## 4 Discussion

Table 6: Leaf sugar concentrations of the olive plants among the treatments. N, 0.16% for P, and 2.99% for K). Thus, it can be concluded that SM is of approximately equal importance for macronutrient supply as goat manure. In contrast to our data, it was supported that SM is of lower importance as an N, P, and K supplier compared to goat manure [20]. The difference between our data and those of [PERSON] (1996) for SM may be attributed to different feed rations between sheep and/or to different conditions of manure fermentation and preservation [20]. The micronutrient (Fe, Mn, Zn, and Cu) content of SM (3142, 283, 81, and 18 mg kg\({}^{-1}\), respectively) (Table 1) was of similar importance to that determined for goat manure in another study [5]. [PERSON] (1996) [20] states that the different kinds of animal manure contain Fe, Mn, Zn, and Cu in amounts of 40-460, 5-90, 15-90, and 5-15 mg kg\({}^{-1}\), respectively. Based on these values, it is clear that the SM used in our experiment contained approximately seven times higher Fe concentrations and three times higher Mn concentrations compared to the relevant maximum values quoted by [PERSON] (1996). These differences in the Fe and Zn concentrations between our data and the values quoted by [PERSON] (1996) could be attributed to the different animal origins, as well as to the different feed rations and/or to different conditions of manure fermentation and preservation [20]. The zinc and copper concentrations in SM (Table 1) were, however, very close to the maximum values quoted by [PERSON] (1996). In a previous study with cow and goat manure applications in olive plants, it was found that the Fe, Mn, Zn, and Cu concentrations were approximately 2000-3000, 300-370, 78-80, and 15-17 mg kg\({}^{-1}\), respectively [5], i.e., they were all close to the micronutrient concentrations determined in the present study for SM. With regard to the influence of SM and EBLS applications on other soil properties, the clear influence of organic materials on organic matter (OM) boosting and the increase in Kjeldahl N should be distinguished. The most beneficial treatment was the combinational application of SM with EBLS, where the OM content was 5.12% (Table 2). Other researchers also found that manure applications boosted soil organic matter contents [33; 34]. Apart from the positive influence of organic amendments on soil organic matter, SM and EBLS applications also positively influenced Kjeldahl N, Olsen P, and exchangeable K (Table 2). These data are in agreement with those found by other researchers [35; 36; 37]. The main shoot length, total plant biomass, and shoot/root values were not significantly influenced by the treatments (Table 3). These data are partially in agreement with a previous comparative study between the impact of inorganic and organic fertilizers on potted olive plants, showing that among the different organic treatments, insignificant differences in plant growth were recorded. Significantly higher shoot/root and total plant biomass values were found when the olive plants were supplied with an inorganic controlled-release fertilizer [5]. In contrast, [PERSON] et al. (2021) [38], who also realized a comparative study between an organic and an inorganic fertilizer application on the growth of young potted and field-grown olive trees, found that the organic fertilizer promoted the growth of both potted and field olive trees (an increment of 22-29% of the trunk cross-sectional area), showing its biostimulant action. In the potted trees, a rapid elongation of the stem (an increment of +30% of the tree height compared to the inorganically fertilized trees) and a higher number of leaves occurred [38]. In the study of [PERSON] et al. (2021) [37], where agri-food composts were used in organically managed almond trees, it was found that sheep manure applications showed similar results with agri-food composts on yields.