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A 2-year field experiment was conducted to analyse the effects of fresh and aged biochar on soil properties, as well as herbicide effectiveness and rice-yield components in a Mediterranean environment. Six managements were used: no-tillage and sprinkler irrigation either without (NoT) or with first-year biochar application (NoTB), conventional tillage and sprinkler irrigation either without (ConvT) or with first-year biochar application (ConvTB), conventional tillage and flooding irrigation either without (ConvTF) or with first-year biochar application (ConvTFB). The measurements done in the first (2018) and second (2019) years after biochar addition were taken to determine its fresh and aged effects, respectively. The application of biochar led to an improvement of the soil properties such as increase in the soil's organic carbon content, pH, and dehydrogenase activity. It also reduced weed pressure, regardless of the management used, and sprinkler systems were found to have the greatest herbicide effectiveness, especially in ConvT and ConvTB. In terms of production, there were significant increases in yield with the application of fresh biochar, in the amended managements under tillage compared with their unamended counterparts. The greatest yields were found under ConvT and ConvTB, with mean values for both treatments of 10,770 and 11,299 kg ha−1 in the fresh and aged years, respectively. Furthermore, water productivity reached its greatest values when sprinkler was used, especially with tillage for which the application of fresh biochar increased water productivity by a factor of 1.09 relative to ConvT. Therefore, sprinkler irrigation in combination with tillage and biochar applications can be regarded as an efficient alternative to flooding irrigation in order to ensure productive viability of rice in water-stressed regions.

This paper reports the preparation and herbicidal evaluation of a small library of acylhydrazones based on the synthetic herbicide metribuzin. The hydrazone linkage easily obtained by reaction of metribuzin with aliphatic and aromatic aldehydes, masks efficiently the exocyclic amino group, thereby altering significantly H-bonding with the receptor and increasing the lipophilicity relative to the parent herbicide. The structures of all compounds, including key stereochemical issues on conformation and E/Z configuration around the CN bond were thoroughly elucidated by spectroscopic methods, and unambiguously corroborated by X-ray diffraction analysis. The herbicidal assays using an aliphatic and an aromatic acylhydrazone were performed on tomato and rapeseed plants grown in greenhouse. Our results demonstrate, regardless of rate application, that such acylhydrazone formulations do not alter the selectivity of metribuzin. Moreover, the herbicide activity was even higher in the alkyl derivative than that achieved by commercial metribuzin, thus suggesting that this substance can be applied with no need of combination with chemical coadjuvants, unlike most formulations of commercially available herbicides. Therefore, the study shows the promising effect of chemical derivatization of a common herbicide as metribuzin, to improve the herbicide activity without compromising selectivity, and allowing the farmers its use in crop protection safely and effectively.

Olive orchards cover over 10 million hectares worldwide, with production techniques undergoing significant changes in the past three decades. The traditional rainfed approach, involving minimal inputs, has given way to irrigated super-intensive systems with higher planting density, increased productivity, a greater use of fertilizers and phytopharmaceuticals, and total mechanization. Its impact on soil chemical properties remains a topic of great debate, and no definitive consensus has been reached. Our main objective was to examine the different effects of traditional olive orchards and super-intensive orchards on soil chemistry over a decade. We collected and analyzed 1500 soil samples from an irrigation perimeter in southern Portugal in 2003 and 2013. Our findings indicate that, compared to traditional olive orchards, super-intensive ones show, in a decade, a significant decrease in soil organic matter (less 22.8%—p < 0.001), namely due to the increase in mineralization caused by an increase in soil moisture content as a result of irrigation practice, and an increase in sodization (more 33.8% of Ext Na—p < 0.001) highlighting the importance of monitoring this factor for soil fertility. In comparison to other irrigated crops in the region, super-intensive olive orchards promote a significant soil acidification (from 7.12 to 6.58), whereas the pH values of the other crops increase significantly (3.3%, 13.5%, and 3.0% more in corn, tomato, and cereals, respectively). Mainly because of the decrease in organic matter levels with soil acidification and soil sodization, we can underline that hedgerow olive orchards can affect soil characteristics negatively when compared with traditional ones, and it is necessary to adopt urgent measures to counter this fact, namely sustainable agriculture practices.

