Estimation of rubberwood production in Cambodia

We estimated the production of rubberwood from 1996 to 2011 in Cambodia. We employed data from interview surveys with three rubberwood processing companies and statistics from estate rubber plantations and wood retailing companies. The result was that the end use of rubberwood in Cambodia was the sawntimber products, being exported to Vietnam and China. The yield rate from rubberwood stumpage into sawn timber was between 11.6 and 14.9%, closely matching the rates of Malaysia and Thailand. The average production of rubberwood roundwood from 1996 to 2011 was 254,697 m³/year, of which sawn timber as well as residuals in secondary processing was 84,559 and 170,138 m³/year, respectively. Although the timber production of Cambodia has declined sharply due to the strict restriction of natural forest logging, rubberwood could explain more than 60% of the domestic industrial roundwood production from 2000. We suggest the necessity of monitoring the expansion of rubber plantations in new rubber producing countries and linking the rubberwood production with the regional wood resource management.     

老挝中部不同利用方式土壤养分状况分析

[目的]了解老挝中部不同利用方式土壤养分状况,为农业生产中合理施肥提高作物产量及提高土壤可持续生产力提供科学依据.[方法]在老挝中部采集3不同利用方式(水田、旱地、荒地)土壤样品,测定土壤pH值,分析其土壤有机质含量、大量元素、微量元素和中量元素含量.[结果]土壤有机质含量大小顺序为旱地>水田>荒地,土壤pH与之相反.荒地的土壤速效养分及全量养分含量均为最高.水田土壤的有效铜和有效铁含量最高,有效锌、有效锰和有效硼及交换性钙、镁则以旱地土壤含量最高.[结论]老挝中部地区土壤均呈酸性,总体肥力较低,不同利用方式土壤养分状况差别也较大.     

Erosion of irrigation facilities in Cambodia paddy farming region and the measures for protection

Paddy and Water Environment - This study investigates the erosion condition of irrigation earth structures and determines the measures for erosion protection in Cambodia paddy farming regions. Most...     

Alleviation of photoinhibition in heliconia grown under tropical natural conditions after release from nutrient stress

We have previously reported that full sun‐grown Heliconia "Golden Torch”; leaves exhibited sustained decreased in PS II efficiency as compared to those grown under shade conditions. In this study, full sunlight plus low level of fertilization caused a further reduction of photosynthesis, chlorophyll content and F_v/F_m ratio while plants grown at high level of nutrient showed higher values of all these parameters. When plants grown under intermediate and deep shade, there was no significant difference in all parameters irrespective of nutrient supply. In the recovery experiments, plants without fertilizer were re‐fertilized weekly. Maximal photosynthetic rates, chlorophyll content, and F_v/F_m ratio increased gradually after re‐fertilizing the plants grown under full sunlight. However, no significant changes of these parameters were observed in plants grown under intermediate and deep shade over the same period. Total leaf nitrogen (N) was measured parallel with all the parameters. Photosynthetic rates, chlorophyll content, and F_v/F_m ratio showed a clear linear correlation with total leaf N in plants grown under full sunlight while there was no clear relationship observed in those plants grown under intermediate and deep shade. These results suggest that acclimation of Heliconia under full sunlight could be achieved by high level of nutrient fertilization.     

Adaptation of rice (Oryza sativa L.) genotypes in the rainfed lowlands of Lao PDR

Genotype by environment (G×E) interactions for grain yield were investigated in 14 rice genotypes across eight rainfed lowland field environments in Lao PDR, in order to identify stable adapted cultivars for improved farmer livelihood and food security. G×E accounted for 20.3% of the total variance, with three vectors from ordination analysis accounting for 75.1% of the G×E-SS, in 6 genotype?×?6 environment groups. PCA1 indicated water-limited yield potential, PCA2 pre-flowering stress and PCA3 post-flowering stress. Genotype groups (G1–G6) differed in adaptation to these environments. G5 (VT450-2 and TSN9) were widely adapted and high-yielding. G6 (TDK11 and TDK37) were also high-yielding, topping the rankings in three environment groups, but yielded less in Phalanxay 2012 and Phalanxay 2011, where their phenology was unstable under stress. Other genotype groups showed specific adaptations, but failed to exceed yields of G5 and G6. Hence, VT450-2 and TSN9 (G5) were the preferred genotypes for rainfed lowland in southern Lao PDR, due to their high and stable grain yields. Stability in flowering time and high yield in rainfall deficit were desirable traits for improved farmer livelihood and food security.