Cristina Lazcano

Comparison of the effectiveness of composting and vermicomposting for the biological stabilization of cattle manure

Cattle manure is produced in large quantities in industrial breeding facilities and the storage and/or spreading of this waste on land may cause contamination of the atmosphere, soil and water. The aim of the present study was to evaluate the effectiveness of the active phases of composting, vermicomposting, and also a combination of composting and vermicomposting for reducing the polluting potential and for stabilizing cattle manure in the short-term. For this, the degree of decomposition as well as the microbial activity and microbial composition of the resulting products after the active phase of composting and vermicomposting were analysed. None of the treatments significantly reduced the dissolved organic carbon and dissolved organic nitrogen contents relative to the control, and therefore more time may be required for stabilization. Nevertheless, the lowest values of microbial biomass and activity corresponded to the earthworm-worked substrates, in which fungal growth was also promoted; the combined treatment (composting + vermicomposting) was the most effective in terms of stabilizing the cattle manure. Moreover, earthworms promoted the retention of nitrogen and gradual release of P, as well as a reduction in electrical conductivity, thereby producing improved substrates for agricultural use.

Compost benefits for agriculture evaluated by life cycle assessment. A review

As compost use in agriculture increases, there is an urgent need to evaluate the specific environmental benefits and impacts as compared with other types of fertilizers and soil amendments. While the environmental impacts associated with compost production have been successfully assessed in previous studies, the assessment of the benefits of compost on plant and soil has been only partially included in few published works. In the present study, we reviewed the recent progresses made in the quantification of the positive effects associated to biowaste compost use on land by using life cycle assessment (LCA). A total of nine environmental benefits were identified in an extensive literature review and quantitative figures for each benefit were drawn and classified into short-, mid-, and long-term. The major findings are the following: (1) for nutrient supply and carbon sequestration, the review showed that both quantification and impact assessment could be performed, meaning that these two benefits should be regularly included in LCA studies. (2) For pest and disease suppression, soil workability, biodiversity, crop nutritional quality, and crop yield, although the benefits were proved, quantitative figures could not be provided, either because of lack of data or because the benefits were highly variable and dependent on specific local conditions. (3) The benefits on soil erosion and soil moisture could be quantitatively addressed, but suitable impact assessment methodologies were not available. (4) Weed suppression was not proved. Different research efforts are required for a full assessment of the benefits, apart from nutrient supply and carbon sequestration; additional impact categories—dealing with phosphorus resources, biodiversity, soil losses, and water depletion—may be needed for a comprehensive assessment of compost application. Several of the natural mechanisms identified and the LCA procedures discussed in the paper could be extensible to other organic fertilizers and compost from other feedstocks.

Vermicompost enhances germination of the maritime pine (Pinus pinaster Ait.)

We investigated the effect of vermicompost on the germination and early development of six different progenies of the maritime pine (Pinus pinaster Ait.). We compared the effects of incorporating solid vermicompost into the potting media to those of vermicompost water extract. The incorporation of vermicompost in the growing media of maritime pine increased germination by 16%, and particularly, addition of vermicompost water extract produced the best results. Plants germinated with vermicompost showed higher N content as compared to control plants, and this could have determined the faster maturation of the treated seedlings. Since the best effects on pine germination were observed after application of vermicompost water extract, other mechanisms, rather than the physical amelioration of the substrate, such as the presence of water soluble nutrients and organic compounds (i.e. humic acids and plant growth regulating substances) in the vermicompost, might be involved in the promotion of germination. We also report variation in the response of the different pine progenies to vermicompost application thereby confirming the necessity of taking into account genetic variability in order to study the potential of vermicompost and other biologically-active organic materials as a potting amendments.

Yield and fruit quality of four sweet corn hybrids (Zea mays) under conventional and integrated fertilization with vermicompost.

