Soil organic matter of a sandy soil influenced by agronomy and climate

Abstract

Long term field experiments are being conducted at Humboldt University of Berlin (Germany) to obtain information regarding sustainable management of arable land with sandy soils. In Thyrow, a location in the south of Berlin with silty and sandy soil (85 % sand, 12 % silt, 3 % clay, 0.5 % Corg, pH 5.5) several experiments have been carried out since 1937. They include the study of the long-term effects of the agronomic factors of: crop rotation; organic fertilization; mineral fertilization and irrigation on soil and crops. The results of annual Corg measurements make it possible to describe the influence of agronomic management and climate on the development of soil organic matter (SOM). The following ranking of agronomic factors was observed from greatest to lowest influence: Organic fertilization > crop rotation > mineral N-fertilization > irrigation. Organic fertilization with Farm Yard Manure (FYM) increases the content of Organic Carbon by 53 % compared with the control. A crop rotation consisting of cereals only leads to 34 % higher carbon contents than crop rotations including cereals and maize or potatoes respectively. Mineral nitrogen fertilization increases the Corg content from between 19 to 32 % but only a minor effect of 2 to 8 % was detected with irrigation treatments. At the Nutrient Deficiency Experiment Thyrow, contents of SOM have been analysed since 1965. In general, the results show a decreasing level of SOM contents with all treatments of fertilization. Over a period of 40 years the organic carbon content lost 10 to 13 % while the average air temperature rose by 1.2 °C.