Peatlands are characterized by high groundwater levels, low pH, and low nutrient contents. The growth rate and size of sago palms (Metroxylon sagu Rottb.) grown on peatlands are low. Two field experiments were conducted on Tebing Tinggi Island, Riau Province, Indonesia. In Experiment 1, the importance of minor elements was investigated by excluding each from the composite fertilizer. In Experiment 2, four treatments were prepared by combining the presence/absence of dolomite and chemical fertilizers, consisting of the major and minor elements. Solid fertilizers were spot-applied. The effects of minor element and dolomite applications were evaluated based on the growth parameters and their concentrations in leaves of 5-yearold sago palms from the transplanting time, when sago palms were still at the rosette stage. Plant height and the number of leaves did not differ significantly among the treatments in both experiments. In Experiment 1, there were no significant differences in the amounts of minor elements in the leaves among the treatments. Although the application of dolomite plus chemical fertilizer exerted a small beneficial effect on the K content in leaves, no other differences were observed in the contents of major and minor elements among the treatments in Experiment 2. Our findings indicate that spot application of solid salts is an ineffective means of delivering fertilizer to sago palms growing in peat soils.
An analysis was performed on chili pepper (Capsicum annuum (L.) cv. Huay Si Thon and Shishito) seed vigor and quality produced by plants grown under control and high temperature conditions (29} 2/24}2 and 36 + 2/27} 2, mean day and night temperatures, respectively) after anthesis to elucidate the effect of high temperature during seed development on seed quality. High temperature significantly reduced fruit growth in both varieties . More than 20 % of the seeds produced under the high temperature regime were flat with a dark brown color and did not germinate. High temperature inhibited seed fresh and dry weight increase and the seed size was slightly reduced. Standard germination of Huay Si Thon and Shishito seeds occurring under the high temperature conditions was lower than that of the control seeds by 28 and 25 %, respectively. Similarly, seed vigor was reduced, as evidenced by the reduction in the accelerated aging germination rate and the higher value of the germination index. Protein content was maximal during the early stages of seed development and decreased afterwards continuously during the seed maturation stage, while no conspicuous reduction of the protein content by heat was observed. High temperature reduced the carbohydrate content of seeds by 40 % in Huay Si Ton and 50 % in Shishito, respectively. High temperature reduced the lipid content to less than half. These results suggested that high temperature during seed development reduced chili pepper seed germination and vigor, presumably due to the limitation in the accumulation of storage products, especially carbohydrates, and lipids.
'Touki' plants, Angelica acutiloba Kitagawa, are usually cultivated in soil, under which its yield and root quality are unstable. Although fertilizer application exerts a substantial impact on yield, the optimal level has not been known for the cultivation in soil. Therefore, the present study was undertaken to examine the growth of Touki plants with different concentrations of nutrient solution in aeroponic and drip irrigation systems. Four nutrient concentrations, i.e., 100%, 200%, 50%, and 25% of the standard nutrient solution ('Enshi' formula) were tested. In the aeroponic system, where a mist of nutrient solution was sprayed around suspended roots of the plants, the plants were grown from March 15 to June 6, 2005. In the drip irrigation system the plants were grown from May 2 to July 25, 2006. In the aeroponic system, the values of the growth parameters of the Touki plants at 12 weeks after transplanting were higher in the order of 100% 50% 200% 25% of the standard solution. In the drip irrigation system the growth parameters were higher in the order of 100% 200% 50% 25% of the standard solution. The 'Enshi' nutrient solution of 100% was optimal for the growth of the Touki plants in both systems. The plant growth, especially root growth, was more vigorous in the aeroponic system than in the drip irrigation system. In the drip irrigation system, however, the root/shoot ratio and root C/N ratio were higher, and the development of secondary roots was stimulated. As the secondary roots of Touki plants are mainly used as raw materials for medicine in Viet Nam, the drip irrigation system is recommendable as an advanced culture system.
The application of nitrogen (N) fertilizer is an important cultivation option to enhance profitable production in general, and especially in the Southeast Asian countries or other tropical countries. In some cases, large amounts of N remain in soils after the crops are harvested, leading to the deterioration of the groundwater quality through nitrate leaching and of air quality through nitrous oxide (N2O) emission. The purpose of the present study was to determine the effects of three types of controlled-release N fertilizers (CRFs) on: a) leafy vegetable growth, b) nitrate leaching from the surface (0-20cm) soil, and c) N2O flux in the soil surface. Komatsuna (Brassica campestris L.) plants were grown in plastic containers filled with arable soil, and five treatments were applied as follows: application of CDU, UBF, UBM2 and urea fertilizers, and control (no N fertilizer). Three types of CRFs and urea were applied at the rate of 150 kg N ha-1. The treatments with UBM2 and urea resulted in the highest values for the growth parameters and N uptake of Komatsuna plants. The amounts of total nitrate in the leachate were significantly higher in the UBM2 and UBF treatments than in the CDU and urea ones. The highest N2O emission from soil was observed in the CDU treatment, followed by UBF, UBM2, urea and the control. The nitrogen use efficiency was highest in the treatments with UBM2 and urea.
