The status of phosphorus levels in Iranian agricultural soils — a systematic review and meta-analysis

Mohsen Jalali*, Wolfram Buss, Fatemeh Parviznia, Mahdi Jalali

*Corresponding author for this work

    Research output: Contribution to journalReview articlepeer-review

    1 Citation (Scopus)


    Phosphorus (P) inputs are essential for maximizing agronomic potential, yet high P inputs and subsequent P losses can cause eutrophication of water bodies. There is a need to evaluate P contents in agricultural soils globally both from an agronomic and environmental perspective. This systematic review and meta-analysis estimated the pooled mean levels of P contents of Iran. In this study, data on available and total P contents of Iran’s calcareous soils was compiled (main focus on Olsen P) and compared to (i) estimated Iranian background and global agricultural soil P contents, and (ii) agronomic and (iii) environmentally critical Olsen P values. The pooled mean estimate from the meta-analysis indicates that the levels of Olsen P across 425 soil samples (27 studies) were 21.3 mg kg−1 and total P across 190 soil samples (12 studies) 805.5 mg kg−1. Using 26 mg kg−1 as the agronomic critical Olsen P value above which no increase in crop yield occurs, crops grown on 61% of the soil samples in the investigated region would respond to P fertilizer and 20% of soils are currently in the optimum category (26–45 mg kg−1 Olsen P). The environmentally critical Olsen P value (~ 63 mg kg−1), defined as the amount above which P leaches from soil rapidly, was exceeded by 11% of soils with a further 4% of soils with elevated eutrophication risk. To maximize crop yields while maintaining a minimal risk of P leaching in Iran’s calcareous soils, we suggest an ideal Olsen P of 26 mg kg−1. The outcomes from this study inform about the P status of Iranian soils and could help update recommendations for P fertilizer applications in calcareous soils globally. The framework presented here could further be adopted to evaluate the P status in other soil types.

    Original languageEnglish
    Article number842
    JournalEnvironmental Monitoring and Assessment
    Issue number7
    Publication statusPublished - Jul 2023


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