Sorghum Agronomic Performance and Soil Chemical and Microbiological Properties as Influenced by Burkina Faso Phosphate Rock-Enriched Composts

Abstract Purpose The low availability of phosphorus (P) severely limits crop production in sub-Saharan Africa. We evaluated phosphate rock-enriched composts on soil properties and sorghum growth for use as environment-friendly fertilizers. Methods Treatments were sorghum straw, compost (Comp), Phosphate Rock (BPR), BPR-enriched compost (P-Comp), BPR-soil-enriched compost (P-Comp-Soil), nitrogen-phosphorus-potassium (NPK, 60-90-30), and control without phosphorus and organic material (CT). Sorgum straw and composts were applied at 1.34 tons ha-1. The amounts of nitrogen, phosphorus, and potassium in treatments, except in CT, were adjusted to 60, 90, 30 kg ha-1, with urea, BPR, and KCl, respectively. Sorghum vr. Kapelga was cultivated and soil samples were collected on days 52, 93, and 115 (harvest) for analysis. Results NPK and P-Comp-Soil provided the best sorghum yields. Soil available P was less in these treatments. P-Comp-Soil-amended soils recorded higher populations of bacteria (16S rRNA), acid phosphatase (aphA), phosphonatase (phnX), glucose dehydrogenase (gcd) and its cofactor pyrroloquinoline quinone (pqqE) genes. Phosphate-specific transporter (pstS) and arbuscular mycorrhizal fungi (AMF) abundances were generally higher in P-Comp-Soil soils, especially at the early growth stage. This active microbial activity in the P-Comp-Soil added to its initially higher available P justified a better nutrient uptake and yields comparable to NPK. Multivariate analysis also revealed the contribution of nitrogen, carbon, and exchangeable cations in sorghum growth. Conclusion This study demonstrated that direct phosphate rock application is not effective in sub-Saharan African upland cultivation. Alternative to chemical fertilizers, soils may be amended with phosphate rock-enriched composts, a niche of beneficial microbes improving soil health.