1. INTRODUCTION
Oil palm (Elaeis guinensis ) is one of the plantation crops grown
in some tropical countries of the world especially Nigeria in addition
to cocoa, kola, teak, gmelina, rubber, and cashew as a result of
transformations in agriculture. It is cultivated mostly in the southern,
eastern, and western parts of the country. Recently, planted areas had
increased at a rapid pace, and the increase is significantly evident.
Oil palm was adopted and cultivated among the high-value perennial tree
crops by individual small-scale growers, private agencies, and
government agencies (state and federal). Global oil palm production is
approximately 272,055,131 tonnes from 18,917,400 hectares, with Asia
(84.1%) taking the lead, followed by Africa (9%) (FAO, 2020). It is a
major source of oils and fats for human food, livestock feed, and
manufacturing of several other domestic products, such as cosmetics,
soap, and detergents (Reiger, 2006).
The increase in oil palm demand has resulted in the conversion of
natural vegetation into oil palm plantations. The conversion of some
rainforests and the use of abandoned logged-off forests into oil palm
plantations is expected to have contributed significantly to nutrient
losses from both soil and vegetation (Brahene et al., 2016; Rozieta et
al., 2016). Deforestation and loss of habitat of critically endangered
species (Clay, 2004), a decrease in soil productivity, an increase in
soil erosion, and soil biodiversity loss (Comte et al., 2012; Savilaakso
et al., 2014), and a substantial increase in greenhouse gas emissions
are the detrimental effects of oil palm on the climate (Bates et al.,
2008; Hassan et al., 2011). Rising tillage intensity and the conversion
of the natural environment to agricultural land have contributed to a
decline in soil organic matter levels due to decreased organic carbon
inputs and decreased physical conservation of soil organic carbon
contents (Chibsa and Ta’a, 2009).
As a consequence of the combined effects of physical, chemical, and/or
biological processes operating at various intensities and on different
scales, the classification of soils depends on the degree of spatial
heterogeneity (Priyabrata et al., 2008). Research has shown that crop
age also leads to soil variability because nutrients are extracted from
the soil during harvest for grain, fiber, wood, and crop residues as the
crops grow older (Basiron, and Weng, 2004; Aweto and Enaruvbe, 2010). If
replenishment with inorganic and/or organic fertilizers is insufficient,
nutrient removal can result in a decrease in soil fertility (Okon et
al., 2017). There seems to be little or no knowledge as touching the
impact of oil palm plantations of different ages on soil
physico-chemical properties in the research region to date on various
studies on oil palm plantations in Nigeria. Therefore, it is of great
importance to assess the quality of soil nutrients in existing oil palm
plantations of various maturity ages and to analyze the variability
(differences) in the soil properties of these oil palm plantations.