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This article in AJ

  1. Vol. 71 No. 2, p. 243-247
     
    Received: May 17, 1978


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doi:10.2134/agronj1979.00021962007100020007x

Critical Boron Concentrations in Plant Tissues of Two Sunflower Cultivars1

  1. F. P. C. Blamey,
  2. Diana Mould and
  3. J. Chapman2

Abstract

Abstract

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.

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