Best Management Practices for Sustainable Crop Nutrition in Bulgaria

In 2008, a 5-year project was established in Bulgaria with the general goal of improving cultivation systems in Bulgaria’s agriculture through efficient and sustainable use of plant nutrients. About 50 researchers and discipline specialists took part in the project. Project activities included: 1) evaluation of soil nutrient status through summarization of past national soil surveys and more recent localized regional surveys; 2) systematic summarization of past relevant soil fertility research and identification of information gaps; 3) nutrient omission/addition plot trials on target crops; 4) development of tools for site-specific nutrient management that deliver updated recommendations to farmers and farmer advisers; and 5) outreach activities to assure appropriate use of the developed tools.

After conducting a soil test survey of pilot regions and creating a GIS database with soil and field data attributes in 2009 and 2010, layers were created with low, medium, and high content of P and K. The emphasis in 2011 was in the Northwest and Southwest parts of Bulgaria where additional soil sampling was conducted to better assess the soil fertility tendencies of these regions. In 2009, an Access database was structured for past soil fertility research and to accommodate new project data. In 2010, data obtained from long-term crop field experiments conducted after 1974 were entered into the database.

The resulting archive consists of data from 87 experiments at 26 sites and 8 main soil types. Four years of new fertilizer omission/addition field plot trials (NPK or NPKMg as complete treatments) were completed and added to the database. Crops tested were wheat, barley, maize, sunflower, oilseed rape, potatoes, tomatoes, pepper, apricots, peaches, chokeberry, and wine grapes. The average yield increase over four sites and four years from the NPK treatment compared to the no-fertilizer control for the five field crops was 56%.

Average yield declines from omitting a nutrient from the NPK treatment for the field crops were 23%, 7% and 8% for N, P and K, respectively. This was less response than expected for P and more response than expected for K, based on the soil test levels of the study sites.

In 2014, the project culminated in producing a 62-page Bulgarian-language manual to help farmers select appropriate fertilization practices based on 4R Nutrient Stewardship. Project personnel presented the manual to extension staff, farmers, and various public institutions at five locations across Bulgaria. Special software for advisory services is under development to help farmers implement their own site-specific fertilization management.