A pot experiment was carried out inside a plastic greenhouse under natural light conditions at the Bangabandhu Sheikh Mujibur Rahman Agricultural University during the winter period 10 November 2000-15 February 2001, to analyze the effect of potassium on productivity and water relations in bushbean (Phaseolus vulgaris L.) under water stress conditions. Bushbean plants, var. BARI bushbean-1, were grown in nutrient-poor soil. Three levels of fertilizer potassium (37.5, 75.0 and 112.5 kg ha^-1) and soil moisture, viz, control [less than 25% depletion from field capacity (FC) ], mild stress (more than 37.5% depletion from FC) and severe water stress (more than 50% depletion from FC) were selected as treatment variables. Water stress led to a considerable decrease in the leaf area, shoot dry weight, and grain yield, and or increase in the root dry weight. Dry matter accumulation in different plant organs except for the root dry weight was more impaired by severe water stress than that by mild water stress. Irrespective of the levels of soil moisture, potassium exerted beneficial effects on plant growth characteristics including yield. Plants that received a higher level of potassium exhibited a higher relative water content and transpiration rate, and lower diffusion resistance than the plants that received a lower level of potassium. The beneficial effect of fertilizer potassium on dry matter production and distribution in bushbean plants was probably associated with the maintenance of better water relations in the plants due to potassium application.

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The present study was conducted to evaluate the effects of the temperature and planting date (month) on the emergence, growth and yield of turmeric (Curcuma longa L.) plats in Okinawa Prefecture, Southern Japan. Turmeric rhizomes were planted on February 15, March 15, April 15, May 15 and June 15 as treatments for the planting date. Temperature range of 25-35°C was optimum for the sprouting of turmeric rhizome-buds, and sprouting did not occur below 10°C or above 40°C. Seedlings elongated well in the temperature range between 25 and 30°C, but could not survive at above 40°C. The emergence of the turmeric seedlings in the February, March and April plantings started at nearly the same time, and was completed within June. Shoots of turmeric plants differing in the planting month started to wither at the same time in November, and completely withered in January. Shoot dry weight and yield of turmeric plants were significantly higher in the February planting followed by the March and April plantings than in late planting in the glasshouse experiment, whereas in the field experiment the values of these two parameters were significantly higher in the April planting followed by the March and February plantings than in the late planting. The fields of the turmeric plants in the February and March plantings required additional weeding before emergence because winter and spring weeds emerged earlier and grew vigorously. The order of total weed dry weight was as follows: February planting> March planting >April planting >May planting >June planting. The emergence pattern, growth and yield of turmeric plants, and weed growth in the field experiment suggested that turmeric should be planted in April followed by March in Okinawa, Japan.

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Plot experiments were conducted in a hilly farmland of northern Vietnam to evaluate the effects of slope, soil, land cover and rainfall on soil erosion. Each plot (100m² in area) had a low or medium slope (8% or 14.5 % gradient) and either had a land cover of cassava or was bare. Rainfall in 10-minute intervals, daily soil loss from each plot, and monthly canopy cover for cassava plots were observed during the rainy season (May-September) of 2000. The effect of slope was evident, as bare and cassava plots on the medium slope yielded 3.3 and 5.0 times, respectively, greater soil losses than plots with low slope. Surface soil components of gravel, sand, silt and clay (>2.0, 2.0-0.02, 0.02-0.002 and <0.002mm in diameter, respectively) was not identified as affecting soil loss. There was a site-specific effect on the soil loss. The effect of crop cover on the soil loss did not exceed the maximum of the site-specific effect. The maximum 10-minute rainfall was 18.5mm. The percentage of 10-minute rainfall intensity greater than 25mm h^-1, a threshold value proposed for soil detachment under tropical conditions, was characterized as low (7%) . A positive correlation between the daily maximum 10-minute rainfall and daily soil losses was found. The threshold 10-minute rainfall for the loss of soil was 2.3mm or 13.8mm h^-1.

