Fertility status of soils under selected land use types in Orlu, Imo State, Southeastern Nigeria

The study evaluated the fertility status of some land use types in Orlu area of Imo State using elemental ratio. Soil samples were collected from three land use types namely; plantain plantation, oil palm plantation and cassava. A total of 18 samples were collected. Six soil samples were randomly collected from each land use at depths of 0 - 15 cm and 15 - 30 cm. Routine analyses were conducted and Ca/Mg and K/Mg were used to determine the fertility status of the soils. The result of physical properties indicated that mean sand content of the soils ranged from 820.1 - 910.1 g/kg. The mean silt content of the soils ranged from 13.3 – 56.7 g/kg while the clay content ranged from 76.5 – 136.5 mg/kg. Bulk density was highest under oil palm (1.43 g/cm3) and lowest under cassava (1.10 g/cm3). The results of the chemical properties showed that mean pH varied from 5.0 – 5.7. Soil organic carbon was highest under plantain (16.9 g/kg) and lowest under oil palm (9.3 g/kg). Ca/Mg ratio was highest under plantain (1.78) and lowest under cassava (1.20). The K/Mg was highest under oil palm (0.14) and lowest under plantain (0.02). Ca/Mg ratio of the soils indicates possible Ca deficiency and phosphorus inhibition. The K/Mg ratio of the soils shows non inhibition of the uptake of magnesium Ca/Mg ratio varied highly under plantain and cassava but had medium variation under palm oil. There was significant negative relationship between K/Mg and Mg, ECEC, Ca, base saturation (BS) and available phosphorus (-0.85, -0.85, - 0.86, -0.77, and -0.47) respectively. Key words; Elemental ratio, soil fertility, land use, Imo state, southeastern Nigeria