Yield Evaluation of Three Sesame ( Sesamum indicum L.) Varieties Intercropped with Maize ( Zea mays L.) in a Southern Guinea Savannah Location, Nigeria

Field experiments were conducted from July to November during the 2012 and 2013 cropping seasons, at the Research Farm, University of Agriculture, Makurdi, Nigeria, to evaluate the yields of two newly introduced sesame varieties (Ex Sudan and SN 603) against the commonly grown variety “E-8” under intercropping with maize variety ‘Oba 98’. The trial area consisted of a total of seven treatments, replicated three times in a randomized complete block design. The results showed that, though maize yield was not significantly (P ≤ 0.05) affected by intercropping with sesame varieties, however, intercropped yield of sesame variety ‘Ex Sudan’ was significantly (P ≤ 0.05) greater by 26.8 % and 25.6 % respectively, in years 2012 and 2013, compared to that obtained from intercropped sesame variety ‘SN 603’, and by 19.5 % and 20.9 % respectively, in years 2012 and 2013, compared to that produced from intercropped popular sesame variety ‘E-8’. Intercropping maize variety ‘Oba 98’ with sesame variety ‘Ex Sudan’ gave the highest total intercrop yield, greatest biological efficiency with a relative yield total values of 0.87 and 0.91 respectively, in 2012 and 2013. The combination also recorded the highest land equivalent ratio (LER), highest land equivalent coefficient, highest area x time equivalent ratio (ATER), highest total monetary returns (N584,200 and N588,600 respectively, in years 2012 and 2013) and highest monetary equivalent ratio (MER). The implication of study showed that sesame variety ‘Ex Sudan’ performed best and could therefore be recommended as a potential replacement for the popular variety ‘E-8’ under intercropping with maize variety ‘Oba 98’ in Makurdi, Nigeria.


INTRODUCTION
Sesame (Sesamum indicum L.) is cultivated in almost all tropical and subtropical African countries for its highly nutritious and edible seeds (Kafiriti and Deckers, 2001).In Nigeria, it is cultivated in the northern, southern guinea, sudan and sahel savannah zones (Dudley et al., 2000).The country is the second largest producer after Sudan (Alam et al., 2007).Sesame oil is of good quality, and according to Kafiriti and Deckers (2001), the oil is used for cooking, baking, candy making, soaps and alternative medicine (in the control of blood pressure, stress and tension).Leaves are used in vegetable soup, while seeds are consumed when fried and mixed with sugar.Stems are used as wood and source of potash after burning.The sesame oil cake is a very good cattle feed, since it contains protein of high biological value (Alam et al., 2007).
Maize (Zea mays L.) is the country's third most important cereal crop following sorghum and millet (Uzozie, 2001).Maize is used mainly for human food and livestock feed.In the industry, it is important in the production of starch, oil and alcohol (Kling and Edmeades, 1997).Intercropping has been associated with such advantages as better utilization of environmental factors, greater yield stability, soil protection, variability of food supply, increasing the return per unit area and insurance against crop failure (Beets, 1982).
In Makurdi, a location in the Southern Guinea savannah, sesame variety 'E-8' is popularly grown by farmers in intercrop with maize, both for home use and source of income.It is the only variety available currently with an average yield of 0.3 t ha -1 .The yield is low, compared to that of other varieties grown elsewhere and in intercrop (Alam et al., 2007;Jakusko et al., 2013).This study was therefore carried out to evaluate the yields of two newly introduced sesame varieties (Ex Sudan and SN 603), against that of the commonly grown variety 'E-8', with the objective of identifying the variety with a higher yield that could displace the low yielding popular variety under intercropping with maize.

1. Location of study and crop varieties
The experiments were conducted from July to November, 2012 and 2013 cropping seasons at the Research Farm of the University of Agriculture, Makurdi, Nigeria, to evaluate the yield of three sesame varieties in intercrop with maize.The varieties of sesame were: 'Ex Sudan', 'SN 603' and 'E-8' (a popular variety), while that of maize was 'Oba 98'.

Experimental area, design, treatments and cropping pattern
The experimental area (175.5 m 2 ), which consisted of sandy-loam soil, was ploughed, harrowed, ridged and divided into 21 plots.Each plot consisted of 3 ridges with an area of 6.0 m 2 .The trial area consisted of seven treatments, replicated three times in a randomized complete block design.The intercrop treatments consisted of the three sesame varieties, each sown in mixture with maize.The three varieties of sesame sown as soles and that of sole maize constituted the fourth, fifth, sixth and seventh treatments, which also served as control plots.In the intercrop, maize was sown in a single row on top of the ridge, while sesame was sown by the side of the ridge.In the sole maize and sole sesame plots, seeds were sown about 2 cm deep, in a single row on top of ridge.

