Low efficiency of manganese fertilization of soybeans on a haplaquept soil

Abstract

Abstract Manganese deficiency is frequently encountered in soybeans (Glycine Max. L., Merrill) on naturally high pH, fine textured, poorly drained soils (Vertic Haplaquept) in Kentucky. Information is needed for diagnosing deficient fields by soil tests and on the efficiency of Mn fertilizer applied to these soils. At two locations where Mn deficiency had occurred, MnSO4 was applied at annual rates up to 360 and 600 kg of Mn/ha. At site 1, where DTPA extractable Mn averaged 5.9 pg/g on untreated soil with pH of 7.4, seed yields were increased significantly in 1977 and over the three‐year period by Mn fertilization. Yields were unaffected by treatment at site 2, where extractable Mn averaged 5.8 pg/g and pH was 6.3. Concentrations of Mn in trifoliates of plants growing in untreated soil averaged 15–16 pg/g for three of the five site‐years. However, there were apparent seasonal effects of climate on Mn availability in certain years which resulted in Mn levels of 24–29 pg/g in trifoliates of plants growing i...