Effects of Boron Fertilization on Sunflower Grown on Low Boron Sandy Soil

Abstract

<span>Agronomists evaluate soil boron fertility with the threshold of around 0.5 mg kg^-1(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^-1. 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^-1) in 2015 and (0, 2, 5, 10, 15, and 20mg kg^-1) in 2016. Boron was applied as Solubor-C (Na₂B₈O₁₃.4H₂O, 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^-1resulted in visible leaf damage. Also, a significant decrease in kernels weight was recorded at high boron levels (15 and 20 mg kg^-1). The kernels boron content did not increase with a successive increase in dose of boron supply. It was sufficient, around 16mg kg^-1, 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^-1for each boron application of 2 mg kg^-1.</span>