1.1 Background to the study
Jatropha curcas is a species of flowering plant in the spurge Family, Euphorbiaceae, that is the native to American tropics, most likely Mexico and Central America (Janick et al., 2008). The name was derived from the Greek words ‘’jatros’’ meaning ‘’physician and ‘’trophie’’ meaning nutrition, hence the common name is Jatropha plant (United States Department of Agriculture, 2015). Although, Jatropha plant can grow easily from fully matured seeds, it can be propagated by nursery and stem cutting. In some cases, Jatropha plant naturally forms a symbiosis with soil mycorrhiza that increases the nutrients and water plant uptake from the soil by plants. The presence of mycorrhiza increases the plant tolerance to drought and shortage of nutrients (Rashid et al, 2005).
It is scientifically classified as follows:
Sub Kingdom: Tracheobionta
Binomial: Jatropha curcas
Jatropha curcas is a plant that produces toxic, non – edible seeds with high oil content (Orwa et al 2009). It is a drought resistant monoecious large shrub or small tree 5 – 8m tall. The leaves appear alternately with a petiole (3-20cm long) and a blade broadly ovate in outline, usually shallowly 5-lobed (Heller et al 1996). The inflorescences are terminal or axillary umbel-like cymes, often paired, with solitary female flower terminating each major axis and many male flowers on lateral branches. The flowers are unisexual. The fruits are broadly ellipsoid capsule, smooth-skinned, initially fleshy green, turning yellow and eventually dry and black and are 3-seeded. The seeds are ellipsoid; 1-2cm long, mottled black and coarsely pitted (Heller et al, 1996).
All parts of the plant exude sticky, bitterly pungent and astringent latex, which can be used for making ink. The bark contains tannin, wax, resin and saponins for industrials purposes. The kernel and seeds contain oil. Seed oil is used for illumination without smoke, substitute of diesel, kerosene, lubricants, soaps and candle manufacturing. It can be used as hair oil and livestock against sores. The oil from jatropha curcas family is mainly converted into biodiesel. The cake resulting from oil extraction, a protein rich product, can be used for fish or animal feed (if detoxified). It is also a biomass feedstock to power electricity plants or to produce biogas and a high quality organic fertilizer (Dehgan et al, 1994; Heuze 2016).,
In agriculture, the term weed is applied to any plant that grows or reproduces aggressively or is invasive outside its native habitat (Janick et al 1979). When a plant is found in an unwanted place and at an unwanted, time it is considered to be a weed. Taxonomically, the term “weed” has no botanical significance, because a plant that is a weed in one context is not a weed when growing in a situation where it is in fact wanted. According to Annecke, (1979), nature has bestowed the following qualities on weeds:
- Produces larger number of seeds compare to crops.
- Most of the weed seeds are small in size and contribute enormously to the seed reserves.
- Weed seeds germinate earlier and their seedlings grow faster.
- They flower earlier and mature ahead of the crop they infest.
- They have the capacity to germinate under varied conditions, but very characteristically, season bound. The peak period of germination always takes place in certain seasons in regular succession year after year.
- Weeds seeds possess the phenomenon of dormancy, which is an intrinsic physiological power of the seed to resist germination even under favorable conditions.
- Weed seeds do not lose their viability for years even under adverse conditions.
- Most of the weeds possess C4 type of photosynthesis, which is an added advantage during moisture stress.
- They possess extensive root system, which go deeper as well as of creeping type.
According to (Muhamed et al 2012), weeds cause reduction in crop yield through competition for light, nutrient, water and space. They can also reduce the yield of crop through the release of toxic substances or exudates which inhibit crop growth. Weeds can reduce the quality of harvested agricultural products. The cost of controlling weeds is high. The presence of weeds can impede water flow in irrigation canals. The presence of weeds in lakes and reservoir can increase loss of water by transpiration. Weeds serve as alternate hosts to many plant diseases and animal. The presence of weeds imposes a limit on farm size. The presence of weeds can also reduce the economic value of lakes by preventing or limiting fishing activities. Weeds such as Imperata cylindrical become fire hazards in the dry season throughout the savanna vegetation zone. Weeds affect health of humans and the flowers of some other weeds can be associated with allergies in humans. Weeds impair visibility along roads and railway lines. Uncontrolled weed growth reduces the value of real estates.
Beneficial effects of weeds are listed below: A number of weeds, such as dandelion (Taraxicum) are edible and their leaves or root maybe used for food or herbal medicine (Baker 1974). Some weeds attract beneficial insects, which in turn can protect crops from harmful pests. Weeds can also prevent pest insects from finding a crop because their presence disrupts the incidence of positive cues which pests use to locate their food. Weeds may also act as living mulch providing ground cover that reduces moisture loss and prevents erosion, weed also improve soil fertility, dandelion for example, bring up nutrients like calcium and nitrogen from deep in the soil with their tap root (Preston et al 2002).
1.2. Literature review
A survey of weed flora and ecological study on weeds adjacent to Jai Prakash university campus, Bihar was conducted by Juraimi et al. (2016). The study was based on different plots of cropland adjacent to the university campus at different month of the year. Weeds were collected randomly by quadrate method. A total number of 23 weed species made up of 3 monocots and 20 dicots were recorded. Family Poaceae, made up of monocots had 13 weed species. Families Astereceae and Verbinaceae were found to have 10 and 6 weed species respectively. The family Paperveraceae was represented by 6 weeds. The family Paplionaceae was represented by 5 weeds species while the families Solanaceae, Fabaceae, Portulaceae, Primulaceae had 4 weed species each. The family Oxiliadaceae and Chenopodaceae were represented by 3 weeds species each while Fumeraceae, Compositae contained 2 weeds each. The remaining families like Amaranthaceae, Cucurbitaceous, Convolvulaceae were represented by 1 weed species each (Juraimi, et al 2016).
Adesina et al., (2012) reported that Fifty-seven weed species were found in all the different cropped area of Teaching and Research Farm of Obafemi Awolowo University, Ile-Ife, Nigeria including the fallow land. The type and number of weed vary in the different cropping systems studied. Maximum number of weeds was present in the oil-palm plantation (19), followed by cashew plantation (17) and maize/cassava plot (16), maize plot (13), fallow land (10) and cocoa plantation (10).
1.3Statement of the research problem
Weeds affect crop plants both positively and negatively, with the negative effects out weighing the positive effects. Jatropha is a very important source of oil, biodiesel and organic manure. Weed species are threatening the existence and productivity of Jatropha plants on the Jatropha Plantation of University of Ilorin.
Sum dominance ratio is an important phytosociological parameter whose value will instigate adoption of an effective weed management practice. Determining the sum dominance ratio of weed species on the University of Ilorin Jatropha plantation would promote effective weed control programme.
This study was aimed at providing a comprehensive overview of the sum dominance ratio of weed species on the university of ilorin jatropha curcas plantation.
Objectives of the study were to provide comprehensive over view of both the composition and the abundance of weed species on the University of Ilorin Jatropha plantation.