P. YANKOV, T. K. TONEV and V. ENCHEVA
Dobroudja Agricultural Institute, BG-9520 General Toshevo, Bulgaria
YANKOV, P., T. K. TONEV and V. ENCHEVA, 2002. Independent and combined effect of genotype and some agronomy factors on yield and Phomopsis helianthi infection in sunflower. I. Effect on seed yield. Bulg. J. Agric. Sci., 8: 167–173
The effect of different agronomy factors on the yield from hybrids Albena, Santa Fe and Diamant was studied under conditions of slightly leached chernozem during the period 1997–1999. The effect of the following factors was investigated: ploughing and disking as main types of soil tillage, fertilization with nitrogen and three densities varying from 45 000 to 65 000 plants/ha. It was established that hybrid Santa Fe demonstrated the highest productivity under the conditions of North-eastern Bulgaria. The type of soil tillage had considerable importance for growing of sunflower on slightly leached chernozem. When using disking instead of ploughing seed yield decreased significantly – with average 25.5 % in hybrid Albena, 21.5 % in hybrid Santa Fe, and 30.4 % in hybrid Diamant. The use of nitrogen fertilization after previous crop triticale optimally fertilized with nitrogen, did not have a significant effect on sunflower yield. A significant effect of crop density was registered only in hybrid Albena. The density of 55 000 plants/ha can be considered the optimal level of this factor in all three hybrids. Specific reaction was observed in hybrid Diamant, which can be successfully grown also at crop density of 45 000 plants/ha. The combined effect of two of the studied factors was established during the individual years, but there was no such effect averaged for the whole period of study. The type of soil tillage and the crop density had a combined effect during two of the years (1997 and 1998), and the genotype specificity interacted with crop density during 1998, and with the type of soil tillage during 1999. No interaction between more than two factors was determined.