Effect of organic amendements on the evolution of soil organic matter in soils stressed by intensive agricultural practices

Losses of soil organic carbon often occur because of intensive agricultural practices that lead to removal of organic carbon following harvest production and to insufficient inputs. Organic amendments can be a very appropriate matrix for enhancing organic carbon content in very stressed agricultural soils. In general, they, enhancing soil organic matter, play an important role in environmental matrices due, for example, to their capacity in retaining water, in interacting with organic and inorganic pollutants, and in enhancing nutrient availability to plants. For this reason, the understanding of the mechanisms with which organic amendments interact with other chemicals in the environment is of paramount importance. The attention was focused on farms near Sele river (Campania region, Italy), an area characterized by intensive agriculture. Two farms, with contrasting geopedologic properties (clay vs. sandy), were selected in order to study the effect of different doses of organic amendments containing compost from municipal solid wastes and wood-wastes (scraps of poplars pruning), at different ratio.. The organic fractions were extracted from soil, after one and twelve months from amendment, and were analysed in order to understand their elemental composition and properties by FT-IR, CPMAS 13C NMR spectroscopy and FFC-NMR relaxometry. Results showed an important role of soil geopedologic characteristics and experimental time in the evolution of humic acids. In fact, in less aerobic conditions, such occur in a clay soil, the organic matter was more stable, rich in carbonyl groups belonging to aldehydes and ketones, whereas more aerobic conditions, such occur in a sandy soil, the organic matter had undergone a faster degradation, due to due to oxidative conditions and more intensive microbial activity.