Tropical Agriculture and Development
Online ISSN : 1882-8469
Print ISSN : 1882-8450
ISSN-L : 1882-8450
62 巻 , 1 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
  • Impacts on Banana Growth and Yield
    Raphaël ACHARD, Philippe TIXIER, Marc DOREL, Jean ROGER ESTRADE
    2018 年 62 巻 1 号 p. 1-8
    発行日: 2018年
    公開日: 2018/05/29
    ジャーナル フリー

    Intercropping banana crop with a grass cover controlled by mowing is a possible alternative to chemical weed control. However, before adopting this biological way to control weeds, it is crucial to study the impact of the cover crop on banana productivity. In a field experiment, we studied the impact on the banana (Musa spp., cv Cavendish) growth and yield of two grass covers, Cynodon dactylon (Cyn) and Brachiaria decumbens (Bra), managed by mowing every two months, in comparison to conventional weed chemical control (control). The experiment was conducted during two banana cycles. Two months after banana plantating, Bra produced more biomass than Cyn (0.94 kg DM m-2 vs 0.53 kg DM m-2); afterwards both biomass productions became equivalent (0.24 kg DM m-2) when the banana plants shaded the grass. Results showed that these cover crops have impeded the banana growth and development during the first cycle: in comparison to the control, the flowering date was delayed in both cover treatments and the number of fruits per bunch was reduced in the Cyn cover treatment. During the second cycle, as a consequence of the delayed flowering date at the first cycle, banana development was also delayed on Cyn and Bra treatments. However, the presence of Cyn and Bra cover crops had no influence on the size and weight of the banana plants at flowering date, nor on the final crop productivity. These results were interpreted as a result of contrasted conditions of competition for nutrient during the two cycles: an important production of biomass and nutrient demand of the two cover crops during the first cycle, impacting the banana growth and delaying the flowering date and, during the second cycle, a lower biomass production of the both covers crops shaded by the banana canopy and a contribution to the nutrient supply provided by the decomposition of the mowed residues.

  • Masato ODA
    2018 年 62 巻 1 号 p. 9-13
    発行日: 2018年
    公開日: 2018/05/29
    ジャーナル フリー

    Leaf-yellowing is a continuous phenomenon which is apt to go unnoticed. Among it, top leaf-yellowing is often caused by iron deficiency or salt injury. The latter occurs on dry land and in greenhouses. Majuro atoll in the Pacific Ocean is in the tropical wet climate area. The plants show very severer top leaf-yellowing; however, existing studies have found neither Fe deficiency nor salinity in the soil. Here, I succeeded to reproduce the top leaf-yellowing effect through low salinity irrigation water. I planted water spinach (Ipomoea aquatica) in bottomless pots and watered the plants using different amounts of well water containing agriculturally safe levels of salt (Na+: 16 mg L-1). Leaf-yellowing levels, measured by the chlorophyll content in the leaves, were proportional to the Na+ concentrations in the potted soil. The accumulation of salt was maximized when the amount of watering was equal to evapotranspiration, whereas further watering washed out the salinity. Sandy carbonatic soil, the majority of Majuro atoll, is considered extremely sensitive to salinity because the Na+ concentrations in the soil were far less than the threshold of US soil Lab. The evidence presented here suggests that salt injury can also occur in wet climates.

  • Md. Abdul KARIM, Hirokazu HIGUCHI, Eiji NAWATA
    2018 年 62 巻 1 号 p. 14-23
    発行日: 2018年
    公開日: 2018/05/29
    ジャーナル フリー

    The Kurigram district of northern Bangladesh has 222 chars (newly-developed lands), which have 23,000 ha cultivated lands. This study was initiated to introduce mungbean and short duration aman rice in the Kharif (summer) seasons in the chars. Both of these were grown successfully in 2013 on 4 ha of char land of 30 farmers in both Kurigram Sadar and Nageshwary upazillas. To introduce the pattern among large number of farmers, both mungbean and short duration aman rice were grown on 133.33 ha, involving 1,000 farmers on eight chars of three upazillas, namely Kurigram Sadar, Nageshwary and Bhurungamari of Kurigram district in 2014. However, there was serious drought concomitant with an extreme high temperature in April 2014 and the mungbeans were damaged seriously. Short duration aman rice was transplanted from 20 July to 10 August 2014. That year the flood appeared in mid-August and continued for more than three weeks, damaging the rice crop severely. Several recommendations, such as no fertilizers should be applied in mungbean if the crop is grown after wheat or potato (winter season crops), irrigation scheduling should be designed based on the intensity of drought and prevailing temperatures, a second-time seedbed, which may be called ‘backup’ or ‘insured’ seedbed, may be considered if the rice crop is totally submerged for more than two weeks, were made from the discussion meetings with farmers and extension personnel for successful crop production in the chars.

