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1.
Field studies carried out in a forest transition site on a tropical Alfisol in southwestern Nigeria, show that shading by
gliricidia (Gliricidia sepium (Jacq.) Steud) and leucaena (Leucaena leucocephala (Lam.) de Wit) hedgerow species reduced density of speargrass (Imperata cylindrica (L.) Raeuschel) by 67% and 51%, respectively. Shoot biomass of speargrass decreased by 81% and 78% in gliricidia and leucaena
hedgerows, respectively. Reduction in speargrass rhizome biomass in gliricidia plots was 96% while rhizome reduction in the
leucaena plots was nearly 90%. Rhizome mortality was significantly higher in gliricidia plots than in leucaena and control
plots. The bulk of rhizomes was found between 10 cm and 20 cm of soil depth but rhizome did not penetrate further than 30
cm depth in the Alfisol in which this study was carried out. Gliricidia was better than leucaena hedgerow species in suppressing
speargrass. 相似文献
2.
An agroforestry project was funded by the US Agency for International Development and implemented by the Pan American Development Foundation in Haiti from 1981 to 1991. This project is considered by many to be one of the most successful projects of its kind in Haiti, and in the tropics as a whole. Over the ten years of its implementation, the project, referred to in Haitian Creole as Pwoje Pyebwa (Tree Project), evolved from a tree production and planting project to a much broader soil-conservation-based program involving trees. This paper summarizes the training and extension systems that developed during that period. The socioeconomic background studies that were done before the project began, and the flexible, consultative mode of field-team implementation, incorporating elements of the learning process approach, were important to the success of the project. During the implementation of the project, however, concern for farmer input and participation should have been incorporated more systematically into the field operations of the regional teams. 相似文献
3.
This paper reports on 5 experiments conducted to assess the effect of cleaning regime and predation on growth and survival
of blacklip pearl oyster (Pinctada margaritifera) juveniles in north Queensland, Australia. P. margaritifera juveniles with a mean (±SE) dorso-ventral shell height (DVH) of 4.5 ± 0.1 mm were placed into plastic mesh trays and cleaned
either every 4 or 8 weeks or left uncleaned for 16 weeks. Cleaning regime had a significant effect on growth and survival
(P < 0.005). Lowest DVH (16.2 ± 1.0) was shown by oysters in uncleaned trays during 16 weeks compared to oysters in cleaned
trays; however, there was no significant difference in DVH between oysters held in trays cleaned every 4 (19.4 ± 1.2) or 8
weeks (21.2 ± 0.8). In contrast lowest survival was shown by oysters held in trays that were cleaned every 4 weeks (30 ± 5%),
but no differences were noted between oysters cleaned every 8 weeks (63 ± 4%) and oysters that were left uncleaned for 16
weeks (75 ± 8%). Predators of P. margaritifera in northern Australia included crabs, stomatopods, flatworms, gastropods and fish. The stomatopod, Gonodactylus falcatus, was the most destructive predator with individuals consuming in excess of 20 juvenile pearl oysters per week. The leather
jacket, Paramonocanthus japonicus, did not kill pearl oysters, but trimmed the margin of oysters shells significantly reducing DVH when compared to control
groups cultured without fish. Removing predators monthly had a significant effect on growth of pearl oysters compared to oysters
in non-inspected trays; however monthly inspection of culture trays did not significantly improve oyster survival.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
4.
V. A. Tenebe U. R. Pal C. A. C. Okonkwo B. M. Auwalu 《Journal of Agronomy and Crop Science》1996,177(3):207-215
Field experiments were conducted during the wet seasons of 1991,1992 and 1993 at the Abubakar Tafawa Balewa University Farm, Bauchi (10 ° 22'N, 09 ° 47'E) to study the response of sunflower ( Helianthus annaus L.) to N rates and plant population under rainfed conditions. Four N rates (0, 50, 100 and 150 kg N ha -1 ) and four plant populations (40000,80000,120000 and 160000 plants ha-1 ) were factorially combined in a randomized complete block design with three replications. Leaf area index, shoot dry weight and seed yield (kg ha-1 ) increased significantly with increasing N rates from 0 to 100 kg N ha-1 . The growth and yield parameters per plant decreased significantly with increasing plant populations from 40000 to 160000 plants ha-1 , but the seed yield (kg ha-1 ) obtained at 80000 plants ha-1 was significantly higher than all the other plant populations. The interactions of N x plant population confounded the main effect of each factor on the growth and yield of sunflower. The seed yield (3425 kg ha-1 ) obtained from the use of 100 kg N ha-1 at 80000 plants ha-1 was significantly higher than those obtained from all other combinations of N x population and out-yielded the main effects of 100 kg N ha-1 and 80000 plants ha-1 by 18 % and 25 %, respectively. The use of 100 kg N ha-1 at 80000 plants ha-1 is therefore recommended for maximum yield of sunflower in Bauchi. 相似文献
5.
