Soil nitrogen pool and its fractions in German apple orchards under organic vs conventional management

Agriculture is a massive production with intensive practices, like large variety of agro-chemicals, heavy machinery etc., that support food security. However, recently more and more attention is given to food safety in relation to human, environment and soil health. An alternative strategy is organic agriculture that avoids the use of synthetic chemicals and maintain the sustainable food production. But organic farming cannot completely support the worlds foods demand, so adaptation is needed to reach a sustainable productivity while protecting the environment.

Soil nitrogen (N) pool consists of inorganic and organic fractions. Inorganic and a part of labile organic N is a primary nutrient source for plants and microbes. Different nitrogen fractions play various roles in soil ecosystems and can be strongly influenced by the site management. Soil nitrogen transformations are directly relatable to plant health, thus strongly influence healthy functioning of soil ecosystem. Knowledge about the soil nitrogen pools is necessary to assess the proper and sustainable fertilization approaches under various management practices. To evaluate various N fractions, fresh soil samples were sampled (20 cm depth, row and near tree) at 8 conventional and 8 organic apple farms (Germany: states of Brandenburg, Saxsony and Saxony-Anhalt), with various age, locations and management practices. Soil samples were analyzed using CNS, Kjeldhal digestion, spectrophotometer and chloroform fumigation. The aim of this study is to compare the total and labile (particulate organic, microbial biomass and water extractable organic) N fractions in soil samples considering various site management approaches, topography and climate.