*Section C2: Effects of fertilizers and age of oil palm on agronomic and physiological efficiencies of N use by alley crop species.*

In general, the fertilizers following their application to the strip intercrops in the alleys of 3, 5 and 6 years old palm influenced most of the indicators of nutrients use efficiencies (**Table 10**). Agronomy Efficiency (AE) differed significantly. Apparent Recovery Efficiency (RE), Apparent recovery Efficiency by difference(RE%), Physiological Efficiency(PE), Utilization Efficiency(UE), Internal utilization Efficiency(IE) and partial factor productivity (PFP) were not significantly different among the intercrops under the fertilizers. Fertilizer treatments enhanced most of measured variables of nutrient use efficiencies compared to unfertilized plots (control) (**Tables 10** and **11**).The ages of oil palm significantly affected most of the measured variables among the intercrops except the N removed at harvest. However, apparent recovery of N differed among intercrops and ages of oil palm plots. The values of the measured parameters were highest for 5 and 6 years oil palms across the intercrops (**Table 10**). For cassava, poultry manure enhanced the utilization efficiencies while ferti plus promoted the efficiencies of N recovery from the applied fertilizers and physiological efficiency of its use. NPK enhanced both recovery and utilization efficiencies of nutrients, partial factor productivity, N removed at crop harvest and the competitive ability for uptake and use of nutrients


Elaeis guineensis

**Table 10.**

 *Effects of fertilizers and intercrops on indices of N uptake and use efficiencies.*


**Table 11.**

*Summary of N uptake, agronomic*

 *and physiological*

 *efficiencies*

 *of N use.*

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

from the applied fertilizers (**Table 10**). In maize, NPK enhanced recovery efficiency from applied fertilizers, partial factor productivity, N removed at harvest and competitive ability for nutrients (**Table 10**). Ferti plus enhanced physiological, utilization and conversion efficiencies of nutrients while poultry manure improved physiological and utilization efficiencies of nutrients. In pepper, ferti plus and poultry manure enhanced the utilization efficiency of nutrients while NPK significantly enhanced N removed at harvest. The fertilizers affected almost all variables measured as indicators of agronomic and physiological efficiencies of nutrient use (**Table 10**). The effects of fertilizer was significant on utilization and recovery efficiencies of N and competitive ability for nutrients, agronomic and physiological efficiency of N use and apparent recovery of N (**Table 10**). Poultry manure and ferti plus fertilizer enhanced agronomic efficiency, apparent recovery of nutrients from above ground biomass, internal utilization efficiency as well as N conversion efficiency while NPK enhanced partial factor productivity and NHI for both sole and intercrop mixtures (**Table 10**). The summary of uptake, recovery, agronomic and physiological efficiencies of N use, N removed at harvest and conversion efficiencies is presented in **Table 11**. Maize and pepper were efficient in terms of ANR, agronomic and physiological efficiencies of N use and its conversion efficiencies while cassava was outstanding for N uptake and its recovery at harvest. Among the fertilizers tested, poultry manure and Ferti plus were outstanding with respect to ANR, agronomic and physiological efficiencies of NUE and N conversion efficiencies while NPK out-performed other fertilizers for NHI and N recovery at harvest. The interactions of intercrop species and fertilizer was significant for most of the variables of agronomic and physiological efficiencies of N use evaluated (**Table 11**). The fertilizers (NPK compound fertilizer, ferti plus and poultry manure exerted significant effects on nitrogen uptake for biomass and yield production. While NPK enhanced N uptake and apparent recovery of N in above ground biomass, ferti plus and poultry manure promoted most other indicators of agronomic and physiological N use efficiencies. The efficiencies of uptake and use of N were higher for NPK and ferti plus compared with poultry manure across the ages of oil palm fields. The values of the measured indicators of N uptake and use efficiencies were highest for 4 and 6 years compared with the 3 years old fields across the intercrop species. The uptake and yields of N were higher for the respective sole crops of cassava, maize and pepper compared with the intercrops across the fertilizers compared with the control.

The age of oil palm fields and fertilizers influenced nutrient uptake and use efficiencies of the intercrop species (leaf, tuber of cassava, fruits of pepper and seeds of maize) in the alleys of 3, 4 and 6 years old oil palm trees and thus, the resultant yield improvement compared with unmanure treatments [42]. The intercrop species differed in shoot morphological and physiological attributes, and rooting patterns of rooting, biomass and nutrient accumulation and partitioning. These attributes have implications for nutrient uptake, use efficiencies and yield production among the alley crop species [22]. Crop species and fertilizer type affected the uptake and accumulation oof nutrients to the vegetative and reproductive structures [20, 23]. Information about differences among species and varieties with respect to N use efficiencies have been used to develop cultivars adapted to low fertilizer input management systems. The sole crops of the intercrop species under NPK treatment recorded the highest nutrient contents in their leaves which indicates that physiologically, nutrients uptake may depend of the degree of competition (below ground) for resources [20, 23]. The fertilizer NPK, contains high N content which is released rapidly into soil solution and promoted its availability, this must have enhanced its uptake by the plant and utilization for biomass production (improved plant growth) compared with organic fertilizers (poultry manure for

