Critical Boron Concentrations in Plant Tissues of Two Sunflower Cultivars1
- F. P. C. Blamey,
- Diana Mould and
- J. Chapman2
Marked responses of sunflowers (Helianthus annuus L.) to boron fertilization have been recorded but little information exists on the B nutritional requirements of this crop. In order to study this aspect, field trials were conducted in which five rates of B fertilizer (0 to 4 kg B/ha) were applied to two cultivars, ‘Smena’ and ‘SO 320’, on two soil types. The cultivars differed in visual susceptibility to B deficiency in the vegetative stage but differed only slightly in B uptake. B fertilization increased seed yields by an average of 48% in both cultivars. To establish critical B concentrations in plant tissues, relationships were investigated between seed yield and the B concentrations in I-mo-old seedlings and in the top most mature leaf at flowering. Seedlings proved unsatisfactory as index tissue, particularly with SO 320, but meaningful relationships were recorded between seed yield and B concentration in the topmost mature leaf at flowering in both cultivars. Critical concentrations in this tissue were determined as 32 and 35 ppm B for Smena and SO 320, respectively. No significant differences were recorded between the two cultivars in the relationship between seed yield and the B concentration in the leaf below the critical levels, and the data were combined. The critical concentration in the topmost mature leaf at flowering was determined as 34 ppm B for both cultivars, the confidence interval (95%) being from 31 to 38 ppm B.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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