Investigator: Mohsen Jalali, Department of Soil Science, College of Agriculture, Bu-Ali Sina University, Hamadan, Iran
Objectives: To investigate the effect of time and organic residue addition on P availability in some calcareous soils. The use of organic residue is appropriate in maintaining long-term phosphorus (P) requirement of crops. Five plant residues and two manures in a wide range of C/N ratios were added to the soil samples at rates of 20 g kg-1 soil. The samples were incubated for 2, 72, 336, 672, 1440, and 2160 hours at constant temperature and moisture. Extractable phosphorus (Olsen-P) was determined after the incubation. There were decreases in the Olsen-P in all five amended soils during 2160 hours of incubation. The power model was found to be suitable to describe P transformation rates from amended soils. The constant b in the power model (mg kg-1 min-1) of P for amended soils was defined as transformation rate were in the order (average of five soils) vegetables waste > sheep manure > potato > poultry manure > sunflower > rape > weeds residues. There were significant correlation between C/P in residues and parameters a and parameter b. There were significant correlation between clay content and calcium carbonate and transformation rate of P in soils. The model parameters of P are suitable to estimate the P-fertilizer effect of organic residues.
Characterization and evaluation of compost utilized as ornamental plant substrate
Investigators: I. Estévez-Schwarz, S. Seoane, A. Núñez, Dep. Edafoloxía e Química Agrícola; M.E. López-Mosquera, Dep. Produción Vexetal, Escola Politécnica Superior, Campus Universitario, Universidad de Santiago de Compostela
Objectives: To determine the physical and chemical characteristics of two types of compost obtained in spring and autumn from green waste, sewage sludge and biomass combustion ash, and to evaluate the suitability of the composts as substrates for growing ornamental plants. Two composts produced at different times of the year from garden waste, sewage sludge and wood ash were evaluated for use as ornamental plant substrates. The maturity and lack of phytotoxicity of both composts, as well as the absence of E. coli were first confirmed by use of laboratory procedures and rapid test kits. A greenhouse experiment was then carried out with two ornamental species, Petunia sp. and Tagetes sp., to evaluate the suitability of the composts as plant substrates. The performance of the composts as well as mixtures of each with 25, 50 and 75% acid peat moss was compared with that of a commercial universal substrate. Addition of the peat to the composts improved some of the physical and chemical properties. However, the results of the pot experiments indicated that under the experimental conditions used, the compost produced from green waste was suitable for use as a plant substrate, without the need for the addition of other components; this appears a good way of utilizing the type of urban waste considered in the study.
Inhibitory effects of organic acids on bacteria growth during food waste composting
Investigators: Hui Yu, Guo H. Huang, Xiao D. Zhang, Environmental Systems Engineering Program, Faculty of Engineering, University of Regina, Regina, SK, Canada; Yu Li, Center of Energy and Environmental Research, North China Electric Power University, Beijing, China Objectives: To determine effects of organic acids on bacteria growth during food waste composting. During the process of food waste composting, organic acids, such as acetic and lactic acids, are products of microbial breakdown of easily degradable substrates. These organic acids could inhibit microbial activities and sequentially reduce decomposition. Experimental results indicate that there are significant relationships among pH, organic-acid concentrations and microbial activities. In order to systematically investigate inhibitory effects of four organic acids on composting bacteria, multivariate experimental designs were implemented in pH decreasing (day 5) and increasing (day 9) phases during the initial stage of composting. Butyric and propionic acids had significant inhibitory effects on the growth of thermophilic bacteria on day 5; The inhibitory effects of organic acids on composting bacteria became significantly milder on day 9, and all of organic acid and their interactions showed insignificant inhibitory effects. The effects of different pH control amendments on the mitigation of microbial inhibition were also preliminarily examined. The addition of NaAc resulted in the largest population of thermophilic bacteria.
Optimization of farm vermicomposting technology
Investigators: A. Hanc, Department of Agro-Environmental Chemistry and Plant Nutrition, Czech University of Life Sciences, Prague, Czech Republic; P. Pliva, Research Institute of Agricultural Engineering, Prague, Czech Republic
Objectives: Tto find optimal portion of feedstocks in term of vermicomposting process. The research will be focused on problematical wastes (especially biogas digestate, food waste and sewage sludge) with addition of straw and green waste; to verify an effect of thermophilic precomposting on vermicomposting; to find technically effective solution for transfer of heat from thermophilic stage of composting to vermicomposting; to design and optimize vermireactor for institutional use; to find influence of various types of vermicomposts on agrochemical parameters of soils yields and quality of products. The experiments will be accomplished in small and bigger containers in special laboratory room with controlled temperature and moisture. The field and operational experiments will follow. The project started in June 2009 and will be finished in 2013.