Agricultural systems are facing the negative impacts of erosion and water scarcity, directly impacting the hydro-mechanical behavior of soil aggregation. Several technologies have been proposed to reduce hydro-mechanical soil-related problems in agriculture. Biopolymer-based hydrogels have been reported to be a great tool to tackle these problems in soils. In this study, we investigated the hydro-mechanical behavior of different soils media treated with Ca-bacterial alginate hydrogel. We used an unconfined uniaxial compression test, aggregate stability test and hydraulic conductivity measurements to investigate the mechanical and hydraulic behavior of treated soils media. Our results from unconfined uniaxial compression test showed that yield stress (i.e., strength) increased in treated soils with higher kaolinite and water content (i.e., HCM3), compared with untreated coarse quartz sand (i.e., CM1). Furthermore, we found that temperature is an important factor in the gelation capacity of our hydrogel. At room temperature, HCM3 displayed the higher aggregate stability, almost 5.5-fold compared with treated coarse quartz sand (HCM1), while this differential response was not sustained at warm temperature. In general, the addition of different quantities of kaolinite decreased the saturated hydraulic conductivity for all treatments. Finally, bright field microscopy imaging represents the soil media matrix between sand and clay particles with Ca-bacterial alginate hydrogel that modify the hydro-mechanical behavior of different soils media. The results of this study could be helpful for the soil-related problems in agriculture facing the negative effects of climate change.

Climate change is generating severe changes in the physical behavior of soils (i.e., soil structure, mechanical resistance, and water conductivity), causing negative impacts on different agricultural systems and, therefore, threatening food security. To cope with this situation, hydrogels based on biopolymers have been proposed to modify the mechanical and hydraulic behavior of complex porous materials such as soils, yet most of them are nonsoluble, making their application at field level laborious. In this study, we investigated the effect of a water‐soluble hydrogel based on bacterial alginate on the mechanical and hydraulic behavior of coarse quartz sand. The results from unconfined uniaxial compression test showed that the strength of the sand treated with hydrogel increased by 94.5%, whereas hydraulic conductivity decreased 33%. Interestingly, we observed that bacterial alginate and hydrogel shifted the mechanics of the fluid phase toward a Darcy regime. The aggregate stability tests showed that coarse quartz sand treated with hydrogel displays larger mean weight diameter, reaching 1.5 mm compared with 0.12 mm of the control (i.e., coarse quartz sand). Finally, transmission light microscopy imaging of the hydrogel treatment revealed a new three‐dimensional matrix between the quartz sand particles, changing the microaggregates and macroaggregates and providing a modified structure of the sand material. Our findings suggest that the use of the water‐soluble hydrogel improves the mechanical and hydraulic behavior of coarse quartz sand, allowing better soil conservation against climate change‐related phenomena, and is also potentially applicable in agricultural systems facing water scarcity.

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Avocados (Persea americana Mill.) are one of the crops with the highest water footprints in Chile and the production is at risk due to severe and frequent droughts. The current production is mostly based on sexually (seed) propagated rootstocks, while clonally propagated rootstocks are on the rise. In a recent study, we found differences in aerial, root growth and water use efficiency between trees grown on these two different rootstocks under controlled continuous fertigation and environmental conditions. In this study, we further describe possible mechanisms which drive the differences. Avocado cv. “Hass” grafted on “Dusa” (D, clonally propagated) and “Mexicola” (M, sexually propagated) rootstocks and different root segments (3, 5 and 8 cm from root tip) were investigated using a combination of hydraulic measurements and polar metabolite (GC-MS) techniques. The results show significant differences in root hydraulic properties, indicating that “Mexicola” fine roots have higher water uptake capacity. The polar metabolites analysis revealed 13 compounds significantly different between rootstocks while nine were found significantly different among root segments. Principal component analysis (PCA) revealed differences between rootstocks and root segments. The data presented here highlight the importance of considering key physiological knowledge in avocado rootstocks breeding programs to be better prepared for future challenging environmental conditions.

Succulent plants possess traits that allow them to complete physiological functions under extreme environments and root are at the frontline of the stress: the drying soil. Previous works in succulent plants have reported the extraordinary reversible mechanism of root shrinkage that disconnects plants from drying soils, reestablishing the hydraulic connection when water availability is restored. Yet, this rectifier-like mechanism would require complex biomechanical and hydraulic control at organ, tissue, and cell level. In here we evaluated the changes in hydraulic and mechanical behavior of Opuntia fine roots under extreme drought stress. Using a combination of techniques, we found that fine roots get more elastic as drought stress gets more extreme, allowing cells to modify their shape while preventing permanent damage. Furthermore, we found abrupt decreases in Lpr, that coincided with increased root shrinkage, suberin deposition and structural damage inside the endodermis via lacunae formation and possibly cell wall folding. Our data suggest that, in drought stressed succulent plants, the biomechanics of organs, tissues, and possibly cell walls are deeply coupled with belowground hydraulics, highlighting the need to continue working on deciphering the physiological mechanism that governs the interplay between mechanics and hydraulics at cell level in fine roots during drought.