Nutrient accumulation in plough layers with respect to the protection of soils, climate and waters.

摘要

Since the 1950s, high amounts of N, P and K have been accumulated in agricultural soils of Germany due to a surplus in the balance between the amounts of nutrients applied and those removed in harvested crops. A significant part of the surplus N hasbeen incorporated into newly formed soil organic matter after deepened tillage since about 1970. Mass change calculations of total N in southern Lower Saxony reflect an N accumulation (from 1970 until 1998) of up to 2.4 t N/ha in sandy soils of livestock production farms and of about 1 t N/ha in loess soils of cash crop production farms. Particularly the extremely high amounts of N accumulated in the sandy soils have to be evaluated with respect to mineralizable fractions. This is urgently needed for an adaptation of the N fertilization recommendations. If the annual surplus N will remain at the present level, the N losses from the system will increase significantly after the reestablishment of soil organic matter equilibria around the year 2005. In spite of decreasing P and K surpluses, more than 80% of the arable soils of Lower Saxony presently show an optimum, high or even very high nutrient supply with regards to P and K. Especially in soils with a high risk of P and K leaching, plant available Pand K concentrations in the arable layers should be reduced immediately. With respect to sustainable nutrient and energy cycling, fertilizer applications should not exceed the nutrient export by field crops.