Abstract
When organic matter with a high ratio of carbon to nitrogen is applied to soil, inorganic nitrogen in the soil is consumed by soil microorganisms to decompose and increase the organic matter. This causes a shortage of inorganic nitrogen available for plants. On the other hand, when organic matter with a high ratio of carbon to nitrogen is applied to soil, the soil can contain more pore space and humus, and physical properties are expected to improve. In this study, we investigated the dynamics of inorganic nitrogen in soil when rice straw, wheat straw, rice husks, or bamboo, which have a high ratio of carbon to nitrogen and are easily available, were mixed with soil. When the soil was incubated at 30℃ for 8 weeks, the amount of inorganic nitrogen in the soil with each type of organic matter decreased compared to that without mixing. In particular, the most significant decrease in inorganic nitrogen was observed when wheat straw was used. In cultivation tests, when wheat straw was applied, leaf discoloration and a reduction in nitrogen absorption were observed. These effects were considered to be based on a decrease in inorganic nitrogen due to the decomposition of organic matter in the soil. These results suggest that when organic matter with a high ratio of carbon to nitrogen is applied to soil, the amount of inorganic nitrogen in the soil decreases, which may affect plant growth depending on the type of organic matter applied, and that nitrogen fertilization should be increased.
