Utilization of municipal organic wastes in agriculture: where do we stand,where will we go?

Generation of organic waste is increasing worldwide and strategies for its environmentally sound use must be developed and optimized. Regulations in European countries and the USA differ largely with respect to requirements of organic waste quality and the quantities of pollutants which can be added to the soil. Research has shown beneficial effects regarding the improvement of soil fertility. Enrichment of total metals in soil was attributed to long‐term sludge application but the effect on bioavailability of metals must be further clarified. A number of organic pollutants, such as hydrophobic persistent organic contaminants and surfactants, are known to accumulate in organic wastes. However, the former interact strongly with organic matter in the sludge‐soil‐plant system and systemic plant uptake is generally assumed to be minimal. Surfactants may cause adverse environmental impacts when they enter sewage systems in high loads and accumulate in sludge. Surfactants and some of their metabolites are not readily biodegraded in non‐aerated environments. Due to their toxicity and estrogenic activity, of nonylphenol for example, more research is needed to optimize analytical techniques and to trace their behavior in soil. Some options to cope with the risks of huge amounts of organic waste and also some benefits are presented: (1) further limitation of standards for pollutants and reduced application rates; (2) improved treatment of sewage sludge to reduce the total and bioavailable portions of both heavy metals and organic pollutants; (3) adaptation of waste application rates to soil properties such as sorption capacity for pollutants; (4) harmonization of analytical protocols for organic contaminants, i.e. surfactants and metabolites, enabling a more thorough monitoring of the wastes which are to be applied onto soils.     

Saline water and MSW compost: Effects on yield of maize crop and soil responses

A field experiment was carried out in Southern Italy from 2007 to 2010 adopting a two-year rotation of tomato and maize. In this paper, the results of maize cultivation were reported, with the aim to investigate the effects of different water qualities and fertilizers on yield and soil properties. The following treatments were compared: mineral nitrogen (N) fertilizer and irrigation with fresh water (FWF); mineral N fertilizer and irrigation with saline water (SWF); Municipal Solid Waste (MSW) compost and irrigation with fresh water (FWC); MSW compost and irrigation with saline water (SWC). These treatments were compared with an unfertilized control and irrigation with fresh-water (FW0) and an unfertilized control and irrigation with saline water (SW0). At harvest, yield, grain moisture content, dry matter, grain protein, starch, fat content and soil characteristics were determined. The treatments with compost increased the average grain yield of the 11% compared to mineral fertilizer treatments. Furthermore, the grain yield in SWC increased of the 19% respect to average of SWF and SW0, indicating that MSW compost applied as amendment mitigated the adversely effects of saline water. Compost application significantly increased the Total Organic Carbon (TOC). In particular, the FWC and SWC treatments showed an average increase of the 25% compared to the mean TOC value of FWF and SWF. Moreover, at the end of the experiment, electrical conductivity decreased in SWC treatment respect to the SWF (?21%).     

Analysis of total inositol phosphates in municipal solid waste compost-treated soils by two extraction methods

 Humic substances are the most dynamic component of agricultural soils. In this study, humic substances were extracted from soils based on standard acid/base solubility and by gel filtration using Sephadex G25. Organic P is a component of humic substances, and inositol phosphates are considered to have high prominence in organic P. The objectives of the study were to determine the effects of municipal solid waste (MSW) compost on the amount of inositol phosphates (IP) present in soils, and compare methods of extracting humic substances from soils. Total IP (IP_T) in soil extracts was determined following separation using a AG-1× 8 anion exchange resin, acid digestion and ICAP analysis for P. The percentage of IP (%IP) of the total P in the soil was also determined by colorimetric analysis. The soils were part of an experiment to study the effects of three rates of MSW compost and fertilizers on three crops grown in a Pugwash sandy loam (Humo-Ferric Podzol). The data were compared using ANOVA atP≤0.05; extraction methods, fractions [humic/fulvic, high/low molecular (MW)], and five treatments (three different rates of compost, fertilizer, and untreated soil) were compared. The gel filtration method extracted significantly more IP_T and %IP than the solubility method. In the solubility method, humic and fulvic acids contained the same amounts of IP_T and %IP, while the high MW fraction always contained more IP_T and %IP than the low MW fraction in the gel filtration method. Fulvic acids and the low MW fraction contained similar amounts of IP_T and %IP. There were differences in %IP between compost-treated soils and the non-compost-treated soils, although there were no differences in IP_T due to rate of compost addition. Received: 20 October 1999     

Distribution of total and extractable forms of iron,manganese, and aluminum in development of rice soils of saga polder lands

The distribution of pedogenic oxides of Fe, Mn, and Al was described for rice soils of Saga polder lands and its relationship to soil development with time was investigated. The distribution of Mn largely parallelled that of Fe and in response to the soil development their accumulation occurred in the B horizons of the profiles. Manganese was the clement most susceptible to downward movement, which lad to a pronounced lowering of extractable Mn content in the surface horizons in well-developed soil morphology. By contrast, this is not the case for Al which, in general, had little change in extractable Al and a slight increase in total Al with depth as the time increased. Apparently the distribution of Mn was largely governed by the extent of reduction processes, whereas in the Al distribution clay migration may be a principal controlling factor. The distribution of Fe may be due chiefly to the reduction processes, with some contribution from the clay migration.     

Incorporation of heavy metals by the mud snail,Cipangopaludina chinensis malleata Reeve,in submerged paddy soil treated with composted sewage sludge

Summary The biomass of newborn snails was higher in paddy soil without rice plants than in the soil with rice plants. There was an inverse correlation between shell width and concentratins of Zn and Cu in snail flesh. The Zn and Cu concentrations in snail flesh were extremely high compared with those in the paddy soil surrounding the snails, possibly because snails ingest sludge, one of the main components of the composts. These results suggest that this type of snail may be used to eliminate Zn and Cu from paddy soil when composted sewage sludge has been applied.