We investigated the effect of untreated and biologically treated olive mill wastewater (OMW) spreading on the soil characteristics and the microbial communities. The water holding capacity, the salinity and the content of total organic carbon, humus, total nitrogen, phosphate and potassium increased when the spread amounts of the treated or untreated OMW increased. The OMW treated soil exhibited significantly higher respiration compared to the control soil. However, the C-CO2/C(tot) ratio decreased from 1.7 in the control soil to 0.5 in the soil amended with 100 m3 ha(-1) of untreated OMW. However, it slightly decreased to 1.15 in the soil amended with 400 m3 ha(-1) of treated OMW. The treated OMW increased the total mesophylic number while the number of fungi and nitrifiers decreased. Actinomycetes and spore-forming bacteria were neither sensitive to treated nor to untreated OMW. The total coliforms increased with higher doses of treated and untreated OMW. A toxic effect of the untreated OMW appeared from 100 m3 ha(-1). This toxicity was more significant with 200 m3 ha(-1), where microflora of total mesophilic, yeasts and moulds, actinomycetes, and nitrifiers were seriously inhibited except for total coliforms and spore-forming bacteria.

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The effects of untreated and treated olive mill wastewater on seed germination, plant growth and soil fertility were studied. Tomato (Lycopersicon esculentum), chickpea (Cicer arietinum), bean (Vicia faba), wheat (Triticum durum) and barley (Hordeum vulgare) were tested for the germination index and growth in soil irrigated by olive mill wastewater. Lepidium sativum was used as the standard species for the germination index and phytotoxicity evaluation. We measured soil properties, crop growth, herbage biomass, leaf elongation and productivity. The results show beneficial effects using treated olive mill wastewater. The treated plants showed an improvement in seed biomass, spike number, plant growth, and a similar or even better dry productivity than plants irrigated with water, e.g. Hordeum vulgare 102%, Triticum durum 105%, Cicer arietinum 101% and Vicia faba 102%. An increase in the germination index from 100% to 115% was observed. Soil organic matter, respiration and enzymatic activities were also enhanced by treated olive mill wastewater ferti-irrigation. However, even diluted 10 times, untreated olive mill wastewater inhibited the species germination, e.g. 1.2% for Hordeum vulgare and 40% for Cicer arietinum and Vicia faba, and plant growth (16-42.5%). Leaf necrosis and low productivity were observed in crops ferti-irrigated by untreated olive mill wastewater. olive mill wastewater / germination index / phytotoxicity / crop growth / soil fertility

Purpose The study investigated the effects of poultry and goat manures on the kinetics of potassium fixation and release in some sandy loam and loamy soils of Ogun State, Nigeria. Methods The treatments consisted of poultry and goat manures applied at 25 g and 100 g/5 kg soil set in completely randomized design with three replicates. Potassium fixation and release kinetics were computed from the analytical data. Results Experimental soils was sandy, slightly acidic, low in nutrients with 80% fixed potassium. However, manure application resulted in 74% reduction of the amount of K fixed by the soils. Elovich and power functions had the best fit for K released in soils treated with goat manure. The K release pattern in poultry manure-amended soil is best described by the parabolic diffusion, Elovich, and power functions, while the first-order equation described K release in soils treated with cattle manure. The potassium release rate constant correlated positively with K uptake. Conclusion The ability of the studied soils to fixed K was reduced with the application of organic manures. Potassium fixation decreased with increase in organic manure rates, 100 g/5 kg soil tends to be the optimum rate, and poultry manure had greater effect on the fixing and releasing power of K.

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