Effects of application boron on yields, yield component and oil content of sunflower in boron-deficient calcareous soils

The study was conducted to investigate the effects of five boron ( B) doses; 0, 2.5, 5.0, 7.5 and 10.0 kg B ha(-1) in B-deficient calcareous soils on yield and some yield components of four sunflower genotypes. Genotypes have shown variations with respect to their responses to B applications. AS-615 and Coban had the highest seed yield (3.75 and 3.23 t ha(-1), respectively) at 7.5 kg B ha(-1), whereas S-288 and TR-4098 yielded 4.17 and 3.28 t ha(-1), respectively, at 0 kg B ha(-1). Therefore, S-288 and TR-4098 can be indicator genotypes for B toxicity. The other genotypes appeared to have high sensitivity to B deficiency. For AS-615 and Coban, application at 7.5 kg B ha(-1) level was found to be sufficient for adequate grain yield, whereas further B levels might have detrimental effects on grain yield.