Phosphorus efficiency in nodulating soybeans: Genotype classification and yield response in Nigeria

Abstract Phosphorus is a major nutrient constraint limiting soybean Glycine max (L.) Merrill production in highly weathered tropical soils. This study evaluated phosphorus use efficiency (PUE) of freely nodulating soybean genotypes under contrasting phosphorus conditions in Nigeria, where access to rhizobial inoculants and soluble fertilizers is often limited for smallholder farmers. Field experiments conducted at two locations used three phosphorus treatments: 0 kg P ha −1 (control), 30 kg P ha −1 applied as triple superphosphate (TSP), and 90 kg P ha −1 applied as rock phosphate (RP). Thirteen soybean genotypes were evaluated in a randomized complete block design with four replications. PUE, estimated from grain yield and shoot P uptake, identified TGx 1456‐2E (where TGx is tropical glycine crosses) and TGm 1419 (where TGm is tropical glycine max ) as highly efficient genotypes, producing average grain yields of 1.4 t ha −1 without P application, 1.6 t ha −1 with RP, and 1.65 t ha −1 with TSP. Grain yield increased by 13.3% under RP and 43.3% under TSP relative to the control. Efficient genotypes exhibited greater shoot dry matter production per unit P uptake, indicating improved internal P utilization and adaptation to low‐P environments. Genotype classification followed the grain yield–phosphorus uptake framework of Gerloff, emphasizing agronomically relevant indicators of phosphorus efficiency. Although nodulation and biological nitrogen fixation were not primary objectives of this study, their potential interaction with phosphorus efficiency is recommended for future investigation. These findings improve understanding of genotype variation in phosphorus efficiency and provide practical guidance for breeding and selecting soybean cultivars adapted to phosphorus‐deficient production systems common across West African smallholder agriculture.