*3.4. The Treatment Factor*

The direct uptake of organic compounds from the soil solution by the root system constitutes an important base of nutrients for the plant [57]. The purpose of this essay is to obtain greater knowledge on how the composition of fertilizers can modify the characteristics of residual biomass obtained in almond trees. No significative differences were found in terms of carbon content between the tested biostimulants and the control test; however, biostimulant 1 showed a higher carbon content than biostimulant 2. (Figure 4). The gross calorific value of the samples was not affected by fertilization, either. These results are in agreemen<sup>t</sup> with those obtained by Ercoli [58], in which the supply of N fertilizers in Miscanthus translated into a higher biomass yield, but did not affect the calorific value of the crop. Results obtained for biostimulant 1 regarding hydrogen and nitrogen contents are higher than those of biostimulant 2. These outcomes could be partially explained by the composition of the products, since biostimulant 1 mainly provides saccharides and amino acids (tryptophan, glutamic and GABA), which are very fast absorbing molecules [57]. Similar conclusions were reached by Mantineo [59], where extra doses of nitrogen fertilization led to a higher nitrogen concentration in the studied biomass. As high N produces a negative impact on the environment, due to nitrogen dioxide emissions [19], fertilizers that promote an increase of the percentage of N may be considered to be environmentally disadvantageous for biomasic uses.

**Figure 4.** LSD intervals at 90% level of confidence in the influence of the treatment factor in residual biomass characteristics. (*n* = 108).
