Phosphorus (P) supply plays a critical role in regulating symbiotic nitrogen (N) acquisition in soybeans, yet the mechanisms underlying varietal differences between high-oil and non-high-oil varieties remain poorly understood. This study investigated the varietal-specific mechanisms of phosphorus supply intensity on plant nitrogen acquisition via rhizobial community restructuring using two high-oil (Kenong 18, Kenong 39) and two non-high-oil varieties (Heihe 43, Longken 310) under five phosphorus levels (0, 35, 70, 105, 140 kg·hm− 2). The results showed that high-oil varieties exhibited superior growth performance and nitrogen acquisition efficiency at 105 kg·hm− 2 phosphorus supply, with increases of 20. 0% in plant height, 4. 1% in shoot dry weight and 18. 0% in root dry weight versus controls. Nodule number, dry weight and haemoglobin content increased by 83. 0%, 30. 0% and 33. 0%, respectively, in high-oil genotypes. Enhanced nitrogen metabolism was evidenced by significantly elevated GOGAT/GS activities (9. 3–17. 1%) and leaf total nitrogen content. Crucially, under optimal phosphorus conditions, high-oil varieties enriched specific nitrogen-fixing rhizobia, such as Bradyrhizobium sp. 173₃ₘodule and Rhizobium sp. , and exhibited stronger correlations between community structure and soil available phosphorus (AP), along with a predicted greater potential for nitrogen acquisition and aerobic chemoheterotrophy. This study demonstrates that optimal phosphorus supply enhances symbiotic nitrogen acquisition efficiency in high-oil soybeans by driving the assembly of more specialized rhizobial communities, providing microbial mechanistic insights for varietal-specific phosphorus management in soybean cultivation.
Zhang et al. (Sat,) studied this question.