No abstract

For some years now, part of society has been demanding the implementation of circular economy models and so the use of organic matter as a source of nutrients is once again taking center stage. In this scenario, the aim of this work was to implement an integrated management model for a farm and to study the influence on a celery crop of organic amendments (animal and vegetable) obtained on the farm, as opposed to inorganic fertilization. This influence was evaluated for the yield and the nutritional, organoleptic, and sanitary quality of the resulting crops. The yield and size of the marketable parts of the celery plants were greater with the inorganic treatment; however, the nutritional and sanitary quality was better in the organic treatments, while the chromatic attributes, as well as the total P and Ca, were not affected by the different fertilization treatments applied. It is therefore concluded that the organic management model is environmentally and economically sustainable.

In the present work, a sampling grid of the urban core of the city of Murcia (South East Spain) was designed in order to analyze street dust, focusing on the contents of the heavy metals Cd, Cr, Cu, Ni, Pb, and Zn and their relationships with the color of the sample, the traffic pattern, and the location where they were sampled (sidewalks, ledges, and roads). The characterization of the samples was carried out by X-ray diffraction and scanning electron microscopy, whereas the heavy metals were extracted by acid digestion and determined by inductively coupled plasma mass spectrometry. The concentration (mg/kg) in urban dust of the city of Murcia was highest for Zn (653), followed by Cu (201) > Pb (177) > Cr (117) > Ni (51) >> Cd (0.5). The color expounded statistically significant differences with regard to the heavy metals, including the pollutant load. The same pattern was found when the classification variable was the traffic intensity, except in the case of Ni. The areas with a higher risk of contamination by heavy metals in the urban dust are the ledges of narrow city center streets with moderate traffic, where Zn and Pb seem to accumulate most greatly.

The evolution of soil chemical properties over 20 years was monitored to assess the effects of the change in soil management from a rainfed to an irrigated model and the use of organic amendments and crop rotation. Intensive agriculture has been the activity that has caused most degradation and contamination of this soil. Long-term monitoring of the soil profile made it possible to assess its response to the application of sustainable agricultural techniques intended to offset these effects. Three profiles of the same soil were studied—P1 (1998), P2 (2003), P3 (2017)—to show the evolution in time and space. An incipient degradation process was detected in the first five years, verified by increases in salinity (2.3 dS m−1), exchangeable Na (0.5 g kg−1), and TN (1.3 g kg−1) in P2 in comparison with P1 (1.0, 0.2, and 1.1, respectively). There was also leaching towards the deep horizons for TN (0.4, 0.9, and 0.7 g kg−1 for P1, P2, and P3, respectively), and for assimilable elements such as P (1.1, 6.4, and 3.8), Fe (2.0, 2.1, and 5.6), Mn (0.3, 6.5, and 1.9), Zn (0.3, 0.5, and 0.9), and Cu (0.5, 0.6, and 1.3) (all mg kg−1, for P1, P2, and P3, respectively). Between 2004 and 2017, organic amendments (sheep manure) were reduced by 50%, crop rotation was intensified, and green fertilization and forage maize cultivation were included. As a result, P3 showed an improvement in comparison with P2, with decreases in EC (1.4 dS m−1), exchangeable Na (0.2 g kg−1), and TN (0.8 g kg−1). The change in soil management enhanced some soil functions (carbon sink and chemical fertility) and attenuated soil degradation.

Agriculture practices developed since the middle of the last century have led to the degradation of different resources and made it necessary to promote agricultural models that are less aggressive towards nature. Sustainable agricultural growth requires a more efficient use of land. An experimental model was designed with four treatments in the Campo de Cartagena area (SE Spain): biosolarization with manure (BSM), biosolarization with brassicas (BB), solarization (S), and a pilot test (PT). The general objective was to determine by means of rapid response indicators the changes occurring in soil properties as a consequence of the implementation of these solarization or biosolarization practices and their influence on the quality and yield of a lettuce crop. The results show that there was no significant response in the physical and biological properties of the soil. Physicochemical properties such as pHw, and electrical conductivity (ECe), as well as chemicals such as total nitrogen (TN) and the content of some macro and micronutrients, can be considered as rapid response indicators. The highest yields (Yc) and highest commercial quality (Mc) of lettuce were obtained in the BB and BSM treatments (Yc > 23,000 kg ha−1; Mc > 413 g). These treatments resulted in biological NO3− sequestration and, in the case of BB, salt immobilization (ECe: 6 dS m−1). According to these results, BSM and BB can be recommended for sustainable agriculture and even as valid methods for the recovery of soils affected by salts and NO3−. Our results should increase the feasibility of these techniques in semiarid areas.