Nitrogen Mineralization of Compost and Vermicompost from Different Animal Manure and its Recovery by Lettuce Using 15N

Nitrogen (N) is a limiting nutrient for crop production and there is a lack of knowledge regarding the N availability of different compost and vermicompost and its recovery by short-cycle crops, such as lettuce (Lactuca sativa L.). The N mineralization of compost and vermicompost produced from different animal manure (cattle, pig, and poultry) was evaluated in a laboratory incubation and N recovery by lettuce was evaluated, with 15N application, in a greenhouse experiment. Composts and vermicompost N release ranged from 4.0 to 16.5% and was related to the previous mineral N presented in the materials while organic N mineralization was low (-0.9 to 7.7%). Only one-third of N uptake by lettuce was derived from organic materials, with a greater contribution from soil N. The N recovery by lettuce was below 12%, with higher values (8.5 to 12%) when using composts produced from cattle and pig manure. Our findings indicate that the N release from composts and vermicompost varies according to the nature of the feedstock and the stabilization process (i.e., composting and vermicomposting). Hence, these results should be considered for setting the N recommendation for short-cycle vegetables using compost and vermicompost produced with different feedstock.