Abstracts 01/02 back to overview Editorial MATURITY TESTING FOR COMPOST END-PRODUCT QUALITY CLASSIFICATION William F. Brinton, Eric Evans, Wayne Davis Woods End Research Laboratory - Mt Vernon ME 04352 USA 1. Abstract Two groups have composts have been evaluated for plant performance. In the first group, we prepare compost media for container plants using material of varying maturity and examine oxygen levels and other traits during growth of sorghum-sudangrass, a fast growing cultivar. In another study, we select various composts from several compost facilities and compare Dewar self-heating test results to cress performance. In container studies, only composts ranked very mature did not damage plant roots. Depletion of oxygen was moderate to severe for semi-cured and uncured composts. Compost cured for 250-days had similar performance as the control of commercial peat media. We examine Dewar test results for 119 composts and find a significant relationship to cress performance, but only over a very narrow range of self-heating. Results indicate that initial tests such as VOA, CO2-respiration and Solvita correlated well with container plant growth, but Dewar results are useful only if the rating system of I - V is ignored and instead the maximum temperature (Tmax) is used in a more critical manner. SYSTEMIC RESISTANCE INDUCED IN PLANTS AGAINST DISEASES BY COMPOSTS Harry A.J. Hoitink and Matthew S. Krause Dept. of Plant Pathology, The Ohio State University, Wooster, OH, USA 1. Abstract Composts offer the potential to reduce the severity of plant diseases. Those caused by soilborne plant pathogens such as Pythium and Phytophthora spp. are controlled most readily. Diseases caused by Rhizoctonia and other pathogens that produce sclerotia are more difficult to control. A low percentage of compost-amended potting mixes induce systemic resistance (SR) against plant diseases. Examples include Pythium root rot and anthracnose of cucumber and bacterial leaf spots caused by Pseudomonas and Xanthomonas spp. Both the severity of symptoms of the diseases and the populations of the pathogens are reduced by SR. Biocontrol agents recovered from SR-active composts in decreasing order of efficacy include Trichoderma hamatum 382, endophytic Bacillus spp., Pantoea agglomerans E278a and strains of several fluorescent Pseudomonas spp. SR-active composts activate PR proteins in plants. However, most of the elicitation does not occur until after the plant becomes invaded by a pathogen. Thus, SR-active composts prime plants to better defend themselves against disease. The significance of this subtle defense mechanism in plants and how it relates to soil organic matter quality will be discussed.. THE SUPPRESSIVE ACTIVITY OF THE COMPOSTING PROCESS ON PHYTOPATHOGEN BACTERIA AND VIRUSES F. Suarez-Estrella, M.J. LÛpez, M.A. Elorrieta, M.C. Vargas-GarcÌa, and J. Moreno Unidad de Microbiologia. Departamento de BiologÌa Aplicada. CITE II B. Universidad de AlmerÌa. La CaÒada de San Urban, Spain. 1. Abstract One of the benefits ascribed to composting is the suppression of phytopathogens in disease control. The suppression of pathogenic bacteria and viruses during composting of horticultural wastes was studied. Plants infected with either bacteria (Xanthomonas campestris pv. vesicatoria, Pseudomonas syringae pv. syringae and Erwinia carotovora subsp. carotovora) or viruses (PMMV, TSWV and MNSV) were included in compost piles. Bacteria and TSWV were suppressed after 2-3 days composting. MNSV viral antigens were detected afterwards but infectivity tests were negative. PMMV was the most resistant pathogen since complete suppression at semi-pilot scale composting was achieved after 70 days, a period in which temperatures of 65-70†C were reached. This time was shortened in industrial scale composting (21 days). According to results obtained, the composting process was demonstrated to be effective for plant pathogen biocontrol. Many factors seem to be involved in pathogen survival during composting, temperature being the main factor, especially in the case of PMMV. RESEARCH AND TECHNOLOGIC DEVELOPMENT OF COMPOSTING PROCESSES AND ITS APPLICATION IN THE AGRICULTURE AND FORESTRY SECTORS Alvarez J., Del Campo A., Sancho F. Empresa de Gestión Medioambiental S.A., Spain. 