Prediction of weed seedling emergence under different nitrogen levels in Pisum sativum L.

The knowledge of weed seedling emergence with optimization of the time of control could enhance the efficiency of weed control. Therefore, to develop a seedling emergence model based on thermal-time to predict the emergence of weed seedling, a field experiment was conducted in different levels of nitrogen (control, 50 and 100 kg ha-1) in Pisum sativum. Weed seedling emergence was monitored from mid-December until early May. Percentage of cumulative emergence values was compared with thermal-time using the Goumpertz function. The results showed that, regardless of the nitrogen levels, the Veronica persica L., Galium aparine L., and Polygonum aviculare L., needed 92,164, and 170 units of thermal-time for 10% of emergence, respectively. But, the Setaria viridis L. seedlings started their emergence later. In general, V. persica L., G. aparine, P. aviculare, and the S. viridis L., needed 486, 274, 731, 422 units of thermal- time for 90% of emergence respectively. The results also showed that the weed seedling emergence pattern affected by nitrogen application. Except for S. viridis, the "m" parameter, which indicates the required thermal time for 50% of seedling emergence, significantly changed with the application of nitrogen in all studied species. Overall, the use of nitrogen reduced the time of the seedling emergence in V. persica, but increased this period in G. aparine and P. aviculare when compared with control. Therefore, depending on the dominant weed species, nitrogen application can alter the cost of weed control by increasing or decreasing the weed control period.