Biochar and sewage sludge phosphorus fertilizer effects on phosphorus bioavailability and spinach ( Spinacia oleracea L.) yields under no-till system in semi-arid soils

Abstract

Purpose This field study evaluated the interactive effects of biochar (BC) and sewage sludge (SS) on P bioavailability and spinach yields for two seasons.Method Treatments were combinations of biochar (0, 2.5 and 5 Mg ha-1) and sewage sludge (0, 6 and 12 Mg ha-1), or mineral fertilizer (200, 28, and 18.9 kg ha-1), amended in a randomized complete block design to Luvisol and Cambisol.Results Significant (p 0.05) yields compared to sole amendments. Mehlich – 3 extractable P (M3-P) in control plots (CONT) increased between seasons, presumably due to P inputs from the irrigation water. Co-amendments on the Cambisol resulted in higher M3-P increase over mineral fertilizer than on the Luvisol in both seasons. Accumulation of M3-P in control plots confounded correlations between crop yields and available P. Higher P under BC compared to SS amended soils emphasize biochar capacity to capture P from irrigation water.Conclusion The results suggest that combined low rates of SS and BC can have significant effects on P availability and crop yields. Biochar enhanced plant P uptake, but decrease in yields with simultaneous increase in M3-P between seasons warrants further research.

Keywords

• co-application
• bioavailability
• phosphorus
• spinach
• yield