15N e 13C nella valutazione dell’uso dell’azoto e della conservazione del carbonio da compost

The natural abundance of stable isotopes of nitrogen (15N) and carbon(13C) of four composts (ACV; ACMdig; ACF; ACM) applied at 10 and 20 Mg OM ha-1, was used to estimate the utilization of N in ryegrass and the variation of the soil carbon isotopic signature (13C‰) at the end of a cultivation cycle (112 days). ACMdig and ACF showed the greatest N use efficiency (15NRF: 9-16%), in agreement with their higher mineral-N. At the end of the test the 13C ‰ ranged between -25.39 and -25.55 (control vs. NPK); between -26.76 and -26.55 in ACV and ACMdig, while ACF and ACM were intermediate (-25.94; -26.06). The 13C ‰ in the various treatments was described by a linear relationship with CO2 emissions, highlighting a reduction in the carbon's storage capacity in the less stable products, being this influenced by the application level. The greater the application of not completely stable compost, the smaller is the C conserved in the soil.