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

example). Fertilizers enhance nutrient availability and bring about decreases in competition placed on nutrient resources by intercrop species (crop mixtures) [20]. Literature reports has indicated that differences in soil nutrient status are a major source of variation in uptake and use efficiencies and of crop yields [20, 36]. These reports also attributed crop yield enhancement by fertilizers to improvements in the efficiency of uptake and use of nutrient resources for both sole and intercropping systems. Agele et al. [6] also attributed high yield performance of sole and intercrop combinations of crop species to improvements in efficiency of nutrient utilization. Our study showed that application of poultry manure, ferti plus and NPK fertilizers to alley crops in oil palm soil affected nutrient uptake leaf and tuber/seed nutrient contents compared with the control (un-manure) treatments. The fertilizers enhanced soil nutrients (the sandy loam soil of experimental site appeared to have low fertility status especially N) while improvement in other soil (chemical, physical and biological) properties would have promoted biomass accumulation and yield production by the alley crop species. It is reported that nutrient availability depends on nutrient concentration in the soil and environment and release pattern in synchrony with the crop needs [22, 23]. However, highest N uptake values were obtained for the un-manure. Nitrogen harvest index was higher under ferti plus and poultry manure compared with NPK, this result was in line to the conclusion of Agele et al. [6, 22] that the crop yields and nutrient availability were higher in plots for which farmyard manure was applied, and to longer time availability. Manure decompose slowly and release their constituent nutrients slowly, may be to meet time dynamics of nutrient demand by growing crops [6, 43].

Highest nitrogen harvest index values for seed and leaf of intercrop species were obtained from the un-manure treated plants. The superiority of these may be attributed to more vigorous nutrient exploitation advantage [23]. Oil palm also take up nutrient from the soil for its growth, especially from sandy loam soil of experimental sites, nutrient recycling in palms is slow. However, oil palm provides nutritional elements like phosphorus [44], and nutrient P is reported to decrease species competition placed on nutrient resources [11]. For arable crops grown in the alley of oil palm (1 to 6 years old), supplementary input of nutrients especially nitrogen from fertilizers (organic and inorganic) is needed to meet the nutrient requirements of alley crops.

### **6. Summary and Conclusions**

Based on the measured growth parameters of oil palm seedlings, shading and weekly irrigation enhanced seedling vigor compared with fortnight and open sun (unshaded) treatments. These treatments enhanced vigor, growth and reduce mortality of oil palm seedlings in the nursery in the dry season. Mycorrhizal inoculation of oil palm seedlings, shade and weekly irrigation are recommended. The findings from this study acclaimed the relevance of dry season irrigation and shade to supplement soil moisture and reduced temperature for oil palm seedling growth and development. The drip irrigation-shade strategy adopted ameliorated dry season terminal drought (hydrothermal stresses) in cacao. This is a veritable tool to scale up growth, survival, establishment and flower/pod production. The results of this study will contribute to the development of sustainable cacao production practices and development of shade and irrigation management guidelines for small holder farmers.

Oil palm age significantly affected most of the measured growth variables and indicators of competitive interactions and crop mixture productivity, and agronomic and physiological efficiencies of N use by alley intercrop species. The study established that intercrop mixtures of cassava, maize and pepper in the alleys of oil palm of 2 to 6 years old exhibited some levels of compatibility and complementarity and confirmed low competitive interactions but high growth resource use efficiencies. The results of competitive functions and crop mixture productivity indicate the yield advantage of crop mixtures over sole cropping and hence the overall biological advantage of intercropping of cassava, maize and pepper in the oil palmbased intercropping system. Strip intercropping of cassava, maize and pepper in the alleys of 2 to 6 years old oil palm in the rainforest zone had no detrimental effects on the growth and yield of oil palm. Crop performance results from the behavior of the individual plants interacting through competitiveness (vigor of growth of individual species in the mixture) and complementary which drive resource capture and utilization. The study improved understanding of compatibility and complementarity of growth resource use (space, light, nutrients and possibly water) of oil palm with some selected arable crops in oil palm-based intercropping system of the rainforest of Nigeria. Improved insight to unravel the primary drivers and dynamics of competitive and complementary growth responses of crop mixtures in cropping systems. Such knowledge is relevant to the promotion and adoption of crop mixtures (intercropping systems) for sustainable increases in crop yields at acceptable input levels. Over their respective sole crops, the strip intercrops of cassava, maize and pepper exhibited high values of land equivalence, percentage land saved (PLS) and low aggressivity in the alleys of oil palm which indicates greater yield advantage of crop mixtures over sole cropping. These observations denote the advantage of intercropping in terms of productivity per unit land area, in addition to greater percentage land saved.

The fertilizers (organic and inorganic) enhanced nutrient uptake and use efficiencies in the respective leaf, tuber, seed and fruits of cassava, maize and pepper in the alleys of 3, 4 and 6 years oil palm fields. The indicators of uptake and use efficiencies of N differed among the alley crop species and fertilizer types across the ages of oil palm plants in plantation. While NPK promoted the uptake and apparent recovery of N in above ground biomass, the organic fertilizers enhanced other indicators of agronomic and physiological N use efficiencies, and the efficiencies of uptake and use of N were higher for NPK and ferti plus compared with poultry manure. Uptake and use efficiencies of N were higher for the respective sole crops of cassava, maize and pepper compared with the intercrops across the fertilizers. N content was highest for fruits of pepper while N uptake and yields were highest for cassava tubers and seeds of maize. For arable crops grown in the alley of oil palm (1 to 6 years old), supplementary input of nutrients especially nitrogen from fertilizers (organic and inorganic) is needed to meet the nutrient requirements of alley crops.

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