Pollution is one of the major threats with potential risks to humans, animals and plants, especially pollution with heavy metals, which are characterized by their significant ability to accumulate in environmental systems and induce toxicity to living organisms, even at low concentrations and quantities. This study was conducted on some calcareous soils selected from the province s of Babylon and Diwaniyah. Soil samples were collected from ten sites, five sites from each province , from a depth of 0-30 cm, to determine the concentration of cobalt in its chemical forms (available, bound to calcium carbonate, bound to organic matter and oxides, and residual) and total concentration, in addition to knowing the effect of different soil characteristics on these chemical forms. The results showed that there was a relatively wide range in the total cobalt concentration in the study sites (16.58 - 86.76 mg kg-1), and the percentages of the available chemical phase of the metal ranged from 0.44% - 6.88%, and in the form associated with carbonates from 19.30% - 34.54%, and in the form associated with organic matter and oxides from 28.82% - 55.94%, and in the form associated with the residual fraction from 3.46% - 51.44%. Because the metals in these fractions might dissolve depending on environmental conditions, notably pH values, higher mobility levels of accessible metal ions and those partly bonded to calcium carbonate may suggest environmental contamination and a risk of toxicity in soils.

Maize is an important cereal crop in Ethiopia due to its use as a source of food security. However, its productivity is limited by insufficient application of the NPS fertilizer and inappropriate plant density. A field experiment was conducted during 2020 and 2021 cropping seasons at Liban Jawi and Toke Kutaye districts of West Shoa Zone, Ethiopia to study the effect of plant density and NPS fertilizer rates on growth, yield, and yield components of maize. The experiment consisted of three plant populations (53,300, 66,600 and 88,800 plants ha-1) and five NPS fertilizer rates (100, 150, 200, 250 and 300 kg NPS ha-1) laid out in a randomized complete block design with three replications. The results showed that plant height, ear height and biological yield increased with increasing plant density. On the contrary ear length, number of grains per row, grain yield and harvest index decreased with increasing plant density. Plant density of 53,300 plants ha-1 produced the higher grain yield (5969 kgha-1) compared to that of 88,800 plants ha-1 (5175 kg ha-1). However, grain yield at 53,300 plants ha-1 did not show a significant difference with that of 66,600 plants ha-1 (5746 kg ha-1). In case of NPS fertilizer rates the results showed that plant height, ear height, ear length, number of grains per row, 1000 seed weight, biological yield, grain yield and harvest index increased with increasing NPS fertilizer rates up to optimum rate. Fertilizer application of 200kg NPS ha-1 produced a higher grain yield (6710 kg ha-1). The highest economic (126,423 Birr ha-1) and a higher MRR (2630%) resulted from the application of 200 kg NPS ha-1 with a plant population of 53,300 plants ha-1. Therefore a Plant density of 53,300 plants ha-1 and a blended fertilizer application with 200 kg NPS ha-1 was the most appropriate for highland maize in the study area.