Crop performance in calcareous and alkaline soils is often limited by low nutrient availability and uptake following poor soil fertility. The positive agronomic effects of compost and biochar originated from a distinct biomass on soil fertility, nutrients uptake and crop growth were previously reported in a wide range of different soil types. However, a little is surfaced about the contrasting effects of compost and biochar produced from the same biomass on soil fertility, nutrients uptake and crop growth in the calcareous and alkaline soils. A greenhouse experiment was carried out with an eye of contrasting the effects of compost and biochar made from the same pioneering Oleaster (Oleaster angustifolia L.) tree on improving these limiting factors for crop performance found in the calcareous and alkaline soils. The calcareous and alkaline soil used was either untreated (control) or treated with compost and biochar at a rate of 1, 2 and 4% w/w. The experimental layout was laid in line with completely randomized plot design in quadruplicate. Across the experiment, compost significantly (p < 0.05) exhibited the striking impacts on soil fertility, nutrients uptake and maize growth than biochar treatments. To put the effects of compost and biochar into perspectives, compost exhibited the highest rally in soil fertility through enriching pH, electrical conductivity (EC), extractable cations (Ca, Mg, K and Na), available micronutrients (Fe, Mn, Cu and Zn), available phosphorous (P), NO3-N, NH4-N, total nitrogen (TN) and organic matter (OM), nutrients uptake via enhancing the uptake of total nitrogen, P, K, Ca, Mg, Fe, Zn, Mn and Cu, as well as maize growth via improving leaf chlorophyll content (LCC), plant height (PH), stem girth (SG), aboveground fresh biomass (APFB), aboveground plant dry biomass (APDB), fresh root biomass (FRB) and dry root biomass (DRB) than biochar amendments due to most likely sorption effects of biochar and its recalcitrance to microbial activities. Overall, soil fertility and crop performance increased in the order control < biochar < compost. Based on the findings of this study, it is concluded that compost can be suggested under such type of soils for improving soil fertility and crop performance at the expenses of biochar applications, nonetheless, field demonstration is highly essential for more conclusive results prior to recommending either compost or biochar in soil management practices.