The dynamics of boron when amending agricultural soil of the Mediterranean basin with biosolids: trials in leaching columns.

There is mainly a lack of boron (B) in soils with low amounts of organic matter and in acidic and sandy soils. This is especially true in irrigated land or humid regions, where leaching can occur. The results from studying the amount of available B will reveal the status of B in the soil of a specific plot of land. The experimentation was performed as a controlled study using leaching columns. A container was placed at the end of the columns to collect the infiltrated water. Three treatments were performed by applying different amounts of biosolids (T40: 40,000 kg ha-1, T80: 80,000 kg ha-1, T120: 120,000 kg ha-1), as well as a blank test or control treatment (T0). We conclude that the mobility of B in soil was generally low despite the addition of organic matter and humidity to the soil. This is an indication that there is no clear risk of aquifers being contaminated with B or plants being impacted by toxicity due to this micronutrient.

Bioavailability, mobility and leaching of phosphorus in a Mediterranean agricultural soil (ne Spain) amended with different doses of biosolids.

The precipitation of sparingly soluble calcium phosphate in calcareous soils decreases the bioavailability of macronutrients, which makes their addition by way of fertilisers necessary. Sludge resulting from treating urban wastewater does not only provide significant amounts of phosphorus, but also helps lower the pH, thus increasing its bioavailability. The loss of part of soil nutrients due to irrigation or rain can contaminate groundwater. In order to assess the movement of phosphorus, a experiment was conducted on percolation columns, to which different doses of wastes were applied. The pH decreased by as much as 0.89 units, as well as the assimilable and soluble P, in intervals of 20 cm of depth, obtaining maximum values of 254 mg P kg-1 and 1455 µg P kg-1 respectively, and the P present in the leached water collected, which did not surpass 95 µg PL-1. The intent was to learn which was the majoritarian inorganic formed crystalline phase that immobilised the movement of phosphorus through the percolation column. The results obtained by the diffraction of X-rays are not conclusive, although they point to the formation of octacalcium phosphate. The diffractograms of the studied samples have similar diffraction lines to those of apatites.

Urban areas, human health and technosols for the green deal.

Authors aim to carry out a bibliographic review as an initial approach to state of the art related to the quality of urban soils, as well as its possible link with human health. This concern arises from the need to highlight the consequences that soil could face, derived from the growth and aging of the population, as well as its predicted preference for urban settlement. Urban development may pose a challenge to the health of urban soils, due to degradative processes that it entails, such as land take, sealing, contamination or compaction. A healthy soil is the one which maintains the capacity to support ecosystem services, so it can provide numerous benefits to human health and well-being (carbon sequestration, protection against flooding, retention and immobilization of pollutants and a growth media for vegetation and food production). This article addresses threats facing urban soils, the strategies put forward by the European Union to deal with them, as well as the issues that require further attention. Greening cities could be a consensual solution, so authors analyze whether soils of cities are ready for that challenge and what resources need to maintain soil ecosystem functions. This review proposes to use made by waste Technosols for a sustainable green city. Although the use of Technosols as a type of soil is very recent, the interest of the scientific community in this field continues to grow.

Effect of composted sewage sludge application to soil on sweet pepper crop (Capsicum annuum var. annuum) grown under two exploitation regimes.

The aim of this study is to monitor the effect of the application of three increasing amounts of composted sewage sludge (3, 6 and 9 kg compost m(-2)) on the physico-chemical properties of a horticultural calcareous soil where sweet pepper plants (Capsicum annuum var. annuum) cv. California were grown. A comparative study of two different exploitation regimes was carried out; the first was an open-air field-grown plot and the second plot was kept under controlled conditions in a greenhouse. Changes in physical and chemical properties measured in soil and sweet pepper crop were recorded during crop growth in order to measure the evolution of these properties as a consequence of increasing compost applications. Organic matter, total nitrogen Kjeldahl and available phosphorus contents increased in soil after composted sewage sludge applications. The 9 kg compost m(-2) application promoted the appearance of deleterious effects on the properties of soil, such as salt accumulation, a significant increase in the electrical conductivity and an input of heavy metals (Pb>Cr>Cd). The 6 kg compost m(-2) application provided a supply of nutrients necessary to grow peppers plants under both exploitation regimes. Pepper fruit biomass production under greenhouse was almost 60% higher compared to that of the open-air plot. Lower contents of Ca and increased levels of Cu in fruit under greenhouse growing conditions compared to those of open-air grown peppers seemed to promote the occurrence of blossom-end rot, affecting more than 10% of the harvested fruits.

Effect of irrigation on the survival of total coliforms in three semiarid soils after amendment with sewage sludge.

Sewage sludges are increasingly used in soil amendment programmes, although not without risk since they contain, among other potential hazards, high concentrations of total coliform bacteria. In this paper we have studied the effect of irrigation on the survival of total coliforms in three semiarid degraded soils with different agricultural practices. Fresh sewage sludge was added at 50 g kg(-1) soil, and incubated in both the presence and absence of irrigation. The absence of irrigation led to a sharp decrease in the number of total coliforms in all soils, with the bacteria disappearing in 40 days. Irrigation produced a substantial initial increase in the number of coliforms in the three soils, although after 80 days there was none growing in any of the soils. The results showed that there were significant differences in the survival of coliform bacteria due to the presence or absence of irrigation.