Evolution of biogenic nitrogen from digestates for lettuce fertilization and the effect on the bacterial community
With the rise of human population and the increasing concerns regarding pollution and climate change, agriculture must face its hardest challenges yet. Among the many inputs, nitrogen fertilizers are the main yield-limiting factor in agriculture. Liquid fractions of digestates can be a most promising substitute to synthetic nitrogen fertilizers, using little energy to turn waste into valuable fertilizers. In this study, the efficacy of five digestates (C, cow slurry; P, pig slurry; PCE, Pig slurry, Cow slurry, Energy crops; SS, Sewage Sludge; W organic fraction of municipal Waste) were assessed as fertilizers for the cultivation of Lactuca sativa, compared to traditional mineral fertilization. The yield analyses and chemical parameters of the lettuce plants showed that the digestates all gave results comparable to the mineral fertilizer, showing that the digestates are promising for this use. Analysis of nitrogen evolution showed different patterns between digestates and mineral fertilizers. Another topic investigated in the study is the effect of the digestates on the bacterial populations of the growth substrate, investigated through quantification and sequencing of 16S gene. The results of this investigation varied based on the digestate considered but, in general, an increase in biodiversity could be linked to use of digestates.