Endomycorrhizal inoculant evaluation on soybean in North Carolina under varying potassium levels

Potassium (K + ) is a key macronutrient for plant growth. While arbuscular mycorrhizal (AM) fungi have been shown to enhance K + uptake in model legumes like barrel medic ( Medicago truncatula ), their effect on crop legumes such as soybean [ Glycine max (L.) Merr.] is not well documented. A 2‐year field study across three North Carolina regions assessed the impact of AM inoculation on soybean growth, nutrient uptake, yield, and seed quality. Trials targeted soils low in phosphorus and K + , using K + chloride to establish high (67 kg ha −1 ) and low (0 kg ha −1 ) K + environments. Three commercially available soybean cultivars (maturity groups IV, V, and VI) were either inoculated with AM fungi or left untreated. Measurements at 10 and 16 weeks post‐planting included chlorophyll content estimation, shoot biomass, and tissue nutrient concentrations. Results indicated that environmental conditions and cultivar maturity group had the strongest influence on biomass, K + uptake, yield, protein, and oil content. AM inoculation had limited impact across treatments. These findings, consistent with previous studies, suggest that AM inoculation offers minimal practical benefit for soybean K + nutrition under field conditions in North Carolina. Growers should critically evaluate product claims and use caution when adopting AM inoculants expecting significant yield improvements.