The effect of arbuscular mycorrhizal fungi on biological activity and biochemical properties of soil under vetch growing conditions in calcareous soils.

Due to soils from arid regions with high lime and low organic matter content, farmers receive low yields along with high costs of agricultural inputs, which causes them to look for a solution. In this context, Arbuscular mycorrhizal fungi (AMF) have great potential to reduce fertilizer use by mediating soil nutrient cycles. However, little is known about studies of AMF inoculum on microbial biomass carbon (C), nitrogen (N), and phosphorus (P) cycling during vetch plant vegetation in calcareous areas. In this study, changes in soil biogeochemical properties related to soil C, N, and P cycling were investigated with five different AMF inoculations under vetch (common Vetch (CV; Vicia sativa L.) and Narbonne Vetch (NV; Vicia narbonensis L.) growing conditions. For the field study, a total of five different mycorrhizae were used in the experiment with the random plots design. AMF inoculation decreased the lime content of the soil, and the highest decrease was observed in NV with Glomus (G.) intraradices + G. constrictum + G. microcarpum inoculation (24.41 %). The highest MBC content was recorded in CV vetch G. intraradices (1176.3 mg C kg-1) and the highest MBN content in NV vetch G. intraradices + G. constrictum + G. microcarpum (1356.9 mg C kg-1). CAT activity of soils was highest in CV vetch G. intraradices (31.43 %) and lowest in NV vetch G. intraradices + G. constrictum + G. microcarpum (72.88 %), urease enzyme activity decreased in all treatments except G. constrictum + Gigaspora sp. and G. mosseae inoculations in CV. The highest DHG activity was detected in GF (15.72 %) AMFs in CV and GI (21.99 %) in NV. APA activity was highest in Glomus constrictum + Gigaspora sp. (23.33 %) in CV and Glomus fasciculatum (10.08 %) in NV. In CV plots, G. intraradices + G. constrictum + G. microcarpum (91.67 %) isolates had the highest and G. intraradices community had the lowest RC% (97.33 %) in mixed mycorrhiza species, while in NV plots G. fasciculatum inoculum had the highest and G. intraradices community had the lowest RC%. This study has important implications for the application of AMF for sustainable agriculture. When the results of the study were evaluated, the most effective AMF isolates in terms of C, N, and P cycles were G. constrictum + G. fasciculatum + Gigaspora sp. in Common vetch variety, and G. intraradices in Narbonne vetch variety.

Soil Water Content Prediction Using Electrical Resistivity Tomography (ERT) in Mediterranean Tree Orchard Soils.

Water scarcity in arid and semiarid regions poses problems for agricultural systems, awakening special interest in the development of deficit irrigation strategies to improve water conservation. Toward this purpose, farmers and technicians must monitor soil water and soluble nutrient contents in real time using simple, rapid and economical techniques through time and space. Thus, this study aimed to achieve the following: (i) create a model that predicts water and soluble nutrient contents in soil profiles using electrical resistivity tomography (ERT); and (ii) apply the model to different woody crops under different irrigation regimes (full irrigation and regulated deficit irrigation (RDI)) to assess the efficiency of the model. Simple nonlinear regression analysis was carried out on water content and on different ion contents using electrical resistivity data as the dependent variable. A predictive model for soil water content was calibrated and validated with the datasets based on exponential decay of a three-parameter equation. Nonetheless, no accurate model was achieved to predict any soluble nutrient. Electrical resistivity images were replaced by soil water images after application of the predictive model for all studied crops. They showed that under RDI situations, soil profiles became drier at depth while plant roots seemed to uptake more water, contributing to reductions in soil water content by the creation of desiccation bulbs. Therefore, the use of ERT combined with application of the validated predictive model could be a sustainable strategy to monitor soil water evolution in soil profiles under irrigated fields, facilitating land irrigation management.

Use of Piptatherum miliaceum to enable the establishment success of Salvia rosmarinus in Technosols developed from pyritic tailings.

With this study we aimed to assess the effect of the prior development of Piptatherum miliaceum (Pm) in a Technosol on the establishment of Salvia rosmarinus (Sr) as a cash crop. An experimental pot was performed with two biochar (BCh) doses (BCh1 and BCh2) mixed with marble waste and pyritic tailings, with and without Pm. After 12 months of Pm growth, the pots with this species were divided into two sets: Sr alone and Sr + Pm. An agricultural soil (AGR) was used as an external control. The results showed that the growth of Sr led to similar shoot biomass to AGR. Sr + Pm reduced shoot biomass by 50%. Total soil organic and recalcitrant C, and total and recalcitrant N showed the highest values in vegetated pots, with no effect of the BCh rate. The decrease in the soil metals availability was related with increases in soil pH. BCh1Sr + Pm treatment showed a microbial community structure more similar to AGR, related to higher fungal and bacterial abundance, enzyme activities and soluble carbon. Thus, growing Sr + Pm seems a suitable strategy to improve soil properties, including microbial abundance, with low translocation of metals. Although the BCh rate did not affect plant growth or soil physicochemical properties, the lowest rate contributed to the growth of soil microorganisms better. The simultaneous growth of Sr + Pm reduced biomass production, and a source of available nutrients is also recommended. Further studies are needed to test this strategy in the field, and to ensure its suitability and a constant biomass production.

Bioaugmentaton in Technosols created in abandoned pyritic tailings can contribute to enhance soil C sequestration and plant colonization.

Creation of Technosols in combination with phytostabilization may be a sustainable strategy to minimize the environmental and human health hazards derived from mine tailings. Bioaugmentation can facilitate plant establishment and growth for efficient phytostabilization. In order to assess if bioaugmentation can increase soil quality and fertility, decrease metal(loid) mobility and accelerate plant colonization, a one-year field experiment was designed with creation of Technosols in two tailings ponds with different pH (acidic (AT) and neutral (NT)), with addition of marble waste (MaW) and two organic materials (pig manure (PM) and sewage sludge (SS), without or with inoculation of effective microorganisms (EM) at three rates. Results showed that MaW was the main factor responsible for maintaining pH ~7 in AT and ~8 in NT, decreasing salinity, and decreasing the soluble fraction of metals (70-99%). The soluble fraction of As decreased ~45% in AT, related to increases in pH up to neutrality, while increased ~90% in NT with PM due to pH>8 and higher content of organic compounds. The addition of PM and SS significantly increased soil organic C (SOC), nutrient contents and microbial biomass and activity in both tailings, being PM more effective. However, a positive priming effect was observed in NT with SS addition likely due to higher C/N ratio and lack of nutrients. There was a significant effect of EM rate on inorganic C, SOC, N, K and microbial biomass and activity, with higher values as rate increased. Vegetation richness and density directly increased with increasing EM rate. Multivariate analyses showed that the most important properties contributing to increase richness and plant density were microbial biomass and N. Thus, bioaugmentation contributed to soil C sequestration (as organic and inorganic C) and soil fertility, related to high soil microbial biomass and activity, which facilitated an effective colonization of vegetation.