Sewage Sludge to Fertilise Durum Wheat: Effects on Crop and Soil

The vast quantities of degradable waste generated in urban areas may negatively influence the environment if improperly managed. This study examines effects on soil properties, yield and morphological performance of winter wheat (Triticum turgidum L. cv. Vitron) after applying composted and air-dried sewage sludge. The experiment was conducted on the field scale in two different farm soil plots Toledo, (central Spain) with different characteristics, especially salinity, concentration of chlorides, sulphates and pH. Three fertiliser treatments were considered: commercial fertiliser; air-dried sewage sludge and composted sewage sludge. Sewage sludge promoted better yields than the commercial fertiliser, and preserved soil physico-chemical characteristics. The sewage sludge application (air-dried and composted) to soil improved the results of the morphological characteristics of the studied wheat in relation to the commercial fertiliser. In the saline soil plot, air-dried sewage sludge improved the morphological characteristics of spikes (length, weight, number of grains per spike), but not final grain weight and, consequently, yield. These were upgraded with the composted sewage sludge. Use of sewage sludge for winter wheat production was the better studied option and proved a sustainable approach to recycle such waste on land.

Composted Sewage Sludge Enhances Soybean Production and Agronomic Performance in Naturally Infertile Soils (Cerrado Region, Brazil)

Naturally infertile soils require large amounts of mineral fertilizers to obtain the desired crop yield. In the Cerrado region of Brazil, there is a need to investigate the potential of organic fertilizers to sustainably increase crop productivity and food security. A field study was conducted over two experimental seasons to evaluate the agronomic effectiveness of composted sewage sludge (CSS) as a fertilizer for soybean cultivation in infertile tropical soils. A 4 × 2 + 2 factorial randomized complete block design was applied with the following treatments: (i) CSS: 5.0, 7.5, 10.0, and 12.5 Mg ha−1 on a wet basis applied according to two different methods: whole area (WA) or between rows (BR); (ii) comparison with two alternative treatments: a control with no CSS and mineral fertilizer application, and an area treated with conventional fertilizers only. All the treatments were compared in terms of micronutrient concentrations in surface soil and plant leaves, plant development, crop productivity, and yield. Bi- (ANOVA, correlation matrix, and polynomial regression analysis) and multivariate (PCA, principal factor analysis) statistics were applied to determine statistical differences and relationships/observed variability among the treatments. Results showed that at higher CSS-WA rates: (i) soil and leaf micronutrient concentrations increased; (ii) there was an increase in soybean yield by 12 and 20%, respectively, as compared to control and conventional fertilization; (iii) soybean yield was 67% higher than the mean soybean yields for Brazil. Research outcomes confirm the benefits of CSS application on infertile agricultural soils in the Cerrado region, representing a strong alternative source of micronutrients in the CSS with respect to conventional fertilizers.

Composted Sewage Sludge Influences the Microbiome and Persistence of Human Pathogens in Soil

Composted sewage sludge (CSS) gained attention as a potential fertilizer in agriculture. Application of CSS increases soil microbial activity and microbial biomass, however, it can also lead to increased chemical and microbiological risks. In this study, we performed microcosm experiments to assess how CSS reshapes the microbial community of diluvial sand (DS) soil. Further, we assessed the potential of CSS to increase the persistence of human pathogens in DS soil and the colonization of Chinese cabbage (Brassica rapa L. subsp. pekinensis (Lour.) Hanelt). The results revealed that CSS substantially altered the prokaryotic community composition. Moreover, addition of CSS increased the persistence of Salmonella enterica serovar Typhimurium strain 14028s and S. enterica serovar Senftenberg in DS soil. However, the enhanced persistence in soil had no impact on the colonization rate of B. rapa grown on soil inoculated with Salmonella. We detected Salmonella in leaves of 1.9% to 3.6% of plants. Addition of CSS had no impact on the plant colonization rate. The use of sewage sludge composts is an interesting option. However, safety measures should be applied in order to avoid contamination of crop plants by human pathogens.