The sustainable management of Mediterranean agricultural soils, characterized by salinization and low organic matter content, requires a thorough understanding of their temporal and spatial evolution. The focal point of this investigation encompasses an area of 6769 ha within the Portuguese Mediterranean basin, from which as many as 686 topsoil specimens were acquired during the periods 2001/2002 and 2011/2012 for the purpose of scrutinizing soil organic matter (SOM) content, pH measured in water, and electrical conductivity (EC). The methodology employed both classical and geostatistical techniques, and the terrestrial samples were classified in accordance with the irrigation mechanisms in use (namely, drip and sprinkler systems), subsequently juxtaposed with their counterparts in rainfed systems. Predictive maps were generated using the Ordinary Kriging algorithm for spatial interpolation. The findings demonstrate that irrigated Fluvisols displayed lower SOM content compared to rainfed soils, with sprinkler-irrigated soils experiencing a 16.1% decrease and drip-irrigated soils showing a more pronounced 26.6% decrease. Moreover, drip-irrigated soils contained 12.5% less SOM compared to sprinkler-irrigated soils. The pH levels stabilized at around 6.6 in both rainfed and irrigated soils, with no significant differences observed between the irrigation methods. Furthermore, irrigated Fluvisols exhibited higher EC values compared to rainfed soils, with both sprinkler and drip-irrigated soils showing values that were 35.2% higher. These results underscore the impact of irrigation practices on soil properties, including elevated EC values due to increased soil salt accumulation. The study highlights the necessity of considering specific irrigation systems and associated practices to ensure sustainable soil health and productivity. Adopting management approaches that account for these factors is crucial for preserving optimal soil conditions in Mediterranean agricultural systems.

Traditional rice (Oryza sativa L.) management (tillage and flooding) is unsustainable due to soil degradation and the large amount of irrigation water used, an issue which is exacerbated in the Mediterranean region. Therefore, there is a need to explore rice management strategies in order to improve water-use efficiency and ensure its sustainability. Thus, field experiments were conducted to determine the medium-term effects of different irrigation and tillage methods combined with a single compost application on water and rice productivity, as well as food safety in a semiarid Mediterranean region. The management systems evaluated were: sprinkler irrigation in combination with no-tillage (SNT), sprinkler irrigation in combination with conventional tillage (ST), which were implemented in 2015, and flooding irrigation in combination with conventional tillage (FT), and their homologues (SNT-C, ST-C, and FT-C) with single compost application in 2015. In reference to rice grain yield, the highest values were observed under ST treatment with 10 307 and 11 625 kg ha−1 in 2018 and 2019 respectively; whereas between FT and SNT there were no significant differences, with 8 140 kg ha−1 as mean value through the study. Nevertheless, sprinkler irrigation allowed saving 55% of the total amount of water applied in reference to flooding irrigation. Furthermore, the highest arsenic concentration in grains was found under FT but it decreased with compost application (FT-C) and especially with sprinkler irrigation, regardless of tillage management systems. However, sprinkler irrigation favors the cadmium uptake by plants, although this process was reduced under SNT in reference to ST, and especially under amended compost treatments. Therefore, our results suggested that a combination of sprinkler irrigation and compost application, regardless of the tillage system, could be an excellent strategy for rice management for the Mediterranean environment in terms of water and crop productivity as well as food safety.

Traditional rice (Oryza sativa L.) production by flooding is a source of greenhouse gases (GHG), especially methane. The high consumption of water, as well as the chemical and physical degradation caused by these traditional practices in rice soils, is promoting a decrease in rice production in the Mediterranean area. The aim of this study was to monitor GHG emissions and the net ecosystem carbon balance (NECB) from rice produced with sprinkler irrigation techniques and also assess the impact of olive mill waste compost (C-OW) application and tillage on GHG emissions and the NECB. A field experiment for irrigated rice production was implemented by considering four different treatments: (1) tillage (T); (2) no tillage—direct seeding techniques (DS); (3) application of C-OW followed by tillage (TC); and (4) application of C-OW followed by direct seeding (DSC). The C-OW was only applied in the first year at a dose of 80 Mg ha−1. GHG emissions were monitored over three years in these four treatments in order to estimate the direct (first year) and residual (third year) effects of such practices. The application of C-OW caused an increase of 1.85 times the emission of CO2-C in the TC-DSC compared to the T-DS in the first year. It is noteworthy that the TC treatment was the only one that maintained an emission of CO2-C that was 42% higher than T in the third year. Regardless of the treatments and year of the study, negative values for the cumulative CH4 were found, suggesting that under sprinkler irrigation, CH4 oxidation was the dominant process. A decrease in N2O emissions was observed under direct seeding relative to the tillage treatments, although without significant differences. Tillage resulted in an increase in the global warming potential (GWP) of up to 31% with respect to direct seeding management in the third year, as a consequence of the greater carbon oxidation caused by intensive tillage. DS presented a positive NECB in the accumulation of C in the soil; therefore, it provided a greater ecological benefit to the environment. Thus, under Mediterranean conditions, rice production through a sprinkler irrigation system in combination with direct seeding techniques may be a sustainable alternative for rice crops, reducing their GWP and resulting in a lower carbon footprint. However, the use of C-OW as an organic amendment could increase the GHG emissions from rice fields irrigated by sprinklers, especially under tillage conditions.

