Introduction: In most countries of the world, research and progress in the production and management of fodder plants have been forgotten, so for the development and cultivation of fodder plants and the lack of fodder for livestock and also to reduce the pressure on pastures, the standard and scientific production of fodder should be increased compared to the effort and attention which is directed to other products, the fodder production has been neglected. Today, due to the change in weather conditions, population increase, and the concern of food security, the planting of millet plants has gained special importance, therefore, research and research on their quantity and quality have it is important.

Material and Methods:

To investigate the effect of density and biological fertilizer (Ascophyllum nodosum seaweed) on three varieties of millet, this experiment was carried out during the two crop years of 2019 and 2020, in fields located in Mehdi-Abad region (Keneh-Bist) and Agricultural Research Center respectively. It was done in Mashhad city. The factorial experiment was carried out as a randomized complete block design in three replications. The test factors include plant density in three levels of 300, 400, and 500 thousand plants per hectare with row spacing of 6.5, 5, and 4 cm and row spacing of 50 cm and the use of biological fertilizer in two levels: no use and Application of seaweed biological fertilizer (during two stages: the first stage at the time of tillering and the second stage when the panicum appears) at the rate of one liter per hectare (based on field studies) and spraying on three different species of millet (Panicum miliaceum var. Pishahang, Setaria italica var. Bastan, and Pennisetum gluacum var. Mehran) were implemented. During the plant's growth period, the necessary notes of the characteristics of its growth and reproduction included the number of leaves, the yield of fresh fodder, the weight of 1000 seeds, the period of seed filling, and the number of days until flowering. The exact time of harvesting green fodder was at the stage of 50% grain milkiness. Composite variance analysis was performed for two years with the assumption of randomness of the year factor using MSTATC software.

Results and Discussion: The results showed that there was a significant difference in the investigated traits among all speciess studied. The interaction effect of variable which is “year * species * density * fertilizer on all traits” were insignificant except forage yield. This indicated the absence of similar changes in the years of the experiment for these characteristics among the speciess investigated in the experiment. The highest yield of fodder related to the first year of the experiment and the Panicum miliaceum var. Pishahang and the density of 300 thousand plants per hectare and the absence of fertilizer application were obtained. which statistically did not show much difference with the treatment of pennisetum gluacum var. Mehran at a density of 500,000 plants per hectare and the use of seaweed fertilizer, although in the comparison of the species, Panicum miliaceum var. Pishahang or Setaria italica var. Bastan may be superior in one harvesy, but in total, this capability and superiority in the species There is pennisetum gluacum var. Mehran. Setaria italica var. Bastan and pennisetum gluacum var. Mehran, which had the longest and shortest grain filling period respectively, had the highest and lowest thousand seed weight. With the aim of achieving more fodder yield, it is suggested to cultivate Panicum miliaceum var. Pishahang and pennisetum gluacum var. Mehran and to harvest more seeds, it is suggested to cultivate the Setaria italica var. Bastan speciess in the region. The response of investigated traits in the use or non-use of fertilizer did not follow a specific pattern, and according to the results of this experiment, it seems that the investigated traits were more affected by the genetic difference of species.