Assessment of Fertility Dynamics and Nutritional Quality of Potato Tubers in a Compost-Amended Mars Regolith Simulant.

Mars exploration will foresee the design of bioregenerative life support systems (BLSSs), in which the use/recycle of in situ resources might allow the production of food crops. However, cultivation on the poorly-fertile Mars regolith will be very challenging. To pursue this goal, we grew potato (Solanum tuberosum L.) plants on the MMS-1 Mojave Mars regolith simulant, pure (R100) and mixed with green compost at 30% (R70C30), in a pot in a cold glasshouse with fertigation. For comparison purposes, we also grew plants on a fluvial sand, pure (S100) and amended with 30% of compost (S70C30), a volcanic soil (VS) and a red soil (RS). We studied the fertility dynamics in the substrates over time and the tuber nutritional quality. We investigated nutrient bioavailability and fertility indicators in the substrates and the quality of potato tubers. Plants completed the life cycle on R100 and produced scarce but nutritious tubers, despite many critical simulant properties. The compost supply enhanced the MMS-1 chemical/physical fertility and determined a higher tuber yield of better nutritional quality. This study demonstrated that a compost-amended Mars simulant could be a proper substrate to produce food crops in BLSSs, enabling it to provide similar ecosystem services of the studied terrestrial soils.

How to make the Lunar and Martian soils suitable for food production - Assessing the changes after manure addition and implications for plant growth.

The in-situ resource utilisation (ISRU), in terms of native rocky materials and astronaut wastes, is crucial in contests of soil-based space-farming. Nevertheless, extra-terrestrial soils are very different from Earth soils, lacking any form of organic carbon and associated macro and micronutrients. In this research, we aimed to study and modify two commercially available Lunar and Martian regolith simulants (LHS-1 from Exolith Lab and MMS-1 from Martian Garden) to make them an adequate medium for plant growth. Lettuce was chosen as reference crop to guide the discussion on the results obtained. To reach this main objective, we added to simulants a commercially available monogastric-based organic manure chosen as a substitute of a possible organic amendment produced onboard. The simulant/manure mixture rates were 100:0, 90:10, 70:30, 50:50; w:w. As expected, an approximately linear increase of total and bioavailable contents of macro (N, S, P, Ca, K, Mg) and micro (Fe, Mn, Cu, Zn) nutrients with increasing manure addition to simulants was observed. On the other hand, the very high pH of manure (pH, 9.02) along with its salinity (EC, 6.7 dS m-1) and sodicity (Na, 5.3 g kg-1), did not correct the already high pH of simulants (very high for LHS-1), but rather raised their soluble salt content and sodium amount on the exchange complex. In addition, an increase of toxic soluble aluminium and heavy elements (Pb, Ni, Cr, V) was observed, mainly in the strongly alkaline lunar simulant/manure mixtures. The addition of an organic source also produced a generalised improvement of water retention and hydraulic conductivity of both regolith simulants, in proportion to the percentage of manure addiction. For both situations, the best mixture ratio was 70:30. In terms of water retained, the LHS-1 mixtures benefited more than the MMS-1 ones by manure addition since water was held more in the "dry" (between -100 and -600 cm of matric potential head) than in the "humid" (between -25 and -100 cm of matric potential head) region of water retention. This would make LHS-1 mixtures more useful for cultivation of lettuce, at least in terms of physico-hydraulic properties. Nevertheless, the overall characterisation of the mixtures unveiled that MMS-1-based substrates can ensure better agronomic performances than LHS-1 ones, mainly due to lower pHs and higher nutrient availability; this divergent fertility was particularly evident at 90:10 simulant/manure rate and tend to be mitigated by increasing the levels of manure.

Can Lunar and Martian Soils Support Food Plant Production? Effects of Horse/Swine Monogastric Manure Fertilisation on Regolith Simulants Enzymatic Activity, Nutrient Bioavailability, and Lettuce Growth.

