Influence of micronutrient and phosphorous levels and chelator to iron ratio on growth, chlorosis, and nutrition of bluecrop highbush blueberries

Abstract

‘Bluecrop’ blueberry plants were exposed to 2×2×2 factorial treatments of high and low phosphate and micronutrients (Cu, Zn, Mn, and B) and excess or stoichiometric concentrations of a chelator (EDDHA) added to Fe(NO₃), in pH 6.8 solution cultures. The effects on growth, Fe chlorosis and overall nutrition were accessed. Phosphorous was applied at 20 (low) or 400 (high) μM levels, micronutrients at low or high levels and either a 1:1 or 10:1 ratio of chelator to Fe concentration. Plants grown in excess chelator and low micronutrient supply grew normally. Plants grown in all high micronutrient solutions were chlorotic after 34 days. Plants in low micronutrient and stochiometric chelator to Fe ratio solutions were also chlorotic.

Foliar Fe was not a good indicator of Fe chlorosis development. High Cu levels in roots grown in high micronutrients without excess chelator may have been a causative factor in Fe chlorosis development, but not in reducing foliar Fe levels. There was no indication that excess chelator facilitated Fe transport as has been reported for other crops. However, this work demonstrates that highbush blueberry has an effective ability to absorb Fe from strong Fe chelates and remain non‐chlorotic even at high solution pH levels under an all nitrate‐nitrogen regime. Chemical name used: EDDHA‐ethylenediaminedi‐o‐hydroxyphenlyacetic acid.