EFFECTS OF WATER MANAGEMENT AND COMPOSTED SEWAGE SLUDGE SUBSTRATES ON THE GROWTH AND QUALITY OF CLONAL EUCALYPTUS SEEDLINGS

This study aimed to evaluate the effect of substrates made of composted sewage sludge and irrigation depths on the growth and quality of E. grandis x E. urophylla cuttings to optimize water management for each substrate. The substrates were obtained from sewage sludge composted with sugarcane bagasse or Eucalyptus bark, namely: composted sewage sludge with sugarcane bagasse (1:3 v:v); sewage sludge composted with Eucalyptus bark (1:3 v:v) and a mixture of both substrates in a volumetric proportion 2:1 (v:v). Commercial substrate composed of Sphagnum peat, vermiculite and rice husk (3:1:1 v:v: v) was used as a control. The irrigation depths tested were 11, 14 and 17 mm, applied in two daily applications. The substrates were physically and chemically characterized and height, stem diameter, shoot, root and total dry mass, Dickson quality index and root system conformation were measured to determine the growth and quality of seedlings. The substrates obtained through the composting of sewage sludge with sugarcane bagasse or Eucalyptus bark are fit for producing Eucalyptus cuttings, however, the water specificity of each substrate must be considered. Although an 11mm irrigation depth is indicted for the mixture of both substrates (2:1 v:v), a 17mm irrigation depth is needed for the sewage sludge composted with sugarcane bagasse (1:3 v:v) substrate.

Environmental impacts of landfill covering by use of industrial by-products

Since the introduction of an EC-directive on stronger demands on covering and lining oflandfills, the Swedish Parliament has adopted new legislation on waste deposition.Within a near future, a large number of landfills in Sweden have to be closed down due tothese stronger demands. Covering of landfills has traditionally been carried out with tillas covering material. The use of till causes depletion of a natural resource and in addition,high costs for transportation might arise. Alternative materials have thus been sought for.Two potential materials are sludge and ash. Their behaviour with regard to leaching is notvery well known and the focus of this work is to further investigate this issue. A pilotscale area on a closed-down part of the Gryta landfill site in Viistenis, Sweden; was partlycovered with composted sewage sludge mixed with mineral soil, partly with ash. The aimwas to find out whether the leachate from the covered areas had to be subject for furthertreatment before being discharged into the recipient. The leachate was analysed fornitrogen and phosphorus. The results from the first three months of the experimentshowed high concentrations of both nitrogen and phosphorus in the leachate, probablydue to a washing effect. It is expected that the nutrient concentrations will decrease in thefuture when the content of nutrients in the covering materials have been washed out andwhen vegetation has been established. Further investigations of the leachate will confirmthis. Based on these findings and the fact that the materials fulfil other requirements forcovering materials, it was concluded that both sludges and ashes could be regarded assuitable materials for a sustainable landfill covering. Further investigations on the subjectare however suggested.

Sewage sludge compost in zoysia grass sod production

This study evaluated whether the use of composted sewage sludge in zoysia grass sod production can partially or completely substitute fertilization based on urea. The experiment was conducted on a sod farm located in Itapetininga, São Paulo State, Brazil. The experimental design was a complete randomized block design with five replications and experimental plots of 5 m2 in a 2x6 factorial scheme. The first factor was the method of application (single or split), and the second factor was composted sewage sludge fertilization and two controls (no fertilization and a standard dose of conventional fertilizer). The conventional fertilizer (urea) dose corresponds to 300 kg N ha-1 and the sewage compost doses correspond to 100, 200, 300, and 400 kg N ha-1 . The experiment began with the liming of the total area at 60 days after the previous harvest of zoysia grass sod. Three methods were used to evaluate sod production: soil cover rate, green color intensity, and leaf analysis. At 212 days after the beginning of the experiment, the compost treatment of 30 Mg ha-1 (300 kg ha-1 of N), applied in a single dose, allowed for complete sod formation (100% soil cover rate).