The study on a calcareous soil, Takhli series, collected from Tambol Wang Muang was incubated with increasing quantities of humus under moist condition at field capacity showed that soil pH was decreased, eletrical conductivity of soil was increased and the amount of extractable Fe and Mn determined by using 0.005 M DTPA pH 7.3, 0.1 N HCl and 0.2 M NH(,4) -oxalate were increased. Humus did not affect the quantities of Zn and Cu extracted by these extracting solution. The addition of humus also increased the extractable N ( NH(,4)+No(,3), P,K, Na and Mg. Application of 0,7.5,15,30 and 45 g/3 kg of this soil and planted to corn for 45 days indicated that only the rate of 7.5 and 15 g were effectives in terms of increasing field dried weight and Fe uptake while having no effect with regard to the uptake of Mn and Zn. The Fe uptake of second and third experiment was more than the first. The addition of humus over than 15 g decreased the growth and dry weight of plants for all experiments. The concentration of N,P and K in plant treated with humus and the control was nearly the same but the uptake of N,P and K was decreased as well as plant dry weight in all experiments. The result of study on the effect of humus and cationic micronutrients on peanut grown on Takhli soil series collected from Tambol Wang Muang showed that this soil was very deficient in Fe. The deficiency symptom of corn can be corrected by Fe-DTPA application but with humus. Peanut and corn grown on Takhli soil series collected from Tambol Chongsalika did not show cationic micronutrient deficiencies symptom but the concentration and Fe uptake of peanut received Fe-DTPA and humus were higher than control. The split application of the total rates of 10,20 and 30 g of humus per 5 kg of soil (before planting and 30 days after planting) resulted in the higher Fe concentration and uptake of peanut as compared to the single application.