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Abstract

Two greenhouse experiments were carried out to evaluate the effect of lime on soil pH, Mn level and Al saturation and growth, dry matter production and foliar nutrient content in 6-month old cacao (Theobroma cacao L.) plants. A factorial randomized complete block design (4 genotypes x 5 treatments) was replicated 5 times. Two Ultisols from the humid zone of Puerto Rico were used. A Dystropeptic Tropudult (Maricao) with a pH of 4.8, high in Al, received four levels of lime (0, 4, 8 and 12 meq/lOOg of Ca as Ca(OH)2), and one treatment of 4 meq/lOOg Al as A12(S04)3. A Plinthic Palehumult (Torres) with a pH of 4.9 high in Mn, received four lime levels (0, 3, 6, and 9 meq/100 Ca) plus a treatment of 170 mg/kg Mn as MnSO*. Liming reduced extractable Al, Mn, P and Mg in both soils. Growth of 6-month old seedlings increased as Al and Mn decreased. Foliar P, Ca and Mg increased with liming and Al, Mn and Zn decreased. The leaves of the Al-toxic plants were small and chlorotic. In treatments where toxicity of Mn was observed, leaves had 4000 to 6000 mg/kg Mn. Young leaf interveinal areas were chlorotic and older leaves, stems and apical meristems had necrotic spots.

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