Growth, Yield and Yield components of Sesame ( Sesamumindicum L.) as Influenced by Crop Variety and Different Rates of Herbicides in Mubi, Adamawa State, Nigeria.

— The experiment was conducted to evaluate the growth and yield performance of sesame (SesamumindicumL.) using four levels of herbicides (butachlor and diuron) to control weeds. Field trials were conducted in 2011 and 2012 cropping seasons at the Food and Agricultural Organization (FAO)/Tree Crop Programme (TCP) Farm, Adamawa State University Mubi, Adamawa State, Nigeria. The experiment was laid out in a Complete Randomized Block Design with sesame varieties (Kenana and Muva Local) assigned to the main plot and herbicide levels: Butachlor and diuron ( 0.5, 1.0, 1.5, 2.0 kg a.i.ha -1 ) assigned to the sub plot treatment which was replicated three times. Growth and yield performance parameters measured were plant height, number of leaves per plant, stem girth, number of capsules per plant and total yield (kg/ha). Result showed that both kenana and muva local were significantly affected by herbicide levels in terms of plant height, number of leaves per plant, stem girth, number of capsules per plant and the total yield.Kenana variety showed superior performance in terms of yield over Muva Local. Application of butachlor at the doses of 0.5, 1.0, 1.5, 2.0 kg a.i.ha -1 decreased weeds infestation up to 6WAS compared to the unweeded check and was at par with the hoe – weeded check, but inferior performance to the hoe-weeded check in 2011and combined analysis. Diurons at 1.0-2.0 kg a.i.ha -1 suppressed weed infestation up to 9WAS compared to the unweeded and were at par with the hoe-weeded treatment. Among the herbicides butachlor at 1.0 kg a.i.ha -1 and diuron 0.5 kg a.i.ha -1 produced comparable grain yield to the hoe-weeded treatment in the two seasons and the combined analysis. It is recommended that kenana variety and butachlor at 1.0 kg a.i.ha -1 and diuron 0.5 kg a.i.ha -1 should be used by farmers for effective weed control and increased yield.


INTRODUCTION
Sesame (Sesamumindicum. L.) also known as beniseed is one of the oil seed crops grown in Nigeria. The crop originated in southern parts of Africa andsesame seeds are rich in edible oil (46-52%). After extraction of oil the sesame cake makes very good feed as it is a rich source of protein, carbohydrate and minerals such as calcium and phosphorus (Singh, 2005). The oil is used as cooking oil, anointing oil, manufacturing of perfumed hair oil and medicinal purposes. In Nigeria it is common to find fried sesame seed sold sole or mixed with groundnuts and taken as snacks. The young leaves of the crops are used in soup making in some areas, while the dried stems may be burnt as fuels with the ash used for local soap making (Singh et. al., 2007 In response to the growing export market demand, Nigeria's production of the crop has increased consistently from about 15,000 metric tonnes in 1980 to about100,000 metric tonnes in 2006. Annual exports of sesame from Nigeria have been valued at about US $200 million (USAID, 2010). The country is the main supplier of sesame seed to Japan which is the world's largest importer. Although the country has an estimated 3.5 million hectares of land suitable for the crop, only about 335,000 ha are currently used for sesame production (USAID, 2010). Therefore, there is a vast potential for increased production. In view of the potentials of sesame in contributing significantly to livelihood of rural dwellers and the growth of national economy the Raw Materials Research and Development Council (RMRDC ABUJA), commenced the promotion of the crop through the establishment of 500 ha foundation seed farms in Nasarawa and Benue states in 2006 (USAID, 2010).
Sesame is basically a crop of the warm regions of the tropics and sub-tropics. It grows in plains as well as up to an elevation of 1250 meters. It requires fairly hot conditions during growth to produce maximum yield. A temperature of 25-27 0 C encourages rapid germination and initial flower formation. Low temperature during flowering can result in the production of sterile pollen or pre -flower drop (Singh, et. al., 2007). Sesame can be grown on a wide variety of Soil types ranging from sandyloam to heavy black soil, with a pH ranging from 5.5 to 8.2 (Singh, 2005).
Weed infestation has been one of the major threats to sesame production. Poor weed management could cause significant reduction in yield. The traditional methods of weeds control, hoe weeding and hand pulling are the commonest methods used by farmers in Nigeria (Imoloami, et. al, 2011). This method is not only labor intensive, expensive and strenuous, but can also cause mechanical damage to growing branches and roots of plants. In addition to high cost, labor availability is uncertain thus making timeliness of weeding difficult to attain, which could lead to greater yield losses (Adigun et al., 1993). Therefore, it is important to employ various weed control practices which is economically viable and does not tamper with plant growth and yield.