3. Cultural practices
Weeding was done as the need arose.The recommended rate of compound fertilizer NPK (15:15:15) for sole maize: 100 Kg N ha -1 , 40 Kg P ha -1 and 60 Kg K ha -1 ; for sole sesame: 30 Kg N ha -1 , 30 Kg P ha -1 and 30 Kg K ha -1 and for maize-sesame mixture: 100 Kg N ha -1 , 100 Kg P ha -1 and 100 Kg K ha -1 were applied (Enwezor et al., 1989).The fertilizer was applied twice to each plot at 3 and 6 weeks after planting (WAP) for the sole crops and the intercrops.Maize was harvested at 12 WAP, when the leaves turned yellowish and fallen off, which were signs of senescence and cob maturity (Ijoyah and Jimba, 2012).Sesame was harvested when capsule turned yellowish with shedding of leaves.
International Letters of Natural Sciences Vol. 23

4. Data collection
Data taken for maize include days to flowering, maize plant height at flowering (measured as the distance in cm from the soil surface to the tip of the top most leaf), number of leaves per plant, number of cobs per plant, cob length (cm), cob diameter (the diameters at the head, centre and tail ends were measured in cm and averaged).The cobs were weighed using an electronic weighing balance to obtain cob weight (g).The cobs were later shelled and the total grains for each plot weighed to obtain the yield (t ha -1 ).
Data taken for sesame include days to 50 % flowering, plant height (cm) taken at maturity, number of capsules per plant, length of capsule, number of seeds per capsule and seed yield (t ha -1 ).Other data calculated include total intercrop yield, relative yield total (RYT) as described by Subbian et al., (2006), land equivalent ratio (LER) and percentage (%) land saved (Willey, 1985), competitive ratio (CR) as described by Willey and Rao (1980), aggresivity (McGilchrist and Trenbath, 1971), land equivalent coefficient (LEC) as described by Adetiloye et al., (1983), area x time equivalent ratio (ATER) as described by Hiebsch and McCollum (1987), crop monetary returns for soles and intercrops and monetary equivalent ratio (MER) as described by Adetiloye (1988).

5. Statistical analysis
All data were statistically treated using the Analysis of variance (ANOVA) and the Least Significant Difference (LSD) was used for mean separation (P≤0.05)following the procedure of Steel and Torrie (1980).

1. Yield and yield parameters of maize variety 'Oba 98' as affected by intercropping with varieties of sesame
The yield and yield parameters of maize variety 'Oba 98' as affected by intercropping with sesame varieties in a maize-sesame mixture at Makurdi, Nigeria, during 2012 and 2013 cropping seasons is given in Table 1.Greater number of days to flowering was recorded for intercropped maize compared to that recorded for sole maize (Table 1).The intense overcrowding of the intercrops could have prompted competitive demands on available nutrients, thus prolonging days to flowering.Maize plant height was taller under intercropping with sesame varieties compared to when sown as a sole crop (Table 1).Competition for light under intercropping could have been responsible for the taller plants produced.Sole maize produced higher number of leaves per plant compared to that obtained from maize in intercrop with the sesame varieties.This view agreed with that of Silwana and Lucas (2002) who reported that intercropping reduced vegetative growth of component crops.Planting maize with the sesame varieties reduced number of cobs compared to planting maize as a sole crop (Table 1).The reduction in number of cobs under intercropping could be due to the inter-specific competition of the component crops in mixture.International Letters of Natural Sciences Vol. 23  International Letters of Natural Sciences Vol. 23 Though cob length, cob diameter, cob weight and maize yield were not significantly (P ≤ 0.05) affected by intercropping with sesame varieties (Table 1), however, greater cob weight and higher maize yield were produced from sole maize compared to that obtained from intercropped maize.Higher yield in sole cropping over intercropping had also been reported by Olufajo (1992) and Muneer et al., (2004).Under intercropping, maize variety 'Oba 98' sown with sesame variety 'Ex Sudan' produced the highest cob weight and highest maize yield of 3.8 t ha -1 in years 2012 and 2013.

