News Release

MADISON, WI, March 3, 2008 -- Losses of soil organic matter resulting from intensive agriculture practices are a critical problem in most European cultivated soils. The climatic conditions also increase organic matter oxidation in the Mediterranean area. Thus, organic management is turning into one of the more dynamic productive patterns of the European Union. Spain has a progressive increment of hectares dedicated to organic management from 4,235 hectares in 1991 to 926,390 hectares in 2006. Among the different regions of Spain, Andalusia presents the greatest increase of hectares turned into organic management (57%).

The understanding of soil biological processes is of great relevance to assess soil quality. Soil biological and biochemical properties (microbial biomass and enzymatic activity) are closely linked with soil fertility. Therefore, a study of the soil microbial biomass and its activity may be very useful to evaluate the effects of organic management on soil, as this management relies on an organic input of residues, which are broken down by microorganisms. There are few studies that deal with the conversion period to organic farming on status of soil biological activity.

A scientist at Andalusia Agrarian Training and Research Institute (IFAPA) has investigated the effect of the conversion to organic farming on chemical and biochemical properties of a loamy soil (Xerofluvent), located in the Guadalquivir River Valley in southwest Spain, along a succession of five crops cycles during a three-year period in a study funded by the European Commission, the Spanish Science and Technology Ministry, and the Andalusia Government. Specifically, in this study she measured the quantity and activity of the microbial biomass through determination of microbial biomass carbon and nitrogen, soil respiration and enzymatic activities (dehydrogenase, protease, glucosidase, alkaline phosphatase). Results from the study were published in the January-February 2008 issue of Agronomy Journal.

The study shows that the incorporation of organic matter and crop succession improves the quantity and quality or organic matter. This fact is especially important in Mediterranean soils that are considered poor from a chemical point of view due to its low organic matter content. Also it was observed that soils under organic fertilization show greater microbial biomass and decomposition activity than soils under inorganic fertilization, thus translating to an increase in available substrates for microorganisms and plants.

Sebastiana Melero who conducted the study, comments, “The development of a sustainable and compatible agriculture with environment, such as organic farming, helps to improve soil fertility and diminish soil-water-crop contamination.”