Survey and Identification of Major Weeds of Seeds Spice in Ethiopia

In Ethiopia coriander (Coriandrum sativum L.), fenugreek (Trigonella foenum-graecum) and black cumin (Nigella sativa L.) are economically important seeds spices in the family of Apiaceae, Fabaceae and Apiaceae (Umbelliferae), respectively. They are highly suffering due to weed infestation especially competing for water and nutrient. However, before estimating yield losses due to weeds and devising weed control strategies, identification and quantification of weeds are very important. The weed survey was conducted in East showa, Arsi, Bale, North wollo and North Gondar zones during 2016 and 2018 in main cropping seasons to identify most common and prevalent weeds associated with seeds spice (coriander, fenugreek and black cumin). Weed species characteristics, density, frequency, relative density, relative frequency, summed dominant ratio over locations and seasons were calculated. The result shows that a total of 22, 37 and 21 weed species were identified in coriander, fenugreek and black cumin fields, respectively. The most important families according to the number of represented species were Amaranthaceae, Caryophyllaceae, Primulaceae and Fabaceae in coriander, Amaranthaceae, Fabaceae and Polygonaceae in fenugreek and Chlorideae and Scrophulariaceae in black cumin fields. The frequency of individual weed species in coriander, fenugreek and black cumin field ranged from 0.14% up to 1%, 0.13% up to 1% and 0.25% up to 5% while the dominance value ranged from 0.14 up to 49.1%, 0.25 up to 26.5% and 0.25 up to 4.5%, respectively. The most frequent and dominant weed was Chenopodium album in coriander field whereas, the most frequent weed was Chenopodium album and the most dominant weed was Drymaria cordata in fenugreek field. In black cumin field Cynadon dactylon and Solanum nigrum are most dominat and the most frequent weeds respectively. This survey has ranked the most abundant and troublesome weed species in coriander, fenugreek and black cumin growing areas of Ethiopia. Therefore this information is vital for setting research and developmental work priorities concerning coriander, fenugreek and black cumin weeds of the study area

hosts to insect pests and pathogens attacking seeds spice. Research indicated that, worldwide, over 10% of agricultural production is lost as a result of crop weed competition for the resources light, water and nutrients [7]. According to Akobundu [8] when weeds are left uncontrolled, yield losses range from 20-100%, depending upon the crop and its environment. The author reported loss estimates of 5% in developed countries, 10% in the less developed countries and 25% in the least developed countries.
Coriander, fenugreek and black cumin productions are the major activity in Tepi National Spices and other national and regional research centre. These three crops are grown almost anywhere in the in the mid altitude and high land areas of Ethiopia as source of income.
Surveys are commonly used to characterize weed populations in cropping systems [9]. Therefore, to develop an effective weed management program, a thorough survey is necessary to address the current weed problems in the field. In addition, survey information is entirely important in building target oriented research programs. So far, no related study has been conducted regarding the occurrence, distribution and identification of common weeds associated with coriander, fenugreek and black cumin in Ethiopia.
Therefore information generated in this research is important and very useful in predicting the invasive potential of weeds biotypes over time and may provide imminent for effective control strategies. Therefore this survey was conducted with the following objectives: • To identify and classify common weeds associated with coriander, fenugreek and black cumin at a major production areas of Ethiopia and • To document the kinds of weed species and its relative distribution.

METHODS
The weed survey was conducted in East Shewa, Arsi and Bale zone of Oromiya and North Gonder and South Wollo zone of the Amhara regional state. Those areas are major producing areas of seeds spices in Ethiopia. The surveys were conducted during 2016 and 2018 main cropping season using quadrat method. Since the area of seeds spice grown by a household is about 1 ha or less, a 0.5 m × 0.5 m quadrat samples were taken at 2-3 m interval in cross diagonal line by randomly placed in weed infested areas of each of the production fields. All weed species there in were uprooted, cleaned, and separately placed in plastic bags. There were five sampling sites per area taken. After completing the weed collection from the crop fields the specimens were sorted, identified and classified to their family by using the 'Flora of British India' by Hooker [10] 'Flora of Andhra Pradesh' by Pullaiah and Chennaiah [11] Weed Identification and Control Guide [12].

Data analysis
After the quantitative weed measurements i.e., density, relative density, frequency, and relative frequency, summed dominant ratio (SDR) were calculated by the following formula. Initially MS Exal were used to compile the data.  (Table 1).

Fenugreek
From surveyed fenugreek field a total of 37 weed species were identified. The most important families according to the number of

Black cumin
From surveyed black cumin field a total of 21 weed species were identified. The most important families according to the number of represented species were Chlorideae and Scrophulariaceae. The frequency of occurrence of individual weed species ranged from 0.25% up to 5% while, the infestation level (dominance) ranged from 0.25% up to 4.5%. The most frequent weed was Solanum nigrum were as the most dominant weed was Cynadon dactylon (Table 3).
Dominant weeds were those species which occurred in relatively greater number than the other species. Most of the weeds found associated with the coriander, fenugreek and black cumin production areas are weeds that emerge with or before the crop. Weeds that emerge later than the crop are much less competitive in terms of crop yield loss but still may be considered problematic if they influence crop harvest ability or reduce crop quality.
Weed density is an important factor in the control of weed species as explained by Wicks et al. [13]. He elaborated his claim by disclosing that where the average density of the species was <9 weeds/m 2 but, some species were found greater density within the specific field. Similar results were reported by Uddin et al. [9] who found that the density of the most species increased compared to densities obtained from all of the fields. These results are also in accordance with the findings of Javaid et al. [14] where they observed that the highest density and coverage was shown by the most common grass Cynadon dactylon.
Most of common weeds identified in this survey were found in annual nature. This can be explained by the fact that seeds of annual weeds survive in unfavorable conditions and they have able to complete their life cycle from seed to seed in one season    [15]. Moreover, the weeds which appeared common in seeds spice production areas with the highest mean field densities indicate that these weeds were the more difficult to control. So, these species should be carefully monitored.
Since weed succession and distribution patterns in seeds spice fields are dynamic in nature, the composition of the weed flora may differ depending on location [9,16]. The weed vegetation of a particular area is determined not only by the environment but, also edaphic and biological factors that include soil structure, pH, nutrients and moisture status, associated crops, weed control measures and field history especially in local geographical variation [17].

SUMMARY AND CONCLUSION
Survey and identification of weeds were done in the coriander, fenugreek and black cumin production areas of Ethiopia during 2016 and 2018 main cropping season. The results of the survey provide a quantitative comparison of the common weed species in seeds spice production of major growing areas of Ethiopia. The frequency of individual weed species in coriander, fenugreek and black cumin field ranged from 0.14% up to 1%, 0.13% up to 1% and 0.25% up to 5% while the dominance value ranged from 0.14 up to 49.1%, 0.25 up to 26.5% and 0.25 up to 4.5%, respectively. The most frequent and dominant weed was Chenopodium album in coriander field whereas, the most frequent weed was Chenopodium album and the most dominant weed was Drymaria cordata in fenugreek field and in black cumin field Cynadon dactylon and Solanum nigrum are most dominant and the most frequent weeds respectively. This survey has ranked the most abundant and troublesome weed species in coriander, fenugreek and black cumin growing areas of Ethiopia. Therefore this information is vital for setting research and developmental work priorities concerning coriander, fenugreek and black cumin weeds management. In the future, more survey work is needed on a regular basis to identify possible problematic weed and weed population shifts and direct research toward new or improved control measures.