Z. Uhr1*, E. Vasileva2
1Institute of Plant Genetic Resources, 2 Druzhba, 4122 Sadovo, Bulgaria
2University of Agribusiness and Rural Development, 78 Dunav, 4000 Plovdiv, Bulgaria
Abstract. As a consequence of a long-year comparative study of quality, productivity and physiological characteristics of Bulgarian varieties of common winter wheat(Triticumaestivum),wecarriedouta studyontheadaptationofmoderngenotypestotherequirementsofsustainableagricultureandrespectivelytheir effectiveness of breeding methods with respect to these requirements. In the course of this study were also accumulated additional data concerning the influence of the predecessor and nitrogen fertilizer rate on energy productivity of crop, energy and recyclable efficiency of fertilization and profitability of production. In two consecutive publications we summarize and share with the scientific community the data that we have received. The results are up-to-date and useful in both theoretical and practical aspects. The analysis is based on data from field fertilizer experiments carried out with predecessor cereal – regular crop of sorghum, millet, maize and legumes after predecessor–separate sowing of chickpeas. Energy productivity is calculated as a function of yield (grain, straw and total biological yield, (t/ha), multiplied by the energy equivalent unit (MJ/kg). Maximum values of gross energy productivity by grain yields are reported by fertilization rate with 0.18 t/ha nitrogen fertilizer after cereal predecessor and after 0.06 t/ha after legumes. After cereal predecessor the effect of increasing the fertilizer rate to 0.18 t/ha N improves energy productivity of grain by 160% compared to the control N0. After legumes predecessor at N 0.0 t/ha energy productivity with grain was 12%, and in N 0.06 – 21% higher than the maximum (at 0.18 t/ha) after cereal predecessor. Legume predecessor unifies differences between genotypes and fertilizer levels on energy productivity of grain and increases energy productivity of straw by 16% on average. Maximum values of gross energy productivity of straw are reported in fertilization with 0.12 t/ha after wheat and 0.24 t/ha fertilizer nitrogen after legume predecessor. Increasing the fertilizer rate from 0.0 t/ha to 0.18 t/ha nitrogen reduces the difference in the gross energy productivity of crops after legumes and cereal predecessor from 105% in 0.0 t/ha to 10% in 0.18 t/ha. The differences between both varieties regarding the studied parameters are statistically significant at P < 0.001.