MACRONUTRIENTS CONCENTRATION GROWN AT DIFFERENT IN DURUM WHEAT VARIETIES NITROGEN RATES

The concentration of nitrogen, phosphorus and potassium in the grain and straw of seven Bulgarian durum wheat cultivars (Progress, Vazhod, Victoria, Predel, Deana, Zvezdica and Elbrus) in dependence on is' rates 0, 60, 120 and 180 kg.ha(-1) was studied in a field experiment with cotton-durum wheat crops rotation during the period 2010-2014 under non irrigation conditions. It was established that rates N120 and N180 significantly increased N concentration of the is heat grain. Strong genotypic response of durum wheat to the grain N concentration is as obtained in non-fertilized plants with variation from 1.96% N (Vazhod) to 2.40% N (Zvezdica). Predel and Zvezdica varieties showed higher grain N content. Newer varieties (Victoria, Predel, Deana, Zvezdica and Elbrus) were characterized with higher N concentration of the straw. N rates 0-180 kg N.ha(-1) slightly changed the phosphorus concentration in the wheat grain (0.58-0.61% P2O5) and in the straw (0.10-0.19% P2O5). Deana and Vazhod varieties had higher grain phosphorus concentration when they were grown without fertilization, whereas Zvezdica variety was exceeded other varieties at rates N120 and N180. Predel and Zvezdica varieties showed higher potassium concentration of the grain.