Relation of climatic factors to the amount of nitrogen in soils
1928
Jenny, H.
Analysis of soil samples coming from a wide climatic range shows that the total nitrogen content of the soil decreases in the United States from north to south in relation to temperature. The change of the nitrogen content with temperature is a negative exponential function, provided the rainfall-evaporation ratios are constant. For every 10 degrees C fall in mean annual temperature, the average nitrogen content of the soil increases two to three times. Practical aspects of the investigation, such as the maintenance and the increase of organic matter and nitrogen in the soil, are discussed. It seems to be possible to build up the nitrogen content of the soil by adding organic material in the North, because the low temperature would favor its preservation. In the South, however, it will be rather difficult if not impossible to increase permanently the nitrogen content by common green manuring practices, because the high temperature militates against nitrogen accumulation by favoring decomposition.
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