The effect of crude oil pollution of soil on the growth of plants and uptake of nutrients was investigated by growing corn (Zea mays L.) on a soil polluted by crude petroleum. The levels of the crude oil application varied from 0 to 10.6% by weight of soil. Three corn crops were raised in succession, each for a period of 6 weeks, in the same soil. The yields and plant contents of N, P, K, Ca, Fe, and Mn were determined. The soil was analyzed for organic C, total and available N, extractable P, and exchangeable K, Ca, Fe, and Mn after each cropping. Germination and yields were drastically reduced as the level of pollution increased. At 4.2% crude oil pollution level, the average reductions were 50% and 92°/0 in germination and yield, respectively. The amount of organic C, total N, and exchangeable K, Fe, and Mn increased in the soil with level of crude oil addition, while extractable P, NO3-N, and exchangeable Ca were reduced. The poor growth was attributed to suffocation of the plants caused by exclusion of air by the oil or exhaustion of oxygen by increased microbial activity, interference with plant-soil-water relationships, and toxicity from sulfides and excess available Mn produced during the decomposition of the hydrocarbons.Additional Index Words: carbon-nitrogen ratio, crude petroleum, hydrocarbons in soil, manganese toxicity, nitrate immobilization, nitrogen fixation, reducing conditions.

The distribution of total, organic, and various inorganic phosphorus forms was determined for six Nigerian soil profiles selected to cover different ecological zones and geological formations. Total P was generally low in most of the profiles ranging from 144 to 791 ppm. The basaltic Dogon Gaba soil contained the highest amounts while the soil formed on sedimentary deposits had the lowest values. The relative abundance of the extractable inorganic fractions was generally in the order of occluded P > Fe − P > Al − P > Ca − P except in Dogon Gaba and Agbaru (Etinan) where Al − P was more abundant than Fe − P and in Egbeda with Ca − P more important than Al − P (the latter being negligible in this soil). A large fraction of the inorganic P remained in the nonextractable or residual form especially in soils from the savanna region. Organic P was low in the soils from the savanna zone, but high in those soils from the forest region. The high percentage of occluded and residual P and the low level of active P indicated a high degree of weathering and a low available P status of the soils.

Thermodynamic parameters derived from experimental results were determined for the potassium‐calcium and magnesium‐calcium exchange reactions on a kaolinitic soil clay separated from the B horizon of a strongly weathered soil profile. The clay samples were equilibrated at 10° and 30°C with a mixed solution of KCl and CaCl2 for the K‐Ca system or MgCl2 and CaCl2 for the Mg‐Ca system. For the K‐Ca system, the selectivity coefficients were high indicating a greater affinity of the clay for K than for Ca. The high equilibrium constant and the negative values of standard free energy and enthalpy changes for the exchange of Ca for K also revealed a preference of the clay for K relative to Ca ions.In the Mg‐Ca system, the exchange isotherms and the low selectivity coefficients indicated a preference of Ca ions for the clay phase. This exchange of Ca for Mg was accompanied by an increase in the free energy and enthalpy changes also pointing to a more stable Ca‐clay than Mg‐clay.

Zinc adsorption was studied in suspensions of 10 calcareous Arizona soils in dilute ZnSO4 solutions. At low concentrations, Zn2+ adsorption was described by the Langmuir adsorption equation. The calculated Langmuir adsorption maxima were related to the carbonate and organic matter contents of the soils. When the added Zn2+ exceeded the adsorption maximum, the value of the (Zn)(OH)2 ion concentration product in solution corresponded to the solubility of zinc hydroxide or carbonate so long as soil carbonates were present. At lower amounts of adsorbed Zn2+ and/or when the soil carbonates had dissolved, the (Zn)(OH)2 product was about one hundred‐fold less indicating that the soils then retained Zn2+ about as strongly as zinc silicate, and more strongly than zinc hydroxide or carbonate.

Tropical acid soils adsorb a large portion of phosphorus added to them. In order to study the characteristics of phosphorus adsorption in 10 Nigerian acid soils, 2 g of soil were equilibrated in 0.01M CaCl2 containing various amounts of phosphorus for 48 hours. The phosphorus disappearing from solution was taken as the amount adsorbed. The capacity to adsorb phosphorus varied among the soils, but in general the more strongly weathered soils from the eastern area adsorbed more phosphorus than those from western Nigeria. At low concentrations of phosphorus in the equilibrium solution, the adsorption could be satisfactorily described by Langmuir Isotherm equation. The adsorption was significantly correlated with sesquioxides and the exchangeable forms of Al and Fe as well as the clay content and pH. The citrate‐dithionite and the oxalate extractable oxides were of equal significance in the phosphorus adsorption, but the role of Al was more important than that of Fe.