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Darius Phiri Eliud Phiri Robby Kasubika Donald Zulu Chisala Lwali 《Southern Forests》2016,78(1):35-39
The study was undertaken to evaluate form factors for Pinus kesiya growing in the three Zambia Forest and Forestry Industries Corporation (ZAFFICO) plantations – the Ndola, Ichimpe and Chati groups – under different rainfall (900–1 500?mm) and soil conditions (pH 4.0–5.5). Trees were sampled from the three plantation groups and 10 sample plots were established in which 10 trees were randomly sampled for cutting. Height and diameter at breast height (dbh) were the main variables that were measured and constituted the collected data. The trees were then felled and cut into segments of 0.5?m from the bottom to the top of the tree and segment diameters over bark were measured at both ends. The form factor for each tree was then calculated by dividing the sum of the volume of the tree segments by the estimated cylindrical volume of the standing tree. The results showed significant differences (p-value<0.05) in form factors among the three plantation groups. The study further showed a significant difference in form factor when the three plantation groups were compared with a fixed form factor (0.4) used by ZAFFICO plantations, indicating that the form factors are site specific. Therefore, for the benefit of customers and plantation owners, it is important that area-specific form factors should be used for each plantation group, as these groups are affected by different factors such as soils characteristics and rainfall, which have a direct effect on the form factor. 相似文献
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Mukondwa Olivia Manjeru Pepukai Ngirazi Savemore Mavankeni Busiso Olga Kutywayo Dumisani Kamutando Casper Nyaradzai 《Journal of Crop Science and Biotechnology》2021,24(1):71-81
Journal of Crop Science and Biotechnology - Inadequate information is available on trait relations and profiles of sorghum genotypes, yet this information is vital for precise decisions to be... 相似文献
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Mavindidze Peter Mafandizvo Tinashe Gasura Edmore Mavankeni Busiso Olga Kutywayo Dumisani Kamutando Casper Nyaradzai 《Journal of Crop Science and Biotechnology》2020,23(4):337-345
Journal of Crop Science and Biotechnology - The Crop Breeding Institute (CBI) develops new bread-wheat varieties as part of its research mandate. These are tested every year in multi-environmental... 相似文献
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Francis Saiti Daniel M Jamu Busiso Chisala & Patrick Kambewa 《Aquaculture Research》2007,38(4):340-350
A cohort‐based bio‐economic biomass growth and economic model, validated with data from experiments conducted in Malawi, was used to identify an optimal harvesting strategy for mixed‐sex tilapia ponds. Three harvesting scenarios (baseline, economic optimum time +10 days and economic optimum time) were used. In each harvesting scenario four options were explored: (i) no further harvest, harvest every (ii) 60 days, (iii) 90 days and (iv) 120 days after initial harvest. The lowest simulated yield (487 kg ha−1 year−1) was obtained when no partial harvesting was carried out and fish were harvested after 365 days. Maximum yield (4416 kg ha−1 year−1) was obtained when partial harvests were carried out every 90 days starting with a first harvest of fish weighing 60 g or more at day 90. Maximum financial returns (US$2561 ha−1 year−1) were obtained when partial harvests were carried out every 120 days starting with the first harvest at day 90 and removing all fish ≥60 g. The model simulations indicate that mixed‐sex tilapia culture may be profitable for tilapia farmers in Africa where markets accept small (60–150 g)‐sized fish. The study further shows that a cohort‐based population growth model can be reliably incorporated in tilapia production models to simulate fish yields in mixed‐sex tilapia production systems. However, incorporation of intergenerational competition effects could improve the model's utility as a decision support tool for managing mixed‐sex tilapia production. 相似文献
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