1. Abstract Three types of compost were prepared using sewage sludge, the organic fraction of municipal solid waste and yard trimming biomass in different volume ratios. These composts were employed in trials with several agronomic and forestry plants and in forest nurseries. In the case of agronomic plants, compost increased significantly the yield of tomato (+40% of the yield obtained with inorganic fertiliser), strawberry (+17%) and cotton (+25%). Compost treatments also increased the vitamin C content of tomatoes and strawberries. In the case of forestry plants two groups of trials were carried out. Poplar and eucalyptus were included in the first group. In this group, most compost treatments increased significantly the plant height: up to 25% (with respect to inorganic fertiliser treatment) or 39% (with respect to blank, without fertiliser treatment) in eucalyptus. Holm oak, cork tree, carob tree, wild olive and pinion pine were tested in a second group to try reforestation. These results were more heterogeneous, but. in some trials compost incremented plant survival up to 163 % and the plant height up to 156 % (with respect to blank). In the forest nurseries trials, composts were mixed with peat. In this case, compost favoured carob tree development and had a bioremediation effect. NITROGEN MINERALIZATION FOR ASSESSING THE CORRECT AGRICULTURAL USE OF MSW COMPOST F. Madrid, R. LÛpez, F. Cabrera, J.M. Murillo Instituto de Recursos Naturales y AgrobiologÌa de Sevilla. CSIC., Sevilla, Spain. 1. Abstract The nutrient dynamics after compost application to soil are important, especially when compost is going to be used for fertilization purposes. Mineralization of organic N (usually the main N form in composts) to NO3--N and NH4+-N, available N forms for crops, shows the potential availability of this macronutrient and helps to regulate the mineral fertilization. In this work, N mineralization of a Municipal Solid Waste Compost (MSWC) blended with two soils of different textures (sandy and clay) and the emergence of ryegrass plants treated with different N fertilizers are described. Compost-soil samples showed initially a strong immobilization of the mineral N present in the blends. Only after 12 weeks was positive mineralization observed in both soils, although it was more intense in the case of the sandy soil. Net compost mineralization (subtracting mineralization of Control treatments with clay (S1) and sandy soil (S2)) was also calculated. In the compost-clay soil blend (S1C), net compost mineralization was negative during all the incubation period (36 weeks), and it had a lower NO3--N concentration than that of the control (S1). In contrast, in the compost-sandy soil blend (S2C), net compost mineralization was positive after the 19th week of incubation, due to the intense mineralization observed after the 12th week. Ryegrass plants treated with different N sources (MSWC, Mineral Fertilizer 15-15-15 N-P-K (MF), Urea (U), MSWC+MF, MSWC+U and a Control without applying N) showed at the initial emergence stages, differences in biomass and N-content related to the N immobilization observed in the soils treated with MSWC. It may be concluded that these composts must be applied to soils three months before sowing or before the time that a crop needs a continuous supply of N. Compost must be amended with mineral N fertilization to avoid the risk of 'N rob' for the crops. LOAMY SOILS UNDER EROSION RISK: INTEREST OF THE COMPOST AS A SOURCE OF ORGANIC MATTER TO RESTORE AND MAINTAIN PHYSICAL PROPERTIES OF FRENCH SOILS Le Villio Maelenn, Arrouays Dominique, Deslais William, Daroussin JoÎl, Le Bissonnais Yves, Clergeot Dominique1 1. CReeD, Zone Portuaire de LimayLimay, France 2. UnitÈ Infosol, INRA OrlÈans, , Ardon, France 3. UnitÈ de Science du Sol, INRA Ardon, France 1. Abstract Manure and compost remain the most important sources of organic amendment. The latter, however, is poorly developed in France. To ensure its development, it is important to determine when organic matter really presents an interest for French soils. For loamy soils, a decrease in soil organic matter content bellow a threshold value of 2 - 3 % is one of the main controlling factors of the soil's physical degradations like crusting and erosion. This is an increasing problem in France where an estimated 5 millions hectares are suffering from significant erosion. Two solutions can be proposed for this problem: - reducing the losses of organic matter due to mineralisation by reducing the frequency and the depth of ploughing; - increasing the input of organic matter by providing exogenous organic matter. This study sought to estimate if the present production of manure would be sufficient to restore and maintain the organic matter contents of loamy soils under significant erosion risk or if the addition of compost would be necessary. And if the latter case prevailed, which amounts of compost would be necessary. These estimates were made for threshold values ranging from 1 to 1.5 % of organic carbon. Results show local deficiencies of organic amendments in a number of French regions : Picardie, Aquitaine, Ile-de-France, Nord-Pas-de-Calais and Midi-PyrÈnÈes. The sensitivity analysis shows that the reliability of predictions is highly dependant from the target threshold value.