Testing the Impact of the Waste Product from Biogas Plants on Plant Germination and Initial Root Growth

During biogas production, anaerobic digestion of plant material rich in nutrients results in the so-called whole digestate. The application of nutrient-rich material present in digestate could have fertilising effects, especially in intensively used agricultural soils, andin crop yields that can affect the nutrient cycle. The aim of this article is to inform about possibilities of using mixture of digestate andhaylage (use the fertilizing effect of both matters), and at the same time contribute to the improvement of agrochemical properties ofsoil. This study evaluates the effect of applying the mixture of digestate and haylage on germination and early stages of plant development. This article deals with primary test mixtures of digestate and haylage at ratios 10:1, 5:1 and 3:1 and compares the results withwhole digestate applications. Simplified statistically calculated quantities showed that all examined mixtures better fertilizing effect incomparison with the control growing media. Based on the chemical analysis of the growing medias, a growing media with mixtures ofdigestate and haylage characterizing as growing medias with a high content of nutrients and a low amount of hazardous metal wasinvestigated. The examined growing media thus met the limits for organic and commercial fertilizers. Fertilizing effects of growingmedia with mixture of digestate an haylage can also be noted on increasing the proportion of macronutrients in the soil, reducingfertilization only throughout whole digestate.

Application of Individual Digestate Forms for the Improvement of Hemp Production

In a two-year vegetation field experiment, the fertilizing effects of by-products from the agricultural biogas plant—a solid phase of digestate (SPD) and a liquid phase of digestate (LPD)—were studied and compared with mineral fertilization (NPK) on the biomass yield, content and nutrient uptake by Cannabis sativa L. plants. Furthermore, the agrochemical properties of the soil were evaluated at the end of the experiment. In all variants of the experiment, a uniform nitrogen dose of 150 kg/ha was applied. The dose of other nutrients corresponded to the fertilizer used. The biggest fertilizing effect, and therefore the greatest hemp biomass yield and nutrient uptake, was demonstrated when combining SPD and LPD fertilization in one treatment. However, the differences were statically insignificant (p ≤ 0.05). The applied amount appeared to be sufficient for the nutrition of hemp plants and was comparable to mineral fertilization. The distribution of nutrients between leaves and stems varied depending on the nutrient monitored. Analyses after the end of the experiment did not show different contents of accessible nutrients in the soil on the studied variants. The content of accessible risk elements in the soil was not affected by the application of the SPD and the LPD. The experiment showed that cannabis plants are able to achieve equivalent biomass yields (8.68 t/ha) using the combination of LPD and SPD by-products from a biogas plan compared to commercial mineral fertilizer (7.43 t/ha). Therefore, we can recommend a split application of LPD and SPD as a suitable alternative to mineral fertilization. Due to prolonged nutrient release from SPD, we can expect a smaller negative environmental impact than current fertilization practices.

AMORPHOUS SILICA OBTAINED FROM NEPHELINE RAW MATERIALS IN THE DEPHOSPHORIZATION OF MUNICIPAL WASTEWATER

Introduction. The paper addresses the importance of extracting the labile form of phosphorus from wastewater with the possibility of its further use. The advantages of sorption methods and the prospects of using amorphous silica as an ameliorant with a prolonged fertilizing effect are considered. Methods. We performed experimental modeling of phosphates extraction from model solutions and a sludge mixture from regional sewage treatment plants. Amorphous silica obtained from local nepheline raw materials in acid treatment using a patented technology was used as sorbents. Results. A sorbent based on amorphous silica with a pore diameter of 8.41 nm was obtained. Its sorption capacity exceeds 29 mgP/g in the phosphate form, which corresponds to the average level of phosphorus removal, noted for a number of sorbents used in the international practice of wastewater dephosphorization when producing unconventional ameliorants. Conclusion. For effective phosphorus removal from municipal wastewater to obtain an unconventional ameliorant with a fertilizing effect in terms of Si and P, sorbent consumption of 1 g/l is sufficient.

Efficiency of Recycled Biogas Digestates as Phosphorus Fertilizers for Maize

Despite phosphorus resources on Earth being limited, over fertilization in many agricultural situations causes significant resource consumption. Phosphorus-recycling within agricultural production can reduce global dilution into the environment and is thus essential to secure sustainable future supply. This study investigated the fertilization efficacy of phosphorus fertilizers recycled from biogas digestates in maize shoots grown under controlled greenhouse conditions, in two soils, in a pot experiment. Variables investigated were plant-available phosphorus in soil, plant biomass production, and concentration of phosphorus, calcium, and magnesium in shoots. Soils were treated with three different fertilizer fractions, separated from biogas digestates, at equivalent phosphorus concentrations, using different combinations and application techniques, isolated or in combination, and compared to triple superphosphate (TSP) as a reference. One of the fractions (P-Salt) had effects on biomass production and plant phosphorus concentration equivalent to TSP in agricultural surface soil. In the second soil (with less active soil life and nutrient content), equivalence to TSP was achieved with combinations of two recycled fractions (P-Salt and dried solids). The enhancement of the phosphorus fertilizing effect by the solids was synergistic, indicating that the solids had a soil conditioning effect. The results show that biogas digestates are a valuable source for phosphorus recycling of fractions that have equivalent or even superior fertilizing properties compared to TSP.