Experimental site
The experiment was conducted during 2011 and 2012 cropping seasons at Food and Agriculture Organisation (FAO)/ Tree Crop Programme (TCP), Adamawa State University, Mubi, ( latitudes 9 o 30' to 11 o 00'N and longitudes 12 o 00' to 13 o 45'E), at an altitude of 696 metres above sea. In the area rainfall starts in the month of April and terminates in the month of October with a unimodal peak in the month of August (ADSU Metrological Unit, 2011).

Treatments and Experimental Design
The experiment was laid out in splitplot design with three replications. Kenana and Muva local varieties comprised the main treatment. The sub-treatments consisted of butachlor at four rates (0.5, 1.0, 1.5, 2.0 kg a.i. /ha) and diuron at four rates (0.5, 1.0, 1.5, 2.0 kg a.i. /ha) along with hoe weeded and unweeded checks.

Land preparation
The experimental site was ploughed and harrowed with tractor. Suitable seedbed was then prepared before sowing.

Crop establishment
Sowing was done on July 26 and August 1,in 2011 and 2012 respectively.Seeds were sown on the flat at the spacing of 45cm ×15cm at 5-6 seeds/hill and thinned to 2 plants / hill at 2 Weeks After Sowing(WAS).

Herbicides application
Herbicides were applied using knapsack sprayer (CP15) with red nozzle. After calibration using areavolume method, the herbicides were applied at the rate for each treatment.

Fertilizer application
NPK (15:15:15) and Urea(46%) fertilizers were applied at the rate of 30 kg N, 60 kg P205 and 30 kg K20 per hectare (Singh,et.al.,2007). The whole doses of P205 and K20 along with half the rate of N was applied at sowing. The remaining half dose of N was applied at 6 weeks after sowing (WAS).

Harvesting
Harvesting was done manually by cutting at the base of the crop using sickle and the harvested plants were assembled on a polythene bag for sun drying after which it was threshed by gentle shaking and winnowed.

Data collection
Data on the following parameters on sesame growth and development were collected by observation and measurement.

Number of leaves per plant
Number of leaves per plant was taken at 4,8, and 12 WAS. Leaves were counted from 3 randomly selected and tagged plants per plot and the mean determined.

Stem girth
Stem girth was taken at 6, 9 and 12 WAS from three randomly selected plants using Vernier calipers and the mean determined.

Number of capsules per plant
The number of pods from each net plot was counted at harvest and divided by number of plants in the respective plot.

Grain yield (kg/ha)
Grain yield was determined by weighing the grain from each net plot after threshing and winnowing. The weight was converted to yield per hectare using the formula below: Grain yield= (Grain yield/plot (kg) x 10,000m 2 ) Net plot size (20m 2 )

Statistical Analysis
The data collected was subjected to statistical analysis of variance (ANOVA) using Statistical Analysis Software (SAS:R-Version,2005) package. and the treatment means was separated using Duncan Mutiple Range Test (DMRT) at 5 % (0.05) level of probability.

