Effect of differentiated fertilization on the content of soil organic carbon in the conditions of long-term fertilization experiment

On the basis of two long-term fertilization experiments performed on the SGGW experimental field at Łyczyn, the effect of particular fertilizer components (N, P, K, Ca) and manure as well as the application of the increasing doses of mineral fertilizers (0, 2 NPK, 3 NPK, 4 NPK) on the accumulation of organic carbon in the soil was studied. Long-term differentiated fertilization significantly modified the content of organic carbon in the soil. In the light soil, which was the subject of the study, the accumulation of organic carbon depended mainly on the application of manure. The content of organic carbon in the soil on the object fertilized with manure was about 33% higher as compared to the object fertilized with mineral fertilizers exclusively. Out of the main fertilizer components (N, P, K), the positive effect on the organic matter content in the soil was observed in the case of nitrogen fertilization and liming. On the objects fertilized with mineral fertilizers and liming the content of organic carbon in the soil increased about 7% in relation to the initial organic C content in the soil prior to the experiment. On the other hand, no effect of phosphorus and potassium fertilization on the soil organic carbon content was observed. An advantageous effect of liming on the content of organic carbon in the soil was marked mainly on the treatments fertilized with mineral fertilizers together with manure. On the limed treatments the level of the organic carbon content in the soil was about 7% higher as compared with the nonlimed, highly acidified objects. Independently of the NPK dose the exclusive mineral fertilization does not affect the content of organic carbon in the soil. The application of the growing doses of mineral fertilizers (NPK) together with manure resulted in a systematic increase of the organic carbon content in the soil.