G. Panayotova1*, S. Kostadinova2

1Department of Plant Production, Faculty of Agriculture, Trakia University, 6000 Stara Zagora, Bulgaria
2Department of Agrochemistry and Soil Science, Faculty of Agronomy, Agricultural University, 12 Mendeleev, 4000 Plovdiv, Bulgaria

(Manuscript received 19 January 2016; accepted for publication 2 February 2016)

Abstract. This study was conducted at the Field Crops Institute in Chirpan, Bulgaria, on Pellic vertisols soil type under non-irrigated conditions in the period of 2011 –2013. Tests were made on the effect of nitrogen fertilization at rates of 0; 60; 120 and 180 kgN/ha on seven durum wheat cultivars. The cultivar response was studied regarding the yield produced out of a unit of applied nutrient. It was found that the partial nitrogen productivity of grain and protein decreased by increasing the applied amounts of nitrogen fertilizer into the soil. The rate of N60 yielded the highest average partial productivity of nitrogen (69.8 kg/kg). The Elbrus and Deana cultivars had the highest partial nitrogen productivity of grain (47 –50 kg N/kg). The Elbrus cultivar manifested a tendency for the highest efficiency in forming the grain protein yield (7.2 kg N/kg) out of a unit of applied nitrogen fertilizer. The partial nitrogen productivity increased in favourable temperature and moisture weather conditions during wheat vegetation.