Influence of crop variety and herbicide on plant height.
The data on plant height at 4, 8 and 12 WAS are presented in Table 1. At 4 WAS Kenanavariety produced significantly taller plants than Muva in 2011 and the combined analysis; but was at par in 2012. At this stage in the two years and the combined analysis, the unweeded check produced the tallest plants that were only comparable to the hoe-weeded and to butachlor at 0.5 kg a.i. in 2011 only. The hoe-weeded treatment in turn exhibited plants that were appreciably taller than that of the remaining treatments except butachlor at 1.0kg a.i.in 2012, butachlor at 0.5 kg a.i. in both years and combined analysis. Butachlor at 0.5 kg a.i. dose produced plants that were markedly taller than those of butachlor at 2.0 kg a.i. diuron at 1.5 and 2.0 kg a.i rates in the two years and combined analysis. Throughout the study at this stage, diuron at 2.0 kg a.i. showed the shortest plants.
At 8WAS, the two varieties exhibited plants of similar height in the two years and combined analysis. At this growth stage also in the two years and the combined analysis, the hoe-weeded treatment produced the tallest plants which were at par with plants of unweeded-check and diuron at 0.5kg a.i. rate. In 2011 and 2012 plant heights of hoe-weeded treatment was also comparable to those from butachlor at 0.5 and 1.0 kg a.i. rate. It was followed by the unweeded-check, which exhibited appreciably taller plants than butachlor at 2.0 kg a.i.,diuron at 1.5 and 2.0 kg a.i. rates in the both years and the combined analysis. The shortest plants were produced by diuron at 2.0kg a.i./ha in the investigation at this stage.  At 8WASand in 2011 and the combined analysis, all rates of butachlor, the hoe-weeded treatment, the unweeded check,0.5 and 1.0 kg a.i. diuron rates exhibited comparable number of leaves. Application of 2.0 kg a.i. diuron produced the lowest number of leaves per plant at this stage but was comparable only to diuron at 1.5 kg a.i. in 2012 and the combined data. Neither herbicide treatment nor hoe-weeding had any significant effect on number of leaves per plant in 2012.
At 12WAS in the two years and the combined data, application of 1.0 kg a.i. diuron produced the highest number of per plant but comparable with diuron at 0.5 kg a.i. rate. It was also at par with butachlor at 0.5, 1.0, 2.0 kg a.i.anddiuron 1.5 kg a.i. dose in 2011. Similarly it was comparable to butachlor at 1.0, 1.5 kg a.i. and diuron at 1.0 kg a.i. rate in 2012. Varying rates of butachlor had no significant effect on number of leaves per plant at this stage in the study. In the two years and the combined data at this stage the unweeded check exhibited the lowest number of leaves per plant but at par with hoe -weeded and diuron at 2.0 kg a.i. rates. Ns= Not significant at 5% level of probability

