Effects of Boron Fertilization on Sunflower Grown on Low Boron Sandy Soil
<span>Agronomists evaluate soil boron fertility with the threshold of around 0.5 mg kg<sup>-1</sup>(hot water extraction). The nonappearance of boron deficiency on sunflower, when grown on low boron sandy soil, was investigated to test the validity of this boron guideline fertility.<strong> </strong>The soil boron content was around 0.19mg kg<sup>-1</sup>. Pot experiments were conducted during 2015 season and repeated during 2016 season. Six boron levels were applied to soil: (0, 0.2, 0.5, 1, 5, and 10mg kg<sup>-1</sup>) in 2015 and (0, 2, 5, 10, 15, and 20mg kg<sup>-1</sup>) in 2016. Boron was applied as Solubor-C (Na<sub>2</sub>B<sub>8</sub>O<sub>13</sub>.4H<sub>2</sub>O, 21% of boron). The results revealed that soil boron application did not enhance kernels weight and kernels oil and protein contents. However, boron</span><span>supply</span><span>higher than or equal to 1mg kg<sup>-1 </sup>resulted in visible leaf damage. Also, a significant decrease in kernels weight was recorded at high boron levels (15 and 20 mg kg<sup>-1</sup>). The kernels boron content did not increase with a successive increase in dose of boron supply. It was sufficient, around 16mg kg<sup>-1</sup>, for all boron tested amounts. Also, plant content on other nutrients was not affected by boron application. The soil residual boron enrichment was around 0.3 mg kg<sup>-1 </sup>for each boron application of 2 mg kg<sup>-1</sup>.</span>