**Section B1:** *Effects of age of oil palm on the growth and yields of alley crop species.*

The performance of strip intercropped mixtures of Cassava, Maize and Pepper sown in the alleys of 2 to 6 years old oil palm fields were investigated. In the alleys of oil palm ages 2 to 6 years, sole crops of cassava, maize and pepper out-yielded the respective intercrops (**Figures 4**–**6**). Among oil palm ages, yields of the intercrops were higher and similar for the 3 and 4 years and lower for 6 years old fields. The ages of oil palm affected fruit yield and yield components of pepper (**Figure 4**). The weight of fruits of pepper produced was significantly influenced by ages of oil palm. The weight of pepper fruits harvested for 2 years old oil palm was higher followed by 3 and 5 old oil palm. The weight of fruits of pepper obtained for 5 years old oil palm reduced significantly. Seed yield of pepper followed the same trend for number of fruits and fruits yield. The number and weight of fruits harvested decreased as the age of oil palm increased. There were significant differences in the yield components of cassava in oil palm alleys.. Age of oil palm fields also affected number of tubers, tuber yield and harvest index (HI), significant differences were found between values of these variables for 3, 4 and 6 years oil palms (**Figure 5**). Maize cob and seed weight and number of seeds/cob were significantly different among the ages of oil palm to which the maize was alley cropped. The weight of cob was high for 2 and 3 years old oil palm. There was reduction in value for 5 years old oil palm. The seed weight of maize alley in oil palm of 2 years old recoded high compared to other ages of oil palm. The highest seed yield were obtained for 2 and


#### **Table 3.**

*Interaction of shade and irrigation on growth variables of oil palm seedling.*


*Oil Palm-Based Cropping Systems of the Humid Tropics: Addressing Production… DOI: http://dx.doi.org/10.5772/intechopen.98257*

**Table 4.**

*Effect of mycorrhizal inoculation on growth parameters of oil palm seedlings.*

**Figure 1.** *Effect of shading on soil moisture contents.*

#### **Figure 2.** *Effect of irrigation on soil moisture contents.*

3 years oil palm while seed yield of maize sown in the alley of 5 years old oil palm had low yield. While, the shoot biomass yield, cob weight, number of seed, seed weight, seed yield, canopy spread, air and soil temperature were significantly affected by the ages of oil palm (**Figure 6**). Ages of oil palm influenced yield and its components of the alley crop mixtures. The differences in yield of the different ages (2, 3 and 5) can be attributed to low vigorous growth as a result of low nutrient

**Figure 3.** *Effects of irrigation and shading on water use of oil pam seedlings.*

**Figure 4.** *Effect of age of oil palm field on cassava tuber yields.*

**Figure 5.** *Effect of age of oil palm on maize seed yields.*

*Oil Palm-Based Cropping Systems of the Humid Tropics: Addressing Production… DOI: http://dx.doi.org/10.5772/intechopen.98257*

**Figure 6.** *Effect of age of oil palm on pepper fruit yields.*

**Figure 7.** *Effect of age of oil palm on LER of maize.*

content of the soil which led to poor vegetative growth. Contrary to the results obtained from cassava and maize, growth and fruit yields of pepper differed. Height and leaf development were not significantly different among the ages of oil palm fields despite the canopy differentials among palm ages. Although, root and shoot biomass and pepper yields of pepper were better for young palms (2 and 3 years) the differences were not significant for root and shoot biomass and pepper yields of pepper. The effect of age of palm was not significant for harvest index (HI), values were close for the different ages of oil palm.

*Section B2: Effects of age of oil palm in plantation on* **competitive interactions and mixture productivity of alley intercrops of cassava, maize and pepper.**

The effects of strip intercropped species in the alleys of 2 to 6 years old oil palm fields on competitive interactions and mixture productivity were investigated. Compared with their sole crops, the intercrops had yield advantages and higher land-use efficiencies (LER >1: **Figures 7** and **9**). The land equivalent ratio (LER) expresses the magnitude/extent of yield advantage of crop mixtures over sole crops, thus represents the land required for sole crop to produce the total yield by the component crops in intercropping. The intercrop mixtures outyielded the sole crops of the component crops (cassava,maize and pepper). The magnitudes of the LER confirms larger percentage land saved by crop mixtures over the respective sole crops. This observation supported reported advantage of intercropping in terms of productivity per unit land area, use of growth resources, in addition to greater percent land saving. Age of oil palm fields significantly affected LER, lowest LER was obtained for 6 years old palm field and values were close for 3 and 4 years old fields (**Figure 7**). Relative yield (RY) is defined as the sum of relative yields of the

**Figure 9.** *Effect of age of palm and fertilizers on LER of pepper.*

**Figure 8.** *Effect of age of palm on LER of cassava.*

species in mixture expressed as a ratio of its yield in monoculture (**Figure 8**). The values of RY of the intercrops infer that the system is advantageous and complementary being able to utilize growth resources efficiently and were able to stimulate the growth of one another when grown in the alley of oil palm (2 to 6 years after establishment). The relative yields of component crops in the mixture over were lower compare with their counterpart sole crops. The competitive functions were computed in the form of aggressivity (Agg) while the relative species competition was therefore evaluated as competitive ratio (CR) which is a measure of the times by which the component crops are more competitive than the other. Aggressivity values were high (> 0.25) across intercropped compared to sole crops (**Figure 9**). The ages of oil palm affected competition for growth resources (space and soil nutrients) and the productivity of crop mixtures. The intensity of aggressiveness was almost similar for 3 year oil old palm field, differences were found for 4 and 6 years old. Strip intercropping of cassava, maize and pepper displayed yield advantages with high relative yield total (RYT) and land equivalence (LER), and low aggressivity in the alleys of 2 to 6 years old oil palm. These observations denote complementarity and low competitive interactions among intercrops, and the significant advantage of intercropping in terms of productivity per unit land area and greater percentage land saved under intercropping (**Tables 5**–**7**).

Various studies have established that cropping the alleys of oil palm with arable crops is successful for at least the first 5 years of field establishment of oil palm [2, 35]. For oil palm of 2 to 6 years old, palm leaves and canopy extent had fully developed to completely close and cover soil surface and canopy overlap over the alleys and consequent reduction in space and solar radiation interception and transmission. This is in line with [2, 35] who reported that 1, 2 and 3 years of cropping after planting produced no subsequent deleterious effects up to 16 years

*Oil Palm-Based Cropping Systems of the Humid Tropics: Addressing Production… DOI: http://dx.doi.org/10.5772/intechopen.98257*

