Productivity of sunflower grown in a periodic water deficit conditions

R. Petrova, A. Matev, H. Kirchev, A. Sevov
Abstract. The aim of the conducted experiment is to determine the effect of irrigation canceling during the different phases of sunflower vegetation, and single irrigation done at a particular growth stage. The field experiment was conducted during 2006 – 2010 period in the experimental field of Agricultural University – Plovdiv on alluvial-meadow soil (former waterlogged). The following variants were tested: 1) no irrigation, 2) optimal irrigation /pre irrigation humidity at 75% of FC (Field Capacity) for the layer 0–80 cm /; 3), 4) and 5) respectively, with cancellation of the first, second and third irrigations, 6), 7) and 8) and made first, second and third irrigations, respectively. The results show that soil and climatic conditions in Plovdiv region are favorable for sunflower cultivation, while irrigation yields ranged from 1230 to 2070 kg/ha. Optimization of soil moisture in middle and middle dry years needs 2–3 irrigations, depending on rainfall distribution and amount of irrigation rate and humidity 75% of FC is 80 mm. At optimal irrigation yield ranges from 2270 to 4070 kg/ha, and compared to nonirrigated sunflower the additional yield is 46 to 97%. Revocation of one watering does not cause significant yield losses, especially if it happens in the second half of the reproductive period. Losses are more significant in the presence of water deficit during flowering and growth of the head. These have ranged from 4 to 17% (mean 11%). Average for the experimental period the repeal of irrigation in buttoning or during pouring of the seed leads to losses in yield below 10%. The most effective is watering during flowering and head growth, and the additional yield ranges from 14 to 54% (mean 32.5%). At this watering regime productivity of irrigation is high – 6.86 kg/ha an additional yield from each 1 mm irrigation water.