The anaerobic decomposition of organic wastes might lead to the formation of organic-byproducts which can then be successfully used as organic fertilizers. This study evaluated the impact of the application of two fermented liquid organic amendments (commercial vs. farm-made) at two doses of application (optimal vs. suboptimal), compared to mineral fertilization, on lettuce growth and soil quality. To this purpose, two experiments were conducted at microcosm- and field-scale, respectively. In the microcosm experiment, organically amended soils resulted in lower lettuce yield than minerally fertilized soil but, in contrast, they enhanced microbial activity and biomass, thus leading to an improvement in soil quality. The fertilization regime (organic vs. inorganic) significantly affected soil microbial composition but did not have any significant effect on structural or functional prokaryotic diversity. In the field experiment, at the optimal dose of application, organically-amended soils resulted in comparable lettuce yield to that displayed by minerally fertilized soils. The application of organic amendments did not result in an enhanced microbial activity and biomass, compared to mineral fertilization, but led to a higher soil prokaryotic diversity. Among the organically-amended plots, the optimal application dose resulted in a higher lettuce yield and soil microbial activity and biomass, but led to a decline in soil prokaryotic diversity, compared to the suboptimal application dose. Our results indicate that commercial and farm-made fermented liquid organic amendments possess the potential to ameliorate soil quality while sustaining crop yield. Given the strong influence of other factors (e.g., type of soil, dose of application) on the effects exerted by such amendments on soil quality and fertility, we recommend that an exhaustive characterization of both the amendments and the recipient soils should be carried out prior to their application, in order to better ensure their potential beneficial effects.

中文翻译：

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商业和农场发酵的液态有机改良剂，可改善土壤质量和生菜产量。

有机废物的厌氧分解可能导致形成有机副产物，然后可以成功地将其用作有机肥料。这项研究评估了与矿物肥料相比，两种发酵液有机改良剂（商业与农场制造）的两种施用（最佳与次优）的施用与矿物施肥相比对生菜生长和土壤质量的影响。为了这个目的，分别在微观和实地规模上进行了两个实验。在微观实验中，有机改良的土壤比莴苣施肥的土壤莴苣产量低，但是相反，它们提高了微生物活性和生物量，从而改善了土壤质量。受精方式（有机vs. 无机）显着影响土壤微生物组成，但对结构或功能原核生物多样性没有任何显着影响。在田间试验中，在最佳施用剂量下，有机改良的土壤所产生的莴苣产量可与矿物施肥的土壤相比。与矿物肥料相比，施用有机改良剂不会导致微生物活性和生物量的提高，但会导致土壤原核生物多样性更高。在有机改良的地块中，与次优施用剂量相比，最佳施用剂量导致更高的生菜产量，土壤微生物活性和生物量，但导致土壤原核生物多样性下降。我们的结果表明，商业和农场生产的发酵液体有机改良剂具有改善土壤质量同时维持作物产量的潜力。考虑到其他因素（例如土壤类型，施用剂量）对此类改良剂对土壤质量和肥力的影响，我们建议对改良剂和受纳土壤均进行详尽的表征。对其应用，以更好地确保其潜在的有益效果。