**2. The farming Systems of the Humid tropics**

Agroforestry involves growing trees in mixtures and arable/food crops and fruit tree species simultaneously on a farm (growing arable crops and fruit tree species together). Alley cropping is an agroforestry technique in which trees are planted in hedgerows, and annuals (arable or fodder) crops are planted in the "alley ways" between the hedge row plants. Alley cropping involves growing short duration trees and shrubs that are compatible with arable or fodder crops. The trees provide other benefits such as reducing erosion, maintaining soil fertility and providing additional income to farmers crop diversity and food security in the early years of tree establishment [10, 11]. The advantages of alley cropping are attributable to improvement of soil quality, increased economic diversity, carbon sequestration, farm yield, resource use efficiencies, and environmental resilience [12, 14].

Intercropping: the simultaneous growing of two or more species in the same field for a significant period of their growth. Such crop combinations has been reported as promising to sustain soil and crop productivity. Intercropping, systems offer crucial ecosystem service that supports food supplies and other livelihood activities. Intercropping practices provide sustainable and stable yields, diversity of flora and fauna and lower risks of crop failure, and implement, sustain and enhance environmental quality, ecosystem services and livelihoods and sustainable landscapes [15, 16]. Intercropping practices are reported to optimize ecological processes including the cycling of nutrients, maintains carbon stocks (sequestration), conservation of soil water, modification of microclimate and reduce soil degradation [11, 15].

The essential features of intercropping/agroforestry systems are intensification in the use of space and time of space, light, water and nutrients. Advantages of alley cropping improves soil quality, biodiversity, carbon sequestration, farm yield, resource use efficiencies and environmental resilience (Bedou et al., 2010). Agroforestry involving alley and intercropping are important features of the farming systems of the tropics (references). Research on intercropping has shown that fruit trees can be intercropped successfully with arable crops during the early stages (1 to 5 years) of establishment [10, 17, 18].

Variable availability of growth resources with ages of trees following its establishment exist, thus the variability in the capture and use efficiencies by hedge row crops and alley crops (component species) [19]. When plants are grown together, interspecific competition may occur in relation to the use of growth resources [13] Such biophysical interactions may be positive and negative biophysical interactions exist between trees and the alley crop species. Positive and negative biophysical interactions exists between trees and alley crops in agroforestry/alley cropping

systems. Competitive interactions which occur in agroforestry systems based on resource availability for use by the trees and understory plants [20, 21]. In addition, variable complimentality and compatibility between tree crops and the alley crop species in the fruit tree-based intercropping systems is reported. However, proper management of interactions ensures sustainability of the agroforestry systems [20].

Research has shown that tremendous enhancement of growth, development and yield of crops can be obtained through application of fertilizers [11]. Required, is the enhancement of uptake and utilization efficiency by crops without deleterious effect on yield and ecosystem [22]. Nutrient uptake and use efficiencies in crop production is less than 40% worldwide, improvement in the efficiencies of uptake and utilization of nutrients by crops will enhance yields and conserve the environment [23]. Research has shown that nutrient use efficiency indices are affected by cropping systems, fertilizer types and climate [6, 22, 24]. Thus, it is imperative to improve understanding of the use of fertilizers for enhancement of soil fertility, growth and yields of alley crops in the oil palm-based intercropping system of the rainforest zone of Nigeria.

Literature has reported that for most tree crops, the alleys can be intercropped successfully with arable crops during the early stages (1 to 6 years) of establishment. Species combination involving arable crops in oil palm alley and application of fertilizers may enhance competition for resources among intercropped species. Knowledge is however knowledge on the response of oil palm to the presence of cereals, root/tuber and vegetable crops and fertilizers in its alleys, performance of alley crops as sole and intercrops (Cassava, Maize and Pepper) in an oil palm-based agroforestry system, and effects of organic and inorganic fertilizers on soil, alley crops as well as uptake and use efficiencies of fertilizers in an oil palm-based agroforestry system of the rainforest agroecology of Nigeria. There is justification in giving priority to research to improve insights to the performance of cassava, maize and pepper intercrops in the alley of oil palm of different ages (2 to 6 years) as sources of food and income for oil palm farmers during the early stages of oil palm establishment.
