Adding nitrification inhibitors to N fertilisers induces rhizosphere acidification and enhances P acquisition: A meta-analysis

Abstract

Ammonium (NH4+) absorption by crops enhances inorganic phosphate (Pi) acquisition efficiency mediated by rhizosphere acidification. The application of nitrification inhibitors (NIs) prolong NH4+ retention in soil by inhibiting ammonia oxidation and facilitating ammonium uptake by crops which may promote crop P utilisation. However, the efficacy of NIs on enhanced P-utilisation efficiency has not been comprehensively evaluated, and the mechanism underlying these effects remains unclear. Here, a meta-analysis of 92 peer-reviewed articles (1217 paired observations) was conducted to investigate soil pH and crop P absorption changes under NIs amendment, and boosted regression tree model was adopted to identify the primary factor regulating enhanced P-efficiency. The results showed that the addition of NIs reduced the rhizosphere soil pH by 12.37% and increased bulk soil pH by 2.38%, increased plant N and P uptake by 16.09% and 8.49%, respectively, and shoot N and P concentrations by 4.38% and 6.73%, respectively. NIs significantly decreased the crop N/P ratio and alleviated P limitation for crop production. Fertiliser (N and P) application method, NI product type, and soil properties (soil organic carbon, available P, total N content and soil texture) are major factors affecting crop P uptake. Using dicyandiamide (DCD) or 3,4-dimethylpyrazole phosphate (DMPP) as NIs combined with the application of ammonium-based fertiliser, adoption of subsurface or one-time N application, or application of these fertilisers to coarse-textured soils could significantly decrease rhizosphere soil pH while increasing crop P uptake. This study quantitatively demonstrated the positive impact of NIs on crop P acquisition using a meta-analysis approach, enhanced the knowledge on the incidental efficacy of N stabilisers and provide a strategy for the sustainable management of N and P in agriculture.