ผลของปริมาณและสัดส่วนระหว่างธาตุโพแทสเซี่ยมและแมกนีเซียมต่อการเจริญเติบโตของต้นยางเล็ก

Abstract

Negative interaction between potassium (K) and magnesium (Mg) is severe. Optimum nutrient management must be considered both quantity and nutrient balance. Effects of quantity and ratio of potassium to magnesium on growth of rubber tree sapling were studied. This study consisted of 2 experiments. The first experiment was to study status and K/Mg ratio in soils and rubber leaves. The soils and leaves were collected from rubber plantations in lowland and upland areas in Songkhla province for analysis of K and Mg. The values were compared with the standard level. The second experiment was to study effects of quantity and ratio of potassium to magnesium on growth of rubber tree sapling. Rubber tree saplings were planted in soil containing quantity of K and Mg 72:16, 72:36, 108:36, 180:36 and 180:60 mg kg* (K/Mg ratio as 4.5:1, 2:1, 3:1, 5:1 and 3:1 respectively) The results showed that available K and Mg in lowland and upland soil were low as same as total K in leaf and the available K in lowland soil was lower than upland soil, in contrast to the available Mg. However, leaf Mg was high. Average of available K/Mg ratio in lowland soil was lower than upland soil, 2.87 and 6.99 respectively. But the total K/Mg ratio in leaves of rubber grown in lowland areas was higher than upland areas, 3.87 and 3.25 respectively. Appling K at rate of 72, 108 and 180 mg ks increased leaf K concentration but decreased concentration of Ms and Ca. While applying 72 mg kg and Ms 36 mg ks (K:Mg ratio; 2:1) gave highest plant growth and nutrient uptake (N, P, K, Mg, Ca and S) of rubber tree sapling. This quantity and ratio of K and Mg are important for K and Mg management in rubber growing soils. Thus, rubber plantation areas should be applied K fertilizer at 40-72 mg kg while Mg is more than 36.45 mg KS* or ratio of K and Mg at 2:1