From the perspective of material circulation in farmland ecosystems, the nitrogen flow in the soil is a material flow that continuously transforms and has multiple channels. Its first basic feature is that with the continuous strengthening of biological production activities and the organicization of nitrogen, nitrogen will continue to accumulate and accumulate in the soil circle.
Soil is one of the most important reservoirs in the multi-channel cycle of nitrogen. As the biological yield per unit area of farmland increases, nitrogen in the soil circle tends to accumulate; on the contrary, as the biological yield per unit area of farmland decreases, nitrogen tends to decrease.
The accumulation of nitrogen accompanying plant growth in the soil circle is called biological enrichment of nitrogen. This is the most frequently occurring process in a farmland system. It refers to the relatively inert gaseous nitrogen (N2) and inorganic nitrides (NO5, NH4+) that are gradually transformed into organic nitrogen (-NH2, etc.) that actively participate in the cycle through various biological pathways. ) And its various mineralization and humification nitrogen-containing products. The use of the term "enrichment" obviously also includes the purpose of humans wishing to increase the nitrogenous organic matter in the soil circle.