Effect of lignite amendment on carbon and nitrogen mineralization from raw and composted manure during incubation with soil

The application of animal manure as a source of plant nutrients requires the determination of the amount and pattern of nutrient mineralization from manure. A laboratory incubation study was conducted to investigate the influence of lignite amendment and lignite type on carbon (C) and nitrogen (N) mineralization in raw (feedstock) and composted cattle manure following application to soil at 30 and 60 t ha-1. The mineralization of C and N was determined by measuring changes in CO2 evolution and mineral N (NH4+-N + NO3--N) over 40 d. The results showed that lignite amendment suppressed the amount of manure C mineralized in both feedstock and compost, with the effect being more pronounced in the compost. Over the 40-d incubation, the percentage of applied C mineralized was 26.4%–27.8% and 16.3%–21.4% in unamended and lignite-amended feedstocks, respectively. The corresponding C mineralized in the composts was 12.4%–14.1% and 3.5%–6.5%. Lignite had no significant effect on the net N mineralized in compost (4.8%–6.7% and 2.5%–7.8% in unamended and lignite-amended composts, respectively). Lignite had either no effect or increased the net N mineralized in feedstock (from 3.2%–8.7% without lignite to 10.4%–13.5%) depending on the type of lignite used. This study suggests that using lignite-amended manure, especially when composted, has the potential to build up soil organic C without limiting the availability of mineral N.