RUMEN BAZITOV1, ANTONIA STOYANOVA2 and STANIMIR ENCHEV3
1 Agricultural Institute, 6000 Stara Zagora, Bulgaria
2 Department of Plant Production, Faculty of Agriculture, Trakia University, 6000 Stara Zagora, Bulgaria
3 Agricultural Institute, 9700 Shumen, Bulgaria
BAZITOV, R., A. STOYANOVA and S. ENCHEV, 2018. Biophysical coefficients of irrigated Sudan grass grown as a second crop. Bulg. J. Agric. Sci., 24 (Suppl. 1): 47–51
The experiment was conducted in the period 2014-2015 with sudan grass grown as a second crop, variety Endje 1 on the experimental field at the Agricultural Institute - Stara Zagora on the soil type of meadow-cinnamon. The variety was created at the Agricultural Institute - Shumen. Irrigation was performed gravitationally with seasonal flexible polyethylene pipelines. The following variants were tested: Variant 1. Non irrigation (Control); Variant 2. Optimal irrigation, 70-75% of WFD (100% irrigation rate); Variant 3. Irrigation as var. 2, but with removal of first watering; Variant 4. Irrigation as var. 2, but with removal of second watering; Variant 5. Irrigation as var. 2, but with the removal of third watering. Evapotranspiration (ET) for the vegetation period was established by water-based calculations under optimal irrigation for var. 2 for layer 0-80 cm. Based on experimental data, biophysical coefficients Z, R and Kb in sudan grass grown as a second irrigation crop in periods and years vary within certain limits and depend on specific weather conditions. In the years with insufficient rainfall and high pressure of meteorological elements, their values were low. During the growing periods the biophysical coefficients Z, R and Kb have different values which reach their maximum during the period of occurrence of the panicle, respectively: Z - 0.18, R - 0.43 and Kb - 0.84.
Keywords: sudan grass; irrigation; evapotranspiration; biophysical coefficients