Greenhouse gases emitted from agricultural soils entering the atmosphere must be reduced to decrease negative impacts on the environment. As soil management can have an influence on greenhouse gas emissions, we investigated the effects of different soil management systems and enhancer materials on CO 2 and N 2 O fluxes in a vineyard. Five treatments were investigated: (i) no-till management with no fertilizer addition as the control (C); (ii) tilled soil (shallow) with no fertilizer (T); (iii) tilled soil, no fertilizer, and biochar application (T + BC); (iv) tilled soil and manure addition (T + M); and (v) tilled soil, manure, and biochar application (T + M + BC). T treatment showed the highest overall N 2 O emission, while the lowest was observed in the case of T + M + BC, while manure and biochar addition decreased. Tillage in general increased overall CO 2 emissions in all treatments (T 26.7% and T + BC 30.0% higher CO 2 than C), while manure addition resulted in reduced soil respiration values (T + M 23.0% and T + M + BC 24.8% lower CO 2 than T). There were no strong correlations between temperatures or soil water contents and N 2 O emissions, while in terms of CO 2 emissions, weak to moderately strong connections were observed with environmental drivers.

Soil nutrient dynamics, potential biological nitrogen fixation (BNF) changes, and their relations were studied using four land use types. Further, we investigated BNF changes in the presence of biochar in soils. Soil samples were collected from arable, vineyard, grassland, and forest soils during four seasons, and analyzed for abiotic contents of total nitrogen, NH 4 + -N, NO 3 − -N, ammonium lactate (AL)-soluble K 2 O, P 2 O 5 , and soil organic carbon (SOC) concentrations. Potential N 2 fixation was measured as ethylene (C 2 H 4 ) production from acetylene (C 2 H 2 ) reduction (ARA). The study focused on the changes in ARA when different types of biochars (T600, T650, and T700) were applied to soil samples in different amounts (0, 0.5, 2.5, and 5.0% wt wt −1 ) under laboratory conditions. We found strong correlations between soil chemical parameters and ARA values, especially in the case of soil pH, total N, SOC, and P 2 O 5 contents. In the case of arable soil, the ARA measurements were up to 227 times higher compared to grassland and forest samples. Biochar application affected N 2 -fixing microbial responses among land use types, most notably decreases in arable lands and forest soils. We found that a high amount of biochar added to the soils can greatly suppress N 2 -fixing activities. Our results highlight the strong relationship between soil nutrient changes and the intensity of anthropogenic influence. Keywords Arable . BNF . ARA . Forest . Grassland . Vineyard 42 tion (Reddy et al. 1984). In agricultural croplands, such as 43 winter wheat or grapes, fertilizer application and soil tillage 44 are common practices to ensure high crop yield or better water 45 infiltration (Kanwar et al. 1988), while in the case of grassland 46 and forest soils, the anthropogenic impact is less disruptive. 47 Therefore, for a better understanding of the complexity of land 48 use systems on soil nutrient dynamics in a given area, different 49 land uses should be investigated. 50 The fixation of N 2 is a very important path to enhance the 51 soil nitrogen availability in many ecosystems. When nitrogen 52 is present in soils in limited supply, the rates of BNF can 53 increase. N 2 -fixing bacteria, called diazotrophs, can convert 54 N 2 gas to ammonia using nitrogenase enzymes, which provide 55 available nitrogen for plants (Santi et al. 2013). N 2 -fixing bac-56 teria are responsible for approximately 90 × 10 12 g biological-57 ly fixed nitrogen per year in the case of agricultural land, and 58 an additional 50 × 10 12 g biological nitrogen fix per year for 59 forest and non-agricultural lands, globally (Bezdicek and This article is part of the Topical Collection on Implications of Biochar Application to Soil Environment under Arid Conditions

Research on the use of soil enhancer materials such as biochar from soil chemical perspective still provide differing results; therefore, investigations focusing on soil-biochar-plant interactions are still necessary to constrain our understanding of complex biochar effects. The present study investigated the changes in biological nitrogen fixation rates (BNF) and overall nutrient dynamics (NO3−, NH4+, total N, K2O, and P2O5) during the growth of Capsicum annuum (pepper) in pot experiments amended with biochar made of paper fiber sludge and grain husk. Four treatments were studied with 0, 0.5%, 2.5%, and 5.0% (by weight) added biochar (BC) amount to temperate silt loam soil. Peppers were planted at 2–4 leave stages and grown for the duration of 12.5 weeks. Our results showed that total nitrogen had relatively small changes in all treatments over time compared to the dynamic changes observed in the case of inorganic nutrients. NO3−-N and NH4+-N abundances presented a continuous decrease during the course of the study after an initial increase. The pepper plant facilitated the BNF rates to triple in the control soils, while plants were in the growing phase (weeks 1–6), which further increased an additional 61% by harvesting (week 12). A high amount of biochar addition suppressed potential BNF rates of the investigated soil, indicating its potentially negative effects on soil indigenous microbial communities if added in excess. We also found a plateau in plant biomass production that after reaching an optimal (2.5%) biochar amendment in the soils, and excess biochar addition did not result in significant changes in the soils’ pH to achieve better nutrient (potassium, nitrogen, phosphorous) use or crop growth.