Effects of Biofertilizer and Amino Acids on Nitrogen Availability and the Microbial Community in Agricultural Soils

摘要

Rhizosphere microorganisms are able to change soil properties in various ways, including available nitrogen, pH, and organic carbon contents. Certain microorganisms in the soil are known to fix nitrogen and many microbes can also process amino acids to yield usable nitrogen sources for plants. Biofertilizers are microbial broths applied to soil which contain microorganisms with many useful attributes, such as the ones mentioned above, to aid in plant health and growth. This study examined the effect of a biofertilizer (Environoc 401) and an amino acid fertilizer (Micronized N) both in conjunction and alone against untreated controls on greenhouse-grown tomato plants and soil health. Plant fresh weight, chlorophyll a content, and percent nitrogen was measured, as well as the soil pH and soil nitrogen content. Furthermore, the abundance of Bacillus amyloliquefaciens and Pseudomonas taiwanensis in the soil were quantified temporally throughout the duration of the 12-week experiment using quantitative PCR and the activity of the soil microbial community on common carbon substrates was measured using Ecoplates. No significant differences were found among treatment groups concerning plant health except that treated plants yielded less percent nitrogen in leaf tissue than untreated controls. Many differences were also found among treatment groups when analyzing carbon substrates used by soil microbes, including L-arginine, L-asparagine, tween 40, L-serine, alpha-D-lactose, D,L-a-glycerol phosphate, and putrescine (p < 0.01). Overall the abundance of B. amyloliquefaciens was generally constant throughout the study with the most significant increase over controls at 12 weeks. Alternatively, P. taiwanensis concentrations mostly increased over the course of the experiment and only increased in treated samples over controls in the first 24 hrs. This study is the first to compare changes in plant health and the soil microbial community following the use of a biofertilizer and amino acid fertilizer in a controlled greenhouse setting. Future studies will examine ways to improve overall plant and soil health using different combinations of treatments on a variety of plants.