González Cáceres, Marcela Andrea (2013) Effects of sustainable soil management on fertility of agricultural soils. [Tesi di dottorato]

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Abstract

Intensive agriculture and several anthropogenic factor led gradually to decrease soil organic matter and microbial biomass, thereby to a consequent loss of quality and fertility of soil. The sustainability of agricultural practices represents an aspect that could be not anymore negligible if environment protection and defense are the target. In the present thesis chemical and biochemical properties and humic substances characterization of agricultural soils, under greenhouse, amended with a mixture of compost from municipal solid waste enriched with poplar scraps in two different ratio and doses, were studied through a multidisciplinary approach. All parameters studied in a previous one year-experiment were followed for two years more, after yearly supply of organic amendment. This repeated treatment determined a strong improvement in most chemical and biochemical parameters. By increasing organic carbon, humic fraction, especially in the plot with higher C/N ratio and amendment dose supplied, increased to indicate the enhance of organic matter and the slow mineralization of organic mixture due to wood scraps that kept the organic matter input stable over time. The activity of the main enzymes involved in the biogeochemical cycles of nutrients markedly increased after amendments and then, after a visible decrease, remained stable over time without reaching the initial values, before the first amendment. A second study was carried out to assess the fertility of a soil under organic farming in comparison to another under conventional management, both cultivated with processing tomato (Solanum lycopersicum). Besides chemical and biological properties, investigated similarly to the previous study, soil microbiologic characterization and functional gene assess as Phytase from Bacillus sp. were performed. Organic farming favoured the enhance of soil fertility in term of organic carbon, total nitrogen, enzyme activities and in particular in microbial population. In fact soil biomass underwent an improvement of the presence and expression of functional gen Phy. The analyzed sustainable agricultural system improved the fertility of intensive arable soil and positively affected microbial biomass causing change and functional properties of microbial population.

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