System-based phosphorus management in non-flooded rice-lentil rotation in tropical alkaline soil on Gangetic plain: Crop productivity, phosphorus use efficiency and budgeting

Abstract

ContextAerobic rice cultivation, gaining recognition for its water-saving and ecological benefits, often faces productivity challenges due to various deficiencies in the soil-plant system. In absence of flooding-induced P dissolution, reduced soil P availability would have yield-limiting impacts on the non-flooded aerobic rice-based system on tropical alkaline soils. ObjectiveThe study aimed to assess the impact of system-based sole fertilizer-P and integrated P treatments in non-flooded direct-seeded rice (DSR)-lentil system for recommending sustainable P management strategies. MethodsThe experimental treatments included a control with no P application ([DSR0-L0]), three variable seasonal distribution of sole fertilizer-P treatments [subscript value (kg P ha−1)] ([DSR22-L22], [DSR33-L11], [DSR11-L33]), three integrated P treatments ([DSR11-L11+phosphate solubilizing bacteria (PSB)], [DSR16.5-L5.5+rice residue (RR)+PSB], [DSR5.5+lentil residue (LR)-L16.5+PSB] along with a conventional puddled-transplanted flooded rice-lentil using blanket recommended fertilizer-P rate ([PTR22-L22]). These treatments were evaluated over three years to investigate their impact on soil-plant P dynamics, crop productivity, P use efficiency, and budgeting. ResultsThe findings revealed that soil P availability in non-flooded rice (DSR) was lower (8–10 %) compared to transplanted flooded-rice. The integrated P treatment, which included rice residue recycling, PSB, and suboptimal fertilizer-P (22 kg P ha−1y−1) increased soil P availability in both rice (8 %) and lentil (12 %) seasons compared to the recommended sole-fertilizer P treatment. This led to a significant increases in rice (6 %) and lentil (9 %) yields during third year of cropping. Meanwhile, the treatments involving the variable distribution of the annual fertilizer-P rate (44 kg ha−1y−1) to component crops in different ratios [1:1, 3:1, 1:3] exhibited only marginal variations in available-P and crop yields. Integrated P treatments with crop residue recycling increased macronutrient acquisition (N, P, and K), agronomic P use efficiency and fertilizer-P recovery efficiency over sole-fertilizer P treatments (p < 0.05), highest with the rice residue recycling integrated treatment. The apparent P balance was marginally negative in the residue recycling integrated P treatments (-1.9 to −2.1 kg ha−1y−1), but highly positive in the sole fertilizer-P treatments (+15.3 to +15.9 kg ha−1y−1). Conclusion and significanceThe study highlights the potential of integrated P treatments with rice residue recycling in improving soil P availability, nutrient use efficiency, and crop productivity of aerobic rice-lentil system in tropical alkaline soil while saving costly fertilizer-P input.