Occurrence and Correction of Manganese Deficiency in Histosol‐Grown Rice

Rice ( Oryza sativa L.) production is seldom limited by availability of Mn in mineral soils. Manganese deficiency of seedling rice was suspected, however, in drained Histosols with pH values near or exceeding 7.0 in the Everglades Agricultural Area. Several greenhouse and field studies were conducted to verify the occurrence of Mn deficiency, to document its effect on rice growth, and to explore methods for alleviating the deficiency in Histosols. Manganese deficiency was determined to limit the growth of rice seedlings drill‐planted in several drained Histosols having pH values ranging from 6.9 to 7.7. Approximately 3 wk after seedling emergence, deficiency symptoms were evident as interveinal chlorosis on fully expanded leaves. Affected seedlings were shorter, had fewer leaves, weighed less, and had less root mass and length than unaffected seedlings. Affected seedlings contained <20 mg Mn kg −1 tissue. The deficiency also reduced grain yield in the field. In the greenhouse, several methods were investigated for preventing the deficiency. These included soaking seeds in Mn solutions, foliar application of Mn, flooding, or placing Mn fertilizer with the seed at planting. The latter proved to be the best method for preventing the deficiency. The results of the field studies indicated that application of approximately 15 kg Mn ha −1 as MnSO 4 with the seed prevented the deficiency and provided near‐maximum grain yields.