The olive oil industry produces high amounts of waste, which need to be valorized in a more sustainable way as an alternative to its traditional use as an energy source, with high associated CO2 emissions. Rice (Oryza sativa L.) is one of the most important crops for global food security; however, the traditional cropping systems under flooding lead to an important decrease of soil quality, as well as relevant emissions of greenhouse gases (GHG). The aim of this study was to assess the GHG emission from rice fields amended with composted two-phase olive mill waste (C-TPOW), in Mediterranean conditions. A field experiment was carried in rice cultivated by the traditional system, either unamended (Control) or amended with C-TPOW (Compost). GHG emissions were measured over three years following a single C-TPOW application (80 Mg ha−1 only in the first year of study), so that the results found in the first and third years correspond to its direct and residual effects, respectively. Compost decreased CO2 emissions relative to Control by 13% and 20% in the first and third year after C-TPOW application, respectively. However, in the case of CH4 and N2O, increases in the total cumulative emission were recorded in Compost relative to Control throughout the study, in agreement with the highest β-glucosidase and urease activity observed in the amended soil. The values of global warming potential (GWP) and yield-scaled GWP increased by 14% and 11%, respectively, in Compost relative to Control in the first year, but no significant differences between treatments were observed three years after application for GWP and yield-scaled GWP. Therefore, the use of C-TPOW as soil amendment in rice fields could be a good option since its impact on GHG emissions seems to decrease over time, while the benefit for soil remained clear even after 3 years.

There is a small sample of edaphic geochemistry studies over large geographic areas, especially studies that consider major reference soil groups (RSG) that evaluate both native concentrations of elements and anthropogenically contaminated soils in agricultural settings, considering the long-term effect of agricultural practices on landscape sustainability. In this study, four RSGs were analyzed for the available trace elements Ni, Cr, Cd, Pb, Cu, Mn, and Zn, including other edaphic properties from 2002 to 2012. The main objectives were to assess the range of concentrations of the selected elements in the four typical Mediterranean soils, Cambisols, Luvisols, Calcisols, and Fluvisols, with heavy anthropogenic input (HAI) and compare them to minimal anthropogenic input (MAI). For MAI, the background levels of Pb, Ni, Cd, and Cr were highest in Calcisols, differing from those of Cambisols, Luvisols, and Fluvisols (p < 0.01), Cu is highest both in Calcisols and Luvisols while Mn is higher in Cambisols and Fluvisols (p < 0.05). The background concentration of Zn was the same in all RSGs (p > 0.05). For HAI, the reference levels of Pb, Ni, Cd, Mn, and Cr were highest in the Calcisols, and Cu was high in all RSGs except Fluvisols, while Zn presented the lowest concentrations in the Luvisol RSG, with all these results considering a confidence interval of 95%. Predictive maps for the sampled elements, as well as the edaphic bioavailability, are provided. This environmental impact assessment suggests that the land use is departing from sustainable ecosystem service development and that territorial management practices, with conservation goals in mind, should be adopted.

Las corrientes marinas, fuente de energía renovable más predecible, localizan la mayor parte de su energía en altas profundidades. Para aprovechar esta energía se están desarrollando dispositivos flotantes, de tipo fondeado. La viabilidad económica de estos dispositivos requiere el abaratamiento de costos. El desarrollo de sistemas de control que permitan el cambio automático de orientación y profundidad del generador, con el fin de abaratar las maniobras de mantenimiento y aprovechar el recurso energético de forma óptima, resulta imprescindible. En este trabajo se presenta un actuador hidrostático y se realiza un modelo dinámico simple para control, de un dispositivo de dos grados de libertad, con un sistema de control de lastre. A partir de este modelo se ha desarrollado una ley de control multivariable, basada en una matriz de desacoplamiento no lineal y en la compensación de los términos de fricción y compresibilidad. Finalmente, la bondad del controlador ha sido validada mediante simulación.