Abstract

Rubber-growing soils in southern Thailand are usually deficient in both macro- and micronutrients. Omission pot trial is an excellent tool for nutrient assessment because it can indicate the most limiting nutrient and the order of limitation. Maize is generally used as a test plant, but the difference in nutrient response of maize and rubber is not clearly understood. An omission pot trial with 10 treatments (All, -N, -P, -K, -Mg, -S, -Zn, -Cu, -B, and -Lime) was conducted. The soil samples were limed with Ca(OH)₂ to pH 6, except for that used for the -Lime treatment. Equivalent amounts of 400 kg ha^-1 of N, 120 of P, 175 of K, 75 of Mg, 100 of S, 6 of Zn, 4 of Cu and 2 kg ha^-1 of B, were added in the All treatment. Nutrient X was omitted in the -X treatment. Maize and rubber were grown as test plants. The plant growth indices were measured after 30 days for maize and after 9 months for rubber. The limiting nutrients of both plants were N, P, and Ca (lime). Rubber growth in the field, which received government-recommended and omission-based fertilization, were not different.

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