Effects of liming on the extractability of Fe, Mn, Zn and Cu from a peat medium and the growth and micronutrient uptake of highbush blueberry plants

Abstract

Levels of extractable micronutrients in a peat and the growth and nutrient uptake of young highbush blueberry plants (Vaccinium corymbosum L cv. Blueray) were studied in a greenhouse experiment in response to liming and two rates of addition of Fe, Mn, Zn and Cu. Levels of extractable micronutrients showed different trends with liming depending upon the extractant used and the element being considered. Levels of 0.05M CaCl2-extractable Fe, Mn and Zn decreased as the pH was raised whilst those of Cu first decreased and then increased again. There was a general decline in 0.1M HCl-extractable Fe, Mn and Cu with increasing pH but levels of Zn were not greatly affected. Levels of 0.005M DTPA extractable Fe, Mn Zn and Cu generally declined but those extractable with 0.04M EDTA were either unaffected or increased as the pH was raised. Levels of CaCl2-extractable Mn and Zn were the same order of magnitude as those extractable with HCl, DTPA and EDTA. In contrast, the latter reagents extracted considerably more Fe and Cu than did CaCl2. Dry matter yields of plants were increased as the pH was raised from 3.9 to 4.3 but then decreased markedly as the pH was raised further to 6.7. With increasing pH, concentrations of plant Fe generally increased those of Mn were decreased and those of Zn and Cu were not greatly affected except for a marked decline in plant Cu at pH 6.7.