Maize (Zea mays) growth and nutrient uptake following integrated improvement of vermicompost and humic acid fertilizer on coastal saline soil

Soil salinity, poor soil structure and macronutrient deficiencies are three important limitations responsible for poor crop yields in coastal saline soil. Therefore, the objective was to investigate the integrated effects of humic acid fertilizer and vermicompost on maize growth and nutrient uptake in coastal saline soil. The experiment included three treatments: (1) control without humic acid fertilizer and vermicompost (CK); (2) treatment with humic acid fertilizer (H); (3) treatment with vermicompost (V). Soil salinity, aggregates, nutrient availability and uptake, the soil microbial community from next-generation high-throughput sequencing, maize biomass and yield were determined in this study. The results showed that humic acid fertilizer and vermicompost increased soil macroaggregates by 77.59-125.58% and 35.02-91.02%, respectively, which could efficiently decrease soil salinity. Proteobacteria, Actinobacteria and Acidobacteria were the dominant bacterial phyla, and Ascomycota was the dominant fungal phylum in this coastal saline soil. The humic acid fertilizer and vermicompost could affect the fungal community structure in the six-leaf stage (6S) and the bacterial community structure in the harvest stage (HS), which consequently improved soil nutrient availability and maize nutrient uptake. The humic acid fertilizer and vermicompost could enhance nitrogen (N) nutrient absorption of the maize plant in the vegetative growth period (6S) and the phosphorus (P) and potassium (K) nutrient absorption in the reproductive growth period (tasseling stage (TS) and harvest stage (HS)) of maize, which played an important role in increasing the maize yield in coastal saline soil. Therefore, the application of humic acid fertilizer and vermicompost can be integrated as a practice for improving coastal saline soil.