Effects of sustanaible soil management on soil quality

Abstract

The declining of soil fertility due to intensive agriculture represents the main constraint to agricultural productivity. Sustainability of agriculture may be threatened by the progressive reduction of soil organic matter without adequate restoration. Appropriate soil management practices can improve soil quality by utilizing organic amendments as an alternative to mineral fertilizers for increasing soil productivity and plant growth and improve biological fertility. The use of indicators, like physical and chemical properties, as quantitative tools could allow to assess soil quality. Emphasis has been also given to biological and biochemical properties, strictly linked to soil fertility, among which soil enzyme activities and microbial biomass may provide an “early warning” of soil quality and health changes, such as the loss or the increase of organic matter. The research started with a preliminary monitoring phase based on soil sampling in the selected farms in the Plane of Sele river. The obtained results indicated a great variability among the farms. The monitoring phase allowed to evince the most affected properties by agricultural management under greenhouse. The electrical conductivity, the content of phosphorus and sodium were higher in soils under greenhouse than those of controls. The control samples, not subjected to intensive farming, generally richer in organic carbon, showed higher enzymatic activity levels as shown for arylsulphatase and -glucosidase. In conclusion a clear evidence is that the control samples always showed better values of chemical properties and higher enzymatic activities to indicate a negative effect of intensive agriculture practices on fertility of studied soils. Among all studied sites in the preliminary monitoring phase of the research two farms, having different physical-chemical soil properties, were selected. The effect of organic amendments in the medium-long term (1 year) was studied by supplying different kinds and amounts of organic matter. In particular, compost from municipal solid waste, as a source of easily degradable organic matter, and wood (scraps of poplars pruning), as a slow degradation source, were used. Organic amendments (30t/ha and 60t/ha) at compost/wood different ratios (2/1 and 10/1) were added to the chosen soils. The analysis of results shows positive effects of organic amendments on all soil properties of the two farms, but no different response by increasing the amount of amendment or changing the kind of mixture supplied to agricultural soils. Instead the nature of soil was able to affect the response to amendment treatments. In order to better understand the role of organic matter on soil quality and to know its interactions with the natural organic matter a study on humic substances of soils of the two farms under different treatments was conducted. The extracted humic fraction was analyzed by high field NMR spectroscopy, FT-IR spectroscopy and elemental analysis (HCNS). After one year from the application of organic amendments the analysis obtained from high field NMR, FT-IR and the elemental analysis indicated that an interaction of organic matter with soil components, with positive effects on soil fertility. In addition, soil samples of the first sampling were analyzed by low field Fast Field Cycling NMR and the results showed the effect of the mineral amendment is modulated by the nature and the amount of the organic carbon added to the soil.