Influence of crop variety and herbicides onstem girth.
Data on stem girth at 6, 9 and 12 WAS are shown in Table 3. At 6 WAS, in the two years and the combined analysis, the two varieties exhibited stems of similar girth. It was only in 2012 that herbicides affected stem girth significantly at 6 WAS. In 2012, butachlor at 0.5 kg a.i. produced stems with the thickest girth which were only considerably thicker than those of diuron at 1.0, 1. There was no interaction between variety and herbicide treatments at 6 and 12 WAS, while at 9 WAS in 2012 and combined analysis showed significant interaction was observed between variety and herbicide.   Table 4. In the two years and the combined analysis Kenana variety produced appreciably higher number of pods than the Muva variety. In 2011 and 2012, the hoe-weeded treatment and all herbicide treated plots produced similar number of pods per plant that were appreciably higher than that of the unweeded check, except that it was at par with the 2.0kg a.i. rate of diuron in 2011.
In the combined analysis the hoe-weeded treatment and all rates of Butachlor, 0.5 and 1.0 kg a.i. rates of diuron exhibited comparable number of pods per plant which were significantly higher than that of unweeded treatment. Also diuron at the rates of 1.5 and 2.0 kg a.i.ha -1 recorded similar number of pods per plant that were remarkably higher than that of unweeded check. It was only in the combined analysis that there was significant interaction between variety and herbicide.  The data on sesame grain yield is presented in the Table 5. The two varieties did not differ in grain yield in 2011 and 2012; but in the combined analysis Kenana variety gave significantly higher yield than Muva variety. In the two years and combined analysis, the hoe -weeded treatment out yielded all the herbicide treatments and the unweeded check. This was followed by Diuron at 0.5 kg a.i. ha -1 which produced comparable grain yield to butachlor at 1.5kg rate in the two years and the combined analysis.
However it out -yielded the remaining treatments in 2011 and the combined analysis and butachlor at 1.0 kg rate in 2011, diuron at 2.0 kg rate and unweeded check in 2012 only. All the other treatments exhibited comparable grain yield to the unweeded check in both years and the combined analysis, while diuron at the rate of 2.0 kg a.i. ha -1 gave the least grain yield throughout the period of the trial. There was significant interaction between variety and herbicide treatments in the two years and combined analysis.  The mean performance at various growth stages showed that all herbicide treatments and hoe-weeded treatment suppressed weed infestation compared to unweeded-check up to 9 WAS. This can be attributed to efficient residual effect of these herbicides on weed control as noted by (Zimdahl and Gwynm, 1977;Rao, 2000). The ability of diuron to provide season-long effective weed control, could be due to the persistence of this herbicide in the soil ( Akobundu , 1987;Beyer,1988;Imoloame, 2004 The combined analysis has shown that all rates of butachlor (0.5-2.0 kg a.i.) and 0.5-1.0 kg a.i. rates of diuron produced appreciably higher number of pods/plant than unweeded check but comparable to hoe-weeded treatments. Since these treatments had less weeds infestation, they had less competition from weeds for growth factors such as nutrients and water. Therefore they possibly had more available assimilates for production of higher number of pods.
Throughout the two years and the combined data, it was only butachlor at 1.0 kg a.i. that produced comparable yield to the hoe-weeded treatment which gave the highest yield. This shows that butachlor at 1.0 kg a.i./ha is a promising herbicide for use in sesame. From this research, it can be recommended that butachlor at 1.0 kg a.i./ha and diuron 0.5 kg a.i./ha are possible rates for use in sesame production as alternative to first two hoe weeding for effective weed control and high yield in sesame in Mubi, Northern Guinea savanna of Nigeria.

V. SUMMARY
The experiment was conducted during 2011 and 2012 rainy seasons, to evaluate the effect of herbicides for weed control in sesame (Sesamumindicum L), at Food and Agriculture Organisation (FAO)/ Tree Crop Programme (TCP), Adamawa State University, Mubi, latitudes 9 o 30', to 11 o 00'N and longitudes 12 o 00' to 13 o 45'E) in the northern Guinea savanna ecological zone, Nigeria.
The experiment was laid out in a split-plot design replicated three times. Two varieties of sesame (Kenana and Muva Local) were allocated to the main plots, while butachlor and diuron at each at four rates (0.5,1.0,1.5, and 2.0 kg a.i. ha -1 ), a hoe-weeded and un-weeded checks were assigned to the sub-plots.
Kenana variety showed superior performance compared to Muva local variety in number of pods per plant, but higher fresh weed infestation in the combined analysis at 6 and 9WAS.Muva local exhibited significantly higher number of leaves per plant in both seasons and combined analysis at 12WAS and gave appreciably higher straw yield in the combined analysis.
Generally plant height decreased with increasing rates in both herbicides up to 8 WAS. The combined analysis at various growth stages showed that all herbicide treatments and hoe-weeded check suppressed weed infestation up to 9 WAS.
Throughout the two years and the combined data, it was only butachlor at 1.0 kg a.i/ha that produced comparable yield to the hoe-weeded treatment which gave the highest yield. This shows that butachlor at 1.0 kg a.i/ha is a promising herbicide for use in sesame.

VI. CONCLUSION
This research revealed that butachlor at 1.0 kg a.i./ha -1 rate and can be used as alternative to hoe weeding for effective weed control and higher yield of sesame.

VII. RECOMMENDATION
Potentials exist for the production of sesame using herbicides as an alternative to hoe weeding. The information thus generated in this study should further be studied for sesame production by using other herbicide rates.