Inoculation with Bacillus alters nitrogen uptake and metabolism in roots of Diospyros lotus under wheat straw addition in soil

A ¹⁵N-labelling technique was carried out to investigate the effect of wheat straw co-application with Bacillus nealsonii, Cohnella, and Paenibacillus lautus on N uptake and assimilation in Diospyros lotus. Wheat straw combined with Bacillus increased the plant height, biomass accumulation, photosynthetic capacity, and uptake of ¹⁵N by roots, with ¹⁵N accumulating mainly in leaves of D. lotus. The NO₃^–-N content in roots and leaves were decreased by wheat straw co-application with Bacillus, whereas NH₄⁺-N, soluble protein, and total N contents were increased. Wheat straw addition promoted the activities of nitrate reductase, glutamine synthase and glutamate synthase in roots rather than in leaves. These N assimilation enzymatic activities, and glutamic-oxaloacetic transaminase and glutamic pyruvic transaminase activities were markedly increased by wheat straw combined with Bacillus. Moreover, the combined application of wheat straw and Bacillus, particularly B. nealsonii, improved the N use efficiency. These findings suggest that the combined application of wheat straw and Bacillus improved D. lotus growth by increasing N uptake, metabolism, and utilisation efficiency.