Sara Ondoño

Sustained deficit irrigation affects the colour and phytochemical characteristics of pomegranate juice

BACKGROUND No information exists on the consequences of water stress on the pomegranate (Punica granatum L.) tree in terms of the quality and health/nutritional properties of its juice. In this study the influence of two different sustained deficit irrigation treatments on the colour, antioxidant activity and total phenolic compound, total anthocyanin, punicalagin and ellagic acid contents of pomegranate juice was assessed. RESULTS Control plants were irrigated at 75% ETo (crop reference evapotranspiration) in order to ensure non-limiting soil water conditions, while others were subjected to sustained deficit irrigation at 43 and 12% ETo throughout the experimental period. Both moderate (43%) and severe (12%) water stress treatments led to pomegranate juices with a more yellowish colour, lower antioxidant activity and lower total phenolic compound, punicalagin and total anthocyanin contents than those from control plants. CONCLUSION Pomegranate juice from trees under sustained deficit irrigation was of lower quality and less healthful than that from trees without water stress. From a nutritional point of view, this means that a reduction in irrigation provides a dramatic decrease in bioactive phenolic compounds, especially anthocyanins and punicalagin, and consequently a lower visual attraction of the juice owing to the weak red colour of the fruit.

The active microbial diversity drives ecosystem multifunctionality and is physiologically related to carbon availability in Mediterranean semi-arid soils.

Biogeochemical processes and ecosystemic functions are mostly driven by soil microbial communities. However, most methods focus on evaluating the total microbial community and fail to discriminate its active fraction which is linked to soil functionality. Precisely, the activity of the microbial community is strongly limited by the availability of organic carbon (C) in soils under arid and semi‐arid climate. Here, we provide a complementary genomic and metaproteomic approach to investigate the relationships between the diversity of the total community, the active diversity and ecosystem functionality across a dissolved organic carbon (DOC) gradient in southeast Spain. DOC correlated with the ecosystem multifunctionality index composed by soil respiration, enzyme activities (urease, alkaline phosphatase and β‐glucosidase) and microbial biomass (phospholipid fatty acids, PLFA). This study highlights that the active diversity (determined by metaprotoemics) but not the diversity of the whole microbial community (evaluated by amplicon gene sequencing) is related to the availability of organic C and it is also connected to the ecosystem multifunctionality index. We reveal that DOC shapes the activities of bacterial and fungal populations in Mediterranean semi‐arid soils and determines the compartmentalization of functional niches. For instance, Rhizobales thrived at high‐DOC sites probably fuelled by metabolism of one‐C compounds. Moreover, the analysis of proteins involved in the transport and metabolism of carbohydrates revealed that Ascomycota and Basidiomycota occupied different nutritional niches. The functional mechanisms for niche specialization were not constant across the DOC gradient.

Phytochemical and quality attributes of pomegranate fruits for juice consumption as affected by ripening stage and deficit irrigation.

BACKGROUND Pomegranate (PG) is a drought resistant crop, thriving well with scarce water resources. The non-climateric character of PG remarks the importance of determining the optimum harvest time to improve quality and phytochemical properties of PG. RESULTS The influence of two different irrigation treatments on physico-chemical and phytochemical parameters of PG was assessed. Control trees (T0) were over irrigated (105% ETo). From the beginning of the second half of rapid fruit growth period to the last harvest, T1 plants were subjected to sustained deficit irrigation (33% ETo). Results indicated that T1 fruits exhibited a darker and more intense garnet colour than T0 fruits, but deficit irrigation led to a significant decrease in total fruit yield and number of total fruits per tree. T1 fruits showed similar bioactive quality than T0 fruits; however, T1 fruits advanced the optimal harvest time by about 7-8 days with respect to T0 fruits. CONCLUSIONS Late-pomegranate fruits were rich in phytochemicals and could be of great interest to the juice industry. Knowledge of these trends is important, especially to improve PG juice quality and to contribute to the sustainability of PG culture with respect to water, fertiliser and energy saving.