2. Yield and yield parameters of sesame varieties planted as soles and in intercrop
With maize variety 'Oba 98' The yield and yield parameters of sesame varieties planted as soles and in intercrop with maize variety 'Oba 98' at Makurdi, Nigeria, during 2012 and 2013 cropping seasons is given in Table 2. Sesame variety 'SN 603' was the earliest to attain 50 % flowering when sown as a sole crop and in intercrop with maize compared to other sesame varieties sown as soles and in intercrop (Table 2).This could be attributed to varietal response, since varieties differ in the length of time they may remain at the vegetative stage before flowering.Sesame variety 'Ex Sudan' produced the tallest plants when sown as sole and in intercrop (Table 2).This could also be linked to its varietal characteristic.Highest number of branches per plant and highest number of leaves per plant were produced from sesame variety 'Ex Sudan' sown as sole and in intercrop with maize (Table 2).The tallest plants produced by the variety might have enhanced high phothosynthetic absorption, which could have promoted the highest number of branches per plant and highest number of leaves.
Variety 'Ex Sudan' produced the highest number of seeds per capsule and highest seed yield when compared to those obtained from other sesame varieties sown as a monocrop and in intercrop with maize (Table 2).In sole cropping, sesame seed yield obtained from 'Ex Sudan' was significantly (P ≤ 0.05) greater than that produced from 'SN 603' by 25.6 % and 24.4 % respectively, in years 2012 and 2013, and significantly (P ≤ 0.05) greater than that produced from the commonly grown variety 'E-8' by 20.9 % and 20.0 % respectively, in years 2012 and 2013.Under intercropping with maize variety 'Oba 98', sesame yield produced from 'Ex Sudan' was significantly (P ≤ 0.05) greater than that obtained from 'SN 603' (26.8 % and 25.6 % respectively, in 2012 and 2013), and significantly (P ≤ 0.05) greater than that produced from the popular variety 'E-8' (19.5 % and 20.9 % respectively, in 2012 and 2013).

Assessment of intercropping advantages as influenced by intercropping maize variety 'Oba 98' with sesame varieties
In both years, the total intercrop yields were greater than the component crop yields (Table 3).The highest total intercrop yield was obtained when maize variety 'Oba 98' was intercropped with sesame variety 'Ex Sudan' (4.21 t ha -1 and 4.23 t ha -1 respectively, in years 2012 and 2013).The land equivalent ratio (LER) values were all above 1.00, signifying that it was advantageous intercropping maize variety 'Oba 98' with each of the sesame varieties.This could be due to greater efficiency of resource utilization in intercropping.Mohta and De (1980) reported that LER increased to maximum of 48.0 % by intercropping compared with the cereal sole crops.Intercropping maize variety 'Oba 98' with sesame variety 'Ex Sudan' gave the highest LER values of 1.86 respectively, in 2012 and 2013, indicating that the greatest productivity per unit area was achieved intercropping maize variety 'Oba 98' with sesame variety 'Ex Sudan' than growing the crops separately (Table 3).International Letters of Natural Sciences Vol. 23 × time equivalency ratio ATER = (Yai/Yam x ta) + (Ybi/Ybm x tb) + (Yci/Ycm x tc) / T Where: Yai, Ybi, Yci: yields of intercrop A, B and C Yam, Ybm, Ycm: yields of A, B and C as monocrop ta, tb, tc: duration of crop A, B and C in days T: duration of the intercropping system in days

Table 1 .
Yield and yield parameters of maize variety 'Oba 98' as affected by intercropping with sesame varieties in a maize-sesame mixture at Makurdi, Nigeria, during 2012 and 2013 cropping seasons.

Table 2 .
Yield and yield parameters of sesame varieties planted as soles and in intercrop with maize variety 'Oba 98' at Makurdi, Nigeria, during 2012 and 2013 cropping seasons.

Table 3 .
Assessment of intercropping advantages as influenced by intercropping maize variety 'Oba 98' with sesame varieties at Makurdi, Nigeria, during 2012 and 2013 cropping seasons.
LER: Land Equivalent Ratio LER = intercrop yield of crop A sole crop yield of crop A + intercrop yield of crop B sole crop yield of crop B

Table 4 .
Degree of competition, productivity coefficient and biological efficiency of component crops as influenced by intercropping maize variety 'Oba 98' with sesame varieties at Makurdi, Nigeria, during 2012 and 2013 cropping seasons.

Table 5 .
Sole crop monetary returns, intercrop monetary returns, total intercrop monetary returns and monetary equivalent ratios as affected by intercropping maize variety 'Oba 98' with sesame varieties at Makurdi, Nigeria, during 2012 and 2013 cropping seasons.