‐day incubation study at 5°C and 15°C, the following fertilizers were used: coarse faba bean–seed meal (Vicia faba L.), coarse meals of yellow and white lupin seeds (Lupinus albus L. and Lupinus luteus L.), Phytoperls® (waste products of maize [Zea mays L.] processing), coarse meal of castor cake (Ricinus communis L.) as a widely used organic fertilizer, and horn meal as a reference fertilizer‐derived from animal waste products. At 15°C, horn meal showed the highest apparent net N mineralization of fertilizer‐derived N, followed by castor cake and the two lupin meals. At 5°C, apparent net N mineralization of fertilizer‐derived N from horn meal and coarse meal of yellow lupin seeds was nearly identical, followed by castor‐cake meal. Net N mineralization from legume‐seed meals showed no or even a negative temperature response, at least temporarily. In contrast, the other fertilizers showed a positive temperature response of net N mineralization. The content in recalcitrant structural components and the decoupling of decomposition of N‐rich and C‐rich tissue components in time are discussed as controlling factors of fertilizer‐N turnover at low temperature. Microbial residues seem to be an important temporary sink of fertilizer‐derived C and N. Legume‐seed meals induced considerable N‐priming effects. Temperature induced differences in the decomposition of total fertilizer C, indicated by changes in the sum of cumulative CO2‐C evolution, total K2SO4‐soluble organic C and microbial‐biomass C were much smaller than indicated by cumulative CO2‐C evolution alone. Our results indicate that legume‐seed meals have the potential to replace horn meal and castor‐cake meal in organic vegetable production, especially when soil temperatures in early spring are still low.