| 摘要: | 爲探討異葉銀合歡(Leucaena diversifolia K156)最宜生長之土壤pH值範圍，以及土壤pH值對苗木與土壤養分含量之影響。特以施用石灰之方式，將土壤pH值自4.35調整至5.0、6.0、7.0及8.0進行栽植試驗，結果顯示：1. 4個月生異葉銀合歡苗木在土壤pH爲5.5-7.0範圍亦即強酸性至中性土壤生長最適宜。2. 提高土壤pH可增加土壤分N，P，K，之有效性及Ca含量，減少Mn毒害，從而促進根系之生根力及地上部之生長。3. 生長在pH4.35土壤之異葉銀合歡苗木葉部，含低濃度Ca(0.92%)及高濃度Mn(390ppm)，致造成養分不平衡與毒害，抑制異葉銀合歡苗木之生長。若提高土壤pH值，則可改善上述情況。4. 土壤pH值提高後，與異葉銀合歡苗木對養分吸取量除pH8.0例外，均顯著增加，pH5.0、6.0與7.0平均吸取量較對照(pH4.35)超出(%)N130、P172、K79、Ca249、Mg114和S147。5. 根瘤幹乾重，固氮酵素活性，以及固氮量等均隨土壤pH值之提高而增加；至6.0連最高。pH值爲6.0時，其固氮量爲對照(pH4.35)之20倍。
In order to detect the effect of soil pH on the growth and nutrient levels of Leucaena diversifolia seedling over 4 months, and nutrient availability of the soil, a greenhouse pot test was con ducted in May 1987.
Soil pH was adjusted from its indigenous pH values of 4.35 to 5.0, 6.0, 7.0, and 8.0, by using CaCO3. There were 5 levels of soil pHs with 10 replications, and the pots were arranged in randomized block design. One month after germination, seedlings were thinned to one plant per pot. Data of growth and chemical analysis were gathered after harvesting in September, 1987. The results showed:
1. Leucaena diversifolia (K156) grew better in strongly acid to neutral soil, and the optimum soil pH range for its growth was from 5.5 to 7.0.
2. As the soil pH increased, available nutrient N, P, K and calcium levels of soil increased, but manganese levels decreased.
3. Growth of Leucaena diversifolia in soil pH4.35 was retarded because of nutrient unbalance and toxity which were caused by low concentration of Ca (0.92%) and high concentration of Mn (390ppm) in the leaves of Leucaena diversifolia. However, this situation could be improved if the pH value of the soil is increased.
4. Nutrient uptake increased significantly with increasing soil pH values, except at soil pH 8.0. The difference between the average of pH levels 5.0, 6.0 and 7.0 and control were N 130%, P 172%, K 79%, Ca 249%, Mg 114% and S 147%.
5. Dry weight of nodules, nitrogenase activity, and increments of nitrogen level of Leucaena diversifolia increased with increasing soil pH value, and the highest rate is at soil pH6.0. And increments of nitrogen level from nitrogen fixation at soil pH6.0 was twenty times over the control (pH4.35). |
