CHANGES IN THE NUTRIENT POTENTIAL OF A SOIL ACCORDING TO LONG-TERM DRESSING OF FARMYARD MANURE AND MINERAL FERTILIZER

In a trial over a period of 9 years in which a crop rotation of spring cereals was fertilized with farmyard manure in comparison to mineral fertilizer the following changes took place in the soil: 1. Farmyard manuring increases the N(t) content of the top soil considerably in relation to the quantity fertilized. In the subsoil it remains largely constant. Mineral fertilization in-fluences the N(t) content to a lesser scale. 2. The C(t) is enriched only in the soil of farmyard manure plots and is dependent on the quantity used. 3. The phosphorus and potassium contents in the control plots decline considerably not only in the top soil but also in the subsoil. The values of the top soil remain nearly constant at the low fertilization rate, but not in the subsoil. The medium and high fertilization rates cause an enrichment in the top soil. The effect to the subsoil is much less pronounced. 4. The magnesium values remain constant in the control plots and the mineral fertilization plots (here not fertilized) whereas they are increased significantly by farmyard manure in both soil layers. 5. At a fertilization rate orientated to the uptake and with an adjusted balance the P values in the soil remain nearly constant. On the other hand the values for potassium increase in the soil with high K fertilization in spite of a negative balance.