The effect of supplementation of the soil-like substrate with wheat straw mineralized to different degrees on wheat productivity in closed ecosystems.

Successful incorporation of soil-like substrate (SLS) into biotechnical life support systems is often complicated by the necessity to maintain the balance between flows of mineral elements taken up from the substrate by growing plants and mineral elements added to the SLS as components of mineralized plant inedible biomass. An imbalance between these two flows can be caused by the addition of recalcitrant plant waste such as wheat straw. The purpose of this study was to determine whether the availability of essential nutrients to be taken up by the roots of the wheat plants grown on the SLS could be enhanced by supplementing the SLS with the products derived from wheat straw subjected to different levels of physicochemical mineralization in the aqueous solution of hydrogen peroxide. Different degrees of straw mineralization were achieved by using different ratios of the aqueous solution of hydrogen peroxide to straw. The study showed that supplementation of the SLS with insufficiently oxidized products of physicochemical mineralization of straw resulted in a decrease in the grain yields. The inhibitory effect of the straw subjected to physicochemical oxidation increased with a decrease in the degree to which the straw had been oxidized. Only supplementation with the straw mineralized to the highest possible degree did not inhibit plant growth and development, and the crop yield in that treatment was higher than in the other treatments.

Feasibility of incorporating all products of human waste processing into material cycling in the BTLSS.

The present study addresses the ways to increase the closure of biotechnical life support systems (BTLSS) for space applications. A promising method of organic waste processing based on "wet combustion" in hydrogen peroxide developed at the IBP SB RAS to produce fertilizers for higher plants is discussed. The method is relatively compact, energy efficient, productive, and eco-friendly. However, about 4-6 g/L of recalcitrant sediment containing such essential nutrients as Ca, Mg, P, Fe, Cu, Mn, and Zn precipitates after the initial process. These elements are unavailable to plants grown hydroponically and, thus, drop out of the cycling as dead-end products. Possible methods of dissolving that sediment have been studied. Results of experiments show that the most promising method is additional oxidation of the sediment in HNO3 + H2O2. By using the new technological process, which only involves substances synthesized inside the BTLSS material flows, more than 90% of each nutrient can be converted into the form available to plants in irrigation solutions, thus returning them into the material cycling. The results obtained in this study show the efficacy of supplementing the irrigation solutions with the mineral nutrients after sediment dissolution. Lettuce plants grown as the test object on the newly prepared irrigation solutions produced the yield that was more than twice higher than the yield produced on the nutrient solutions prepared without the sediment conversion into a soluble form. Composition of the gases emitted during this process has been analyzed. Dynamics of oxidation of the small fractions of a wax-like sediment remaining after the initial sediment dissolution in HNO3 + H2O2 in the BTLSS soil-like substrate has been studied. The entire technological scheme aimed at the full inclusion of all human wastes into the BTLSS cycling has been suggested and discussed. A process scheme of including products of human waste processing in the biotic cycle of the BTLSS is discussed in the conclusion.

[Optimization of the mineral nutrition of plants constituting the phototrophic component of closed biological life support systems].

Applicability of a new substrate for crops cultivation in bioregenerative LSSs with a high degree of mass-exchange closure was tested. Optimization of leaf cabbage nutrition by supplementing the basic substrate fabricated of plant and animal residues with ion-exchange resins proved to have a success.

Influence of high concentrations of mineral salts on production process and NaCl accumulation by Salicornia europaea plants as a constituent of the LSS phototroph link.

Use of halophytes (salt-tolerant vegetation), in a particular vegetable Salicornia europaea plants which are capable of utilizing NaCl in rather high concentrations, is one of possible means of NaCl incorporation into mass exchange of bioregenerative life support systems. In preliminary experiments it was shown that S. europaea plants, basically, could grow on urine pretreated with physicochemical processing and urease-enzyme decomposing of urea with the subsequent ammonia distillation. But at the same time inhibition of the growth process of the plants was observed. The purpose of the given work was to find out the influence of excessive quantities of some mineral elements contained in products of physicochemical processing of urine on the production process and NaCl accumulation by S. europaea plants. As the content of mineral salts in the human liquid wastes (urine) changed within certain limits, two variants of experimental solutions were examined. In the first variant, the concentration of mineral salts was equivalent to the minimum salt content in the urine and was: K - 1.5 g/l, P - 0.5 g/l, S - 0.5 g/l, Mg - 0.07 g/l, Ca - 0.2 g/l. In the second experimental variant, the content of mineral salts corresponded to the maximum salt content in urine and was the following: K - 3.0 g/l, P - 0.7 g/l, S - 1.2 g/l, Mg - 0.2 g/l, Ca - 0.97 g/l. As the control, the Tokarev nutrient solution containing nitrogen in the form of a urea, and the Knop nutrient solution with nitrogen in the nitrate form were used. N quantity in all four variants made up 177 mg/l. Air temperature was 24 degrees C, illumination was continuous. Light intensity was 690 micromoles/m2s of photosynthetically active radiation. NaCl concentration in solutions was 1%. Our researches showed that the dry aboveground biomass of an average plant of the first variant practically did not differ from the control and totaled 11 g. In the second variant, S. europaea productivity decreased and the dry aboveground biomass of an average plant totaled 8 g. The increase of K quantity in the experimental solutions resulted in an elevated content of the element in the plants. The increase of K uptake in the second experimental variant was accompanied by a 30-50% decrease of Na content in comparison with the other variants. Comparative Na content in the other variants was practically identical. N, Mg and P content in the control and experimental variants was also practically identical. The increase of S quantity in the second experimental variant also increased S uptake by the plants. But Ca quantity, accumulated in aboveground plants biomass in the experimental variants was lower than in the control. NaCl uptake by plants, depending on the concentration of mineral salts in the experimental solutions, ranged from 8 g (maximum salt content) up to 15 g (minimum salt content) on a plant growth area that totaled 0.032 m2. Thus, high concentrations of mineral salts simulating the content of mineral salts contained in urine did not result in a significant decrease of S. europaea productivity. The present work also considers the influence of higher light intensity concentrations on productivity and NaCl accumulation by S. europaea plants grown on experimental solutions with high salt content.

Effect of volatile metabolites of dill, radish and garlic on growth of bacteria.

In a model experiment plants were grown in sealed chambers on expanded clay aggregate under the luminance of 150 W/m2 PAR and the temperature of 24 degrees C. Seven bacterial strains under investigation, replicated on nutrient medium surface in Petri dishes, were grown in the atmosphere of cultivated plants. Microbial response was evaluated by the difference between colony size in experiment and in control. In control, bacteria grew in the atmosphere of clean air. To study the effects of volatile metabolites of various plant on microbial growth, the experimental data were compared with the background values defined for each individual experiment. Expanded clay aggregate, luminance, temperature, and sealed chamber (without plants) for the background were the same. Volatile metabolites from 28-days old radish plants have been reliably established to have no effect on the growth of microbes under investigation. Metabolites of 30-days old dill and 50-days old garlic have been established to have reliable bacteriostatic effect on the growth of three bacterial strains. Dill and garlic have been found to have different range of effects of volatile substances on bacterial growth. Volatile metabolites of dill and garlic differed in their effect on the sensitivity spectrum of bacteria. An attempt has been made to describe the obtained data mathematically.