Tropical Agriculture and Development
Online ISSN : 1882-8469
Print ISSN : 1882-8450
ISSN-L : 1882-8450
61 巻 , 4 号
選択された号の論文の6件中1~6を表示しています
Original Article
  • Keisuke ARAI, Kenichiro YOSHII, Nobuyuki KABAKI, Tsuguhiro HOSHINO
    2017 年 61 巻 4 号 p. 153-158
    発行日: 2017年
    公開日: 2018/05/29
    ジャーナル フリー

    In Madagascar, off-type plants are frequently found in rice fields for breeders’ seed (G0) and foundation seed (G1), which are under the management of official agencies of seed production.

    Accordingly, line cultivation method was introduced in 2013 for the maintenance of G0 of four varieties in 2 research centers, i.e., Mailaka and FOFIFA160 at FOFIFA-Mahitsy Center, and Makalioka34 and Makalioka Malady at FOFIFA-CALA Center (Arai et al., 2015) and the occurrence of off-types in G0 and G1 was investigated for 3 consecutive years. Percentage of off-types in G0 of 4 varieties was reduced to nearly 0% between 2013-2015. Although the percentage of off-types of G1, which utilized the remnant seeds of G0 line cultivation, drastically reduced to less than 1% between 2013-2015 from the initial level of more than 10% in 2012, some varieties could not reach to under the standard upper limit of 0.1%. Accidental events caused by the natural and social conditions of research centers, such as the mixing of the varieties at nursery and flow of foreign seedlings with flooding, seemed to be factors provoking contamination. Proper and strict field management along with the adoption of line cultivation will be indispensable to maintain the purity in rice seed production in Madagascar.

  • Javier MONTANO, Supamard PANICHSAKPATANA, Eiji NAWATA
    2017 年 61 巻 4 号 p. 159-165
    発行日: 2017年
    公開日: 2018/05/29
    ジャーナル フリー

    This study was conducted to quantitatively evaluate the pesticide use by asparagus farmers implementing the Good Agricultural Practices (GAP) standard in Damnoen Saduak, a district of Ratchaburi Province, Thailand. We obtained records from 12 asparagus cultivating plots under the GAP program and compared them with another 12 which were not implementing the standard. We assessed the toxicity classification of the pesticides used, the intensity of their use (in terms of the amount of active ingredients used, expenditure and potential environmental impact exerted) and their relationship with yield, and examined the economic rewards of being GAP certified. The results show that the GAP program was not achieving its goal of reducing the intensity of pesticide use. We argue that greater priority should be given to monitoring and control at the farm level.

  • Hidetoshi ASAI, Pheunphit SOISOUVANH, Pheng SENGXUA, Kenichiro KIMURA, ...
    2017 年 61 巻 4 号 p. 166-178
    発行日: 2017年
    公開日: 2018/05/29
    ジャーナル フリー

    To assess the impact of labour-saving practices on farming management and its economic rationality in swidden agriculture of Laos, field surveys were conducted in a rural village in which herbicide application, outsourcing services in threshing and harvesting and late-maturing varieties for efficient harvesting during the dry season have rapidly expanded. With the enhanced labour efficiency, upland farmers extended the field size and produced a large volume of upland rice far exceeding consumption demand. The extent of swidden agriculture and the dependence on labour-saving practices were higher in the farmer group with field parcels in remote areas (FR) than in the farmer group with field parcels in non-remote areas (FNR). Irrespective of the higher production cost, the FR group represented approximately 70% of total upland farmers and achieved higher upland rice production and higher labour productivity than the FNR group. These findings suggest that the high demand for cash income is a causal factor for the emergence of labour-saving practices, and its wide acceptance could be attributed to its high economic rationality. However, the labour-saving farming strategy for large-area cultivation, together with the increasing population density due to immigration inflow during a past decade, resulted in deforestation and forest degradation at the village scale. For a sustainable development, a gradual shift in cash income sources from swidden agriculture to sedentary agriculture must be achieved by employing the labour force made available by labour-saving practices in new alternatives to field-size extension.

  • Maria Angeles CATELO
    2017 年 61 巻 4 号 p. 179-183
    発行日: 2017年
    公開日: 2018/05/29
    ジャーナル フリー

    This study assessed two OECD-proposed green growth indicators (i.e, environmental and resource productivity of the economy; natural asset base) and examined the effect of structural changes and green technology on swine production in the Philippines. The study used a balanced panel data of 80 farm observations in Central and South Luzon for 2002 and 2015. Swine farms incurred negative mass balance of nitrogen (N) and phosphorus (P) per hectare of land implying that land is insufficient to assimilate manure nutrients. The impact of swine production on the natural asset base was evaluated by estimating the biological oxygen demand (BOD) loads and concentration. Although only 5–15 percent of swine farms achieved the EU standard of 25 mg li-1, BOD levels generally declined. The fixed effects regression model showed that contract farms and those with waste treatment facilities were associated with significantly lower N (kg ha-1), P (kg ha-1), and BOD (mg li-1).

  • A Case Study on Negros Island, the Philippines
    Toshihiko ANZAI, Shinkichi GOTO, Shotaro ANDO, Koji INOSAKO, Patrick B ...
    2017 年 61 巻 4 号 p. 184-193
    発行日: 2017年
    公開日: 2018/05/29
    ジャーナル フリー

    Sugarcane has been cultivated in large areas on Negros Island, the Philippines. Farmers are used to apply nitrogen fertilizer two times. The first application is immediately after planting and the second is three months later. Sugarcane might not absorb much nitrogen during the early growth stage. If a large proportion of the first applied nitrogen cannot be absorbed by sugarcane due to early growth, high risk of groundwater pollution should occur. Since the quality of groundwater is important for the resident people, it is imperative to reduce the nitrogen load from sugarcane cultivation. The objectives of the present study were 1) to clarify the first applied nitrogen-fertilizer use efficiency using the 15N tracer technique, 2) to measure root extension, and 3) to observe nitrate-nitrogen leaching by using the porous cup and the wick sampler methods. The experiment consisted of several treatments including a sugarcane planting or no planting condition with or without application of nitrogenous fertilizer in the field. The 15N tracer experiment revealed that fertilizer use efficiency was 3.8% and the proportion of nitrogen derived from nitrogen fertilizer was 18.1%. Based on the root extension survey, sugarcane roots hardly extended deeper than 30 cm in the soil until three months after planting. High concentration of nitrate-nitrogen was observed in soil layers under the root extension depth, suggesting the leaching of nitrogen. To decrease the nitrogen load in groundwater while maintaining the current sugarcane yield level, it is important to increase fertilizer use efficiency of the first applied nitrogen in the early growth stage of sugarcane by adjusting the timing and the amount of applied fertilizer.

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