Application of calcium nitrate with phosphorus promotes rhizosphere alkalization in acid subsoil

Abstract

Combatting subsoil acidity is a challenge as the incorporation of lime in subsurface layers may not be economically feasible. The use of nitrate to facilitate plant excess anion uptake has shown the potential to increase soil pH. A column experiment was carried out to demonstrate this root‐induced alkalization in various depths in an acid soil with pH 4.28 (0.01 M CaCl2). It consisted of two types of nitrogen (N) fertilizers (urea and Ca(NO3)2, both at 5 atom% 15N enrichment) banded at a depth of 0–10 cm, 10–20 cm or 20–30 cm, with phosphorus (P) fertilizer (NaH2PO4) at 150 mg P per column either applied to the N layers (N+P) or evenly mixed into the remaining layers without N addition (N‐P). Aluminium‐tolerant wheat (ET8) was used as test plants, receiving an initial N dose of 60 mg kg−1 soil at sowing and an additional dose of 30 mg kg−1 every 10 days from 40 days after sowing. Plants had a total N supply of 90 mg N kg−1 at 50 days and 180 mg N kg−1 at 80 days after sowing. The N+P treatments increased plant N uptake and increased rhizosphere and bulk soil pH. Nitrate placement increased pH of treated layers by up to 0.4 and 0.2 units in the rhizosphere and bulk soils, respectively, compared with the control at Day 80. Rhizosphere alkalization was greater with deeper N+P treatments as these encouraged the proliferation of deeper roots in the treated layer. The form of N and the application method of P fertilizer had no effect on shoot biomass over 80 days of growth. The N+P treatments had 7% higher 15N recovery of fertilizer in plants than the N‐P treatments. The current study also showed that P fertilizer enhanced rhizosphere alkalization induced by calcium nitrate. The results suggest that the use of nitrate fertilizer with P treatments can facilitate alkalization of acid subsoils. Highlights Phosphorus facilitates amelioration of subsurface soil acidity with nitrate fertilizer Placement of nitrate induces alkalization of acid soil at various depths Combined addition of nitrate and P at depth enhances nitrate uptake by wheat Balanced nutrient supply enhances excess anion uptake and rhizosphere alkalization

Microbiome convergence enables siderophore-secreting-rhizobacteria to improve iron nutrition and yield of peanut intercropped with maize

“…For instance, soil nutrients like NH 4 + and NO 3 − (the main forms of nitrogen in the rhizosphere) can impact pH and therefore iron availability. Long-term application of NH 4 + decreases rhizosphere pH, while NO 3 − increases rhizosphere pH 37 , 38 . However, in our intercropping system, the pH remained stable across nutrient stages (Supplementary Fig.…”

Nitrate Nitrogen and pH Correlate with Changes in Rhizosphere Microbial Community Assemblages during Invasion of Ambrosia artemisiifolia and Bidens pilosa

“…The higher N-uptake capacity of A. artemisiifolia and B. pilosa , compared with that of the native species, may lead to a decrease in NO 3 -N concentration in the rhizosphere soil of the invasive species. The uptake of nitrate may be effective in increasing the subsurface soil pH through rhizosphere alkalization, which may lead to differences in N-use efficiency and asymmetrical competition between alien and native plants ( 47 – 49 ). Soil microbial mediation plays a vital role in soil N cycling ( 50 , 51 ).…”