David O. EHIZIBOLO Joshua KAMANI Peter O. EHIZIBOLO Kinsley O. EGWU Goni I. DOGO Josiah O. SALAMI-SHINABA 《Journal of Equine Science》2012,23(1):1-4
This study was conducted to determine the prevalence and significance of parasites of
horses in northern Nigeria. Blood and faecal samples were randomly collected from 243
horses from different stables in some states of northern Nigeria for laboratory analyses.
Fifty-seven horses (23.5%) were found infected with parasites. The hemoparasites detected,
21 (8.6%), include Theileria equi, Babesia caballi, Trypanosoma vivax and Trypanosoma
evansi. The endoparasites encountered, 29 (11.9%) were Strongylus spp., Strongyloides
spp., Oxyuris equi, Parascaris equorum, Paragonimus spp. and Dicrocoelium spp., 3 (1.2%)
was Eimeria spp. Four horses (1.6%) had mixed infection of hemo- and endoparasites. This
preliminary finding shows that parasitism is a problem in the horse stables examined, and
calls for proper stable hygiene, routine tick control and regular deworming programme. 相似文献
6.
This study presents four strategies of a novel evolutionary algorithm, multi-objective differential evolution algorithm (MDEA). The four strategies namely, MDEA1, MDEA2, MDEA3 and MDEA4 are adapted to solve the multi-objective crop planning model with multiple constraints in a farmland in the Vaalharts irrigation scheme (VIS) in South Africa. The three objectives of the model are to minimize the total irrigation water (m2) and to maximize both the total net income in South African Rand (ZAR) from farming and the total agricultural output in tons. The total area of the farm is 771,000 m2 and supplied with 704,694 m2 of irrigation water annually. Numerical results produce non-dominated solutions which converge to Pareto optimal fronts. MDEA1 and MDEA2 strategies with binomial crossover method are better for solving the crop planning problem presented than MDEA3 and MDEA4 strategies with exponential crossover method. MDEA1 found a solution with the highest total net income of ZAR 1,304,600 with the corresponding total agricultural output, total irrigation water and total planting areas of 316.26 tons, 702,000 m3 and 725,000 m2, respectively. The planting areas for the crops in the solution are 73,463 m2 for maize, 551,660 m2 for groundnut, 50,000 m2 for Lucerne and 50,000 m2 for Peacan nut. It can be concluded that MDEA is a good algorithm for solving crop planning problem especially in water deficient areas like South Africa. 相似文献
7.
David P. Shelton Rodney A. Wilke Thomas G. Franti Scott J. Josiah 《Agroforestry Systems》2009,75(1):83-89
Farmer-to-farmer outreach was used within a targeted watershed to promote the installation of conservation buffers. In this
program called “FarmLink”, four farmers/landowners were employed part-time as “advisors” and trained by University of Nebraska-Lincoln
Extension, Natural Resources Conservation Service, and Natural Resources District personnel. Topics included basic buffer
design and benefits, availability of incentive programs, and sales techniques. These individuals then contacted their neighbors
to explain the need for and benefits of buffers and other conservation practices. In early 2003, 42 landowners were contacted,
leading to contracts for the establishment of 16 separate conservation practices on 24.8 ha (61.3 acres) of farmland. These
included just over 8 ha (20 acres) of grassed waterways or similar plantings and 14 ha (35 acres) of streamside buffers. In
addition, because of information received in the training sessions, one of the advisors installed 1.7 ha (4.3 acres) of streamside
buffers, 0.45 ha (1.1 acres) of grassed waterways, and 2.0 ha (5.0 acres) of grasses and forbs on his own land. During these
contacts, it became apparent that: (1) many farmers and landowners were not familiar with the multitude of programs available
to assist with the installation and maintenance of conservation practices; and (2) landowners generally appreciated the personal
touch of someone coming out to talk directly to them, pointing out specific areas on their land where conservation practices
could best be implemented, discussing available compensation programs, and describing management needed to help ensure practice
success. Although one-to-one contacts cannot be used in all cases, it was demonstrated to be effective in this watershed. 相似文献
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This study examined rural peoples’ intention to adopt sustainability practices in communally managed forests in Vhembe district, South Africa, using the theory of planned behavior as a conceptual framework. A total of 155 respondents were surveyed. The data was analyzed using structural equation modeling (SEM). The results showed that rural people have a strong intention to adopt sustainable forest-use and management practices. Out of the three constructs comprising the theory of planned behavior, subjective norm (SN) and attitude to behavior (AB) positively correlated with intention, with SN having the strongest influence on intention. Perceived behavioral control (PBC), which is the third construct, negatively correlated with intention. The study indicates that respondents’ subjective belief about the approval or disapproval of sustainable forest management (SFM) practices by other relevant people mainly influenced their intention to adopt or not adopt such practices. Thus, strategies and policies to enhance the sustainable management of communally owned forests in South Africa need to consider local actor contexts and sociocultural norms and values. In this regard, the engagement of influential people at the community level, and the demonstration of the short- and long-term benefits of sustainable forest use and management practices offer promising entry points. 相似文献