Nitrogen Fate of Chemical Fertilizer and Green Manure-Wheat Rotation Using ¹⁵N Tracer Technique

To investigate the accumulation, distribution, and translocation of nitrogen (N) from chemical fertilizers and green manure in wheat plants, we conducted an experiment using leguminous green manure crop hairy vetch and wheat as test materials. During the anthesis and maturity stages of wheat, the N-15 enrichment and Nitrogen content of wheat plant samples were determined in different organs, and N-15 enrichment and nitrogen content of soil samples were measured at maturity. The accumulation and distribution characteristics of nitrogen from different sources during the wheat growth stages were investigated to explore the impacts of green manure and chemical fertilizers on wheat growth and nitrogen uptake. The results showed that nitrogen from chemical fertilizers in the soil-plant system exhibited the following pattern: plant absorption > soil residue > loss, while nitrogen from green manure showed: soil residue > loss > plant absorption. Wheat had higher absorption of nitrogen from chemical fertilizers compared to green manure. The absorption of nitrogen from chemical fertilizers by wheat ranged from 46.00% to 54.08%, while the absorption of nitrogen from green manure ranged from 20.71% to 28.21%. The residual nitrogen from green manure in the soil (38.47% to 58.22%) was higher than that from chemical fertilizers (31.44% to 40.69%), and the nitrogen loss from green manure (21.07% to 33.31%) was higher than that from chemical fertilizers (5.22% to 22.56%). Supply of nitrogen from the two sources could coordinate the distribution of nitrogen in various organs and increase the proportion of nitrogen allocation in grains. This was beneficial for facilitating nutrient transfer to reproductive organs.