To make feasible the crewed missions to the Moon or Mars, space research is focusing on the development of bioregenerative life support systems (BLSS) designed to produce food crops based on in situ resource utilisation (ISRU), allowing to reduce terrestrial input and to recycle organic wastes. In this regard, a major question concerns the suitability of native regoliths for plant growth and how their agronomic performance is affected by additions of organic matter from crew waste. We tested plant growth substrates consisting of MMS-1 (Mars) or LHS-1 (Lunar) simulants mixed with a commercial horse/swine monogastric manure (i.e., an analogue of crew excreta and crop residues) at varying rates (100:0, 90:10, 70:30, 50:50, w/w). Specifically, we measured: (i) lettuce (Lactuca sativa L. cultivar 'Grand Rapids') growth (at 30 days in open gas exchange climate chamber with no fertilisation), plant physiology, and nutrient uptake; as well as (ii) microbial biomass C and N, enzymatic activity, and nutrient bioavailability in the simulant/manure mixtures after plant growth. We discussed mechanisms of different plant yield, architecture, and physiology as a function of chemical, physico-hydraulic, and biological properties of different substrates. A better agronomic performance, in terms of plant growth and optically measured chlorophyll content, nutrient availability, and enzymatic activity, was provided by substrates containing MMS-1, in comparison to LHS-1-based ones, despite a lower volume of readily available water (likely due to the high-frequency low-volume irrigation strategy applied in our experiment and foreseen in space settings). Other physical and chemical properties, along with a different bioavailability of essential nutrients for plants and rhizosphere biota, alkalinity, and release of promptly bioavailable Na from substrates, were identified as the factors leading to the better ranking of MMS-1 in plant above and below-ground mass and physiology. Pure Mars (MMS-1) and Lunar (LHS-1) simulants were able to sustain plant growth even in absence of fertilisation, but the amendment with the monogastric manure significantly improved above- and below-ground plant biomass; moreover, the maximum lettuce leaf production, across combinations of simulants and amendment rates, was obtained in treatments resulting in a finer root system. Increasing rates of monogastric manure stimulated the growth of microbial biomass and enzymatic activities, such as dehydrogenase and alkaline phosphomonoesterase, which, in turn, fostered nutrient bioavailability. Consequently, nutrient uptake and translocation into lettuce leaves were enhanced with manure supply, with positive outcomes in the nutritional value of edible biomass for space crews. The best crop growth response was achieved with the 70:30 simulant/manure mixture due to good availability of nutrients and water compared to low amendment rates, and better-saturated hydraulic conductivity compared to high organic matter application. A 70:30 simulant/manure mixture is also a more sustainable option than a 50:50 mixture for a BLSS developed on ISRU strategy. Matching crop growth performance and (bio)chemical, mineralogical, and physico-hydraulic characteristics of possible plant growth media for space farming allows a better understanding of the processes and dynamics occurring in the experimental substrate/plant system, potentially suitable for an extra-terrestrial BLSS.

Design of a Module for Cultivation of Tuberous Plants in Microgravity: The ESA Project "Precursor of Food Production Unit" (PFPU).

Plant cultivation systems for Bioregenerative Life-Support Systems in Space developed on Earth need to be tested in space, where reduced gravity alters the liquid and gas behavior both within the plant and between the plant and its surrounding environment, making the distribution of water and nutrients a critical issue. The ESA project "Precursor of Food Production Unit" (PFPU) aims to design a modular cultivation system for edible tuberous plants (such as potato and sweet potato) in microgravity, to be preliminary tested in ground conditions in the view of successive space application. Among the different modules of the PFPU demonstrator, the Root Module (RM) is the component physically hosting the plant and accommodating tubers and roots. This paper describes the step-by-step procedure adopted to realize the RM, including the design, the building, and the ground testing of its prototype. Specifically, the hydrological characterization of possible cultivation substrates, the set-up of the water distribution system, and the validation test of the assembled prototype in a tuber-to-tuber growing cycle of potato plants are described. Among six substrates tested, including three organic materials and three synthetic materials, cellulosic sponge was selected as the best one, based on the hydrological behavior in terms of air and water transport and water retention capacity. The water sensor WaterScout was successfully calibrated to monitor the water status in cellulosic sponge and to drive irrigation and fertigation management. The designed porous tubes-based distribution system, integrated with water sensors, was able to provide water or nutrient solution in a timely and uniform way in cellulosic sponge.

