Integrated phosphorus management in maize–chickpea cropping system on alkaline Fluvisol

In tropical agro-ecosystem, crop production is constrained by the reduced availability of soil phosphorus (P) due to strong P fixation. A field experiment was conducted for five cropping seasons on an alkaline Fluvisol to assess the integrated effect of six system-based fertilizer P rate (kg P₂O₅ ha⁻¹) in maize (M)–chickpea (C) rotation [M₀–C₀, M₀–C₄₀, M₃₀–C₀, M₃₀–C₄₀, M₆₀–C₀, M₆₀–C₄₀], two manure treatments [no farmyard manure (FYM), FYM at 5 t ha⁻¹], and two phosphate solubilizing bacteria (PSB) treatments [no PSB, PSB seed treatment in chickpea] on soil available-P, soil–plant P dynamics, balance, P use efficiency, and system productivity. Combined application of fertilizer P and FYM had a strong positive impact on soil available-P, soil biochemical properties, P acquisition and crop productivity. Conversely, the effect of PSB was marginal. Treatment M₆₀–C₄₀ + FYM + PSB increased soil available-P by 56% at the end of 5-year rotation; where 53% depletion was noticed in treatment M₀–C₀ − FYM − PSB (control). Treatments M₃₀–C₄₀ + FYM ± PSB, M₆₀–C₀ + FYM ± PSB, and M₆₀–C₄₀ + FYM ± PSB had a positive trend of soil available-P. The order of fertilizer P treatments for P uptake and annual P balance was M₆₀–C₄₀ > M₃₀–C₄₀ > M₆₀–C₀ > M₀–C₄₀ > M₃₀–C₀ > M₀–C₀. FYM application improved P recovery efficiency by 71%. Soil microbial biomass carbon, dehydrogenase and alkaline phosphatase, and soil pH had significant relationship with available-P (p < 0.01). Notably, treatments M₃₀–C₀ + FYM + PSB and M₆₀–C₄₀ − FYM − PSB had a similar effect on maize productivity (4.1–4.2 t ha⁻¹). Likewise, treatments M₆₀–C₀ + FYM + PSB and M₆₀–C₄₀ − FYM − PSB were comparable for chickpea productivity (p > 0.05). Therefore, integration of manure and fertilizer P is recommended for increasing the productivity and P use efficiency in maize–chickpea rotation in tropical alkaline soil.