Introduction: Nitrogen, duo to the high demand of plants and its vital role in food production for humans and livestock, has a special position in agricultural systems. Therefore, proper management of it is essential for food production. Also, the amount and timing of fertilizer application play an important role in improving the efficiency of nitrogen use. Considering that wheat is the most important grain on the Earth and in Iran (25% of the country's agricultural land), any improvement in management methods and cultivation systems for this crop alone can, in addition to increasing food and feed supply, lead to improved production sustainability, improved ecosystem services, and reduced climate change. Also, the historical history of inefficient use of nitrogen fertilizers, along with the low organic matter content of most agricultural soils, has caused a significant decline in the ecological services of organic farming, including low nitrogen efficiency. This research seeks to provide scientific solutions to increase nitrogen efficiency in agricultural fields in the semi-arid climate of eastern Iran.

Materials and methods: The present study was conducted for two years (2022-2023 and 2023-2024) and during four cropping seasons in Mashhad city, located in Khorasan Razavi province, Iran. In order to monitor nitrogen efficiency and other desired traits, some agronomic practices including planting cover crops, adding animal manure to the soil, adding plant residues (wheat straw) to the soil, as well as a treatment without adding residues, were all applied to the field before wheat planting. The field was also dedicated to wheat cultivation in the year before the experiment. Tillage operations were carried out in a protective manner and solely using a chisel plow. Then, plots with a width of 4 meters and a length of 5 meters were created, with a distance of one meter between plots and three meters between blocks. Also, before conducting the research, and based on soil tests, nitrogen fertilizer application was used for wheat cultivation at three levels: 100% nitrogen fertilizer requirement, 50% nitrogen fertilizer requirement, and no nitrogen fertilizer supply (320, 160, and 0 kg/ha of nitrogen fertilizer, respectively). Therefore, considering two factors: planting systems and nitrogen fertilizer levels, this experiment was conducted with a total of 12 treatments and three replications, in a factorial manner and in a randomized complete block design; the plot allocated to each treatment was considered constant in both years of the experiment.

Results and discussion: The results showed that organic additives entering agricultural soils and its interaction with increasing nitrogen fertilizer supply (from zero to 320 kg/ha) and also with the year significantly affects plant nitrogen, nitrogen harvest index, nitrogen efficiency, total plant nitrogen, grain nitrogen, and straw nitrogen. While the best agronomic efficiency of nitrogen and ecological and physiological efficiency of the plant were observed in treatments without nitrogen fertilizer supply with the addition of organic matter. The green fertilizer -wheat system achieved higher indices related to nitrogen compared to the animal’s fertilizer -wheat system, and the lowest indices related to this factor mainly belonged to the residue-wheat system (due to the high C/N ratio of plant residues) and then to the no organic additive-wheat system, both without nitrogen fertilizer supply. The mentioned indicators recorded a higher value in the second year compared the first year, and the results of the first two systems together and the second two systems with each other did not show much significant difference.

Conclusion: In general, based on the results of this research, management practices such as using cover crops in rotation, adding manure, and returning wheat residues to the soil, along with eliminating fallow, will increase soil nitrogen content and, consequently, plant nitrogen content.

Keywords: Animal fertilizer, Green fertilizer, Harvest index, Nitrogen