Mars Regolith Simulant Ameliorated by Compost as in situ Cultivation Substrate Improves Lettuce Growth and Nutritional Aspects.

Heavy payloads in future shuttle journeys to Mars present limiting factors, making self-sustenance essential for future colonies. Therefore, in situ resources utilization (ISRU) is the path to successful and feasible space voyages. This research frames the concept of planting leafy vegetables on Mars regolith simulant, ameliorating this substrate's fertility by the addition of organic residues produced in situ. For this purpose, two butterhead lettuce (Lactuca sativa L. var. capitata) cultivars (green and red Salanova®) were chosen to be cultivated in four different mixtures of MMS-1 Mojave Mars simulant:compost (0:100, 30:70, 70:30 and 100:0; v:v) in a phytotron open gas exchange growth chamber. The impact of compost rate on both crop performance and the nutritive value of green- and red-pigmented cultivars was assessed. The 30:70 mixture proved to be optimal in terms of crop performance, photosynthetic activity, intrinsic water use efficiency and quality traits of lettuce. In particular, red Salanova® showed the best performance in terms of these quality traits, registering 32% more phenolic content in comparison to 100% simulant. Nonetheless, the 70:30 mixture represents a more realistic scenario when taking into consideration the sustainable use of compost as a limited resource in space farming, while still accepting a slight significant decline in yield and quality in comparison to the 30:70 mixture.

Phenolic Constitution, Phytochemical and Macronutrient Content in Three Species of Microgreens as Modulated by Natural Fiber and Synthetic Substrates.

The present study examined the modulatory effects of natural fiber substrates (agave fiber, coconut fiber and peat moss) and synthetic alternatives (capillary mat and cellulose sponge) on the nutritive and phytochemical composition of select microgreens species (coriander, kohlrabi and pak choi) grown in a controlled environment. Polyphenols were analyzed by UHPLC-Q-Orbitrap-HRMS, major carotenoids by HPLC-DAD, and macro-minerals by ion chromatography. Microgreens grown on peat moss had outstanding fresh and dry yield but low dry matter content. Natural fiber substrates increased nitrate and overall macro-mineral concentrations in microgreens compared to synthetic substrates. The concentrations of chlorophylls, carotenoids and ascorbate were influenced primarily by species. On the contrary, variability in polyphenols content was wider between substrates than species. Out of twenty phenolic compounds identified, chlorogenic acid and quercetin-3-O-rutinoside were most abundant. Hydroxycinnamic acids and their derivatives accounted for 49.8% of mean phenolic content across species, flavonol glycosides for 48.4% and flavone glycosides for 1.8%. Peat moss provided optimal physicochemical conditions that enhanced microgreens growth rate and biomass production at the expense of phenolic content. In this respect, the application of controlled stress (eustress) on microgreens growing on peat moss warrants investigation as a means of enhancing phytochemical composition without substantial compromise in crop performance and production turnover. Finally, nitrate deprivation practices should be considered for microgreens grown on natural fiber substrates in order to minimize consumer exposure to nitrate.

Geo-mineralogical characterisation of Mars simulant MMS-1 and appraisal of substrate physico-chemical properties and crop performance obtained with variable green compost amendment rates.