Evaluation of Hybrid Constructed Wetland Performance and Reuse of Treated Wastewater in Agricultural Irrigation

Agriculture is being negatively affected by the decrease in precipitation that has been observed over the last few years. Even in the Czech Republic, farmers are being urged to irrigate their fields despite the fact that sources of water for irrigation are rapidly being depleted. This problem might be partially solved via the reuse of treated wastewater in certain agricultural sectors. However, the public perception of the reuse of wastewater remains negative primarily due to unknown risks to the environment and public health. To overcome this barrier, a semi-operated irrigation field was established at Kostelec nad Ohří in the Central Bohemian region of the Czech Republic and planted with common garden crops such as tomatoes (Lycopersicon esculentum), potatoes (Solanum tuberosum) and lettuces (Lactuca sativa L.) irrigated with two different water sources, i.e., treated wastewater from a local nature-based treatment system, a hybrid constructed wetland (HCW), and local fresh water from well. The HCW was put into operation in 2017 and was reconstructed in 2018 and includes both horizontal and vertical flow beds; the trial irrigation field was added in the same year. The reconstruction of the facility significantly enhanced the removal efficiency with respect to all monitored parameters, e.g., biochemical oxygen demand (BOD5), chemical oxygen demand (COD), N–NH4+, total N and the suspended solids (TSS), except for total P. The HCW also ensured the significant removal of several observed pathogenic microorganisms (E. coli, intestinal enterococci and thermotolerant coliforms). During the 2018 and 2019 growing seasons, we observed the significantly enhanced growth of the crops irrigated with wastewater from the HCW due to the fertilizing effect. The risks associated with the contamination of crops irrigated with treated water are not negligible and it is necessary to pay sufficient attention to them, especially when introducing irrigation with wastewater into practice.

Predicting the Future Distribution of Ara rubrogenys, an Endemic Endangered Bird Species of the Andes, Taking into Account Trophic Interactions

Species distribution models (SDMs) are commonly used with climate only to predict animal distribution changes. This approach however neglects the evolution of other components of the niche, like food resource availability. SDMs are also commonly used with plants. This also suffers limitations, notably an inability to capture the fertilizing effect of the rising CO2 concentration strengthening resilience to water stress. Alternatively, process-based dynamic vegetation models (DVMs) respond to CO2 concentration. To test the impact of the plant modelling method to model plant resources of animals, we studied the distribution of a Bolivian macaw, assuming that, under future climate, DVMs produce more conservative results than SDMs. We modelled the bird with an SDM driven by climate. For the plant, we used SDMs or a DVM. Under future climates, the macaw SDM showed increased probabilities of presence over the area of distribution and connected range extensions. For plants, SDMs did not forecast overall response. By contrast, the DVM produced increases of productivity, occupancy and diversity, also towards higher altitudes. The results offered positive perspectives for the macaw, more optimistic with the DVM than with the SDMs, than initially assumed. Nevertheless, major common threats remain, challenging the short-term survival of the macaw.

Assessment of the N- and P-Fertilization Effect of Black Soldier Fly (Diptera: Stratiomyidae) By-Products on Maize

To meet the growing demand for an alternative animal protein source, the Black Soldier Fly (BSF) (Hermetia illucens) industry is expanding. Thus, the valuation of its byproducts, foremost BSF frass, is getting more economic and ecological weight. Three different residues, BSF frass, larval skins, and dead adult flies, were compared with a mineral and an organic commercial fertilizer in a pot trial with maize (Zea mays L., [Poales: Poaceae]). byproducts were applied in three nutrient-based application rates (180; 215 kg N/ha; 75 kg P2O5/ha), and plant nutrients, physiological and yield parameters were measured at harvest date. Ground flies had the highest N-fertilizing effect of all byproducts, similar to commercial mineral and organic fertilizers used as controls, whereas its proportion of the BSF production systems’ output is low. Frass as the abundant byproduct showed comparably low N-fertilization effects. Its low N availability was attributed to volatilization losses, mainly driven by high pH and ammonium contents. BSF frass as the main byproduct output is more suited as a basic fertilizer or potting substrate amendment than as a short-term organic fertilizer. Postprocessing of frass seems reasonable. For a profound assessment of frass as fertilizer, several aspects (e.g., the overall impact of postprocessing, plant strengthening and plant protection potential, effects on microbial processes) must be clarified.

Earthworms (Lumbricus terrestris L.) Mediate the Fertilizing Effect of Frass

With the forecasted dramatic growth of insect rearing in the near future, frass (insect excreta) has been increasingly considered a sustainable resource for managing plant nutrition in cropping systems and a promising alternative to conventional fertilizer. However, the impact of soil fauna on its fertilizing effect has not been investigated so far. In this study, we investigated the effect of earthworms (Lumbricus terrestris L.) on nitrogen (N), phosphorus (P), potassium (K) and calcium (Ca) uptake and crop growth in the presence of frass from mealworm (Tenebrio molitor L.). Using a pot experiment, we found that earthworms increased N, P, K and Ca concentration in barley (Hordeum vulgare L.) in the presence of frass, suggesting that earthworm activity enhances the short-term recycling of nutrients from frass. Compared to treatments with and without frass and earthworms, the specific leaf area of barley was the highest in the presence of both earthworms and frass. This confirms that earthworms and frass have a synergistic effect on soil fertility. Overall, our study shows that earthworms may improve the efficiency of organic fertilizers and argues therefore for the importance of developing sustainable agricultural practices that promote earthworm populations.