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Amorphophallus variabilis plants grow wild in Java. The Indonesian government planned to use A. variabilis as raw material for the food industry, but the genetic variability has not yet been studied. The objective of this study was to analyze the morphological characteristics of 63 accessions collected from 6 districts in West Java.
The length of the peduncles ranged from 13.5 to 75 cm. Appendix (asexual part of spadix) length and diameter were 5.5 to 42.5 cm and 0.7 to 3.2 cm, respectively. The length of the male zones ranged from 2.5 to 8.0 cm, and the color of the part surrounded by pollen sacs was different from that of pollen sacs in some accessions. Spathe length ranged from 8 to 24 cm, and green spathe was most common. Principal component analysis of 10 morphological characteristics of the inflorescences showed that 69% of the total variation could be explained by the first four components. Scatter diagrams of the second and third components showed that the 63 accessions could be divided into 7 groups, A to G. Using cluster analysis, the 63 accessions could be divided into four groups. Cluster I comprised groups B and C except for two accessions in group A, and cluster III comprised groups D and E. Cluster II corresponded to group F. Accessions in groups A and G corresponded to cluster IV. It appeared that the classification of A. variabilis accessions based on morphological characteristics of inflorescences was not related to the geographical origin. The coexistence of accessions belonging to several clusters in the same area suggests the existence of a large genetic variability of A. variabilis.

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Kenaf is a kind of fiber crop, and recently, research has been carried out to evaluate its suitability as a source of paper. In the present study, we analyzed the differences in the growth, morphological and physiological characteristics of 4 kenaf varieties (Yuefeng 1, Thai strain, Myanmar strain and National Agriculture Research Center (NARC) strain) .
We made six ridges in a field (5.4m×6m) at the Agricultural and Forestry Research Center, Univ. of Tsukuba, and all the ridges were divided into 4 blocks. Seedlings of the 4 varieties were transplanted to blocks in each ridge with a randomized block design (hill distance: 15 cm, row distance: 1 m) on May 18-22, 2002. All the varieties were harvested on October 29 and 30.
Plant height and the number of nodes of the kenaf plots increased till September, especially Yuefeng 1 showed the highest values among the four varieties. Plant height of the Thai strain was the lowest, but the nodal number, fresh and dry weight were the highest among the 4 varieties during the cultivation period. Number and weight of the main stem leaves of the Yuefeng 1 and Myanmar strains were higher than those of the Thai strain and NARC strain at harvest time. Most of the leaves of the main stem of the NARC strain had fallen at harvest time.
Differences in the photosynthetic rate among the four varieties were not significant of the early stage of cultivation. Photosynthetic rate of the Thai strain decreased at the middle stage remarkably, and was lower than that of any other varieties at the harvest stage.

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Phalaenopsis Hybrid is an orchid plant which has been mainly grown in the tropical and sub-tropical regions of Southeast Asia in recent years. Although sphagnum moss is commonly used as potting material, it is expensive and the resources for this material are becoming scarce. Consequently, a viable alternative potting material should be identified.
This study examined four potting materials: rock wool, cryptomeria bark, coconut husk and peat moss. For each material, we evoluted the performance in water retention and nitrate nitrogen retention ability. Based on these determinating, we grew Phalaenopsis Hybrid in the respective materials, with a view to evoluting them as possible substitutes for sphagnum moss.
The results indicated that the water retention ability varied considerably; peat moss displayed the highest water retention ability, and cryptomeria bark the lowest. Also, both the pF value and moisture content of the materials appeared to be important factors for estimating the timing of irrigation. In this experiment, we considered that when the moisture content of the media reached 40% of the water-holding capacity, irrigation was required. Furthermore, since most of the water applied was drained, most of the nitrate nitrogen applied leached for all the materials. Moreover, there was a high correlation (r=0.99) between the amount of nitrate nitrogen leached and EC, suggesting that the timing of fertilizer application could be estimated appropriately by measuring EC.
Based on previous findings, we selected the optimum irrigation and fertilization frequencies for each potting material, and cultivated Phalaenopsis Hybrid to determine which materials could be substituted for sphagnum moss. There was no difference in Phalaenopsis Hybrid growth among all the potting materials, except for peat moss.
The results indicated that, considering the running cost and the availability of the materials in the tropics, coconut husk may be the best alternative potting material.

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