The development of long-term field fertilizing experiment started in 1959 at the Department of Agrochemistry was studied. The most important 50 years results were shown. The main studied problems of long-term field fertilizing experiment were connected with the effect of different fertilizing systems (mineral, mineral-organic, reduced - without one of the main elements P or K) on the crops productivity and quality, regulation and preservation of soil fertility by system fertilizing. It was demonstrated the importance of mineral-organic fertilizing on the studied crops.
Fifthy years long-term fertilizing experiment of Agricultural University - Plovdiv