**Table 5.**

*Effects of age of oil palm on growth and yield of pepper.*


#### **Table 6.**

*Effects of age of oil palm on growth and yield of maize.*


#### **Table 7.**

*Effects of age of oil palm on growth and yield of cassava.*

after planting. A similar trial conducted on forest land near Benin in Nigeria including cropping for 2 years concluded that alley cropping remained possible in the early years of oil palm before complete canopy closure [2]. This early experiment evaluated maize, yams and cassava, and shade-resistant cocoyam as the only crop up until 12 years. For the first 2 or 3 years on the cropped plots, good yields from crops and growth from palms were obtained. Results were also obtained for

cocoyam (*Xanthosoma sagittifolium*) in a more recent experiment near Benin City, in the fifth and sixth years after planting [2, 35]. The relative yields of component crops in the mixture were low compared with their counterpart sole crops. The strip intercrops of cassava, maize and pepper in the alleys of 2, 3 and 4 years old were characterized by relative yield (RY) values less than one (< 1). This may be attributed to inter-specific competition among oil palm of 2, 3, 4, 5 and 6 years old and the intercrop species [2, 35]. Relative yield greater than one (1) indicates that intercropping system has high competitive advantage and complementary in the utilization of resources efficiently [13]. In general, relative yield total (RYT) was best for cassava among the intercrops and lowest for maize. Apart from the yield advantage, RYT is often used to express economic feasibility of intercropping system. The low competition between intercrops implies that one component stimulated the growth of the other [13]. This is however, contrary to other reports that RYT less than one (<1) showed inter-specific competition among species. The envisage advantage of growing crops in mixture for enhanced use efficiency of growth resources and input (fertilizer) attract farmers to intercropping [10, 13, 39]. The greater yield advantage of crop mixtures was established from the land equivalent ratio (LER), land equivalence and percentage land saved (PLS)variables of competitive interaction of crop mixtures confirmed high yield advantage of cassava, maize and pepper intercrops in alleys of oil palm of 2–6 years, and also indicated high productivity of the intercropping system. This observation is consistent with those of Miller and Pallardy [40] and Agele et al. [10] on intercrop species. These results confirmed that cassava, maize and pepper can grow together in mixture without adverse effect on each other but offer yield advantage when intercropped with oil palm alley of 2 to 6 years old. Similar findings were reported by Malay et al. [13] on maize-legume intercropping systems and Agele et al. [20] on cashew-based intercrop of Sesame and bambara groundnut in the southern guinea savanna of Nigeria. Aggressivity of the intercrops was about 0.01 for sole crops of cassava, maize and pepper intercropped into 6 years old oil palm implying equal competition. However, cassava, maize and pepper had both negative and positive symbol greater than one (1). This is consistent with the report of Koohi et al. [41] who stated that crowing coefficient greater than one (>1) had yield advantage, RCC of equal to one (1) and above one (>1) has yield advantage while less than one (< 1) is disadvantageous (**Figures 10** and **11**).