  • Hiroko GONO, Tsutomu TAKANE
    2018 年 62 巻 1 号 p. 24-34
    発行日: 2018年
    公開日: 2018/05/29
    ジャーナル フリー

    Malawi continues to adopt social protection policies for food security by increasing maize production. Drawing on cross-section panel data collected in three villages, this study reports on the household food security situation under social protection policies in rural Malawi. The study focuses on three dimensions (availability, accessibility, and stability) of food security and clarifies whether food security at the household level has been accomplished. We found that many households had not achieved food security with their own maize production and heavily relied on non-maize income to purchase maize from the market to supplement deficiency. Our panel data also indicated that the household food security situation is highly unstable due to unreliable weather, changing levels of input use, unstable off-farm income opportunities, and increased household dependency ratios. The study calls for a more comprehensive approach to food security that enhances both household maize production and non-maize economic activities. The current approach focuses mainly on increasing maize production.

  • Byoung-Jae PARK, Takuma KOUGE, Takuma HASHINOKI, Hiroaki SAMEJIMA, Mic ...
    2018 年 62 巻 1 号 p. 35-42
    発行日: 2018年
    公開日: 2018/05/29
    ジャーナル フリー

    This study compared the growth and curcumin contents of in vitro regenerated and conventionally propagated Curcuma longa, C. aromatic, and C. zedoaria plants. The in vitro regenerated plants (IRPs) of all three species had an acceptable survival rate in the field (≥93%), suggesting that it is feasible to transplant Curcuma IRPs. In C. longa, the shoot and total rhizome dry weights (DWs) of conventionally propagated plants (CPPs) were 137.3 and 225.2 g, respectively, which were similar to or lower than the corresponding values in IRPs that were transplanted in April and similar to the corresponding values in IRPs that were transplanted in May. In C. aromatic and C. zedoaria, there was no significant difference in shoot growth between IRPs that were transplanted in April and CPPs, but the total rhizome DWs tended to be higher in the latter. In all three species, the shoot growth and rhizome yield of the IRPs increased as the planting time was brought forward, and there was a significant positive correlation between the shoot and rhizome DWs in the IRPs across all transplanting times (r = 0.88, p < 0.01). The curcumin contents of the rhizomes of C. longa and C. aromatic decreased as the transplanting time was delayed, but there was no significant difference in the curcumin contents of the rhizomes of IRPs that were transplanted in April and May and CPPs. These findings suggest that acceptable rhizome and curcumin yields can be obtained by cultivating IRPs of Curcuma spp. However, it is also necessary to consider bringing the planting time forward to increase these yields.

  • Keiichi HAYASHI, Iris BUGAYONG, Idri Hastuty SIREGAR, JONHARNAS, Lalu ...
    2018 年 62 巻 1 号 p. 43-54
    発行日: 2018年
    公開日: 2018/05/29
    ジャーナル フリー

    Two rainfed rice areas in Indonesia were studied to evaluate their current production practices. In North Sumatera (NS), double rice cropping is commonly practiced because its annual rainfall is evenly distributed. Pests, diseases and weather were the primary risks considered by farmers. Sowing timing is critical for a smooth transition from one season to the other, and to avoid water shortage at the later stage of rice growth. In West Nusa Tenggara (WNT), farmers plant around October and harvest around the end of March. They do not grow a second rice crop despite favorable rainfall condition. Farmers incurred a large rice deficit after every cropping due to large production cost and/or loan with interest. Labor accounted for 43% and 64% of the total production cost in NS and WNT, respectively. To improve this situation, mechanization is recommended by national government. However, mechanization entails additional costs which could be a burden to subsistence farmers. Farmers in WNT did not grow a second rice crop due to the high risk of weather extremes at the beginning and end of the rainy season. Results of the grain yield simulation indicated that farmers in NS used substantial amount of supplementary water throughout the cropping seasons to boost grain yield which burdened the household economy. The application of seasonal climate predictions to generate relevant information including an optimum cropping calendar could help farmers plan their production and use their finite resources more efficiently.

feedback
Top