Differential sensitivity of total and active soil microbial communities to drought and forest management

Climate change will affect semiarid ecosystems through severe droughts that increase the competition for resources in plant and microbial communities. In these habitats, adaptations to climate change may consist of thinning-that reduces competition for resources through a decrease in tree density and the promotion of plant survival. We deciphered the functional and phylogenetic responses of the microbial community to 6 years of drought induced by rainfall exclusion and how forest management affects its resistance to drought, in a semiarid forest ecosystem dominated by Pinus halepensis Mill. A multiOMIC approach was applied to reveal novel, community-based strategies in the face of climate change. The diversity and the composition of the total and active soil microbiome were evaluated by 16S rRNA gene (bacteria) and ITS (fungal) sequencing, and by metaproteomics. The microbial biomass was analyzed by phospholipid fatty acids (PLFAs), and the microbially mediated ecosystem multifunctionality was studied by the integration of soil enzyme activities related to the cycles of C, N, and P. The microbial biomass and ecosystem multifunctionality decreased in drought-plots, as a consequence of the lower soil moisture and poorer plant development, but this decrease was more notable in unthinned plots. The structure and diversity of the total bacterial community was unaffected by drought at phylum and order level, but did so at genus level, and was influenced by seasonality. However, the total fungal community and the active microbial community were more sensitive to drought and were related to ecosystem multifunctionality. Thinning in plots without drought increased the active diversity while the total diversity was not affected. Thinning promoted the resistance of ecosystem multifunctionality to drought through changes in the active microbial community. The integration of total and active microbiome analyses avoids misinterpretations of the links between the soil microbial community and climate change.

Compost, leonardite, and zeolite impacts on soil microbial community under barley crops

There is little information about the potential effects of compost and zeolite or zeolite with leonardite as soil amendments in barley cultivation. Thus in this study, the following objectives were proposed: i) to compare the effects of the addition of compost, alone or simultaneously with zeolite, and of the addition of leonarditeenriched zeolite with those of the conventional NPK fertilization used in barley cultivation, on the soil nutritional status, microbial community structure, and enzyme activity in different stages of barley cultivation; and ii) to establish relationships between the different soil parameter trends, soil microbial community structure, and barley crop yield. In the field experiment carried out with a barley crop, the alternative fertilization treatments tested had an overall positive effect, in comparison with conventional fertilization with a mineral NPK fertilizer, when soil quality parameters, the nutritional level and yield of the barley crop were analyzed. Zeolite with leonardite increased barley yield in comparison with the compost treatments, either with zeolite or without, but had an excessive contribution to the water soluble contents of Na and N in soil. So, using environmental and agronomic criteria, the most rational action would be the use of compost in agriculture.

Chapter 14 – Impacts of Raw and Purified Pig Slurry on Carbon and Nitrogen Contents in Mediterranean Agricultural Soil

Abstract The agricultural valorization for pig slurry (PS) used in soils as an amendment and nutrient source contributes to management this residue. As a nutrient source, PS is considered potentially valuable. Conversely, the overapplication of PS in soils could lead to environmental problems such as water and soil pollution by nitrates leaching, especially in vulnerable zones. However, if PS has a sustainable use and rational application on the land, it can trigger many benefits related to soil quality improvement in dryland areas such as Mediterranean soils. Particularly, it can increase the total amount of soil organic matter, microbial biomass, and macro and micronutrients. A low-cost system as horizontal subsurface flow constructed wetlands (HSFCW) used to purify PS minimize potential pollutants, and aid to restoring soil properties. It is a sustainable environmental practice. The objectives were to study the application of raw PS and different treated PS in agricultural soil focusing on the impact of nutrients to soil, especially nitrogen, carbon, and available Zn, Cu, and P. The NO 3 − and NH 4 + contents showed a similar pattern when different treated pig slurries were applied to soils. The ratio C/N experienced any significant variation after PS application and the basal respiration of soil was reduced. The addition of PS from a hydraulic retention time of three and 7 days entailed greater Cu bioavailability in soil. As a conclusion, the addition of different stages of PS to the soil did not eject a negative effect in soil macro and micronutrient contents, especially on C and N dynamics.