Abstract
There is a possibility that plants absorb not only inorganic nitrogen but also amino acids to utilise as a nitrogen source. However, the contribution of amino acids uptake in nitrogen acquisition of plants remains unclear. We applied amino acids mixture and three kinds of organic fertilisers to elucidate the amino acid dynamics in soils. After the addition of the amino acid mixture, all amino acids degraded to 10% or less within 12 hours. Organic fertiliser showed the highest concentration after application and decreased dramatically in about 3 days, however, the concentrations maintained until 30 days were high. The initial amino acid compositions were different, however, Gln, Arg, Lys, Thr, Glu, Asn, Ala were detected at high proportions during incubation. The microbial cell walls comprised of these amino acids. These are suggested to be supplied by the turnover of microbial biomass in a relatively early phase (after 3 days). In incubating soil, the amino acids always degraded with a half-life of less than 2 hours. The daily amount of amino acids supplied to the soil per day should be estimated from 15 to 20 times compared with the amount (concentration) at some point in the day. The related studies showed the ability of amino acids uptake of plants is high. It was suggested the amino acids supplied in organic fertiliser added soils could be absorbed by plant roots.