The configuration of a biologically fertile substrate for edible plant growth during long-term manned missions to Mars constitutes one of the main challenges in space research. Mars regolith amendment with compost derived from crew and crop waste in bioregenerative life support systems (BLSS) may generate a substrate able to extend crew autonomy and long-term survival in space. In this context, the aim of our work was threefold: first, to study the geochemistry and mineralogy of Mojave Mars Simulant (MMS-1) and the physico-chemical and hydraulic properties of mixtures obtained by mixing MMS-1 and green compost at varying rates (0:100, 30:70, 70:30, 100:0; v:v); secondly, to evaluate the potential use of MMS-1 as a growing medium of two lettuce (Lactuca sativa L.) cultivars; thirdly, to assess how compost addition may impact on sustainability of space agriculture by exploiting in situ resources. MMS-1 is a coarse-textured alkaline substrate consisting mostly of plagioclase, amorphous material and secondarily of zeolite, hematite and smectites. Although it can be a source of nutrients, it lacks organic matter, nitrogen, phosphorus and sulphur, which may be supplied by compost. Both cultivars grew well on all mixtures for 19 days under fertigation. Red Salanova lettuce produced a statistically higher dry biomass, leaf number and area than Green Salanova. Leaf area and plant dry biomass were the highest on 30:70 simulant:compost mixture. Nevertheless, the 70:30 mixture was the best substrate in terms of pore-size distribution for water-plant relationship and the best compromise for plant growth and sustainable use of compost, a limited resource in BLSS. Many remaining issues warrant further investigation concerning the dynamics of compost production, standardisation of supply during space missions and representativeness of simulants to real Mars regolith.

Assessing long-term impact of land-use change on hydrological ecosystem functions in a Mediterranean upland agro-forestry catchment.

During the second half of the 20th century farming systems in hilly and mountainous areas of Mediterranean Europe were progressively abandoned and the forest cover subsequently re-expanded. This paper investigates the environmental impacts of land-use/land-cover (LULC) changes on hydrological ecosystem functions (HEFs) in the Upper Alento River Catchment (UARC) in southern Italy. We document the human-driven post-war landscape in 1955 with its maximum expansion of pasture and crops. By 1998 forest cover had doubled and cropland had roughly halved due to decades of land abandonment and reduction in human pressure. In 2015 secondary forests occupied about 70% of the catchment and orchards about 20%. The 1998 land-use scenario was implemented within the Automated Geospatial Watershed Assessment (AGWA) model which was calibrated and validated by direct water yield measurements recorded in the period 1995-2004 in the water reservoir delimited by an earth-dam located at the UARC outlet. Numerical simulations, assumed under "steady" climate conditions, offer "pseudo-realistic" scenarios that help interpret differences in water budget and sediment transport when the 1998 land-use scenario is compared to those of 1955 and 2015. With reference to funding opportunities offered by the European Union in the recent decades, this study provides some practical guidance on the impact of cropland reconversion on HEFs and on measures to mitigate soil erosion in this Mediterranean area. Viewed from the demand-side perspective, natural re-expansion of forest and afforestation reduce water yield and increase actual evapotranspiration. However, our modeling results are framed also within a supply-side approach examining the sensitivity of water yield to precipitation characteristics.

An Integrated Approach for the Environmental Characterization of a Wide Potentially Contaminated Area in Southern Italy.

This paper deals with the environmental characterization of a large and densely populated area, with a poor reputation for contamination, considering the contribution of environmental features (air, soil, soil hydraulic and groundwater) and the potential effects on human health. The use of Geographic Information System (GIS) has made possible a georeferenced inventory and, by overlaying environmental information, an operational synthesis of comprehensive environmental conditions. The cumulative effects on environmental features were evaluated, taking into account superposition effects, by means of the Spatial MultiCriteria Decision Analysis (S-MCDA). The application of the S-MCDA for converging the combination of heterogeneous factors, related to soil, land and water, deeply studied by heterogeneous groups of experts, constitutes the novelty of the paper. The results confirmed an overall higher potential of exposure to contaminants in the environment and higher mortality rates in the study area for some tumours, but hospital admissions for tumours were generally similar to the regional trend. Besides, mortality data may be strictly dependent on the poor socioeconomic conditions, quality of therapy and a lack of welfare in the area relative to the rest of Italy. Finally, as regards the possible relationship between presence of contaminants in the environment and health conditions of the population no definite conclusions can be drawn, although the present study encourages the use of the new proposed methods, that increase the possibilities for studying the combined effect of more environmental factors.