Investigations on some physical and physicochemical properties, and on the regime of important bioelements under the effect of long-term mineral fertilization of strongly leached Chernozem in southeast Bulgaria
Stoyanov, D.; Atanasona, I.; Tsolova, V.; Dimitrov, D.
Pochvoznanie, Agrokhimiya y Ekologiya 32(2): 21-28
Critical lower limits of supply with labile P and K have been found in strongly leached Chernozem, resulting from long-term mineral fertilization. These limits are 4 mg P2O5/100 g soil for phosphorus, and 20 mg K2O/100 g soil for potassium.