Diagnosis and Correction of B Deficiency in Beans and Mungbeans in a Mollisol from the Cauca Valley of Colombia1
- Reinhardt H. Howeler,
- Carlos A. Flor and
- Carlos A. Gonzalez2
On a high pH Mollisol in the Cauca Valley of Colombia, bean (Phaseolus vulgaris) yields were seriously limited by B deficiency, resulting occasionally in complete crop losses. Effective methods of B fertilization were studied and critical levels of B in soil and leaf tissue were determined for diagnosing B deficiency.
When B was applied directly before seeding, beans responded to 1 kg B/ha. However, this rate was not sufficient to supply enough B for subsequent crops, and applications of 2 and 4 kg B/ha were necessary for optimum yields of the second and third crop, respectively. No significant differences were observed between two common B sources, Borax and Solubor. Lateral band placement was slightly superior to .central band or broadcast placement. Band application at or shortly after seeding was more effective than that at 20 or 30 days after emergence. Foliar spray with solutions of 0.1 to 0.2% B as Solubor or Borax are recommended when B deficiency does not limit early growth. Critical levels for B deficiency were 20 to 24 ppm B in leaves and 0.65 ppm B as hot water soluble B in soil. Toxicity is expected above 40 to 45 ppm in leaves and 1.3 to 1.5 ppm in soil.
Large cultivar and species differences were observed with respect to tolerance to low levels of B. Black beans were more susceptible than two local red beans. One mungbean (Vigna radiata) cultivar was highly tolerant, showing negative responses to B fertilization.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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