The experiment transpired during the crop season 2021 using a clay mixture soil. The aim was to study the effects of different concentrations of nitrogen fertilizer and the date of its application on some growth and yield characteristics of peanut (Arachis hypogaea L.) in the College of Sciences, University of Al-Qadisiyah, Al-Diwaniyah, Al-Qādisiyyah, Iraq. Using the randomized complete block design (RCBD) in the arrangement of split plots had three replications. The first factor was on three additional dates: addition at the beginning of the vegetative growth stage, the start of the flowering stage, and when flowering is complete. The second factor included three nitrogen fertilizer concentrations (50, 100, and 150 kg N ha^-0.1). The results showed the following: The concentration of nitrogen fertilizer (50 kg N ha^-0.1) was significantly superior in some vegetative growth characteristics, i.e., the highest plant height (35.51 cm), maximum number of branches (8.31 branches plant^-1), and heaviest dry weight (104.60 g plant^-1). For yield characteristics: The concentration of 50 kg N ha^-0.1 recorded a significant increase in the yield characteristics—the highest average number of pods was 39.21 pods plant^-1, and the 100-seed weight was 50.91 g plant^-1. The 100 and 150 kg N ha^-0.1 treatments gave higher plant height (39.8 and 41.02 cm) and dry weight (120.40 and 124.50 g plant^-1), respectively. On the effect of time of adding, the addition at the beginning of flowering was significantly superior for plant height (37.41 cm), dry weight (114.30 g plant^-1), number of pods per plant (36.40 pods plant^-1), and 100-seed weight (46.61 g), compared with adding during the vegetative growth stage, which showed the lowest values for the studied characteristics. The interactions between nitrogen concentrations and the adding time resulted in a significant effect from the concentration of 50 kg added as the flowering starts on the number of pods and seeds compared with the control treatment.

Keywords: Peanut (A. hypogaea L.), nitrogen fertilizer, fertilizer application timings, growth and yield-related traits

Key findings: Peanut (A. hypogaea L.) is an oil crop containing essential fatty acids, such as, linoleic and oleic acids. Nitrogen fertilizer and the time to add fertilizer are resources to improve plant production and increase the oil percentage. This review presents these resources and ways to apply them to increase growth and productivity of A. hypogaea.