Yield, Yield Components and Soil Characteristics of Sunflower (Helianthus annuus L.) Cultivars under Effect of Nitrogen Fertilizer and Defoliation

Abstract

This study was conducted in 2017 and 2018 seasons to investigate the effects of 3 nitrogen fertilizer rates (100, 200 and 300 kg N/ha), 3 defoliation levels (0.0, 2 and 4 leaves/plant) on yield attributes and yield of 3 different sunflower cultivars (Egyptian cv. Sakha-53, Argentina cv. Argentina-11 and Turkish cv. May Hybrid). The experiments were conducted in the Agriculture Research station of king abdulaziz university at Hada Al-sham. The experiments were laid out in split plot design using 4 replicates. The results showed that there were significant effects of the treatments and their interactions on sunflower yield and yield parameters, and on soil characteristics. Nitrogen fertilizer rate 300 kg N/ha increased sunflower head diameter, seed weight per plant, seed yield per hectare, and increased soil nitrogen percentage and soil organic matter (OM%), while soil pH was significantly reduced. Defoliation of 4 leaves of the plant bottom at flowering stage significantly affected yield components of sunflower cultivars, head diameter, seed weight per plant, weight of 100 seeds and total seed yield kg/ha. The highest seed weight/plant, 100-seed weight and total seed yield/ha were obtained by the sunflower cultivar 'Argentina' under nitrogen rate 300 kg/ha and removal of 4 leaves. The highest head diameter was obtained by 'Sakha' under nitrogen rate 300 kg/ha and removal of 4 leaves from plant bottom at flowering stage. Highest soil nitrogen continents was obtained by 'Sakha' and applying 300kg/ha and removal of 4 leaves, and highest soil organic matter (OM%) was obtained by 'May Hybrid' and applying 300 kg/ha nitrogen and removal of 2 leaves.