Organic amendments enhance transpiration efficiency of corn plants via changes in soil microbial abundance and leaf hormones

Background and Aims: The use of organic amendments improves soil functioning and thus crop productivity. Our previous studies have shown that the banding of organic amendments increases the transpiration efficiency (TE) of wheat plants, but the underlying mechanism remained unclear. This study aims to determine whether and how the organic amendments can increase the TE of corn plants (Zea mays L.). Methods: The effects of nutrient-enriched poultry litter, compost and brown coal on TE were compared with inorganic fertilizer. Corn plants were grown in Chromosol topsoil in pots for 50 days. Results: The poultry litter and compost but not brown coal, increased the TE of corn plants by 25% and 14%, respectively (P < 0.05), compared to inorganic fertilizer. At the leaf level, poultry litter and compost also increased the instantaneous TE due to either decreased transpiration or increased instantaneous CO2 assimilation rates. The increased TE at the plant level was closely associated with increased abundances of soil fungi, bacteria and bacteria in genus Bacillus. Meanwhile, there were increases in the concentrations of leaf hormones abscisic acid (ABA) (> 50%), methyl jasmonate (JA) (> 80%) and indole acetic acid (IAA). Conclusion: Organic amendments enhanced the population of plant beneficial soil microorganisms such as those in the Bacillus genus, which likely led to the increased biosynthesis of leaf hormones ABA and JA, resulting in stomatal close, reduced total transpiration and increased transpiration efficiency of the corn canopy.