BACKGROUND Vermicompost has been proposed as a valuable fertilizer for sustainable agriculture. The effects of vermicompost on yield and quality of sweet corn were evaluated in this study. In two field trials, sweet corn plants were grown under (i) a conventional fertilization regime with inorganic fertilizer, and integrated fertilization regimes in which 75% of the nutrients were supplied by the inorganic fertilizer and 25% of the nutrients were supplied by either (ii) rabbit manure, or (iii) vermicompost. All three types of fertilization regime were supplied at two doses. Two pairs of nearly isogenic sweet corn hybrids homozygous for sugary1 and shrunken2 mutants were included in the trials to explore fertilizer × genotype interactions. Growth, yield and ear quality of the plants were evaluated in relation to the three fertilization regimes. RESULTS In general, the integrated regimes yielded the same productivity levels as the conventional treatment. Moreover, both vermicompost and manure produced significant increases in plant growth and marketable yield, and also affected the chemical composition and quality of the marketable ear. Nevertheless, most of the observed effects of the organic fertilizers were genotype-dependent. CONCLUSION The results confirm that the use of organic fertilizers such as vermicompost has a positive effect on crop yield and quality. Nevertheless, these effects were not general, indicating the complexity of the organic amendment-plant interactions and the importance of controlling genetic variation when studying the effects of vermicompost on plant growth.

Short-term stabilization of grape marc through earthworms

The winery industry generates vast amounts of organic waste during the various stages of wine production. Among the possible methodological alternatives available for its treatment, vermicomposting is one of the best-known processes for the biological stabilization of solid organic wastes by transforming them into safer and more stabilized materials suitable for application to soil. In this study we carried out a mesocosm experiment to evaluate the effectiveness of the active phase of vermicomposting for the stabilization of grape marc, an enriched lignocellulosic by-product obtained after the grape crushing and pressing stages in wine production. For this we analysed the chemical, biochemical and microbiological properties of the product resulting from this phase, in comparison with those in a control treatment. Earthworm activity reduced the abundance of both bacterial and fungal PLFA biomarkers. Decreases in microbial activity and in protease and cellulase activities were also attributed to the presence of earthworms. The differences in microbial communities were accompanied by a reduction in the labile C pool and the cellulose content. These results indicate that earthworms played a key role in the stabilization of the grape marc in the short-term, via its effects on organic matter decomposition and microbial biomass and activity.

Assessment of Plant Growth Promotion by Vermicompost in Different Progenies of Maritime Pine (Pinus pinaster Ait.)

The feasibility of incorporating vermicompost as a plant growth promoter into pine (Pinus pinaster Ait.) nurseries was investigated. Pines were grown in conventional peat-based nursery potting media where the peat was substituted by 0%, 2.5%, 5%, 10% and 25% solid vermicompost. In addition, in order distinguish between possible physical and biochemical mechanisms, the effects of solid vermicompost and vermicompost extracts on pine seedling growth were compared. Five different open-pollinated pine progenies were used in order to evaluate the possible genotype-dependent effects of vermicompost. All pots were provided with adequate mineral fertilization in order to avoid nutrient limitations and arranged in the greenhouse following a bifactorial randomized block design. Twenty weeks after sowing, seedlings were harvested and their aerial and root growth were measured, as well as biomass partitioning and seedling maturity. Amendment with solid vermicompost at 2.5% and 10% significantly stimulated pine seedling height, but not aerial biomass. Vermicompost also produced seedlings with greater shoot:root biomass ratios than the control. Besides, we noticed a significant inhibition of aerial and root biomass with the higher dose of solid vermicompost (25% substrate substitution). No effects, either positive or negative, were detected in plant growth due to the vermicompost extracts. All the reported results were the same for all the different progenies assayed, and therefore no genotype dependent effects were detected.

Assessing the Environmental Benefits of Compost Use-on-Land through an LCA Perspective

Due to increasing compost use in agriculture, there is an urgent need to evaluate compost benefits and impacts versus other fertilizers. Here we review the recent progress made in the quantification of positive effects associated with compost use on land using life cycle assessment (LCA), an internationally recognised environmental tool. Nine environmental benefits were identified in an extensive literature review: nutrient supply, carbon sequestration, weed pest and disease suppression, increase in crop yield, decreased soil erosion, retention of soil moisture, increased soil workability, enhanced soil biological properties and biodiversity, and gain in crop nutritional quality. Quantitative figures for each benefit were drawn from the literature and classified into short-term: less than 1 year; mid-term: less than 10 years and long-term: less than 100 years.