This study conducted the influence of sheep manure and biochar on the retention of soil phosphorus in both calcareous and non-calcareous soils. Soil samples were taken from the plowing depth (0–30 cm) of agricultural areas at two locations: Bakrajo (calcareous soil) (35°32′03.9″ N, 45°21′57.1″ E) and Arbat (non-calcareous soil) (35°23′40″ N, 45°39′27″ E) in the Sulaimani Governorate, Iraqi Kurdistan region . A soil incubation experiment was performed using 200 g of soil which mixed with four levels of biochar (0, 0.25, 0.5, 0.75%) and four level of sheep manure (0, 0.5, 1, 2%) in glass jars at 28±2°C at 60% of its available water, the samples were incubated for 2,4 and 6 months and soil available phosphorous was measured after 2,4 and 6 months, Phosphorus availability was influenced by different levels of manure and biochar across the incubation periods of 2, 4, and 6 months. Manure P mineralization increased over time, leading to a substantial rise in soil phosphorus levels after 2 months, with the highest value 13.565 mg kg-1 observed at the 1% manure application in non-calcareous soil, and decreased significantly afterwards. At similar soil test P values, non-calcareous soils with high buffering capacities had larger P reserves than calcareous soils with low buffering capacities, and 14.15 mg kg-1 in calcareous soil at manure level 2% after 6 months. The findings indicate that the impact of biochar and sheep manure increased with increasing application rates. Biochar at a 0.75% application rate and sheep manure at 2% had the greatest impact.
Karim et al. (Sun,) studied this question.